Note: Descriptions are shown in the official language in which they were submitted.
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CONTRA-ROTATING AXIAL FAN SYSTEM AND TRANSMISSION FOR DRY AND EVAPORATIVE
COOLING EQUIPMENT
FIELD OF THE INVENTION
[0001] The present invention is directed to systems, methods, and
arrangements for
providing contra-rotating axial fans, and fan drive systems. More
specifically, the present
invention is directed to systems, methods, and arrangement for providing
contra-rotating fans
and fan drive systems for condenser and evaporative cooling equipment. Even
more specifically,
the present invention is directed to axial fans and fan drive systems for dry
and evaporative
cooling equipment, as well as for heating, ventilation, air conditioning,
refrigeration, and/or
industrial processes. More specifically, the present invention is directed to
axial fan drive
assemblies for evaporative, dry, and hybrid wet/dry cooling equipment.
BACKGROUND OF THE INVENTION
[0002] The present invention is directed to axial fans and fan drive
systems for
evaporative, dry, and hybrid wet/dry cooling equipment. Common applications
for evaporative
cooling equipment, such as cooling towers, include providing cooled process
medium for
heating, ventilation, air conditioning, and refrigeration ("HVACR"),
manufacturing,
refrigeration, electric power generation, and industrial processes (oil
refineries, chemical
manufacturers, etc.). In operation, the cooling towers serve to transfer heat
from the process
medium into the surrounding environment. Similarly, common applications for
air- and
water-cooled equipment, such as condensers, include providing cooled process
medium for
HVACR, manufacturing, refrigeration, and electric power generation. Finally,
common
applications for hybrid cooling equipment, such as wet/dry evaporative
coolers, include
providing cooled process medium for HVACR, manufacturing, refrigeration, and
electric power
generation. Generally speaking, as is generally known in the art, condensers
and coolers serve to
transfer heat from the process medium into the surrounding environment. Such
condensers may
be a standalone piece of equipment or a part of a larger "packaged" piece of
HVACR equipment
and/or industrial process equipment.
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[0003] In an open circuit cooling tower, the process fluid to be cooled is
delivered to the
cooling tower and is typically distributed by a series of nozzles that atomize
the process fluid
over a heat-transfer medium located inside the heat-exchanger section,
commonly referred to as a
"fill." The fill facilitates heat transfer by promoting evaporation through
commingling the
process fluid with dry, outside air. The fill provides a large surface area
and facilitates contact
between the process fluid and the dry, unsaturated airstream supplied by a fan
within the cooling
tower. As the process fluid droplets pass through the fill, heat is
transferred to the atmosphere
through the discharge airstream of the cooling tower. A portion of the process
fluid is lost
through the endothermic process of evaporation, leaving the remaining process
fluid at a lower
temperature than it was before it entered the cooling tower. The cooled
process fluid is collected
in a collection basin at the bottom of the cooling tower and then withdrawn
therefrom.
[0004] Closed-circuit cooling towers, also known as fluid coolers, have
similar
functionality, with a difference being that the process fluid is contained
within one or more
heat-transfer coils and not directly exposed to the surrounding environment.
Water stored in the
collection basin of the unit is typically sprayed over the coil(s) to promote
heat transfer from the
liquid to the make-up water, while at the same time promoting the endothermic
process of
evaporation. The end result is the process fluid within the coil is cooled
through evaporation of
spray water on the outside surface of the coil, and to a lesser degree, heat
is transferred through
the temperature gradient between the spray water/intake air temperature and
the coil when
atmospheric conditions allow.
[00051 Evaporative condensers are nearly identical to a closed-circuit
cooling tower, or
fluid cooler, except for the process medium. In the case of an evaporative
condenser, the process
medium is a refrigerant delivered directly from the evaporator of an HVACR
machine. The
evaporative condensers are typically used in the refrigeration industry, cold
storage, ice skating
rinks, cryogenics, and so forth. Hybrid versions of closed-circuit cooling
towers employ the
addition of fins to the coil circuits, similar in design to those employed on
air-cooled condensers.
Where atmospheric conditions and/or system load conditions allow, the fluid
cooler is switched
from the conventional evaporative, a.k.a "wet operation," cooling mode to an
air-cooled, a.k.a.
"dry operation," by switching off the spray water pump. This effectively
changes the machine
from a closed-circuit cooling tower into an air-cooled condenser. The purpose
of these hybrid
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cooling units is to save water and energy by arresting the evaporation of
water and the
elimination of the energy required to operate the spray water pump when
atmospheric conditions
and system load conditions allow.
100061 Dry coolers and condensers have similar functionality to closed-
circuit cooling
towers with the difference being that they rely solely on heat transfer
through direct and/or
indirect contact of the process medium and the heat exchanger surface with
outside air. Dry
coolers and condensers have similar construction and component arrangements to
closed-circuit
cooling towers with a difference being that they omit components associated
with the
evaporative cooling process, such as, but not limited to, spray water pump and
distribution
systems, drift eliminators, and collection basins. Air-cooled condensers use
heat exchangers of
the "Liquid to Air" or "Gas to Air" variety, while and water-cooled condensers
use heat
exchangers of the "Liquid to Liquid" or "Gas to Liquid" variety, which are
similar in design and
construction to those employed in closed-circuit cooling towers.
[00071 In operation, airflow through dry and evaporative cooling equipment
is typically
facilitated by a fan in combination with an intake air conduit and an exhaust
air conduit, which
are provided for each heat transfer section, unit, or cell, of the equipment.
In induced-draft
equipment, the fan is typically mounted near the exhaust of the unit and used
to draw air from
the intake through the interior of the unit and across the heat-exchange
surface located inside the
heat-exchanger section. In forced-draft equipment, the fan is typically
mounted near the intake
and pushes the air through the interior of the cooling unit, across the heat
exchange surface
located inside the heat exchanger section, and out via the exhaust.
[0008] Several considerations are present during the installation and
design of dry and
evaporative cooling systems, including airflow, sound output, space
requirements, energy
requirements, and vibration transmission. It is desirable to minimize noise
emitted by operation
of the fan, the energy consumed by the fan drive system, and the vibrations
emitted by the fan
drive system. However, minimizing these negative attributes requires reducing
the rotational
speed of the fans, which limits the heat exchange capacity of a given unit
design by falling below
the required minimum airflow and static pressure. Independent of minimizing
negative attributes
of the conventional axial fan systems currently in use, it is also desirable
to employ a fan
arrangement with a higher overall efficiency that can generate an increased
amount of airflow
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and static pressure at a given energy input value. Such a fan arrangement
would increase the
thermal capacity ratings of existing dry and evaporative equipment designs,
while at the same
time increasing the energy efficiency of the units themselves, as well as that
of the entire
HVACR and/or industrial process system in which they are installed.
[0009] As disclosed herein, one solution to minimize the negative
attributes and/or increase
thermal capacity ratings and energy efficiencies of dry and evaporative
cooling equipment is the
use of a contra-rotating, multi-stage fan arrangement. A contra-rotating,
multi-stage fan
arrangement is capable of meeting minimum airflow and static pressure
requirements at
rotational speeds that are lower than that of currently employed, axial fan
systems. A
contra-rotating, multi-stage fan arrangement is also capable of increased
airflow and static
pressure at a given energy input than that of currently employed, axial fan
systems.
[0010] A solution to minimize the negative attributes of condenser and
cooling tower
operation, while meeting minimum airflow and static pressure requirements of a
given piece of
dry or evaporative cooling equipment unit is therefore desired.
BRIEF SUMMARY OF THE INVENTION
[0011] According to a first aspect, a contra-rotating fan system for dry
and/or evaporative
cooling equipment is disclosed. The system can include a first axial fan
disposed in an air
conduit of an evaporative equipment unit, a second axial fan disposed in the
air conduit and
arranged coaxially with the first fan, a transmission for driving the first
axial fan and the second
axial fan and a motor for driving the transmission, wherein the direction of
rotation of the first
axial fan is opposite to the direction of rotation of the second axial fan.
[0012] According to a second aspect, a contra-rotating fan system for an
air-cooled heat
exchanger comprises: a first axial fan disposed in an air conduit of an
evaporative equipment
unit; a second axial fan disposed in the air conduit and arranged coaxially
with the first fan; a
transmission means; a first power output means for transferring power from the
transmission
means to the first axial fan; a second power output means for transferring
power from the
transmission means to the second axial fan; a power input means for
transferring power to the
transmission means; wherein the direction of rotation of the first axial fan
is opposite to the
direction of rotation of the second axial fan.
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[0013] According to a third aspect, a contra-rotating fan system for
evaporative cooling
equipment comprises: an evaporative cooling equipment unit enclosure having
evaporation fill
therein; an air conduit coupled to the unit enclosure and having a narrower
width than the unit
enclosure; a first axial fan disposed in the air conduit; a second axial fan
disposed in the air
conduit and arranged coaxially with the first fan, walls of the air conduit
closely enclosing the
tips of the first axial fan and the second axial fan; a power transmission
structure configured to
drive the first axial fan and the second axial fan, wherein the power
transmission structure
comprises (a) a lower drive unit having a first drive assembly with a first
predetermined drive
ratio and (b) an upper drive unit having a second drive assembly with a second
predetermined
drive ratio, wherein the first drive assembly comprises a center pinwheel
driver, an outer
pinwheel receiver, and a plurality of intermediate pinwheels, wherein the
lower drive unit is
operatively coupled to a motor, the lower drive unit being configured to (1)
drive the upper drive
unit, and (2) rotate the first axial fan at a first speed of rotation in a
first direction; and a motor
for driving the power transmission structure, the motor, and the power
transmission structure
driving the first axial fan and the second axial fan with at least one speed
configured to
(i) maintain airflow through the air conduit at a minimum value necessary to
maintain an
endothermic process of evaporative cooling, and (ii) maintain static pressure
within the unit
enclosure at a minimum value necessary to move air through the unit enclosure
at the minimum
value of airflow; wherein the direction of rotation of the first axial fan is
opposite to the direction
of rotation of the second axial fan.
[0014] According to a fourth aspect, an evaporative cooling equipment unit
comprises: an
evaporative cooling equipment unit enclosure; at least one air conduit coupled
to the enclosure,
the at least one air conduit being narrower than the unit enclosure; a first
axial fan disposed in the
at least one air conduit; a second axial fan disposed in the at least one air
conduit and arranged
coaxially with the first fan, walls of the at least one air conduit closely
enclosing the tips of the
first axial fan and the second axial fan; a motor; a transmission structure
operatively coupled to
the motor, to the first axial fan, and to the second axial fan; and wherein
the transmission
structure drives the first axial fan in an opposite direction of rotation to
the second axial fan, and
wherein the motor and the transmission structure drive the first axial fan and
the second axial fan
with at least one speed configured to (i) maintain airflow through the at
least one air conduit at a
minimum value necessary to maintain an endothermic process of evaporative
cooling, and
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(ii) maintain static pressure within the unit enclosure at a minimum value
necessary to move air
through the unit enclosure at the minimum value of airflow.
[0015] According to a fifth aspect, an evaporative cooling equipment contra-
rotating fan
system comprises: an evaporative cooling equipment unit enclosure; an air
conduit coupled to
the enclosure and being narrower than the unit enclosure; a first axial fan
and a second axial fan
disposed inside the air-restricted conduit and arranged coaxially with respect
to each other, walls
of the conduit closely enclosing the tips of the first axial fan and the
second axial fan; a
transmission structure for driving the first axial fan and the second axial
fan in opposite
rotational directions, the transmission structure having first and second
shafts respectively
coupled to the first and second axial fans and extending from the enclosure
into the air conduit;
and a means for driving the transmission to (i) maintain airflow through the
air conduit at the
minimum value necessary to maintain an endothermic process of evaporative
cooling, and
(ii) maintain static pressure within the unit enclosure at a minimum value
necessary to move air
through the unit enclosure at the minimum value of airflow.
[0016] In certain aspects, the transmission structure comprises (a) a lower
drive unit having
a first drive assembly with a first predetermined drive ratio, and (b) an
upper drive unit having a
second drive assembly with a second predetermined drive ratio, wherein the
first drive assembly
comprises a center pinwheel driver, an outer pinwheel receiver, and a
plurality of intermediate
pinwheels, wherein the lower drive unit is operatively coupled to a motor, the
lower drive unit
being configured to (1) drive the upper drive unit, and (2) rotate the first
axial fan at a first speed
of rotation in a first direction.
[0017] According to a sixth aspect, a contra-rotating axial fan system
comprises: a first
axial fan disposed in an air conduit; a second axial fan disposed in the air
conduit and arranged
coaxially with first axial fan; a transmission, the transmission comprising of
two main
assemblies; lower drive assembly and an upper drive assembly; wherein the
lower drive
assembly is configured to receive power from a motor and is configured to (i)
transfer power to
the upper drive assembly and (ii) rotate the first axial fan in a first
direction; wherein the upper
drive assembly is configured to rotate the second axial fan in a second
direction; wherein the
direction of rotation of the first direction is opposite to the direction of
rotation of the second
direction. The lower and upper drive assemblies may be housed in separate
enclosures and
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coupled externally, housed in a common enclosure internally coupled, fully
integrated into a
single assembly housed in a single enclosure, or one or both assemblies
integrated within an
axial fan hub and/or fan motor.
[0018] According to a seventh aspect, a contra-rotating transmission
comprising: a lower
drive assembly; and an upper drive assembly, wherein the lower drive assembly
is configured to
receive power from a motor and is further configured to (i) transfer power to
the upper drive
assembly and (ii) rotate a first axial fan in a first direction; wherein the
upper drive assembly is
configured to rotate the second axial fan in a second direction; wherein the
direction of rotation
of the first direction is opposite to the direction of rotation of the second
direction.
