Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02550277 2006-09-O1
Attorney Docket No.: ~ _4-0045-O1
METHOD AND SYSTEM FOR DEHUMIDIFICATION AND
REFRIGERANT PRESSURE CONTROL
FIELD OF THE INVENTION
[0001] The present invention relates generally to heating, ventilation and air
conditioner systems (HVAC), including systems that can dehumidify air.
BACKGROUND OF THE INVENTION
[0002] An HVAC system generally includes a closed loop refrigeration system
with
at least one evaporator, at least one condenser and at least one compressor.
As the
refrigerant travels through the evaporator, it absorbs heat from a heat
transfer fluid
and changes from a liquid to a vapor phase. After exiting the evaporator, the
refrigerant proceeds to a compressor, then a condenser, then an expansion
valve, and
back to the evaporator, repeating the loop. The heat transfer fluid to be
cooled (e.g.
air) passes through the evaporator in a separate fluid channel and is cooled
by the
evaporation of the refrigerant. The heat transfer fluid can then be sent to a
distribution
system for cooling the spaces to be conditioned, or it can be used for other
refrigeration purposes.
[0003] Other refrigeration purposes may include dehumidification.
Dehumidification
of air in HVAC systems can occur through the use of the evaporator in the
cooling
mode. One drawback to using just an evaporator for dehumidification is an
excess
reduction in air temperature that results, which is commonly referred to as
overcooling. Overcooling occurs when air that is subject to dehumidification
is
cooled to a temperature that is below the desired temperature of the air.
Overcooling
is a particular problem when dehumidification is required in a room that is
already
relatively cool and does not require additional cooling. Overcooling generally
involves air temperatures of approximately 50 °F to SS °F or
lower.
[0004] The problem of overcooling has been addressed in one solution by
utilization
of a reheat coil in one solution. Air that is overcooled by the evaporator is
passed
over the reheat coil in order to increase the temperature of the overcooled,
2
CA 02550277 2006-09-O1
Attorney Docket No.: 4 _4-0045-O1
dehumidified air to a desired temperature. The reheat coil can be heated by
diverting
hot refrigerant through the reheat coil when dehumidification is required.
Reheat may
also be provided by alternate heat sources, such as electric heat or gas heat.
The
reheat coil system for providing heat to the dehumidified, overcooled air has
several
drawbacks including the requirement of additional equipment and/or piping
and/or
additional energy input.
[0005] Another dehumidification method known in the art is disclosed in U.S.
Patent
No. 4,182,133 (the ' 133 Patent). The ' 133 Patent is directed to a
dehumidification
method that controls refrigerant flow through circuits within the indoor coil
of an air
conditioning/heat pump unit. The '133 Patent system, when providing
dehumidification, has a header that distributes the refrigerant across several
circuits
within the indoor coil. At the opposite end of the indoor coil, the outlets of
the
various circuits of the coil are allowed to flow into a single common vapor
header.
The header at the inlet of the indoor coil contains a solenoid valve that may
be closed
to prevent refi-igerant flow to one or more of the circuits within the coil.
The '133
Patent system operates such that when humidity reaches a certain level, the
valve in
the inlet header is closed in order to limit the number of available circuits
for
refrigerant flow. The area of the indoor coil that remains in the active
circuit and
receives refi~igerant flow, experiences an increase in refrigerant flow
through a given
heat transfer area. The increased flow of refrigerant results in a greater
amount of
moisture being removed from the air in that portion of the indoor coil. One
drawback
of the '133 Patent system is that the dehumidified air is not reheated and may
be
overcooled. Another drawback of the '133 Patent system is that the inlet
header does
not distribute flow across the circuits of the evaporator, leading to uneven
phase
distribution of refrigerant across the evaporator heat exchanger. Another
drawback of
the '133 Patent system is that it is nearly impossible for a properly
functioning system
to deliver supply air that has not been sensibly cooled.
[0006] One type of HVAC system is a split system where there is an indoor unit
or
heat exchanger, which is generally the evaporator, and an outdoor unit or heat
exchanger, which is generally the condenser. Often, the outdoor unit is placed
3
CA 02550277 2006-09-O1
Attorney Docket No.: i. _4-0045-O1
outdoors and is subject to outdoor ambient conditions, particularly
temperature.
When the outdoor ambient temperature falls, the amount of heat being removed
from
the refrigerant in the condenser increases. The increased heat removal in the
condenser can result in a decrease in the refrigerant pressure at the suction
line to the
compressor, commonly referred to as head pressure. The decrease in head
pressure
results in a lowering of the temperature of the refrigerant at the evaporator.
When the
temperature of the refrigerant at the evaporator becomes too low, icing of the
evaporator can occur. Icing is a condition when the temperature at the
exterior of the
system is sufficiently low to freeze water present in the atmosphere. The ice
formed
by the water frozen on the surface reduces the available heat transfer surface
and
eventually prevents the proper operation of the HVAC system by inhibiting heat
transfer and/or damaging system components.
[0007] Some attempts to address the problem of icing have utilized the control
of
system pressure. In one approach, a variable speed condenser fan or a
plurality of
condenser fans having independent controls are used to control airflow over
the
condenser coil. As the amount of air passing over the coil decreases, the
amount of
heat transfer taking place at the coil decreases. Therefore, the temperature
of the
refrigerant in the condenser and the pressure of the system increase to allow
the
indoor coil to cool the air without icing problems. The use of the variable
speed
condenser fan or a plurality of condenser fans having independent controls has
the
drawback that it is expensive and requires complicated wiring and controls.
[0008] An alternate approach for the problem of low system pressure or icing
is a
parallel set of condensers in the refrigerant cycle, as described in U.S.
Patent No.
3,631,686 (the '686 Patent). In the '686 Patent system a parallel set of
refrigerant
condensers allows for two modes of operation. One mode of operation allows
refrigerant to flow from only one of the refrigerant condensers. During this
mode of
operation, the condenser that does not permit the flow of refrigerant fills
with liquid
refrigerant. Because of this flooding, there is a reduction in the effective
surface area
of the condenser. The reduced surface area thereby reduces the ability of the
condenser to remove heat from the refrigerant. Therefore, the temperature of
the
4
CA 02550277 2006-09-O1
Attorney Docket No.: ~ _4-0045-O1
refrigerant in the condenser and the head pressure of the system increase,
allowing the
indoor coil to cool the air without icing. The use of parallel refrigerant
condensers
has the drawback that it requires an additional condenser coil and additional
piping,
thereby increasing the space and cost required for installation. Another
drawback
associated with refrigerant flooding of the condenser coil is the resultant
decrease in
system capacity. Refrigerant normally available in a properly operating system
is
trapped in the condenser coil and not available to the compressor, thereby
decreasing
system capacity.
[0009] Therefore, what is needed is a method and system for dehumidification
that
dehumidifies air without overcooling, provides control of the refrigerant
pressure and
provides a system that can be retrofitted into existing systems without the
drawbacks
discussed above.
SUMMARY OF THE INVENTION
[0010] The present invention is directed to a method for dehumidification and
controlling system pressure in a refrigeration system. The method comprises
the step
of providing a refrigeration system having a compressor, a condenser and an
evaporator connected in a closed refrigerant loop. Each of the condenser and
evaporator have a plurality of refrigerant circuits. A first heat transfer
fluid is flowed
over the condenser. A second heat transfer fluid is flowed over the
evaporator. The
flow of refrigerant is controlled in the refrigerant circuits in the condenser
to control
the amount of heat transfer between refrigerant in the condenser and the first
heat
transfer fluid. The flow of refrigerant is controlled in the refrigerant
circuits in the
evaporator to control an amount of heat transfer between refrigerant in the
evaporator
and the second heat transfer fluid. At least one of the refrigerant circuits
of the
condenser is isolated to provide a decreased amount of heat transfer area
within the
condenser and to increase the refrigerant pressure within the refrigeration
system
when the refrigerant pressure within the refrigeration system is at or below a
predetermined pressure. At least one of the refrigerant circuits of the
evaporator is
isolated to dehumidify the second heat transfer fluid and maintain the
temperature of
CA 02550277 2006-09-O1
Attorney Docket No.: 2~ . .4-0045-O1
the second heat transfer fluid at or above a predetermined temperature when
dehumidification is required.
[0011] Another embodiment of the invention includes a method for
dehumidification
and controlling refrigerant pressure in a heating, ventilation and air
conditioning
system. The method comprises providing a closed loop refrigerant system
comprising
a compressor, a condenser and an evaporator. Each of the condenser and
evaporator
having a plurality of refrigerant circuits configured and disposed to allow
isolation of
at least one of the refrigerant circuits from refrigerant flow. Pressure is
measured at a
predetermined location in the refrigeration system. An operational mode is
determined for the refrigeration cycle. The operational mode is selected from
the
group consisting of cooling and dehumidification. At least one of the
refrigeration
circuits in the condenser is isolated from refrigerant flow when the measured
pressure
at the predetermined location is equal to or less than a predetermined
pressure. A first
set of refrigerant circuits in the evaporator is isolated from flow of
refrigerant from
the condenser when the operational mode is dehumidification. Flow of
refrigerant is
permitted from the condenser to both the first and second set of refrigerant
circuits in
the evaporator when the operational mode is cooling. The refrigerant pressure
is
increased by isolation of at least one of the refrigerant circuits in the
condenser from
refrigerant flow until the measured pressure is greater than the predetermined
pressure.
[0012] Another embodiment of the invention includes a heating, ventilation and
air
conditioning system. The system comprises a compressor, a condenser
arrangement
and an evaporator arrangement. The condenser arrangement comprises a plurality
of
circuits arranged into a first and second set of circuits, and a valve
arrangement
configured and disposed to isolate the first set of circuits of the condenser
arrangement when the refrigerant pressure is below a predetermined pressure.
The
evaporator arrangement comprises a plurality of circuits arranged into a first
and
second set of circuits, at least one distributor configured to distribute and
deliver
refrigerant to each circuit of the plurality of circuits in the evaporator,
and a valve
arrangement configured and disposed to isolate the first set of circuits of
the
6
CA 02550277 2006-09-O1
Attorney Docket No.: 2,. . .4-0045-Ol
evaporator arrangement from refrigerant flow in a dehumidification operation
of the
HVAC system.
[0013] The present invention provides an inexpensive method and system to
control
head pressure, while also being capable of repeating dehumidified air. The
method
and system requires little or no additional piping in order to implement the
method
and system in an existing HVAC unit. The system requires less in materials and
therefore costs less than systems having separate components, such as separate
repeat
coils.
[0014] Another advantage of the present invention is that the air conditioning
or heat
pump unit can operate at lower outdoor ambient temperatures by providing an
increase in system pressure to avoid icing of the system components.
[0015] Another advantage of the present invention is that the system and
method
distributes refrigerant substantially uniformly across the evaporator to
provide
substantially uniform refrigerant phase distribution and heat exchange across
the
evaporator.
[0016] Another advantage of the present invention is that the system can
repeat air
and control head pressure without the need for a separate airflow system.
[0017] Another advantage of the system is that the simultaneous control of the
head
pressure of the system and repeating of the air during dehumidification
permits the
system to be operated in a manner that increases the efficiency and
reliability of the
system, while maintaining greater control of the temperature and humidity of
the
conditioned air.
[0018] Other features and advantages of the present invention will be apparent
from
the following more detailed description of the preferred embodiment, taken in
conjunction with the accompanying drawings which illustrate, by way of
example, the
principles of the invention.