BRIEF DESCRIPTION OF THE FIGURES
[0019] These and other advantages of the present invention will be readily
understood with
reference to the following specifications and attached drawings, wherein:
[0020] Figure 1 a shows a first exemplary embodiment of a contra-rotating
fan system for
dry or evaporative cooling equipment.
[0021] Figure lb shows an exemplary embodiment of a transmission for a
contra-rotating
fan system.
[0022] Figure 1 c shows a variant of the first exemplary embodiment of the
contra-rotating
fan system for dry or evaporative cooling equipment using two motors.
[0023] Figure 2a shows a second exemplary embodiment of a contra-rotating
fan system
for dry or evaporative cooling equipment.
[0024] Figure 2b shows an exemplary embodiment of a transmission and fan
hub for a
contra-rotating fan system.
[0025] Figure 2c shows a variant of the second exemplary embodiment of the
contra-
rotating fan system for dry or evaporative cooling equipment using two motors.
[0026] Figure 3a shows a third exemplary embodiment of a contra-rotating
fan system for
dry or evaporative cooling equipment.
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[0027] Figure 3b shows a variant of the third exemplary embodiment of the
contra-rotating
fan system for dry or evaporative cooling equipment using two motors.
[0028] Figure 4a shows a fourth exemplary embodiment of a contra-rotating
fan system for
dry or evaporative cooling equipment.
[0029] Figure 4b shows a variant of the fourth exemplary embodiment of the
contra-
rotating fan system for dry or evaporative cooling equipment using two motors.
[0030] Figure 5a shows a fifth exemplary embodiment of a contra-rotating
fan system for
dry or evaporative cooling equipment.
[0031] Figure 5b shows a variant of the fifth exemplary embodiment of the
contra-rotating
fan system for dry or evaporative cooling equipment using two motors.
[0032] Figure 6a shows a sixth exemplary embodiment of a contra-rotating
fan system for
dry or evaporative cooling equipment.
[0033] Figure 6b shows an exemplary embodiment of a transmission for a
contra-rotating
fan system.
[0034] Figure 7a shows an exemplary embodiment of a contra-rotating fan
system for an
induced-draft, air-cooled heat exchanger.
[0035] Figure 7b shows an exemplary embodiment of a contra-rotating fan
system for a
forced draft air cooled heat exchanger.
[0036] Figure 8a is an exemplary embodiment of a first contra-rotating
axial fan system for
evaporative cooling equipment.
[0037] Figure 8b is an exemplary embodiment of a second contra-rotating
axial fan system
for evaporative cooling equipment.
[0038] Figure 8c is an exemplary contra-rotating transmission and motor for
use with the
system of Figure 8b.
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[0039] Figure 8d is a first view of an exemplary contra-rotating axial fan
assembly for use
with the system of Figure 8b.
[0040] Figure 8e is a second view of the exemplary contra-rotating axial
fan assembly for
use with the system of Figure 8b.
[0041] Figure 9a is a front, isometric view of an exemplary embodiment of a
contra-rotating transmission for use in a contra-rotating axial fan system.
[0042] Figure 9b is a side, cross-sectional view of the exemplary
embodiment of a
contra-rotating transmission.
[0043] Figure 10a is a front, isometric view of a lower drive unit of the
exemplary
embodiment of a contra-rotating transmission.
[0044] Figure 10b is a top, plan view of the lower drive unit of the
exemplary embodiment
of a contra-rotating transmission.
[0045] Figure 1 1 a is a front, isometric view of an upper drive unit of
the exemplary
embodiment of a contra-rotating transmission.
[0046] Figure 1 lb is a top, plan view of the upper drive unit of the
exemplary embodiment
of a contra-rotating transmission.
DETAILED DESCRIPTION OF THE INVENTION
[0047] Embodiments of the present invention will be described hereinbelow
with
references to the accompanying drawings. Alternate embodiments may be devised
without
departing from the spirit or the scope of the invention. In the following
description, well-known
functions or constructions are not described in detail because they would
obscure the invention in
unnecessary detail. Further, to facilitate an understanding of the
description, discussion of
several terms used herein follows. According to at least one exemplary
embodiment, contra-
rotating fan systems for dry coolers (e.g., an air-cooled heat exchanger,
HVACR condenser, etc.)
and evaporative cooling equipment are disclosed. The fan systems may include a
pair of axial,
contra-rotating fans (or other rotating components) and associated drive and
transmission
components.
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[0048] As used herein, the word "exemplary" means "serving as an example,
instance, or
illustration." The embodiments described herein are not limiting, but rather
are exemplary only.
It should be understood that the described embodiments are not necessarily to
be construed as
preferred or advantageous over other embodiments. Moreover, the terms
"embodiments of the
invention," "embodiments," or "invention" do not require that all embodiments
of the invention
include the discussed feature, advantage, or mode of operation.
[0049] As used herein, the term "input shaft" shall be understood to refer
to any device that
applies torque to the transmission (e.g., a contra-rotating transmission so as
to initiate and/or
maintain rotation of the transmission gearing arrangement(s)).
[0050] As disclosed herein, a multi-stage axial fan system may be
configured to enable
contra-rotation, as well as co-rotation, of two or more axial fans or other
rotating components
(e.g., impellers, fans, gears, mechanical linkages to another device or
system, etc.). Indeed,
multi-stage axial fan systems may deliver and reap the benefits of co- and
contra-rotating, multi-
stage axial fan systems, including, but not limited to, altering static
pressure, flow rate,
horsepower ("HP") consumption, fan system efficiency, sound, harmonics,
thermal efficiency of
cooling unit (e.g., an evaporative cooling unit or HVACR system), thermal
performance of
cooling unit, layout, and sound quality of cooling unit, etc.
[0051] Employing a pair of coaxial, axial fans (e.g., coaxial, contra-
rotating axial fans), in
lieu of a single fan, provides a number of advantages. For instance, a pair of
contra-rotating axial
fans can produce a higher cubic foot per minute ("CFM") output while
maintaining minimum
static pressure required for air to travel from intake to discharge in
evaporative cooling
equipment and air- or water-cooled equipment, thus increasing the amount of
heat exchanged
from the process fluid to the waste airstream. Accordingly, a pair of contra-
rotating axial fans
provides greater thermal efficiency in terms of total heat rejection typically
measured in British
Thermal Units per Hour ("BTUh"). Thus, the axial fan system provides increased
thermal and/or
energy efficiency. Table 2 provides exemplary target design parameters for an
exemplary
air-cooled heat exchanger.
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Description English Metric
Total Heat: Duty 15.0 Million Btu/Hr 4.4 MW
Hot Fluid Inlet Temperature 250 F 121 C
Hot Fluid Outlet Temperature 150 F 95.6 C
Air Flow Rate 869,000 lb/Hr 109 Kg/s
Air Inlet Temperature 100 F 37.8 C
Outlet Temperature 172 F 77.8 C
Transfer Rate 90.0 Btu/(Hr-Sq.Ft.- F) 511 W/(Sq.M- C)
Table 1
100521 Indeed, employing a pair of contra-rotating axial fans enables dry
and evaporative
cooling equipment manufacturers to substantially increase and maximize thermal
capacity in
existing or new coil products by utilizing a denser coil design, thereby
allowing for more surface
area in a given coil-space volume. The surplus static pressure generated by
contra-rotating axial
fans also allows for the use of larger coils with, or without, increased fins
per inch ("FPI") and
coil rows that can carry larger pressure drops than existing equipment, thus
increasing the
thermal capacity of air-cooled equipment in every coil, cross-sectional area
size currently in use.
Additional opportunities for thermal capacity increases can be realized due to
the present axial
fan system's allowance for the use of denser and higher performance heat
transfer mediums with
higher associated pressure drops. In addition, this arrangement allows the use
of increased
heat-exchanger air travel (e.g., taller fill drifts, additional coil rows,
etc.) than those that are
currently being used.
[0053] In other words, contra-rotating axial fans enable the system to
generate large
amounts of static pressure at a given power input, while maintaining minimum
airflow
requirement, thereby creating the opportunity to utilize the surplus static
pressure advantageously
in dry and evaporative cooling equipment design. In a contra-rotating
configuration, one fan is
generally responsible for the increase in static pressure while the other fan
is generally
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responsible for the gross air flow. A leading fan may be primarily responsible
for air flow
(moving air), while the leaving fan is mainly responsible for generating
static pressure
(compressing air). The surplus static pressure generated by the contra-
rotating fan system allows
for the use of higher performance components with higher pressure drops,
including, but not
limited to, the components discussed previously in detail. This may be
accomplished using the
same amount of (or less) power to the motor (e.g., a 10 HP motor) depending on
the goals for a
given piece of equipment (low sound, efficiency, layout footprint, layout
height, layout
restrictions, etc.).
[0054] An example use of the resulting surplus static pressure includes the
ability to
increase the heat transfer surface area by utilizing larger heat-exchanger
sections with increased
air travel, which is not possible with single stage and co-rotating multi-
stage axial fan systems.
The surplus static pressure is used to overcome the higher pressure drop
across the heat
exchanger section as the overall air travel of the heat exchanger section is
increased.
[0055] When it is not advantageous to use heat-exchanger sections with
increased air travel
(for reasons such as dimensional constraints, manufacturing costs, etc.), the
surplus static
pressure can alternatively be utilized by increasing the amount of heat-
transfer surface area in a
given heat-exchanger section at the expense of pressure drop across the heat-
exchanger section.
For example, in dry cooling equipment, the density of coil fins can be
increased and/or the coil
surface area may be increased by more densely packing the existing coil frame.
Coil finning is
rated in the industry as FPI. This concept is also true for cooling units that
utilize finned coils
such as hybrid wet/dry coolers and more increasingly standard, closed-circuit
cooling towers.
[0056] Evaporative cooling equipment that does not use a coil can take
advantage of the
surplus static pressure by increasing the air travel (drift) of the heat-
transfer medium's surface
(e.g., the fill). Alternatively or conjunctively, the heat-transfer medium's
surface can be more
densely packed to provide more heat-transfer surface area at the expense of
pressure drop across
the heat-exchange medium.
[0057] Yet another possible way to take advantage of the surplus static may
be to use drift
eliminators of a denser design with larger pressure drop that would allow the
maximum amount
of airflow in a given heat exchanger size to be increased without forcing the
process medium to
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be ejected out of the air discharge. Current industry maximum-flow-rate
velocities are
approximately 800 feet per minute (FPM).
[0058] The ability to utilize heat-exchanger sections with increased air
travel leads to the
opportunity to increase thermal capacity in any given cross-sectional area or
"footprint" of the
condenser or cooler. In the evaporative cooling industry, this is also
referred to as "box size."
Thus, the increase in efficiency stemming from using a pair of contra-rotating
axial fans provides
the user a thermal "box advantage." That is, a user can deliver the same
output using evaporative
cooling equipment having a smaller footprint, or, in the alternative, provide
increased output
without requiring larger footprint, cooling equipment. This is particularly
pertinent when the
footprint of the evaporative cooling equipment is a consideration or
limitation (e.g., in urban
areas). For example, HVAC systems installed in tall buildings require a great
amount of cooling
capacity, but provide limited rooftop space for mechanical equipment (e.g.,
building ventilation
equipment, exhaust flues, elevator equipment, window-washing equipment, etc.).
Similarly, such
configurations allow for evaporative cooling equipment to be placed closer to
solid objects,
making it more suitable for tight layouts and reducing the minimum requirement
for overall air
intake sizes allowing for reduction in height opportunities on contra-flow-
induced-draft units.
Contra-flow-induced-draft units are typically taller than other configurations
due to the air intake
at bottom of the equipment. However, the air intakes can be shortened at the
expense of pressure
drop by use of surplus static pressure, thus shortening the overall height of
the equipment.
[0059] Finally, a contra-rotating axial fan system can also be configured
with standard
axial fans that operate at a lower rotation per minute ("RPM"), as opposed to
specialized axial
fans, which are often utilized by evaporative cooling equipment manufacturers.
That is,
specialized axial fans may be specifically engineered to produce minimum
design CFM and
static pressure at the lowest possible RPM. However, enabling the contra-
rotating axial fan
system to operate with standard axial fans allows evaporative cooling
equipment manufacturers
to utilize inventory standard fans in lieu of having to stock two or more
types of fans to
accommodate low-sound projects. In addition, specialize axial fans (e.g.,
engineered, low-RPM
fans) are typically more than double the cost of standard fans. Generally, the
lower the RPM of a
fan system, the lower the sound power level generated. The sound power level
difference
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between two identical fan systems running at different RPMs is described by
the following
equation:
RPM gystern 412's
Sound Power Level Difference = 2 0 log io _______________________
RPM System 412
[0060] The surplus static pressure, as described previously, can also be
applied to the use
of more substantial sound attenuators with higher pressure drops that are
unable to be used with
current fan systems, further enhancing the low-sound capabilities of the
equipment utilizing this
fan arrangement.
[0061] Fans may be selected (e.g., by cooling equipment manufacturers)
utilizing fan
manufacturer-provided fan curves or fan manufacturer selection software that
generates fan
curves. Indeed, the cooling equipment manufacturer determines the minimum
pressure drop for a
particular piece of equipment, minimum/maximum fan diameter for use with the
equipment, and
the power input maximum for use with the equipment. Using that information,
the equipment
manufacturer may generate a fan curve with software, or look up existing fan
curves, and select a
specific fan that meets the criteria with the maximum amount of flow (i.e.,
CFM). Fan curves
typically have an X-axis of airflow (CFM) and a Y-axis of static pressure.