7
CA 02550277 2006-09-O1
Attorney Docket No.: 2,. _4-0045-O1
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 schematically illustrates a refrigeration or HVAC system.
[0020] FIG. 2 schematically illustrates one embodiment of an evaporator and
piping
arrangement of the present invention.
[0021] FIG. 3 schematically illustrates another embodiment of an evaporator
and
piping arrangement of the present invention.
[0022] FIG. 4 schematically illustrates further embodiment of an evaporator
and
piping arrangement of the present invention.
[0023] FIG. 5 schematically illustrates one embodiment of a condenser and
piping
arrangement of the present invention.
[0024] FIG. 6 schematically illustrates another embodiment of a condenser and
piping
arrangement of the present invention.
[0025] FIG. 7 schematically illustrates one embodiment of a refrigeration or
HVAC
system according to the present invention.
[0026] FIG. 8 schematically illustrates another embodiment of a refrigeration
or
HVAC system according to the present invention.
(0027] FIG. 9 schematically illustrates a refrigeration or HVAC system of
another
embodiment of the present invention.
[0028] FIG. 10 schematically illustrates a refrigeration or HVAC system of a
further
embodiment of the present invention.
[0029] FIG. 11 illustrates a control method of the present invention.
[0030] FIG. 12 illustrates a control method of another embodiment of the
present
invention.
8
CA 02550277 2006-09-O1
Attorney Docket No.: i. :4-0045-O1
[0031] FIG. 13 illustrates a control method of a further embodiment of the
present
invention.
[0032] FIG. 14 illustrates a control method of a further embodiment of the
present
invention.
[0033] FIG. 15 illustrates a control method of a further embodiment of the
present
invention.
[0034] FIG. 16 illustrates a control method of a further embodiment of the
present
invention.
[0035] Wherever possible, the same reference numbers will be used throughout
the
drawings to refer to the same or like parts.
DETAILED DESCRIPTION OF THE INVENTION
[0036] FIG. 1 illustrates a HVAC, refrigeration, or chiller system 100.
Refrigeration
system 100 includes a compressor 130, a condenser 120, and an evaporator 110.
The
compressor 130 compresses a refrigerant vapor and delivers it to the condenser
120
through compressor discharge line 135. The compressor 130 is preferably a
reciprocating or scroll compressor, however, any other suitable type of
compressor
can be used, for example, screw compressor, rotary compressor, and centrifugal
compressor. The refrigerant vapor delivered by the compressor 130 to the
condenser
120 enters into a heat exchange relationship with a first heat transfer fluid
150,
preferably air, and undergoes a phase change to a refrigerant liquid as a
result of the
heat exchange relationship with the first heat transfer fluid 150. The first
heat transfer
fluid 150 is moved by use of a fan 170, which moves the first heat transfer
fluid 150
through the condenser 120 in a direction perpendicular the cross section of
the
condenser 120. In a preferred embodiment, the refrigerant vapor delivered to
the
condenser 120 enters into a heat exchange relationship with air as the first
heat
transfer fluid 150. The refrigerant leaves the condenser through the condenser
discharge line 140 and is delivered to an evaporator 110 after passing through
an
expansion device (not shown). The evaporator 110 includes a heat-exchanger
coil.
9
CA 02550277 2006-09-O1
Attorney Docket No.: 2~ _4-0045-O1
The liquid refrigerant in the evaporator 110 enters into a heat exchange
relationship
with a second heat transfer fluid 155 to lower the temperature of the second
heat
transfer fluid 155. The second heat transfer fluid 155, preferably air, is
moved by use
of a blower 160, which moves the second heat transfer fluid 155 through
evaporator
110 in a direction perpendicular the cross section of the evaporator 110.
Although
FIG. 1 depicts the use of a blower 160 and fan 170, any fluid moving means may
be
used to move fluid through the evaporator and condenser 120. In a preferred
embodiment, the refrigerant vapor delivered to the evaporator 110 enters into
a heat
exchange relationship with air as the second heat transfer fluid 155. The
refrigerant
liquid in the evaporator 110 undergoes a phase change to a refrigerant vapor
as a
result of the heat exchange relationship with the second heat transfer fluid
155. The
vapor refrigerant in the evaporator 110 exits the evaporator 110 and returns
to the
compressor 130 through a suction line 145 to complete the cycle. The
conventional
refrigerant system 100 includes many other features that are not shown in FIG.
1.
These features have been purposely omitted to simplify the figure for ease of
illustration.
[003?] FIG. 2 illustrates a partitioned evaporator 200 according to one
embodiment of
the present invention. The inlet of the partitioned evaporator 200 includes a
condenser discharge line 140 from the partitioned condenser 500 (see FIG. 7),
a first
and second thermostatic expansion valve (TXV valve) 260 and 265, an isolation
valve
250, and a first and second distributor 240 and 245. Although FIGS. 2-4 and 7-
9
illustrate TXV valves, any suitable pressure reduction or expansion device may
be
used to control refrigerant flow, such as a fixed orifice. The first TXV valve
260 and
the isolation valve 250 are positioned between condenser discharge line 140
and the
first distributor 240. The second TXV valve 265 is positioned between the
condenser
discharge line 140 and the second distributor 245. The partitioned evaporator
200
includes refrigerant circuits 210. Although refrigerant circuits 210 are shown
as
curved lines in FIGS. 2-4, the shape shown is merely schematic and any
suitable
configuration of refrigerant circuit 210 can be used. Refrigerant circuits 210
can
include any configuration of device capable of transferring heat. An example
of a
suitable device includes a finned tube. The number of refrigerant circuits 210
may be
CA 02550277 2006-09-O1
Attorney Docket No.: ~,. . ~4-0045-O1
any number of refrigerant circuits 210 that provide sufficient heat transfer
to maintain
operation of the partitioned evaporator 200 within the refrigeration system
100. The
partitioned evaporator 200 is preferably partitioned into a first and second
evaporator
portions 220 and 230. The first and second evaporator portion 220 and 230 may
be
sized in any proportion. For example, the first evaporator portion 220 may be
60% of
the size of the partitioned evaporator 200 and the second evaporator portion
230 may
be 40% of the size of the partitioned evaporator 200 or the first evaporator
portion
220 may be 40% of the size of the partitioned evaporator 200 and the second
evaporator portion 230 may be 60% of the size of the partitioned evaporator
200 or
the first and second evaporator portions 220 and 230 may each represent 50% of
the
size of the partitioned evaporator 200.