Multiple curves may
be shown per plot, with each curve representing a specific fan blade angle.
Each plot represents a
specific fan RPM, input HP, number of blades, diameter, and tip clearance,
thus the number of
plots possible for a single fan size is seemingly infinite; which is why
selection software is
typically employed when selecting fans for new equipment designs.
[0062] For example, a single-stage fan system may have an airflow output of
36,000 CFM,
while maintaining the design minimum of 0.9 inches of static pressure.
Increasing the rotational
speed of the single fan system will result in an increase in CFM output and
required HP input
power, however, because the static pressure drops below the 0.9 inch minimum
at air flows
higher than 36,000 CFM, the fan system would cause a thermal capacity de-rate
in the cooling
equipment rather than achieving the goal of a thermal capacity increase. If
the airflow of that fan
is increased, the fan would be running "off the curve," meaning that the fan
system is no longer
operating at the maximum airflow at the minimum 0.9 inches of static pressure
required by the
design of the cooling equipment.
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[0063] There are at least two methods of increasing the airflow of an
existing fan system.
A first method to increase the RPM at the expense of input power (HP). If
input power (HP) is
unable to be increased, a second method is to re-pitch (e.g., changing the
blade angle) the fan
blades to increase airflow, at the expense of static pressure, regardless of
whether the RPM is
increased or left constant. However, by using a pair of contra-rotating axial
fans, a user can
achieve, as an example, 39,000 CFM with 1.25 inches of static pressure at the
same RPM as the
previous single-stage fan system example of 36,000 CFM at 0.9 inches of static
pressure, thus
providing an additional 3,000 CFM and a static pressure surplus of 0.35 (i.e.,
air horsepower).
The 39,000 CFM at 1.25 inches of static pressure would be performance-based on
a fan
manufacturer fan curve generated by software or through actual wind tunnel
data.
[0064] However, the data used in the above examples represents only one
solution. For
example, the contra-rotating system may produce 45,000 CFM at the same 0.9
inches of static
pressure or conversely the same 36,000 CFM at 1.5 inches of static pressure.
Indeed, an
objective of these examples is to illustrate that the contra-rotating axial
fan system extends the
design palette of a given axial fan design on both the X-axis (air flow) and Y-
axis (static
pressure). Co-rotating fans expand the design palette single dimensionally on
the X-axis of
airflow only. Increasing the HP input of a fan system with an extended fan
curve design palette
(e.g., using a contra-rotating system) enables a user to achieve performance
beyond that of a
single, or even a multi-stage, co-rotating axial fan system. Thus, the contra-
rotating system
yields unmatched performance that generates unprecedented cooling equipment
thermal
efficiencies.
[0065] Surplus static pressure is particularly beneficial with multi-cell,
counter-flow,
induced-draft units as the intermediate cells experience large thermal de-
rates associated with an
air HP deficiency with a higher minimum static pressure requirement than the
end cells. This
may be attributed to the intermediate cells competing for outside air with the
cells they are
sandwiched between, while the end cells have the luxury of not having to
compete for air on
one full face of the four-sided air intake.
[0066] This contra-rotating fan system mitigates, or removes, the thermal
de-rate in the
affected cells by properly utilizing and applying its ability to create a
large surplus of static
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pressure (i.e., air HP) across the cells in a manner that allows each cell to
draw the same amount
of intake air.
[0067] Turning now to the figures, Figure 1 a shows a first exemplary
embodiment of a
contra-rotating fan drive system 100 for dry and evaporative cooling
equipment. The contra-
rotating fan drive system 100 can include a first fan 102 and a second fan
104, which may be
disposed in an air conduit 106. Air conduit 106 may be in fluid communication
with the interior
of evaporative cooling equipment unit 10 and the exterior environment. The
first and second fans
102, 104 and air conduit 106 may be provided in any location on an evaporative
cooling
equipment unit 10 that enables system 100 to function as described herein. In
some exemplary
embodiments, air conduit 106 may be an exhaust air conduit, for example, in an
induced-draft
cooling unit. In other exemplary embodiments, air conduit 106 may be an intake
air conduit, for
example, in a forced-draft cooling unit. Air conduit 106 may also function as
a fan cowl for fans
102, 104.
[0068] The first fan 102 and second fan 104 may be axial fans and may be
arranged
coaxially with respect to each other. In some exemplary embodiments, fans 102,
104 may
include removable airfoil-type blades which may be pitched to a desired angle.
The blades may
be pitched such that the blade pitch of first fan 102 may be different from
the blade pitch of
second fan 104.
[0069] A motor 108 may be provided to drive system 100. Motor 108 may be an
electric
motor, or any motor known to one having ordinary skill in the art that enables
system 100 to
function as described herein, and may have any power rating suitable for the
particular
application of system 100. Motor 108 may drive an output shaft 110 on which a
drive pulley 112
is mounted. Drive pulley 112 may engage a belt 114, which can in turn engage a
driven
pulley 116 that is coupled to an input shaft 118 of transmission 120.
[0070] Transmission 120 may drive fans 102, 104 via first and second output
drive
shafts 122, 124. First fan 102 may be rigidly coupled to first output drive
shaft 122, while
second fan 104 may be rigidly coupled to second output drive shaft 124. First
and second output
drive shafts 122, 124 may be arranged coaxially with respect to each other
such that first output
drive shaft 122 drives first fan 102 and second output drive shaft 124 drives
second fan 104. To
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that end, second output drive shaft 124 and second fan 104 may each have a
bore defined therein,
the bores being sized such that first output drive shaft 122 may pass through
the bore.
Transmission 120 may include gearing arrangements for rotating the first and
second output
drive shafts 122, 124 at speeds different from the speed of the input shaft
118.
[0071] Transmission 120 may also include gearing arrangements, for example
a
planetary-gear set, that are adapted to drive first fan 102 in a direction
counter to that of
second fan 104. Furthermore, transmission 120 may be adapted to drive first
fan 102 at a
different speed than second fan 104.
[0072] An exemplary embodiment of transmission 120 is shown in Figure lb.
In some
exemplary embodiments of transmission 120, input shaft 118 may engage first
output drive shaft
122 via a gear or belt drive that may be adapted for gearing reduction.
Alternatively, input shaft
118 may be rigidly coupled to, or may function as, first output drive shaft
122, with gearing
reduction provided by pulleys 112, 116. The first output drive shaft 122 can
carry a sun gear
126a that engages a plurality of planet gears 126b, which, in turn, engage a
ring gear 126c. The
planet gears 126b are coupled to a carrier 128 that can maintain the positions
of the planet gears
126b. Carrier 128 may be held stationary so as to allow the planet gears to
act as idlers. The ring
gear 126c may be coupled to second output drive shaft 124. Thus, in operation,
first output drive
shaft can rotate sun gear 126a, causing ring gear 126c to rotate in a
direction opposite to the sun
gear 126a, and thereby rotating second output drive shaft 124 in a direction
opposite to that of
first output drive shaft 122. The ratios of the gears may further be adapted
to rotate second output
drive shaft 124 at a speed different than that of first output drive shaft
122.
[0073] In yet other exemplary embodiments, transmission 120 may be
substantially similar
to that disclosed in U.S. Patent 6,540,570, entitled Counter Rotating
Transmission, the disclosure
of which is hereby incorporated by reference in its entirety. Therefore, while
Figure lb generally
illustrates a planetary speed reducer with a spur gear output, other
arrangements known in the art
are entirely possible and contemplated. For example, Figure 2b illustrates
another arrangement
suitable for the transmission of Figures la and lc.
[0074] An exemplary layout for contra-rotating fan drive system 100 is
shown in
Figure I a. A support member 130 may be coupled to an evaporative cooling
equipment unit 10.
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Motor 108 and transmission 120 may be mounted on support member 130. Motor 108
may be
mounted in a substantially laterally offset position from transmission 120 and
oriented such that
belt 114 can engage drive pulley 112 and driven pulley 116. Transmission 120
may be mounted
proximate air conduit 106 such that first and second output drive shafts 122,
124 can extend
towards fans 102, 104, which may be disposed within air conduit 106. In the
exemplary
embodiment, support member 130, as well as motor 108 and transmission 120, may
be mounted
within the interior space of the dry or evaporative cooling equipment unit 10.
The specific layout
and positioning of the components of system 100 may depend on the
configuration of the
particular dry or evaporative cooling equipment unit 10 with which system 100
may be used and
may be adapted or modified as desired by one having ordinary skill in the art.
[0075] Another exemplary layout for contra-rotating fan drive system 100b
employing two
motors is shown in Figure lc. In certain situations, it may be advantageous to
employ two motors
when controlling the two fans. For example, the first fan 102 and second fan
104 may be
separately powered. Indeed, a user may wish to power or throttle a single fan
without
disengaging or adjusting the transmission. Another reason to employ two motors
would be
"power matching" and lack of a transmission solution for a particular need.
Moreover,
two motors will precisely control the amount of torque applied to each fan
without any
interference or power loss through a transmission, which can be advantageous
because contra-
rotating transmissions are often expensive and generally require frequent
maintenance. For
convenience of illustration, substantially similar functional elements to
those in the first
exemplary embodiment are represented by similar numerals, wherein the
duplicated components
are designated with the trailing "a" or "b." Thus, a detailed description of
the substantially
similar elements may be omitted.
[0076] As illustrated, a first support member 130a may be coupled to an
evaporative
cooling equipment unit 10. A first motor 108a and transmission 120a may be
mounted on the
lower support member 130a. Motor 108a may be mounted in a substantially
laterally offset
position from transmission 120a and oriented such that a first belt 114a can
engage a first drive
pulley 112a and driven pulley 116a. Transmission 120a may be mounted proximate
air conduit
106a such that output drive shafts 122, 124 can extend towards fans 102, 104,
which may be
disposed within air conduit 106. Similarly, a second motor 108b and
transmission 120b may be
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mounted on the upper support member 130b. Motor 108b may be similarly mounted
in a
substantially laterally offset position from transmission 120b and oriented
such that a second belt
114b can engage a second drive pulley 112b and driven pulley 116b.
Transmission 120b may be
mounted proximate air conduit 106a such that output drive shafts 122, 124 can
extend towards
fans 102, 104, which may be disposed within the upper end air conduit 106. In
this embodiment,
support member 130a, as well as motor 108a and transmission 120a, may be
mounted within the
interior space of the evaporative cooling equipment unit 10, while the upper
support member
130b, as well as motor 108b and transmission 120b, may be mounted within the
upper end of the
interior space of the air conduit 106. The specific layout and positioning of
the components of
system 100c may depend on the configuration of the particular dry or
evaporative cooling
equipment unit 10 with which system 100c may be used and may be adapted or
modified as
desired by one having ordinary skill in the art.
[0077] Figure 2a shows a second exemplary embodiment of a contra-rotating
fan drive
system 200 for evaporative cooling equipment. For convenience of illustration,
substantially
similar functional elements to those in the first exemplary embodiment are
represented by similar
numerals, with the leading digit incremented to 2. Thus, a detailed
description of the
substantially similar elements may be omitted. The second exemplary embodiment
has
substantially similar structure and functionality to the first exemplary
embodiment, except for the
features described below.
[0078] In the second exemplary embodiment, motor 208 may be coupled to a
transmission 240 that may function as, or be coupled to, output drive shaft
242.
Transmission 240 can include any gear arrangement that enables the contra-
rotating fan drive
system 200 to function as described herein. The gear arrangement can function
to rotate output
drive shaft 242 at a speed different from that of output shaft of motor 208.
For example, the gear
arrangement may include an output gear rigidly coupled to output drive shaft
242.
[0079] Output drive shaft 242 of transmission 240 may extend to first fan
202 and may be
rigidly coupled thereto so as to drive first fan 202. Second fan 204 may be
arranged coaxially
with output drive shaft 242. Second fan 204 is integrated with second
transmission 250 through
the fan hub. Therefore, as illustrated, the second transmission 250 may be
integral with the fan
hub. Second transmission 250 can be configured to receive the drive shaft 242
and, using a gear
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arrangement, cause the integrated second fan 204 to operate at a different
speed and/or direction.
So as to support the integrated second transmission 250 and second fan 204 in
place, a support
structure 256 can extend between, and be coupled to, transmission 240 and the
hub of second fan
204 housing the integrated second transmission 250.
[0080] Second transmission 250 can further include a gear arrangement that
can be
operatively engaged with both output drive shaft 242 and second fan 204. For
example,
transmission 250 may be a simple planetary arrangement wherein the shaft 242
passes through as
a single shaft and drives fan 202. Fan 204 may be attached to the ring carrier
whereby the fan
hub becomes the ring carrier by integrating the gear assembly with the fan
hub. The shaft 242
that passes through will engage the sun gear inside the fan hub that in turn
engages the idlers and
counter rotates the ring carrier/fan hub as an integrated assembly. The gear
arrangement can be
operable to rotate second fan 204 in a direction opposite to that of output
drive shaft 242 and
consequently in a direction opposite to that of first fan 202. The gear
arrangement can further be
operable to rotate second fan 204 at a speed different from that of output
drive shaft 242 and
consequently first fan 202.