[0038] Although FIG. 2 shows the partitioned evaporator 200 as only including
two
portions, any number of portions may be used in the present invention. Where
more
than two evaporator portions are present, the flow may be regulated to each of
the
portions. For example, in the embodiment where the evaporator is split into
three
portions, two of the three portions include valve arrangements that allow
independent
isolation of each of these portions. One or both of the two portions with
valve
arrangements may be isolated, dependent on a signal from a controller and/or
sensor.
The outlet of the partitioned evaporator 200 includes first and second
discharge
headers 270 and 275, first and second thermostatic expansion valve bulbs (TXV
bulbs) 264 and 269, and an evaporator discharge line 145 to the compressor
130. The
first discharge header 270 receives refrigerant from the refrigerant circuits
210 in the
first evaporator portion 220. The second discharge header 275 receives
refrigerant
from the refrigerant circuits 210 present in the second evaporator portion
230. The
first TXV bulb 264 is positioned between the first discharge header 270 and
the
evaporator discharge line 145. The first TXV bulb 264 senses the temperature
of the
refrigerant leaving the first discharge header 270 and compares the
temperature of the
refrigerant to the temperature of the refrigerant at the first TXV valve 260
through
line 262. The flow of refrigerant through the first TXV valve 260 is increased
as the
temperature difference at the first TXV bulb 264 and the first TXV valve 260
increases. The flow of refrigerant through the first TXV valve 260 is
decreased as the
11
CA 02550277 2006-09-O1
Attorney Docket No.: ~. .4-0045-O1
temperature difference at the first TXV bulb 264 and the first TXV valve 260
decreases. The second TXV valve 265 operates in the same manner with respect
to
the refrigerant discharge from the second discharge header 275 and
communicates the
temperature measurement to the second TXV valve 265 through line 267. The
isolation valve 250 allows the first evaporator portion 220 of the partitioned
evaporator 200 to be isolated from flow of refrigerant. In one embodiment, to
accommodate an increased flow of refrigerant to the second evaporator portion
230,
as discussed in detail below, the size of the second TXV valve 265 (i.e., the
amount of
flow permitted through the valve) is greater than the size of the first TXV
valve 260.
[0039] During operation of the refrigeration system 100 in cooling mode,
refrigerant
flows from the partitioned condenser 500 to the partitioned evaporator 200
through
condenser discharge line 140. The flow is split into two refrigerant flow
paths prior to
entering the partitioned evaporator 200. Although FIG. 2 shows two paths
leading to
the first and second distributors 240 and 245, the refrigerant flow may be
split into
two or more paths. If the system is in a cooling only mode, isolation valve
250 is
open and refrigerant is permitted to flow into both the first and second
evaporator
portions 220 and 230 of the partitioned evaporator 200. The two refrigerant
flow
paths are further split by a first and second distributor 240 and 245 into a
plurality of
lines, corresponding to the individual refrigerant circuits 210. The first and
second
distributors 240 and 245 may include any arrangement that distributes the
refrigerant
to the individual refrigerant circuits 210 within the partitioned evaporator
200. The
first and second distributors 240 and 245 can preferably distribute the
refrigerant to
provide uniform phase distribution across the refrigerant circuits 210 of the
partitioned evaporator 200 and, thus, provide substantially uniform heat
transfer. The
first and second distributors 240 and 245 also may include combinations of
distributor
tubes and orifices to provide the uniform refrigerant flow. The refrigerant
flows into
the refrigerant circuits 210 of first and second evaporator portions 220 and
230. The
refrigerant circuits 210 permit the refrigerant to enter into a heat transfer
relationship
with the second heat transfer fluid 155 to cool the second heat transfer fluid
155. Due
to the heat transfer with the second heat transfer fluid 155, the refrigerant
entering the
first and second discharge headers 270 and 275 has a higher temperature than
the
12
CA 02550277 2006-09-O1
Attorney Docket No.: ~ .4-0045-O1
temperature of the refrigerant entering the partitioned evaporator 200. The
refrigerant
then travels from the first and second discharge headers 270 and 275 past the
first and
second TXV bulbs 264 and 269. The TXV bulbs 264 and 269 sense the temperature
of the refrigerant leaving the partitioned evaporator 200 and communicate the
temperature to the first and second TXV valves 260 and 265 in order to
determine the
appropriate refrigerant flow into the partitioned evaporator 200. After
traveling past
the first and second TXV bulbs 264 and 269, the refrigerant is delivered to
the
compressor 130 through evaporator discharge line 145.
[0040] If the system shown in FIG. 2 is operated in a dehumidification mode,
isolation valve 250 is closed and refrigerant flow to the first evaporator
portion 220 is
prevented. The refrigerant flow in the second evaporator portion 230 occurs
substantially as described above with respect to evaporator portion 220 in
cooling
mode. However, the flow of refrigerant to the first evaporator portion 220 is
prevented. Since flow to the first evaporator portion 220 is prevented, the
flow to the
second evaporator portion 230 is increased. Due to the increased flow of the
refrigerant through the second evaporator portion 230, the amount of heat
transfer per
unit area is increased and the dehumidification per unit area is likewise
increased.