[0081] This embodiment is useful in that it enables the fans to counter
rotate using a single
shaft which is otherwise impossible. Specifically, the fans are able to
counter rotate because the
shaft 242 passes through the transmission to rotate fan 202 while also
imparting power to the sun
gear of transmissions. However, a double-shaft arrangement may be employed
wherein a first
shaft is placed between from transmission 240 and transmission 250 and a
second shaft from
transmission 250 to fan 202. The double shaft arrangement yields substantially
the same outcome
as a one piece shaft that passes through transmission 250. Each transmission
may employ a
planetary gear arrangement as disclosed herein, an equivalent thereof, or
other gear arrangements
known in the art are entirely possible and contemplated. As is known in the
art, a standard
planetary arrangement for counter rotation generally comprises one or more
outer gears, or
planet gears, revolving about a central, or sun gear. Typically, the planet
gears are mounted on a
movable arm or carrier which itself may rotate relative to the sun gear.
Simple planetary-gear
systems have one sun, one ring, one carrier, and one planet set. Compound
planetary gears
typically involve one or more of the following three types of structures:
meshed-planet (there are
at least two more planets in mesh with each other in each planet train),
stepped-planet (there
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exists a shaft connection between two planets in each planet train), and multi-
stage structures
(the system contains two or more planet sets).
[0082] In some exemplary embodiments, a sun gear 254a may be carried by
output drive
shaft 242. The sun gear 254a can engage a plurality of planet gears 254b that
are disposed within
second transmission 250. The planet gears 254b can, in turn, engage a ring
gear 254c. The planet
gears 254b may be coupled to a carrier 258, which can maintain the positions
of the planet gears.
Carrier 258 may in turn be coupled to stator portion 252 of second
transmission 250, thereby
allowing carrier 258 to be held stationary so as to allow the planet gears to
act as idlers. The ring
gear 254c may be coupled to, or may be part of, the rotor of second fan 204.
Thus, in operation,
first output drive shaft can rotate sun gear 254a, causing ring gear 254c to
rotate in a direction
opposite to the sun gear, thereby rotating second fan 204 in a direction
opposite to that of first
output drive shaft 222. The ratios of the gears may further be adapted to
rotate second fan 204 at
a speed different than that of first output drive shaft 222.
[0083] An exemplary layout for contra-rotating fan drive system 200 is
shown in
Figure 2a. A support member 230 may be coupled to an evaporative cooling
equipment unit 20.
Motor 208 and transmission 240 may be provided as an integrated unit and may
be mounted on
support member 230. Second fan 204 may be integrated with second transmission
250 through
the fan hub. Therefore, as illustrated, the second transmission 250 may be
integral with the fan
hub. Motor 208 and transmission 240 may be mounted proximate air conduit 206
such that
output drive shaft 242 can extend towards fans 202, 204, which may be disposed
within air
conduit 206. In the exemplary embodiment, support member 230, as well as motor
208 and
transmission 220, may be mounted within the interior cavity of the dry or
evaporative cooling
equipment unit 20. The specific layout and positioning of the components of
system 200 may
depend on the configuration of the particular dry or evaporative cooling
equipment unit 20 with
which system 200 may be used and may be adapted or modified as desired by one
having
ordinary skill in the art.
[0084] As discussed above, in certain situations, it may be advantageous to
employ
two motors when controlling the two fans. Again, for convenience of
illustration, substantially
similar functional elements are represented by similar numerals, wherein the
duplicated
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components are designated with the trailing "a" or "b." Thus, a detailed
description of the
substantially similar elements may be omitted.
[0085] An exemplary layout for contra-rotating fan drive system 200b
employing
two motors is shown in Figure 2c. As illustrated, a lower support member 230a
may be coupled
to a dry or evaporative cooling equipment unit 20. Motor 208a and transmission
240a may be
provided as an integrated unit and may be mounted on lower support member
230a. Motor 208a
and transmission 240a may be mounted proximate air conduit 206 such that a
first output drive
shaft 242a can extend towards second fan 204, which may be disposed within air
conduit 206.
Similarly, an upper support member 230b may be coupled within the upper end of
the air conduit
206. Motor 208b and transmission 240b may be provided as an integrated unit
and may be
mounted on upper support member 230b. Alternatively, as illustrated and
described with regard
to Figure 2a, either, or both, of transmissions 240a, 240b may be integral
with a fan hub (see
second transmission 250, Figure la). Motor 208b and transmission 240b may be
mounted
proximate air conduit 206 such that a second output drive shaft 242b can
extend towards second
fan 202, which may be disposed within air conduit 206.
[0086] In this embodiment, support member 230a, as well as motor 208a and
transmission 220a, may be mounted within the interior cavity of the dry or
evaporative cooling
equipment unit 20, while the upper support member 230b, as well as motor 208b
and
transmission 220b, may be mounted within the upper end of the interior space
of the air conduit
206. The specific layout and positioning of the components of system 200b may
depend on the
configuration of the particular dry or evaporative cooling equipment unit 20
with which
system 200b may be used and may be adapted or modified as desired by one
having ordinary
skill in the art.
[0087] Figure 3a shows a third exemplary embodiment of a contra-rotating
fan drive
system 300 for dry or evaporative cooling equipment. For convenience of
illustration,
substantially similar functional elements to those in the first exemplary
embodiment are
represented by similar numerals, with the leading digit incremented to 3.
Thus, a detailed
description of the substantially similar elements may be omitted. The third
exemplary
embodiment has substantially similar structure and functionality to the first
exemplary
embodiment, except for the features described below.
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[0088] In the third exemplary embodiment, motor 308 may drive a drive shaft
310 that can
function as, or be coupled to, an input shaft of transmission 320.
Transmission 320 may drive
fans 302, 304 via first and second output drive shafts 322, 324 and may have
substantially
similar structure and functionality to any of the embodiments of transmission
120.
[0089] An exemplary layout for contra-rotating fan drive system 300 is
shown in Figure 3.
A first support member 330 and a second support member 332 may be coupled to a
dry or
evaporative cooling equipment unit 30. Motor 308 may be mounted on first
support member 330
while transmission 320 may be mounted on second support member 332. Motor 308
may be
mounted substantially proximate transmission 320. Transmission 320 may be
mounted
proximate air conduit 306 such that output drive shafts 322, 324 can extend
towards fans 302,
304, which may be disposed within air conduit 306. In the exemplary
embodiment, support
members 330, 332, as well as motor 308 and transmission 320, may be mounted
within the
interior space of the dry or evaporative cooling equipment unit 30.
Alternatively, as illustrated
and described with regard to Figure 2a, transmission 340 may be integral with
a fan hub (see
second transmission 250, Figure 1 a).The specific layout and positioning of
the components of
system 300 may depend on the configuration of the particular dry or
evaporative cooling
equipment unit 30 with which system 300 may be used and may be adapted or
modified as
desired by one having ordinary skill in the art.
[0090] In certain situations, it may be advantageous to employ two motors
when
controlling the two fans. Again, for convenience of illustration,
substantially similar functional
elements are represented by similar numerals, wherein the duplicated
components are designated
with the trailing "a" or "b." Thus, a detailed description of the
substantially similar elements may
be omitted.
[0091] An exemplary layout for contra-rotating fan drive system 300b
employing
two motors is shown in Figure 3b. As illustrated, a first set of support
members comprising a
first support member 330a and a second support member 332a may be coupled to a
dry or
evaporative cooling equipment unit 30. A first motor 308a may be mounted on
support member
330a while transmission 320a may be mounted on support member 332a. Motor 308a
may be
mounted substantially proximate transmission 320a. Transmission 320a may be
mounted
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proximate air conduit 306a such that output drive shaft 324 can extend towards
second fan 304,
which may be disposed within air conduit 306.
[0092] Similarly, a second set of support members comprising a first
support member 330b
and a second support member 332b may be coupled to a dry or evaporative
cooling equipment
unit 30. A first motor 308a may be mounted on support member 330a while
transmission 320a
may be mounted on support member 332a. Motor 308a may be mounted substantially
proximate
transmission 320a. Transmission 320a may be mounted proximate air conduit 306a
such that
output drive shaft 322 can extend towards first fan 302, which may be disposed
within air
conduit 306. Alternatively, as illustrated and described with regard to Figure
2a, either, or both,
of transmissions 320a, 320b may be integral with a fan hub (see second
transmission 250,
Figure 1a).
[0093] In this embodiment, support members 330a, 332a, as well as motor
308a and
transmission 320a, may be mounted within the interior space of the dry or
evaporative cooling
equipment unit 30, while support members 330b, 332b, as well as motor 308b and
transmission
320b, may be mounted within the upper end of the interior space of the air
conduit 306. The
specific layout and positioning of the components of system 300b may depend on
the
configuration of the particular dry or evaporative cooling equipment unit 30
with which system
300b may be used and may be adapted or modified as desired by one having
ordinary skill in the
art.
[0094] Figure 4a shows a fourth exemplary embodiment of a contra-rotating
fan drive
system 400 for dry or evaporative cooling equipment. For convenience of
illustration,
substantially similar functional elements to those in the first exemplary
embodiment are
represented by similar numerals, with the leading digit incremented to 4.
Thus, a detailed
description of the substantially similar elements may be omitted. The fourth
exemplary
embodiment has substantially similar structure and functionality to the first
exemplary
embodiment, except for the features described below.
[0095] In the fourth exemplary embodiment, motor 408 may drive an output
shaft 410,
which may be coupled to a connecting drive shaft 415 via a first coupling 411.
Connecting drive
shaft 415 may in turn be coupled to an input shaft 418 of a transmission 420
via a second
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coupling 411. Couplings 411 may be rigid couplings or may be flexible
couplings. In certain
embodiments, a connecting shaft may be unnecessary. Rather, the same end goal
may be
accomplished using only the couplings 411, which can function as a very short
connecting shaft.
The couplings 411 may further comprise an elastomer-housed inside for
vibration dampening
and act as a designed failure point, should the fan drive lockup suddenly, to
prevent the motor
from being damaged or destroyed. A suitable type of coupling may be chosen for
a particular
application by one having ordinary skill in the art.
[0096] Transmission 420 may drive fans 402, 404 via first and second output
drive
shafts 422, 424 and may have substantially similar structure and functionality
to any of the
embodiments of transmission 120. Alternatively, as illustrated and described
with regard to
Figure 2a, transmission 420 may be integral with a fan hub (see second
transmission 250,
Figure la).
[0097] The drive shaft 410 and connecting shaft 415 may be oriented at an
angle to the first
and second output drive shafts 422, 424 of transmission 420. Therefore, an
angle gearing
arrangement may be combined with gearing arrangements described in previous in-
line
embodiments to achieve a right angle input/output shaft arrangement (or other
desired
arrangement) while achieving the desired function of the system 400. The angle
gearing
arrangement may be any known gearing arrangement that enables system 400 to
function as
described herein and may include gear reduction capabilities. In some
exemplary embodiments,
the angle gearing arrangement may be disposed external to transmission 420. In
other exemplary
embodiments, transmission 420 may be adapted by one having ordinary skill in
the art to include
an angle gearing arrangement therein.
[0098] An exemplary layout for contra-rotating fan drive system 400 is
shown in
Figure 4a. A support member 430 may be coupled to a dry or evaporative cooling
equipment
unit 40. Motor 408 may be mounted in a substantially laterally offset position
from
transmission 420 and disposed externally to dry or evaporative cooling
equipment unit 40, while
transmission 420 may be mounted on support member 430 and disposed within the
interior space
of unit 40. For example, motor 408 may be mounted on an exterior surface of
the enclosure 42 of
unit 40. Connecting shaft 415 may extend from motor 408 to transmission 420
via an aperture in
the air conduit 406. Transmission 420 may be mounted proximate air conduit 406
such that
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output drive shafts 422, 424 can extend towards fans 402, 404, which may be
disposed within air
conduit 406. The specific layout and positioning of the components of system
400 may depend
on the configuration of the particular dry or evaporative cooling equipment
unit 40 with which
system 400 may be used and may be adapted or modified as desired by one having
ordinary skill
in the art.
[0099] In certain situations, it may be advantageous to employ two motors
when
controlling the two fans. Again, for convenience of illustration,
substantially similar functional
elements are represented by similar numerals, wherein the duplicated
components are designated
with the trailing "a" or "b." Thus, a detailed description of the
substantially similar elements may
be omitted.
[001001 An exemplary layout for contra-rotating fan drive system 400b
employing
two motors is shown in Figure 4b. A first support member 430a may be coupled
to a dry or
evaporative cooling equipment unit 40. Motor 408a may be mounted in a
substantially laterally
offset position from transmission 420a and disposed externally to dry or
evaporative cooling
equipment unit 40, while transmission 420a may be mounted on support member
430a and
disposed within the interior space of unit 40. For example, motor 408a may be
mounted on an
exterior surface of the enclosure 42 of unit 40. Connecting shaft 415 may
extend from motor
408a to transmission 420a via an aperture in the air conduit 406. Transmission
420a may be
mounted proximate air conduit 406a such that output drive shaft 424 can extend
towards fan 404,
which may be disposed within air conduit 406. Alternatively, as illustrated
and described with
regard to Figure 2a, either, or both, of transmissions 420a, 420b may be
integral with a fan hub
(see second transmission 250, Figure la).
[00101] Similarly, a second support member 430b may be coupled to a dry or
evaporative
cooling equipment unit 40. Motor 408b may be mounted in a substantially
laterally offset
position from transmission 420b and disposed externally to dry or evaporative
cooling equipment
unit 40, while transmission 420b may be mounted on support member 430b and
disposed within
the interior space of unit 40. For example, motor 408b may be mounted on an
exterior surface or
bracket. Due to the close proximity of the motor 408b to transmission 420b, a
connecting shaft
may be unnecessary. Rather, the same end goal may be accomplished using only
the
couplings 411, which can function as a very short connecting shaft. The
couplings 411 may
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further comprise an elastomer-housed inside for vibration dampening and act as
a designed
failure point, should the fan drive lockup suddenly, to prevent the motor from
being damaged or
destroyed. Transmission 420b may be mounted proximate air conduit 406b such
that output drive
shaft 422 can extend towards fan 402, which may be disposed within air conduit
406.
[00102] The specific layout and positioning of the components of system
400b may depend
on the configuration of the particular dry or evaporative cooling equipment
unit 40 with which
system 400b may be used and may be adapted or modified as desired by one
having ordinary
skill in the art.
[00103] Figure 5a shows a fifth exemplary embodiment of a contra-rotating
fan drive
system 500 for dry or evaporative cooling equipment. For convenience of
illustration,
substantially similar functional elements to those in the fourth exemplary
embodiment are
represented by similar numerals, with the leading digit incremented to 5.
Thus, a detailed
description of the substantially similar elements may be omitted. The fifth
exemplary
embodiment has substantially similar structure and functionality to the fourth
exemplary
embodiment, except for the features described below.
[00104] In the fifth exemplary embodiment, motor 508 may drive a drive
shaft 510, which
may be coupled to an input shaft 518 of a transmission 520 via a coupling 511.
Couplings 511
may be rigid couplings or may be flexible couplings. A suitable type of
coupling may be chosen
for a particular application by one having ordinary skill in the art. The
drive shaft 510 may be
oriented at an angle to the output drive shafts 522, 524 of transmission 520.
Therefore, an angle
gearing arrangement may be provided, substantially as described in the
exemplary embodiment
of system 400. In certain embodiments, a connecting shaft may be unnecessary.
Rather, the same
end goal may be accomplished using only the couplings 511, which can function
as a very short
connecting shaft. The couplings 511 may further comprise an elastomer-housed
inside for
vibration dampening and act as a designed failure point, should the fan drive
lockup suddenly, to
prevent the motor from being damaged or destroyed.
[00105] An exemplary layout for contra-rotating fan drive system 500 is
shown in
Figure 5a. A support member 530 may be coupled to a dry or evaporative cooling
equipment unit
50. Motor 508 may be mounted in a substantially laterally offset position from
transmission 520.
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Transmission 520 may be mounted proximate air conduit 506 such that output
drive shafts 522,
524 can extend towards fans 502, 504, which may be disposed within air conduit
506.
Alternatively, as illustrated and described with regard to Figure 2a,
transmission 520 may be
integral with a fan hub (see second transmission 250, Figure la). In the
exemplary embodiment,
support member 530, as well as motor 508 and transmission 520, may be mounted
within the
interior space of the dry or evaporative cooling equipment unit 50. The
specific layout and
positioning of the components of system 500 may depend on the configuration of
the particular
dry or evaporative cooling equipment unit 50 with which system 500 may be used
and may be
adapted or modified as desired by one having ordinary skill in the art.
[00106] In certain situations, it may be advantageous to employ two motors
when
controlling the two fans. Again, for convenience of illustration,
substantially similar functional
elements are represented by similar numerals, wherein the duplicated
components are designated
with the trailing "a" or "b." Thus, a detailed description of the
substantially similar elements may
be omitted.
[00107] An exemplary layout for contra-rotating fan drive system 500b
employing
two motors is shown in Figure 5b. A first support member 530a may be coupled
to a dry or
evaporative cooling equipment unit 50. Motor 508a may be mounted in a
substantially laterally
offset position from transmission 520a and disposed within dry or evaporative
cooling equipment
unit 50, each of which may be mounted on support member 530a and disposed
within the interior
space of unit 50. Alternatively, as illustrated and described with regard to
Figure 2a, either, or
both, of transmissions 520a, 520b may be integral with a fan hub (see second
transmission 250,
Figure la).
[00108] Connecting shaft 515 may extend from motor 508a to transmission
520a via an
aperture in the air conduit 506. Transmission 520a may be mounted proximate
air conduit 506a
such that output drive shaft 524 can extend towards fan 504, which may be
disposed within air
conduit 506. Similarly, a second support member 530b may be coupled to a dry
or evaporative
cooling equipment unit 50. Motor 508b may be mounted in a substantially
laterally offset
position from transmission 520b and disposed within air conduit 506 on support
member 530b.
Due to the close proximity of the motor 508b to transmission 520b, a
connecting shaft may be
unnecessary. Rather, the same end goal may be accomplished using only the
couplings 511,
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which can function as a very short connecting shaft. The couplings 511 may
further comprise an
elastomer-housed inside for vibration dampening and act as a designed failure
point, should the
fan drive lockup suddenly, to prevent the motor from being damaged or
destroyed.
[00109] In this embodiment, first support member 530a, as well as motor
508a and
transmission 520a, may be mounted within the interior space of the dry or
evaporative cooling
equipment unit 50, while second support member 530b, as well as motor 508b
and/or
transmission 520a, may be mounted within the interior space of the air conduit
506. For example,
the motor 508b may be external to the air conduit 506. The specific layout and
positioning of the
components of system 500 may depend on the configuration of the particular dry
or evaporative
cooling equipment unit 50 with which system 500b may be used and may be
adapted or modified
as desired by one having ordinary skill in the art.
[00110] Figure 6a shows a sixth exemplary embodiment of a contra-rotating
fan drive
system 600 for dry or evaporative cooling equipment. For convenience of
illustration,
substantially similar functional elements to those in the fifth exemplary
embodiment are
represented by similar numerals, with the leading digit incremented to 6.
Thus, a detailed
description of the substantially similar elements may be omitted. The sixth
exemplary
embodiment has substantially similar structure and functionality to the fifth
exemplary
embodiment, except for the features described below.
[00111] In the sixth exemplary embodiment, motor 608 may drive a drive
shaft 610, which
may be coupled to a connecting shaft 615 via a first coupling 611. Connecting
shaft 615 may in
turn be coupled to an input shaft 618 of a dual output transmission 660 via a
second coupling 611. Couplings 611 may be rigid couplings or may be flexible
couplings. A
suitable type of coupling may be chosen for a particular application by one
having ordinary skill
in the art. In other exemplary embodiments, connecting shaft 615 may be
omitted and drive
shaft 610 may be coupled to input shaft 618 via a rigid or flexible coupling
611. In certain
embodiments, a dual output motor may be used in place of the dual output
transmission 660 of
Figure 6a.
[00112] Dual output transmission 660 may be disposed in between first fan
602 and second
fan 604. A first output drive shaft 662 may extend to, and be rigidly coupled
to, first fan 602;
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while a second output drive shaft 664 may extend to, and be rigidly coupled
to, second fan 604.
Furthermore, input shaft 618 may be oriented at an angle to the output drive
shafts 662, 664 of
dual output transmission 660. Dual output transmission 660 can therefore
include a gearing
arrangement for transferring power from input shaft 618 to output drive shafts
662, 664. An
exemplary gearing arrangement is shown in Figure 6b. For example, the gearing
arrangement
may include an input gear 666 carried by input shaft 618, a first output gear
668a carried by first
output drive shaft 662 and engaged with the input gear and a second output
gear 668b carried by
second output drive shaft 664 and engaged with the input gear. The input and
output gears may
be bevel gears and may have differing ratios. Dual output transmission 660 can
thus drive output
drive shaft 662 at a different speed than, and in a direction counter to,
output drive shaft 664.
However, any other configuration for dual output transmission 660 that enables
system 600 to
function as described herein may be contemplated and provided by one having
ordinary skill in
the art.
[00113] An exemplary layout for contra-rotating fan drive system 600 is
shown in
Figure 6a. A support member 630 may be coupled to a dry or evaporative cooling
equipment unit
60 and disposed within the interior space thereof Fans 602, 604 may be
disposed within air
conduit 606 and dual output transmission 660 may be mounted within air conduit
606 between
fans 602, 604. The fan and transmission assembly may be supported on support
member 630 by
second shaft 664, which may be coupled to a turntable 634. Turntable 634 may
include a fixed
portion coupled to support member 630 and a rotating portion to which second
shaft 664 may be
coupled. The rotating portion may be rotatably coupled to the fixed portion of
turntable 634.
Bearings, rollers or any other friction reducing members may be provided to
facilitate the
rotatable coupling between the rotating portion and the fixed portion of
turntable 634.
[00114] Motor 608 may be mounted in a substantially laterally offset
position from dual
output transmission 660 and disposed externally to dry or evaporative cooling
equipment unit 60.
For example, motor 608 may be mounted on an exterior surface of the enclosure
62 of unit 60. A
motor mount 636 may be provided so as to position motor 608 relative to dual
output
transmission 660 so as to facilitate the coupling between motor 608 and dual
output
transmission 660. Connecting shaft 615 may extend from motor 608 to dual
output
transmission 660 via an aperture in the enclosure 62. The specific layout and
positioning of the
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components of system 600 may depend on the configuration of the particular dry
or evaporative
cooling equipment unit 60 with which system 600 may be used and may be adapted
or modified
as desired by one having ordinary skill in the art.
[00115] In certain situations, it may be advantageous to employ two motors
when
controlling the two fans. Again, for convenience of illustration,
substantially similar functional
elements are represented by similar numerals, wherein the duplicated
components are designated
with the trailing "a" or "b." Thus, a detailed description of the
substantially similar elements may
be omitted.
[00116] An exemplary layout for contra-rotating fan drive system 600b is
shown in
Figure 6b. A first support member 630a may be coupled to a dry or evaporative
cooling
equipment unit 60 and disposed within the interior space thereof Fans 602, 604
may be disposed
within air conduit 606, a first dual output transmission 660a may be mounted
within air conduit
606 between fans 602, 604 and second dual output transmission 660b may be
mounted atop of
fan 602.
[00117] The fan and transmission assembly may be supported on support
member 630 by
second shaft 664, which may be coupled to a first turntable 634a. First
turntable 634a may
include a fixed portion coupled to support member 630 and a rotating portion
to which
second shaft 664a may be coupled. Similarly, second turntable 634b may include
a fixed portion
coupled to first dual output transmission 660a and a rotating portion to which
second shaft 664
may be coupled. The rotating portion may be rotatably coupled to the fixed
portion of
turntables 634a, 634b. Bearings, rollers, or any other friction reducing
members may be provided
to facilitate the rotatable coupling between the rotating portion and the
fixed portion of
turntable 634.
[00118] Motor 608a may be mounted in a substantially laterally offset
position from dual
output transmission 660a and disposed externally to dry or evaporative cooling
equipment
unit 60. Motor 608b may be similarly mounted in a substantially laterally
offset position from
dual output transmission 660b and disposed externally atop motor 608a. For
example,
motor 608a may be mounted on an exterior surface of the enclosure 62 of unit
60. A first motor
mount 636a may be provided so as to position motor 608a relative to dual
output
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transmission 660a so as to facilitate the coupling between motor 608a and dual
output
transmission 660a. A second motor mount 636b may be provided so as to position
motor 608b
relative to dual output transmission 660ab so as to facilitate the coupling
between motor 608b
and dual output transmission 660b.
[00119] Connecting shaft 615a may extend from motor 608a to dual output
transmission
660a via a first aperture in air conduit 606. Similarly, connecting shaft 615b
may extend from
motor 608b to dual output transmission 660b via a second aperture in air
conduit 606. The
specific layout and positioning of the components of system 600a may depend on
the
configuration of the particular dry or evaporative cooling equipment unit 60
with which
system 600a may be used and may be adapted or modified as desired by one
having ordinary
skill in the art.
[00120] As described with regard to Figures 1 through 6, the contra-
rotating fan drive
systems may be employed with dry or evaporative cooling equipment. Examples of
such dry
cooling equipment include air-cooled heat exchangers. Indeed, an air-cooled
heat exchange
refers to a pressure vessel that cools a circulating fluid within finned tubes
by forcing ambient air
over the exterior of the tubes. Air-cooled heat exchange is a "green" solution
as compared to
cooling towers and shell and tube heat exchangers because they do not require
an auxiliary water
supply (water lost due to drift and evaporation, plus no water treatment
chemicals are required).
[00121] Figures 7a and 7b illustrate exemplary air-cooled heat exchangers.
An air-cooled
heat exchanger generally comprises, one or more tube bundles 714 (e.g.,
bundles of heat transfer
surface), an air-moving device (e.g., a fan, blower, or stack), a plenum 708
between the one or
more tube bundles 714 and the first and second fans 702, 704 and a support
structure high
enough to support the various components while allowing air to enter beneath
the air-cooled heat
exchanger at a reasonable rate. The plenum 708 may be an enclosure that
provides for the
smooth flow of air between the first and second fans 702, 704 and one or more
tube bundles 714.
[00122] The support structure may comprise a support member 724, fan ring
706, column
support 718, and inlet bell 720. Here, the air-moving device may be a contra-
rotating fan drive
system as discussed with regard to Figure 2a. That is, the contra-rotating fan
drive system may
comprising a first fan 702, a second fan 704, and a drive assembly comprising
a motor 716
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coupled to a transmission 722, which mechanically rotates the first and second
fans 702, 704.
Indeed, motor 716 and transmission 722 may be provided as an integrated unit
and may be
mounted on support member 724. The contra-rotating fan drive system may
comprise a
variable-pitch fan hub for further increased temperature control and power
savings.
[00123] The air-cooled heat exchanger may further comprise one or more
headers and/or fan
maintenance walkways with ladders to grade and louvers for process outlet
temperature control.
The air-cooled heat exchanger may further comprise recirculation ducts and
chambers for
protection against freezing or solidification of high-pour point fluids in
cold weather.