Therefore, when the second heat transfer fluid 155 is passed through the
second
evaporator portion 230 the second heat transfer fluid 155 is cooled and
dehumidified,
and the second heat transfer fluid 155 passing through the first evaporator
portion 220
remains substantially unchanged in temperature and humidity from inlet to
outlet.
The second heat transfer fluid 155 passed through the second evaporator
portion 230
is generally overcooled and the second heat transfer fluid 155 passed through
the first
evaporator portion 220 is about ambient temperature. The ambient second heat
transfer fluid 155 that passes though the first evaporator portion 220 mixes
with the
second heat transfer fluid 1 SS passing through the second evaporator portion
230 and
produces an outlet heat transfer fluid, preferably air, that is dehumidified
and not
overcooled. As shown in FIG. 2, the flow of the second heat transfer fluid 155
is
substantially perpendicular to the cross-section of the evaporator. The
direction of the
flow is such that the heat transfer fluid 155 flows simultaneously through
first
evaporator portion 220 and second evaporator portion 230. A single system for
13
CA 02550277 2006-09-O1
Attorney Docket No.: ~, :4-0045-O1
moving the second heat transfer fluid 155, such as an air blower 160, can be
used to
simultaneously move air through first evaporator portion 220 and second
evaporator
portion 230.
[0041] FIG. 3 illustrates a partitioned evaporator 200 according to another
embodiment of the present invention. The inlet of the partitioned evaporator
200
includes substantially the same arrangement of components as FIG. 2, including
a
condenser discharge line 140 from the partitioned condenser 500, first and
second
TXV valves 260 and 265, and first and second distributors 240 and 245. FIG. 3
further includes check valve 255 that prevents flow of refrigerant into
evaporator
portion 220 and allows flow of refrigerant out of evaporator portion 220. The
partitioned evaporator 200 includes substantially the same arrangement of
refrigerant
circuits 210 as FIG. 2. The outlet of the partitioned evaporator 200 shown in
FIG. 3
includes the first and second discharge headers 270 and 275, first and second
TXV
bulbs 264 and 269, an evaporator discharge line 145 to the compressor 130 and
a first
discharge header discharge line 310 to a 3-way valve 910 (see FIG. 8). The
first
discharge header 270 receives refrigerant from the refrigerant circuits 210
present in
the first evaporator portion 220. The second discharge header 275 receives
refrigerant
from the circuits 210 present in the second evaporator portion 230. The first
TXV
bulb 264 is positioned on the first discharge header discharge line 310. The
first TXV
bulb 264 senses the temperature of the refrigerant leaving the first discharge
header
270 and compares the temperature of the refrigerant to the temperature of the
refrigerant at the first TXV valve 260 through line 262. The flow of
refrigerant
through the first TXV valve 260 is increased as the temperature difference at
the first
TXV bulb 264 and the first TXV valve 260 increases. The flow of refrigerant
through
the first TXV valve 260 is decreased as the temperature difference at the
first TXV
bulb 264 and the first TXV valve 260 decreases. The second TXV valve 265
operates
in the same manner with respect to the refrigerant discharge from the second
discharge header 275 and communicates the temperature measurement to the
second
TXV valve 265 through line 267. The use of independent first and second TXV
valves 260 and 265 allows independent control of the flow through each of the
portions of the partitioned evaporator 200.
14
CA 02550277 2006-09-O1
Attorney Docket No.: ~_ ~4-0045-O1
[0042] During operation in cooling mode, FIG. 3, like in the system shown in
FIG. 2,
refrigerant flows from the partitioned condenser 500 into the partitioned
evaporator
200 through condenser discharge line 140, through the valve arrangement,
including
the first and second TXV valves 260 and 265, and into the first and second
distributors 240 and 245. The refrigerant circuits 210 permit the refrigerant
to enter
into a heat transfer relationship with the second heat transfer fluid 155 that
flows
through the circuits perpendicular to the cross-section shown in FIG. 3. Due
to the
heat transfer with the second heat transfer fluid 155, the refrigerant
entering the first
and second discharge headers 270 and 275 has a higher temperature than the
temperature of the refrigerant entering the partitioned evaporator 200. The
refrigerant
flow through discharge line 310 from the first discharge header 270 travels
past the
first TXV bulb 264 and travels to a 3-way valve 910, discussed in greater
detail
below. The refrigerant flow through evaporator discharge line 145 from the
second
discharge header 275 travels past the second TXV bulb 269 to the compressor
130.
[0043] During dehumidification mode, refrigerant flow in the first evaporator
portion
220 is received from the 3-way valve 910 through the discharge line 310, as
discussed
in greater detail below. The flow from the 3-way valve 910 is hot refrigerant
gas
taken from the compressor discharge. The flow from the 3-way valve 910 travels
through the discharge line 310 in the direction of the first discharge header
270. From
the first discharge header 270, the hot refrigerant gas enters the first
evaporator
portion 220 and travels through circuits 210 to the first distributor 240. The
refrigerant in refrigerant circuits 210 of the first evaporator portion 220
can heat the
second heat transfer fluid 155 as the fluid passes over the refrigerant
circuits 210. The
hot refrigerant gas is at least partially condensed to a liquid in the first
evaporator
portion 220. The refrigerant, which is at least partially condensed to a
liquid, then
bypasses the TXV valve 260 by traveling through check valve 255. The flow
through
check valve 255 combines with the condenser discharge line 140 and enters the
second evaporator portion 230 through the second distributor 245. Due to the
increased flow of the refrigerant through the second evaporator portion 230,
the
amount of heat transfer per unit area is increased and the dehumidification
per unit
area is likewise increased. Simultaneously, hot gas refrigerant entering the
first
CA 02550277 2006-09-O1
Attorney Docket No.: i. . ~4-0045-O1
evaporator portion 220 of the partitioned evaporator 200 provides an increase
in the
temperature of the first evaporator portion 220 due to the at least partial
condensing of
the hot gas. Therefore, the second heat transfer fluid 155 passing through the
second
evaporator portion 230 is cooled and dehumidified, while the second heat
transfer
fluid 155 passing through the first evaporator portion 220 is heated by the
hot gas
refrigerant from the compressor discharge. This second heat transfer fluid 155
simultaneously is circulated through first and second evaporator portions 220
and 230
by a fluid moving system, such as an air blower 160, when the second heat
transfer
fluid 155 is air. The warmer second heat transfer fluid 155 that passes though
the first
evaporator portion 220 mixes with the second heat transfer fluid 155 passing
through
the second evaporator portion 230 and produces an outlet heat transfer fluid,
preferably air, that is dehumidified and not overcooled.