[00124] A tube bundle 714 generally refers to an assembly of tubes,
headers, side frames,
and tube supports. Usually the tube surface exposed to the passage of air has
extended surface
area in the form of fins to compensate for the low heat transfer rate of air
at atmospheric pressure
and at a low enough velocity for reasonable fan power consumption. The tube
bundle 714 may
further comprise, operatively coupled thereto, a nozzle 710 and header 712. A
plenum 708 may
be configured between the one or more tube bundles 714 and the first and
second fans 702, 704.
[00125] Figure 7a illustrates an air-cooled heat exchanger arrangement 700a
that or pulls it
across the bundles, which is generally referred to as an induced-draft
arrangement, while
Figure 7b illustrates an air-cooled heat exchanger arrangement 700b that
forces the air across the
bundles, which is generally refer to as a forced-draft arrangement. As
illustrated, the plenum 708
may be either box type (Figure 7a) or slope-sided type (Figure 7b). The slope-
sided type
typically gives an increased distribution of air over the bundles and is
commonly used with
induced-draft arrangements because hanging a machinery mount from a slope-
sided, forced-draft
plenum can present structural difficulties.
[00126] Generally speaking, advantages of an induced-draft arrangement
typically include:
(1) better distribution of air across the bundle; (2) less possibility of hot,
effluent air recirculating
into the intake ¨ that is, the hot air is discharged upward at approximately
2.5 times the intake
velocity, or about 1,500 feet per minute; (3) better process control and
stability because the
plenum covers 60% of the bundle face area, reducing the effects of sun, rain,
and hail; and
(4) increased capacity in the fan-off or fan-failure condition, since the
natural draft stack effect is
much greater. Advantages of a forced-draft arrangement, on the other hand,
typically include:
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(1) possibly lower horsepower requirements if the effluent air is very hot
(horsepower varies
inversely with the absolute temperature); (2) better accessibility of fans and
upper bearings for
maintenance; (3) better accessibility of bundles for replacement; and (4)
accommodates higher
process inlet temperatures. Table 2 provides exemplary target design
parameters for an
exemplary air-cooled heat exchanger ("ACHE").
Description English Metric
Tube Material (Includes Headers) Steel
Tube Length 32.0 Feet 9.75 Meters
Tube Outside Diameter 1.00 Inch 25.4mm
Tube Thickness (12 BWG) 0.110 Inches 2.79 mm
Fin Material Aluminum
Fin Height 5/8 Inch 15.9 mm
Fin Spacing 10 Fins/Inch 0.40 Fins/mm
Fin Type Extruded
Number of Tube Rows 6
Number of Tubes/Row 53
Total Number of Tubes 316
Equilateral Tube Pitch 2.5 Inches 63.5mm
Bare Tube Surface Area 2,660 Sq. Ft. 247 Sq. M.
Fin Tube Surface Area 56,500 Sq. Ft. 5,250 Sq. M.
ACHE Length 32.0 Feet 9.75 Meters
ACHE Width 11.0 Feet 3.35 Meters
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ACHE weight 30,900 lbs 14,000 Kg
Motor Shaft Power 33.4 HP 24.9 KW
Table 2
[00127] While the air-cooled heat exchanger is illustrated with a contra-
rotating fan drive
system as shown and described with regard to Figure 2a, the contra-rotating
fan drive systems of
the other figures may be similarly employed. For example, a belt-driven
assembly, such as the
arrangement shown and described in Figures 1 a and lb, may be employed.
Alternatively, the
transmission 722 and motor 716 may be separate components, as shown and
described in
Figures 3a and 3b. Similarly, the contra-rotating fan drive system may employ
a drive shaft
between the motor 716 and transmission 722, as shown and described in Figures
4a, 4b, 5a, and
5b. Finally, the contra-rotating fan drive system may employ a dual output
transmission, as
shown and described in Figures 6a and 6b. Accordingly, a contra-rotating fan
drive system for
use in an air-cooled heat exchanger should not be limited to the specific
arrangements illustrated
in Figures 7a and 7b.
[00128] Turning now to the figures, Figure 8a illustrates another exemplary
embodiment of
a contra-rotating fan drive system 800a for WET/DRY cooling equipment using a
contra-rotating
transmission. As discussed with respect to the earlier configurations, the
contra-rotating fan drive
system 800a can include a first fan 802 and a second fan 804, which may be
disposed in an air
conduit 806. Air conduit 806 may be in fluid communication with the interior
of the WET/DRY
cooling equipment unit 820 and the exterior environment. As discussed with
respect to the earlier
configurations, the first and second fans 802, 804 and air conduit 806 may be
provided in any
location on a WET/DRY cooling equipment unit 820 that enables system 800a to
function as
described herein. In some exemplary embodiments, air conduit 806 may be an
exhaust air
conduit, for example, an induced-draft cooling unit. In other exemplary
embodiments, air
conduit 806 may be an intake air conduit, for example, a forced-draft cooling
unit. Air
conduit 806 may also function as a fan cowl for first and second fans 802,
804.
[00129] A motor 808 may be provided to drive the contra-rotating fan drive
system 800a.
Motor 808 may be an electric motor, or any motor known to one having ordinary
skill in the art
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that enables system 800a to function as described herein, and may have any
power rating suitable
for the particular application of system 800a. Motor 808 may drive an output
shaft 810 on which
a drive pulley 812 is mounted. Drive pulley 812 may engage a belt 814, which
can in turn engage
a driven pulley 816 that is coupled to an input shaft 1012 of transmission
900.
[00130] An operator may change the ratios of the fan drive system 800a by
adjusting the
size (e.g., diameter) of drive pulley 812 and driven pulley 816. If the belt
drive ratio is greater
than 1:1, then the fan drive system may be classified as a double reduction
fan drive system and
the ratio for the belt drive would be multiplied by the transmission drive
ratio to determine the
"final fan drive ratio"; conversely an overdriven reduction fan drive system
is achieved when the
belt drive ratio is less than 1:1 (i.e., "overdrive").
[00131] Employing a contra-rotating transmission design enables the user to
employ
alternative gear ratios that are simply not possible with co-rotating fan
arrangements, that is,
without having to replace the transmission. Thus, the contra-rotating
transmission design
provides a fully adjustable, final fan drive ratio in lieu of the existing
fixed-transmission ratios
that are not field adjustable. Finally, while a belt 814 is illustrated,
alternative means for driving
driven pulley 816 would include, for example, chain and sprockets, banded
belts, cogged or
synchronous belts, power band, cable, and rope.
[00132] A support member 830 may be coupled to a WET/DRY cooling equipment
unit 820. Motor 808 and transmission 900 may be mounted on support member 830.
Motor 808
may be mounted in a substantially, laterally offset position from transmission
900 and oriented
such that belt 814 can engage drive pulley 812 and driven pulley 816.
Transmission 900 may be
mounted proximate air conduit 806 such that the drive shaft 1112 can extend
upward such that
first and second fans 802, 804 are disposed within air conduit 806. A
preferred embodiment may
use the transmission output shaft in lieu of a drive shaft 1112, while
alternative embodiments
may have a female output sleeve on the transmission to accommodate a drive
shaft.
[00133] Alternatively, as illustrated in the drive system 800b of Figures
8b through 8e, the
motor 808 may be coupled directly to the transmission 900, thereby obviating
the need for belts
and pulleys. Figures 8c through 8e provide a detailed view of an exemplary
contra-rotating fan
assembly arrangement for use with the system 800b. In yet another embodiment,
the motor 808
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may be integrated with the transmission 900 to form a singular assembly or
component, which is
generally known as a "gearhead" motor in the industry.
[00134] Referring generally to the drive systems 800a, 800b of Figures 8a
and 8b,
transmission 900 may drive first fan 802 via drive shaft 1112. First fan 802
may be rigidly
coupled to the drive shaft 1112, which may be a flanged drive shaft, while
second fan 804 may
be coupled to a fan-hub mounting plate within the transmission 900, which
effectively functions
as a fan hub when not employing a separate fan hub. The transmission 900 may
further comprise
a hollow fan driveshaft 902 that encloses the drive internals and serves as a
protective, sealed
drive case in conjunction with the fan-hub mounting plate.
[00135] Drive shaft 1112 and the hollow fan driveshaft 902 may be arranged
coaxially with
respect to each other such that drive shaft 1112 drives first fan 802 and the
hollow fan
driveshaft 902 drives second fan 804 by way of the fan-hub mounting plate.
Transmission 900
may include gearing arrangements for rotating the drive shaft 1112 and the
hollow fan
driveshaft 902 at speeds different from the speed of the input shaft 1012. As
discussed above,
transmission 900 may also include internal drive component arrangements that
are adapted to
drive first fan 802 in a direction counter to that of second fan 804.
Furthermore, transmission 900
may be adapted to drive first fan 802 at a different speed than second fan
804.
[00136] As is known in the art, power transmission systems, such as
presently disclosed
contra-rotating transmission 900, typically require lubrication. Normally, oil
is introduced to the
transmission 900 or transmission system to reduce wear on the various moving
parts, while also
serving the function of heat dispersion. A problem with oil is that, when two
drive assemblies
(e.g., upper assembly 1100 and lower assembly 1000) rotate in opposite
directions, the oil is
churned to form a foam emulsion. To combat this foam emulsion, a defoamer or
an anti-foaming
agent may be added; however, due to the high rotational speeds, such defoamers
and
anti-foaming agents are insufficient in contra-rotating transmissions. For
example,
contra-rotating transmissions currently used for propulsion in marine and
aeronautical
applications employ expensive and complicated oiling systems that require
frequent
maintenance. An oil-free, contra-rotating transmission, as disclosed herein,
does not require such
maintenance, nor does it require frequent overhauls.
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[00137] Accordingly, the presently disclosed contra-rotating transmission
900 may be
lubricated with grease in lieu of oil. Unlike oil, grease does not suffer the
drawback of foaming.
Indeed, a sealed case and grease lubrication allows for the possibility of a
substantially,
permanently lubricated transmission that requires no maintenance for the
lifetime of the unit,
while conventional gearboxes require regular oil changes. Therefore, according
to at least
one exemplary embodiment, an oil-free, contra-rotating transmission for
evaporative cooling
equipment is also disclosed. The oil-free, contra-rotating transmission
disclosed herein can
provide a compact, integrated arrangement for varying the rotational speed and
rotational
direction of first and second axial fans 802, 804.
[00138] There are a number of suitable types of grease that may be used in
conjunction with
the oil-free, contra-rotating transmission 900. For example, biodegradable,
food-grade grease and
solid lubricants may be used. This reduces the necessity for frequent
maintenance of
contra-rotating transmission 900, while also reducing the environmental impact
of the
contra-rotating transmission 900. Furthermore, the oil-free transmission is an
environmentally
friendly alternative to conventional gearboxes that require oil changes.
Indeed, grease technology
has advanced to the point that the development of this transmission as a
permanent, lubricated
sealed-case unit is feasible. Synthetic grease with an additive package suited
for this transmission
may be employed to repel water infiltration, dissipate heat, withstand wide
temperature ranges,
absorb shock loads, anti-seizing agent, etc. While a synthetic grease solution
may not be as
environmentally friendly as biodegradable grease, since it is permanently
sealed in the case it
would be environmentally friendly in that it never needs to be exposed to the
outside
environment, while eliminating the need for oil changes and the generation of
waste oil over its
lifetime. Permanent, lubricated, sealed ball bearings may be employed to work
in conjunction
with the specially formulated grease.
[00139] Figures 9a and 9b illustrate an exemplary embodiment of a contra-
rotating
transmission 900. Indeed, a contra-rotating transmission 900 may include an
upper drive
assembly 1100 and a lower drive assembly 1000. The lower drive assembly 1000
may be
coupled with an input power source via a transmission input shaft 1012. The
lower portion of the
input shaft 1012 may be hollow and designed to receive the output shaft of a
power source (e.g.,
an electric motor) and configured to transfer torque from the input power
source to a pinwheel
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driver 1002 (e.g., a center-pinwheel driver), which may be operatively coupled
to the solid upper
portion of the input shaft 1012. The torque may then be transferred, via one
or more pinwheels,
to the upper drive assembly 1100. Torque from the input shaft 1012 may
ultimately be used to
rotate two contra-rotating fans 802, 804, which may be operatively coupled
with the upper drive
assembly 1100 and/or lower drive assembly 1000. For example the upper drive
assembly 1100
may be configured to rotate a first fan 802 in a first direction (e.g.,
clockwise), while the lower
drive assembly 1000 may be configured to rotate a second fan 804 in a second
direction, which
may be opposite the first direction (e.g., counter-clockwise). While not
illustrated, as is known in
the art, one or more thrust washers may be positioned throughout the
transmission 900 at the
various connection points to reduce any friction and/or to function as
spacers. The thrust washers
may be fabricated from less corrosive materials, such as brass or bronze.
[00140] While Figure 9a illustrates the contra-rotating transmission 900
with the hollow fan
driveshaft 902 removed, as illustrated in Figure 9b, the hollow fan driveshaft
902 may serve as a
protective casing and may be used to enclose the upper drive assembly 1100 and
a lower drive
assembly 1000 of the contra-rotating transmission 900 in embodiments that
employ integrated
drive assemblies such as illustrated in Figure 9a. For example, the hollow fan
driveshaft 902 may
be constructed by integrating one or more parts to form a hollow fan
driveshaft that ultimately
drives second fan 804. For example, the hollow fan driveshaft 902, or portion
thereof, may be
operatively coupled with the fan-hub mounting plate, or, as illustrated
herein, the fan-hub
mounting plate may also be integral with outer pinwheel receiver 1004. Thus,
as illustrated, the
components used to construct the hollow fan driveshaft 902 may include one or
more pinwheel
receivers 1004a. The hollow fan driveshaft 902 may be coupled at one end to a
hollow driveshaft
base 924 to form a sealed casing for housing upper drive assembly 1100 and
lower drive
assembly 1000. Moreover, as illustrated in Figure 9b, one or more plates 904,
906, 910 may be
provided between the various components or assemblies to increase structural
integrity of the
transmission 900. The one or more plates 904, 906, 910 may be further
configured to receive an
end of one or more shafts (e.g., shaft 908) and/or sleeves (e.g., sleeve 1010)
while permitting the
shafts or sleeves to rotate as needed. Indeed, a stop plate 912 may be
positioned at the end of
each shaft to rotatably secure the distal ends of the one or more shafts
and/or sleeves, thereby
prohibiting unwanted movement in, or against, direction A.
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[00141] The hollow fan driveshaft 902 also serves as a protective casing
and may be further
sealed to protect the components of upper drive assembly 1100 and the lower
drive
assembly 1000 from the elements (e.g., weather, dirt, oxidation, moisture
infiltration or loss,
etc.), thus preserving the lubricant (e.g., grease) inside for a greatly
extended, useful lifespan.
The hollow fan driveshaft 902, or components thereof, may be fabricated from,
for example,
steel (A36, 8018, 8045, etc.), alloy steel (4130, 4140, 8620, etc.), stainless
steel (300 series,
400 series, 600 series, etc.), tool steel (01, A2, M4, etc.), titanium (grade
2, grade 5, alloy, etc.),
aluminum (alloy 6061, alloy 2024, alloy 7075, etc.), cast iron, known metal
alloys, powdered
metals for sintering (e.g., 3D Printers) or a combination thereof. For
example, the hollow fan
driveshaft 902, or components thereof, may be fabricated from aluminum alloy
6061 and may be
further subjected to additional metal treatments to alter the properties of
the metal to meet a
specific design parameter or need. For example, the metal may be heat treated
with one or more
of the following treatments: annealing, case hardening, precipitation,
strengthening, tempering,
quenching, etc. The metal may also be subjected to surface finishing
treatments intended to alter
the metal surface properties and appearance to meet specific design parameter
or need such as,
but not limited to, grinding, polishing, buffing, shot peening, media
blasting, plating, anodizing,
oxidizing, pickling, acid treating, etc. In certain embodiments, the
components of the
transmission 900 may be formed from recycled or recyclable materials such as
aluminum, steel,
iron, other or recycled metals alloys. However, one of skill in the art would
understand that other
materials may be employed to meet a particular need (e.g., corrosion
resistance, weight
limitations, strength requirements, etc.). Furthermore, the outer surface of
the various
components may have a weatherproof coating, chemical application, powder
coating, bonded
polymer, or similar treatment, and/or be made of or enclosed in a ceramic,
plastic, any available
non-corrosive material, or corrosion-resistant metal alloy such as aluminum,
stainless steel,
bronze, or titanium. Moreover, one of skill in the art would understand that
two or more different
materials may be used to fabricate the various case components.
[00142] Turning now to Figures 10a and 10b, a perspective view and top plan
view of the
lower drive assembly 1000 are illustrated, respectively, with the upper drive
assembly 1100
removed. As illustrated, the lower drive assembly 1000 may comprise a center
pinwheel
driver 1002, a plurality of intermediate pinwheels 1006 and an outer pinwheel
receiver 1004,
which may be integrated with, or otherwise coupled to, the hollow fan
driveshaft 902. Indeed,
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the hollow fan driveshaft 902 and the outer pinwheel receiver 1004 may be
formed as a single
component. That is, the inner circumferential surface of the hollow fan
driveshaft 902, or portion
thereof, may comprise thereon a plurality of pinwheel receiver spacers 1004b,
which define a
plurality of gullets 1004a. For illustrative purposes, the upper pin support
plate 1006a of each
intermediate pinwheel 1006 has been removed to better depict the plurality of
perpendicularly
disposed rollers 1008.
[00143] The various power transmission components (e.g., the pinwheel
driver 1002,
intermediate pinwheels 1006, and outer pinwheel receiver 1004) may be
fabricated from a metal
alloy of suitable strength to meet the design loads. The metal alloy may be
further subjected to
one or more heat treatments and surface treatments to alter the metal physical
properties, surface,
and appearance to meet desired strength, hardness, abrasion resistance,
appearance, corrosion
resistance, shock resistance, surface smoothness, etc. However, one of skill
in the art would
understand that other materials may be employed to meet a particular need
(e.g., corrosion
resistance, weight limitations, strength requirements, etc.). For example, the
outer surface of the
various components may have a weatherproof coating, chemical application,
powder coating,
bonded polymer, or similar treatment, and/or be made of or enclosed in a
ceramic, plastic, any
available non-corrosive material, or corrosion-resistant metal alloy such as
aluminum, stainless
steel, bronze, or titanium. Moreover, one of skill in the art would understand
that different
materials may be used to fabricate the various power transmission components.
[00144] As illustrated, the outer pinwheel receiver 1004 and pinwheel
driver 1002 may each
comprise a plurality of gullets 1002a, 1004a (e.g., female components). Center
pinwheel driver
1002 may further comprise a sleeve 1010 for receiving an end of the input
shaft 1012. The sleeve
1010, to prevent slippage and/or rotation, may be sized and shaped to receive
a correspondingly
sized and shaped input shaft 1012. For example, as illustrated the end of the
input shaft 1012
and/or sleeve 1010 may be a polygon (e.g., star-shaped, triangular, square,
pentagonal, hexagon,
etc.), oval, semicircle, asymmetrically-shaped, etc. In certain embodiments,
sleeve 1010 may
include a notch (keyway) that can be aligned with a corresponding notch
(keyway) on the input
shaft 1012, so as to create a space of the same shape and dimension as a piece
of metal stock
(key) to be inserted into the aligned notches (keyways) in order to fix the
rotation of center
pinwheel driver 1002 to the input shaft 1012. In fact, the various shafts,
axles, and the like, or at
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minimal, the ends thereof, may employ similar techniques to prevent slippage
and/or rotation of
the various pinwheels, pinwheel drivers, and pinwheel receivers. For example,
the various shafts
are illustrated as being hexagonal where coupled to the pinwheels, pinwheel
drivers, and
pinwheel receivers.
[00145] In other exemplary embodiments, center pinwheel driver 1002 may be
coupled to
the input shaft 1012 in any suitable manner. For example, the motor 808 may be
integrated with
the transmission 900 to form a combination motor/contra-rotating transmission
apparatus. A
combination apparatus could reduce on-site assembly time and reduce materials
by omitting the
need for coupling between the motor/transition.
[00146] As noted above, and as illustrated herein, one or more outer
pinwheel receivers
1004 may be integrated with one or more components (e.g., pinwheel receiver
spacers 1004b and
hollow fan driveshaft base 924) as a component used to construct the hollow
fan driveshaft 902.
For example, outer pinwheel receiver 1004 can be coupled to hollow fan
driveshaft 902, or
portion thereof, that is coupled to a fan-hub mounting plate. To that end,
outer pinwheel
receiver 1004 transfers torque from pinwheels 1006 through the hollow fan
driveshaft 902 of
which it is integrated with, which in turn transfers torque to the fan-hub
mounting plate that
enables contra-rotating transmission 900 to function as described herein. To
that end, outer
pinwheel receiver 1004 as part of the hollow fan driveshaft 902 that
ultimately drives the fan-hub
mounting plate may include support coupling structures, which may be any
coupling structure
that enables the contra-rotating transmission 1000 to function as described
herein. For example,
coupling structures can be threaded bores that can receive a bolt or other
threaded fastener. In
certain embodiments, fan blades may be coupled (e.g., bolted) directly to fan-
hub mounting
plate, or hollow fan driveshaft 902, which effectively functions as a fan hub.
[00147] In the illustrated example, the pinwheel driver 1002 engages a
first set of
four intermediate pinwheels 1006, which are fixed in place via pinwheel drive
shafts 908, but
rotates their respective drive shafts about their axes in the opposite
direction of rotation as that of
the pinwheel driver 1002, while simultaneously engaging the hollow fan
driveshaft 902 via the
integrated outer pinwheel receiver 1004 rotating it in the same direction as
the pinwheels 1006.
That is, the four intermediate pinwheels 1006 simultaneously transfer and
divide the torque from
the pinwheel driver 1002 to the hollow fan driveshaft 902 via the outer
pinwheel receiver 1004
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and the upper drive assembly via the pinwheel drive shafts 908. Indeed,
pinwheel drive shaft 908
may be rotatably secured in place at its distal ends. Examples include, but
are not limited to, the
use of ball bearings, bushings, sleeves, blind holes with proper clearance,
etc., each of which
may be located and secured in the upper housing plate 904 and lower housing
plate 906. While
four intermediate pinwheels 1006, 1106, are illustrated throughout, one of
skill in the art would
understand that greater or fewer intermediate pinwheels 1006, 1106 may be
used. For example,
additional intermediate pinwheels may be used to increase robustness by
providing additional
engagement points. Alternatively, fewer intermediate pinwheels may be used to
reduce weight
and/or size, or to accommodate a particular casing shape.
[00148] Each intermediate pinwheel gear 1006 may comprise two or more
circular pin
support plates 1006a separated by a plurality of perpendicularly disposed pins
1008. The
pins 1008 may be arranged along the outer circumferences of said two or more
pin support
plates 1006a and configured to receive and drive, therebetween, one or more
pinwheel receiver
spacers 1004b. Each pin 1008 may comprise inner pin 1008a and a hollow
cylinder 1008b.
Indeed, the hollow cylinder 1008b may be hollow as to provide a space for an
inner pin 1008a
such that it is rotationally arranged around said inner pin 1008a. Thus, in
operation, the hollow
cylinder 1008b can rotate around said pin 1008a, thereby greatly reducing
friction between the
pinwheels, pinwheel drivers, and pinwheel receivers.
[00149] While the pins 1008 are illustrated as the hollow cylinder 1008b
that can rotate
around a pin 1008a, other embodiments are possible. For example, solid pins
without inner
pins 1008a may be recessed into pin support plates 1006a with blind holes in
pin support plates
to provide proper clearance to allow pin to rotate in the blind hole. In
another alternatively, both
inner 1008a and hollow cylinder 1008b may be recessed into the pin support
plates 1006a with
the inner pin 1008a recessed further so as to allow the hollow cylinder 1008b
to rotate around the
inner 1008a. Finally, solid pins 1008 with no inner pins 1008a may be recessed
into pin support
plates with the pin fixed into a tight, blind hole with no clearance and
unable to rotate.
[00150] While outer pinwheel receiver 1004 and pinwheel driver 1002 are
illustrated and
described as being female, with the intermediate pinwheels 1006a being male,
the opposite
arrangement may be employed. That is, the outer pinwheel receiver 1004 and/or
pinwheel
driver 1002 may be replaced with pinwheels of the same diameter and
corresponding number of
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pins as there are gullets and the intermediate pinwheels 1006 may be replaced
with a pinwheel
idler of the same diameter and corresponding number of gullets as there are
pins.
[00151]
Notably, the gearing may be multi-phased, or more specifically, as
illustrated,
dual-phased. That is, each drive component may comprise two or more offset
layers of
gullets 1002a, 1004a, and/or pins 1008, wherein the two or more layers are
offset by rotating
each layer by a predetermined number of degrees with respect to the preceding
layer. For
example, in the illustrated dual-phased arrangement, the outer pinwheel
receiver 1004 and
pinwheel driver 1002 may be fabricated with two offset, but otherwise
identical, gullet profiles
1002a, 1004a separated by a gap or spacers 1004b. Similarly, each intermediate
pinwheel 1006
may be fabricated from three pin support plates 1006a, having a layer of pins
1008 sandwiched
between each pin support plate 1006a. As illustrated, a dual-phased offset
pinwheel
driver/receiver may be phased in a manner such that a gullet of the first
layer aligns at the exact
midpoint between the gullets of the second layer.
[00152]
By offsetting two layers, the number of rollers 1008 and/or gullets 1002a,
1004a in
a given wheel diameter can be effectively doubled. This increases the points
of contact between
the power transmission components within the transmission, allowing for a
denser power
distribution within the transmission. Correspondingly, in a tri-phased
arrangement (i.e. ,
three layers), the number of rollers 1008 and/or gullets 1002a, 1004a in a
given wheel diameter
can be effectively tripled, while it is quadrupled in a quad-phased
arrangement (i.e., four layers).
Thus, the greater the number of phases, the denser power distribution within
the transmission.
[00153]
A denser power distribution significantly lowers the power being transferred
at
each point of contact thus significantly increasing the capacity rating of the
transmission. The
increased power density also allows for the overall size of the transmission
to decrease as
compared to single-phased transmissions of same capacity. The denser power
distribution within
the transmission also allows for an increased ability in withstanding shock
loads, which is one of
the most common failure points of conventional transmissions and gearboxes.
The presently
disclosed pinwheel design provides the ability to withstand shock loads;
however, by
multi-phasing the pinwheel design, the shock load resistance is substantially
increased further.
For example, in a dual-phase arrangement, at no time during the 360-degree
rotation of the input
shaft 1012 is there a loss of engagement between the pinwheels and the
pinwheel
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drivers/receivers; in fact, the level of engagement is greater than that of a
single-phase design
across the entire 360-degree span of rotation.
[00154] An advantage of increasing pin engagement is its effect on
backlash. That is, in this
case, the amount of travel in degrees that the input shaft 1012 may be rotated
in reverse direction
before the output shaft 1112 (or hollow fan driveshaft 902) begins to rotate.