[0044] FIG. 4 illustrates a partitioned evaporator 200 according to a further
embodiment of the present invention. The inlet of the partitioned evaporator
200
includes a condenser discharge line 140 from the partitioned condenser 500, a
bypass
line 410 (see FIG. 9) from the discharge of the compressor 130, first and
second TXV
valves 260 and 265, isolation valve 250, and first and second distributors 240
and
245. The first TXV valve 260 and the isolation valve 250 are positioned
between
condenser discharge line 140 and the first distributor 240. The bypass line
410
connects to the line between the first TXV valve 260 and the first distributor
240.
Bypass line 410 is from the discharge of the compressor 130 and includes a
flow
restriction valve 430 and a bypass valve 440. While FIG. 4 shows both a flow
restriction valve 430 and a bypass valve 440, either one or both of valves 430
and 440
may be present. The isolation valve 250 is positioned between the condenser
discharge line 140 and the first TXV valve 260. The second TXV valve 265 is
positioned between the condenser discharge line 140 and the second distributor
245.
The partitioned evaporator 200 includes substantially the same arrangement of
refrigerant circuits 210 as shown in FIG. 2. The outlet of the partitioned
evaporator
200 includes first and second discharge headers 270 and 275, first and second
TXV
bulbs 264 and 269, and evaporator discharge line 145 to the compressor 130.
The
first discharge header 270 receives refrigerant from the refrigerant circuits
210 present
16
CA 02550277 2006-09-O1
Attorney Docket No.: ~ .14-0045-O1
in the first evaporator portion 220. The second discharge header 275 receives
refrigerant from the refrigerant circuits 210 present in the second evaporator
portion
230. The first TXV bulb 264 is positioned between the first discharge header
270 and
the evaporator discharge line 145. The first TXV bulb 264 senses the
temperature of
the refrigerant leaving the first discharge header 270 and compares the
temperature of
the refrigerant to the temperature of the refrigerant at the first TXV valve
260 through
line 262. The flow of refrigerant through the first TXV valve 260 is increased
as the
temperature difference at the first TXV bulb 264 and the first TXV valve 260
increases. The flow of refrigerant through the first TXV valve 260 is
decreased as the
temperature difference at the first TXV bulb 264 and the first TXV valve 260
decreases. The second TXV valve 265 operates in the same manner with respect
to
the refrigerant discharge from the second discharge header 275 and
communicates the
temperature measurement to the second TXV valve 265 through line 267. The
isolation valve 250 allows the first evaporator portion 220 of the partitioned
evaporator 200 to be isolated from flow of refrigerant. In one embodiment, to
accommodate the increased flow of refrigerant to the second evaporator portion
230,
the size of the second TXV valve 265 (i.e., the amount of flow permitted
through the
valve) is greater than the size of the first TXV valve 260.
[0045] During operation in cooling mode, FIG. 4, like in the system shown in
FIG. 2,
refrigerant flows from the partitioned condenser 500 into the refrigerant
circuits 210
of the partitioned evaporator 200 through the condenser discharge line 140,
through
the valve arrangement, including the first and second TXV valves 260 and 265,
and
the isolation valve 250, and into the first and second distributors 240 and
245. In
cooling mode, substantially no flow of refrigerant takes place into or out of
the bypass
line 410 because the bypass valve 440 is closed. The operation of the
refrigerant
circuits 210 and the outlet of the partitioned evaporator 200, including the
first and
second headers 270 and 275, the first and second TXV bulbs 264 and 269 and the
evaporator discharge line 145 to the compressor is substantially similar to
the
operation described above with respect to FIG. 2.
17
CA 02550277 2006-09-O1
Attorney Docket No.: L. s4-0045-OI
[0046] However, if the system shown in FIG. 4 is in dehumidification mode,
isolation
valve 250 is closed and refrigerant flow to the first TXV valve 260 is
prevented.
Refrigerant flaw from the discharge of the compressor 130 through bypass line
410
flows into the first distributor 240 and into the first evaporator portion
220. The hot
gas refrigerant entering the first evaporator portion 220 of the partitioned
evaporator
200 provides an increase in the temperature of the first evaporator portion
220. Due
to the increased flow of the refrigerant through the second evaporator portion
230 by
closing isolation valve 250, the amount of heat transfer per unit area is
increased and
the dehumidification per unit area is likewise increased. Therefore, the
second heat
transfer fluid 155 passing through the second evaporator portion 230 is cooled
and
dehumidified, while the second heat transfer fluid 155 passing through the
first
evaporator portion 220 is warmed by the hot gas refrigerant from the
compressor
discharge. The second heat transfer fluid 155 simultaneously is circulated
through
first and second evaporator portions 220 and 230 by a fluid moving system,
such as a
blower 160. The warmer second heat transfer fluid 155 that passes though the
first
evaporator portion 220 mixes with the second heat transfer fluid 155 passing
through
the second evaporator portion 230 and produces an outlet heat transfer fluid,
preferably air, that is dehumidified and not overcooled.