This is commonly
described as "slop" or "play" and it is the result of gaps present between the
moving parts that
engage inside the transmission. These gaps are present for an infinite
multitude of reasons and, in
most cases, are required for reasons such as lubrication allowance, thermal
expansion allowance,
jam prevention, etc. In =fact, the utilization of multi-phased pinwheels in
the contra-rotating
transmission 900 virtually eliminates backlash due to the high number of pins
engaged during all
360 degrees of input shaft 1012 rotation. This can facilitate greatly reducing
or completely
eliminating the likelihood of generating shock loads, in the event that the
input shaft rotation
were to be suddenly reversed while in motion. For example, "wind milling," a
common problem
for gear-driven WET/DRY cooling equipment with no anti-reversing measures,
where the fans
are being driven in one direction by an outside force such as wind and then
the power input to
the transmission is turned on, suddenly reversing the rotation of the fans. In
some exemplary
embodiments, contra-rotating transmission 900 may further include a locking
mechanism, so as
to allow a particular fan to spin in one direction while impeding the fan from
spinning in the
reverse direction to prevent condition such as "wind milling."
[00155] Multi-phasing also serves to transfer power from the motor in a
more diffuse way
by not concentrating the loads on the pins that are engaged. Continuing with
the prior example,
when four intennediate pinwheels 1006 are employed in a dual-phase
arrangement, the power is
evenly distributed across the four pinwheel engagement points, times two
layers, because
substantial pin engagement is achieved through the entire 360 degrees of
rotation (i.e.,
irrespective of the rotational position of the gear system). Thus, when, for
example,
1 horsepower (11P) is applied at the input shaft, each pinwheel is required to
transfer 1/4 HP
through the pins that are in various stages of engagement times two layers.
Conversely, each
pinwheel in a single-layer system would be required to transfer 1/4 HP
utilizing half as many
pins in various stages of engagement, thereby increasing the force applied to
each individual pin,
increasing abrasion force (wear and tear), increasing heat generation, and
lowering the overall
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capacity of the pinwheel itself. Finally, a dual-phase arrangement further
enables operators to
construct a more compact unit while yielding the same efficiency because the
input power can be
more densely distributed through the gearing system.
[00156] The number of gullets 1002a, 1004a and pins 1008 may be adjusted to
achieve a
particular gearing ratio as desired by one having ordinary skill in the art.
The spacing from center
to center of the pins and gullets is known to those skilled in the arts as
"pitch." As is generally
known in the art, the pitch is a value that has direct implications to
pinwheel engagement,
transmission longevity, overall transmission backlash, etc. Final drive ratio
(i.e., the number of
revolutions of transmission input shaft: one revolution of pinwheel output
shaft) is determined by
dividing the number of gullets of the pinwheel receiver by the number of pins
in a pinwheel for
the upper drive assembly 1100. For the lower drive assembly 1000, the final
drive ratio is
determined by dividing the number of gullets of the pinwheel receiver by the
number of pins in a
pinwheel and then subtracting one revolution.
[00157] Moreover, while a dual-phase arrangement is illustrated throughout,
one of skill in
the art would understand that greater or fewer phases, or layers, may be used.
Alternatively, a
single layer may be used to reduce cost, weight, and/or size. For example,
additional layers may
be added to increase robustness by providing additional engagement points.
However, the phase
will be shifted to accommodate the additional layer. Indeed, the following
equation may be used
to yield the degree of rotation each subsequent layer is to be rotated from
previous layer:
360 d egree
\No. Laver'
Degree Of Rotation Each Subsequent L ayer =- _____________________
No. Pins Gullets)
[00158] For example, referring to the system illustrated in Figure 10a, the
second layer of
the intermediate pinwheel 1006 and the pinwheel driver 1002 is rotated by
11.25 degrees
because each dual phased with 16 pins or gullets.
/360 degree)
2
11.2,5 Degrees Laye-Is
16
[00159] Conversely, the second layer of the outer pinwheel receiver 1004 is
rotated by
3.75 degrees because it is dual phased with 48 gullets.
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(360 degree')
,
3.75 Degrees= 2 Layers ( )i
48
[00160] Turning now to Figures 11 a and 11b, a perspective view and top
plan view of the
upper drive assembly 1100 is illustrated atop, and operatively couple with,
the lower drive
assembly 1000. For convenience of illustration, substantially similar
functional elements to those
in the lower drive assembly 1000 are represented by similar numerals, with the
leading digit
incremented to 4. As illustrated, the upper drive assembly 1100 may comprise a
center pinwheel
receiver 1102, and a plurality of intermediate pinwheels 1106. For
illustrative purposes, the
upper pin support plate 1106a of each intermediate pinwheel 1106 has been
removed to better
show the plurality of perpendicularly disposed pins 1008.
[00161] As illustrated in, for example, Figures 9a and 9b, the center
pinwheel receiver 1102
may be integrated with output shaft 1112, which may be configured to rotate
opposite hollow fan
driveshaft 902. The output shaft 1112 may be configured to receive a fan hub.
For example', the
output shaft 1112 may be flanged, male, keyed male, female, female keyed, etc.
Alternatively,
the fan hub may be integrated with to the output shaft 1112 such that fan
blades can be fixed
directly to output shaft 1112 in manner that the output shaft 1112 functions
as a fan hub.
[00162] As discussed with respect to the lower drive assembly 1000, the
drive assembly
may be multi-phased, or more specifically, as illustrated, dual-phased.
Similarly, as discussed
above, the number of gullets 1102b, 1104b and pins 1008 may be adjusted to
achieve a particular
gearing ratio as desired by one having ordinary skill in the art.
[00163] The operation of the contra-rotating transmission 900 will now be
described. All
rotational directions (e.g., clockwise and counter-clockwise) will be
described as viewed in
direction A. That is, as viewed from the top (e.g., as illustrated in Figures
10b and 11b). In
operation, torque may be applied to the input shaft 1012 in the clockwise
direction via a
motor 808. Torque is then transferred from the input shaft 1012 to the center
pinwheel
driver 1002, which similarly rotates in the clockwise direction. In the
illustrated example, the
center pinwheel driver 1002 engages a first set of four intermediate pinwheels
1006, which are
fixed in place via pinwheel drive shafts 908, but rotate their respective
drive shafts 908 about
their axes in the counter-clockwise direction, while simultaneously engaging
the hollow fan
driveshaft 902 via the integrated outer pinwheel receiver 1004 rotating it
counter-clockwise. As
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discussed above, a second fan 904 may be coupled, directly or indirectly, to
the outer pinwheel
receiver 1004 via hollow output shaft 902 and/or fan-hub mounting plate such
that the second
fan 804 also rotates in the counter-clockwise direction. For example, fan
blades may be coupled
to the hollow output shaft 902 or the fan-hub mounting plate.
[00164] In addition to driving the outer pinwheel receiver 1004, the first
set of
four intermediate pinwheels 1006 drive a second set of four intermediate
pinwheels 1106 via
their respective drive shafts 908, which extend from the lower assembly 1000
to the upper
assembly 1100, as best illustrated in Figures 9a and 9b. For example, the
drive shafts 908 to
which the first set of four intermediate pinwheels 1006 are attached may be
extended to also
serve as the drive shafts 908 for the second set of four intermediate
pinwheels 1106 attached in
the same or similar manner. As a result, first and second set of four
intermediate pinwheels 1006,
1106 rotate coaxially in the counter-clockwise direction at the same rotations
per minute (RPM).
[00165] While the same RPM is output to both sets of pinwheels 1006, 1106,
differing
number of pins 1008 and/or pitch diameters may be used to change the speed of
subsequent
gearing. For example, the first set intermediate pinwheels 1006 may employ
pinwheels having
16 pins 1008 while the second set intermediate pinwheels 1106 may employ
pinwheels having
8 pins 1008. As a result, each set of pinwheels 1006, 1106 can drive their
respective pinwheel
receivers 1004, 1102 at different RPMs while rotating at same RPM via the
common drive
shafts 908.
[00166] The second set of four intermediate pinwheels 1106 engage the
center pinwheel
receiver 1102, which rotates in the clockwise direction. The center pinwheel
receiver 1102 may
be operatively coupled and/or fully integrated with a fan output shaft 1112,
which may then be
configured to drive a first fan 802 in the clockwise direction. As a result,
the second fan 804
rotates in the counter-clockwise direction while the first fan 802 rotates in
the clockwise
direction.
[00167] For a dual-phased arrangement transmission 900 operating fans,
which can range
from 40 to 156 inches in diameter (3.5 ¨ 14 feet) with 20 HP at the input
shaft 1012, the
pinwheel receiver may be approximately 7 inches in overall diameter, the
intermediate pinwheels
1006 and the center pinwheel driver 1002 may be approximately 2 inches in
overall diameter.
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Upper pinwheels may be, for example, approximately 1 inch in overall diameter
while the upper
center pinwheel receiver may be approximately 3 inches in overall diameter.
However, as one of
skill in the art would recognize, these values may be adjusted to meet a
particular need or
durability.
[00168] Each layer of the dual-phased arrangement may be, for example, 5/16
inches thick.
Though, when a single-phased arrangement is employed, the system may be
limited to 10 HP at
the input shaft to not exceed capacity ratings based on the strength of the
materials being used.
That is, the dual-phased arrangement allows for twice the power transmission
capacity for the
contra-rotating transmission 900.
[00169] The presently disclosed contra-rotating transmission 900 may be
employed in
cooling towers having horsepower ranges typically from 1 to 250 HP. For
example, the presently
disclosed contra-rotating transmission may be employed in more traditional,
packaged cooling
towers which have typical motor ranges from 1 to 100 HP. More recently, 100 HP
motors have
been employed in a desperate attempt to generate more capacity. However, using
the present
system and transmission, only a 60 HP motor is required to generate the same
airflow at the same
static pressure.
[00170] Similarly, they may be employed in field-erected cooling towers
that range
typically from 50 HP to 250 HP and up. Generally speaking, the presently
disclosed
contra-rotating transmission may be used to drive fans from, for example, 40
inches up to 40 feet
in diameter with cubic foot per minute (CFM) typically in excess of 10,000
CFM. Indeed, in
addition to the systems 800a, 800b of Figure 8a and 8b, the presently
disclosed contra-rotating
transmission 900 may be used in conjunction with fan drive systems such as
those described in
commonly owned PCT application number PCT/US2013/070430, which was filed on
November 15, 2013, and parent U.S. Patent Serial No. 13/678,095, filed on
November 15, 2012,
both of which are hereby incorporated by reference in their entirety.
Furthermore, the
contra-rotating transmission 900 should not be limited to use with HVACR
systems and devices.
On the contrary, such a contra-rotating transmission 900 may drive other
systems or devices
where contra-rotating of fans, impellers, fans, gears, mechanical linkages
(e.g., to another device
or system), and/or other rotating components are desired, including, without
limitation,
construction machinery, manufacturing machinery, wind tunnels, and propulsion
systems, such
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as those associated with marine vessels (e.g., in connection with bow
thrusters), aerial vehicles,
and land vehicles.
[00171] The embodiments described herein can provide several advantages
over
conventional, single-stage fan systems for dry and evaporative cooling
equipment. First, due to
the increased efficiency inherent to a contra-rotating fan arrangement, lower
rotational speeds are
required for the fans of the contra-rotating systems disclosed herein.
Consequently, utilizing any
of the embodiments disclosed herein in a cooling tower can result in decreased
noise levels and
decreased energy requirements when compared with single-stage fan systems.
Furthermore, the
embodiments disclosed herein can result in reduced vibration transmission to
the evaporative
cooling equipment unit due to the cancelling out of the gyroscopic forces of
the fans. The
reduced vibration can be beneficial for meeting updated building codes that
have strict vibration
requirements and can also facilitate increased life of the mechanical
components of the fan drive
systems.
[00172] Additionally, the dual axial fans of the embodiments disclosed
herein can generate
higher static pressure within the evaporative cooling equipment unit than can
be generated by
conventional single-stage fan units, which can present several advantages. The
higher static
pressure can result in an increased thermal performance of the dry and
evaporative cooling
equipment unit with which the contra-rotating fan system is used. As a result
of this higher static
pressure, air may be drawn from portions of the cooling unit that are
typically known as low
performance areas, such as the corners of the unit or other areas with
suboptimal airflow when
single-stage fans are used. Additionally, the higher static pressure can
shrink the air envelope
requirement for a cooling unit; thereby facilitating improved flexibility for
the layout of the
cooling equipment and air-cooled heat exchangers. Furthermore, as a
consequence of the
increased static pressure, sound attenuation devices may be used in
conjunction with the
embodiments disclosed herein, as the pressure drops created by the sound
attenuation devices are
mitigated by the increased pressure generated by the dual axial fans, allowing
the evaporative
cooling equipment unit or air-cooled heat exchanger to maintain satisfactory
thermal
performance. Additional advantages of the embodiments disclosed herein include
the reduction
of the necessity to de-ice the fan blades, as the contra-rotating action of
the two axial fans
inhibits ice from forming during operation.
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[00173] The foregoing description and accompanying figures illustrate the
principles,
preferred embodiments, and modes of operation of the invention. However, the
invention should
not be construed as being limited to the particular embodiments discussed
above. Additional
variations of the embodiments discussed above will be appreciated by those
skilled in the art.
[00174] Therefore, the above-described embodiments should be regarded as
illustrative
rather than restrictive. Accordingly, it should be appreciated that variations
to those
embodiments can be made by those skilled in the art without departing from the
scope of the
invention as defined by the following claims.
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