[0047] Although the partitioned evaporator 200 has been illustrated as
containing two
evaporator portions 220 and 230, the partitioned evaporator 200 is not limited
to two
portions. Any number of portions may be used, so long as one or more of the
portions
includes valuing to isolate the respective portion from refrigerant flow.
[0048] In another embodiment, refrigerant circuits 210 may also be isolated
individually within the first andlor second distributor. The refrigerant
circuits 210
may be isolated with flow blocking means or flow restriction means on first
and
second distributors 240 and 245. In this embodiment, a controller is used to
determine the number of circuits isolated. .The number of refrigerant circuits
210
isolated relates to the amount of cooling and/or heating of dehumidified air
required
and may be adjusted by the controller.
18
CA 02550277 2006-09-O1
Attorney Docket No.: a i4-0045-O1
[0049] FIG. 5 illustrates a partitioned condenser 500 according to one
embodiment of
the invention. Partitioned condenser 500 includes a plurality of heat transfer
circuits
510. The heat transfer circuits 510 are preferably partitioned into a first
condenser
portion 520 and a second condenser portion 530. Although heat transfer
circuits 510
in the partitioned condenser 500 are shown as lines in FIGs. 5-6, the shape
shown is
merely schematic. Heat transfer circuits 510 are preferably of any suitable
configuration capable of transferring heat. An example of a suitable device
includes a
finned tube. The first and second condenser portions 520 and 530 may be sized
in
any proportion. For example, the first condenser portion 520 may be 60% of the
size
of the partitioned condenser 500 and the second condenser portion 530 may be
40%
of the size of the partitioned condenser 500 or the first condenser portion
520 may be
40% of the size of the partitioned condenser 500 and the second condenser
portion
530 may be 60% of the size of the partitioned condenser 500 or the first and
second
condenser portions 520 and 530 may each represent 50% of the size of the
partitioned
condenser 500. When the first and second condenser portions 520 and 530 are
different sizes, e.g., 60%/40% split, the refrigerant flow may be directed in
any
manner that provides efficient condenser 500 operation. For example, the first
condenser portion 520 may constitute 60% of the size of the partitioned
condenser
500 and the second condenser portion 530 may constitute 40% of the partitioned
condenser 500. When desirable, the flow may be directed to either the 60%
portion or
the 40% portion and the designation of the first and second condenser portions
520
and 530 may be alternated to the isolated portion that provides the desired
condenser
500 operation.
[0050] Inlet flow 550 includes vaporous refrigerant from the compressor 130.
Inlet
flow 550 enters the partitioned condenser 500 and travels through the heat
transfer
circuits 510, where the heat transfer circuits 510 can enter into a heat
exchange
relationship with a heat transfer fluid such as air. The partitioned condenser
500
preferably has two condenser portions; however, the present invention is not
limited
to two condenser portions. The present invention may include more than two
condenser portions. Where more than two condenser portions are present, the
flow
may be regulated to each of the portions. For example, in an embodiment where
the
19
CA 02550277 2006-09-O1
Attorney Docket No.: ~. . l4-0045-O1
condenser is split into three portions, two of the three portions include
valve
arrangements that allow independent isolation of each of these portions. One
or both
of the two portions with valve arrangements may be isolated, dependent on a
signal
from a controller and/or sensor. In FIG. 5, isolation valves 540 are
positioned in the
vapor header 590 and liquid header 592 of the partitioned condenser 500. When
isolation valves 540 are closed, the refrigerant is prevented from flowing
into the
second condenser portion 530. When isolation valves 540 are open, refrigerant
is
permitted to flow to both the first condenser portion 520 and the second
condenser
portion 530. The outlet flow 560 leaving the partitioned condenser 500
comprises
liquid refrigerant resulting from the heat exchange relationship with the heat
transfer
fluid and the resultant phase change. The outlet flow 560 is then circulated
to the
partitioned evaporator 200.
[0051] FIG. 6 illustrates a partitioned condenser 500 according to an
alternate
embodiment of the invention. Partitioned condenser 500 includes a plurality of
heat
transfer circuits 510. The heat transfer circuits 510 are partitioned into a
first
condenser portion 520 and a second condenser portion 530. Although FIG. 6
shows
two condenser portions, the present invention is not limited to two condenser
portions.
The present invention may include more than two condenser portions. Inlet flow
550
is vaporous refi-igerant from the compressor 130 that is split into two
refrigerant
streams. The two refrigerant streams enter the partitioned condenser 500
through two
vapor headers 593 and 594 and travel into the heat transfer circuits 510. Heat
transfer
circuits S 10 can enter into a heat exchange relationship with a heat transfer
fluid such
as air. The two refrigerant streams then exit the partitioned condenser 500
through
two liquid headers 595 and 596. Isolation valves 540 are positioned on the
piping to
the vapor header 594 and on the piping from the liquid header 596 of the
partitioned
condenser 500. When isolation valves 540 are closed, the refrigerant is
prevented
from flowing into the second condenser portion 530. When isolation valves 540
are
open, refrigerant is permitted to flow to both the first condenser portion 520
and the
second condenser portion 530. The outlet flow 560 leaving the partitioned
condenser
500 includes liquid refrigerant that is circulated to the partitioned
evaporator 200.
CA 02550277 2006-09-O1
Attorney Docket No.: ~ t4-0045-O1
[0052] The system for controlling the refrigerant pressure of an air
conditioning or
heat pump unit according to the present invention includes an HVAC unit that
can
operate at lower ambient temperatures. The present invention involves a piping
arrangement that partitions the circuits within the condenser of a
refrigeration system.
The piping arrangement includes valves positioned so that one or more of the
circuits
within the condenser may be isolated from flow of refrigerant. The piping
arrangement may be applied to a new system or may be applied to an existing
system.
Applying the piping arrangement to the existing system has the advantage that
it
allows control of the refrigerant pressure without the addition of expensive
piping,
equipment and/or controls.
[0053] When the temperature around the partitioned condenser 500 decreases
(e.g.,
when the outdoor temperature decreases), the system refrigerant pressure also
decreases. To help increase refrigerant head pressure, the present invention
uses the
valves connected to the refrigerant circuits 510 of the partitioned condenser
500 to
isolate a portion of the partitioned condenser 500 from flow of refrigerant.
The
portion of the partitioned condenser 500 that is not isolated remains in the
active
circuit and receives refrigerant. Because the refrigerant is only permitted to
flow into
a portion of the partitioned condenser 500, the heat transfer area and the
corresponding amount of heat transfer is reduced. Therefore, less heat is
removed
from the refrigerant. Likewise, less heat is transferred to the first heat
transfer fluid
150, thereby maintaining a higher refrigerant temperature. Additionally,
because the
temperature of the refrigerant is higher, the corresponding pressure of the
refrigerant
is also higher. Therefore, the refrigerant pressure of the system is
increased.
[0054] The piping arrangement of the partitioned condenser 500 of the present
invention includes piping sufficient to isolate the one or more heat transfer
circuits
510 within the condenser. In one embodiment, the isolation valves 540 are
positioned
inside the vapor header 590 of the partitioned condenser 500. In an alternate
embodiment, the isolation valves 540 are positioned on piping upstream from
the
vapor headers 594 of the partitioned condenser 500.
21
CA 02550277 2006-09-O1
Attorney Docket No.: _ 14-0045-O1
[0055] The lack of additional piping for both the partitioned evaporator 200
and the
partitioned condenser S00 also allows retrofitting of the system of the
present
invention into existing systems. Because the system utilizes the same
components as
existing systems, the system takes up approximately the same volume as
existing
HVAC systems. Therefore, the method and system of the present invention may be
used in existing systems whose piping is arranged according to the present
invention.
[0056] FIG. 7 shows a refrigeration system 100 incorporating a partitioned
evaporator
200 and a partitioned condenser 500 according to the present invention. FIG. 7
shows
the refrigeration system 100, including evaporator discharge line 145, blower
160,
compressor 130, compressor discharge line 135, partitioned condenser 500, fan
170,
condenser discharge line 140, and first heat transfer fluid 150, substantially
as
described above in the description of FIG. 1. FIG. 7 also shows the
partitioned
evaporator 200, including first and second TXV valves 260 and 265, isolation
valve
250, check valve 255, first and second distributors 240 and 245, first and
second
discharge headers 270 and 275, arranged as discussed above in the description
of FIG.
2. For illustration purposes, FIGS. 7-10 divides second heat transfer fluid
155 flow
into an inlet flow 710 and an outlet flow 715. The inlet flow 710, preferably
air,
flows into the partitioned evaporator 200 substantially evenly across the
first and
second evaporator portions 220 and 230. Blower 160 moves inlet flow 710.
Although FIG. 7 depicts a blower, any fluid moving means is suitable for
moving the
fluid across the first and second evaporator portions 220 and 230. The heat
transfer
fluid enters into a heat exchange relationship with the first and second
evaporator
portions 220 and 230 and exits the partitioned evaporator as outlet flow 715.
During
cooling mode, refrigerant is circulated from the partitioned condenser 500 to
the
partitioned evaporator 200, through the first and second evaporator portions
220 and
230 and to the compressor 130 through evaporator discharge line 145. The inlet
flow
710 of heat transfer fluid is cooled by both the first and second evaporator
portions
220 and 230, providing outlet flow 715 of heat transfer fluid that has been
cooled.
During dehumidification mode, isolation valve 250 is closed, preventing flow
of
refrigerant into the first evaporator portion 220. The inlet flow 710 is
cooled and
dehumidified by the second evaporator portion 230 and is substantially
untreated by
22
CA 02550277 2006-09-O1
Attorney Docket No.: ~,. . i4-0045-O1
the isolated first evaporator portion 220. The outlet flow 715 is a mixture of
the
cooled, dehumidified air that flowed through the second evaporator portion 230
and
the substantially untreated air that flowed though the first evaporator
portion 220.
The resultant outlet flow 71 S is dehumidified air that is not overcooled.
[0057] The partitioned condenser 500 shown in FIG. 7 is a partitioned
condenser
having two partitions, shown as the first and second condenser portions 520
and 530.
Although FIG. 7 shows two condenser portions, the present invention is not
limited to
two condenser portions. The present invention may include more than two
condenser
portions. The piping to the partitioned condenser S00 includes isolation
valves 540 on
the inlet side and the outlet side of the second condenser portion 530 inside
the
partitioned condenser 500. Closing the isolation valves 540 prevents the flow
of
refrigerant to the second condenser portion 530. The isolation valves 540 may
be
operated by a controller 720. One or more controllers 720 facilitates the
closing of
isolation valves 540. The controller 720 may receive inputs from pressure
measuring
or temperature measuring devices and position the isolation valves 540, e.g.,
open or
closed. When the pressure on the compressor suction line 145 from the
partitioned
evaporator 200 to the compressor 130 reaches a predetermined level, the
isolation
valves 540 can be closed to the second condenser portion 530. Once isolation
valves
540 are closed, the refrigerant is only permitted to flow through the first
condenser
portion 520. Because the refrigerant is only permitted to flow into first
condenser
portion 520, the heat transfer area and the corresponding amount of heat
transfer
occurring in the partitioned condenser 500 is reduced. Therefore, less heat is
removed
from the refrigerant. Likewise, less heat is transferred to the first heat
transfer fluid
150, thereby maintaining a higher refrigerant temperature. Additionally,
because the
temperature of the refrigerant is higher, the corresponding pressure of the
refrigerant
is also higher. Therefore, the refrigerant pressure of the system is
increased.
[0058] FIG. 8 shows a refrigeration system according to an alternate
embodiment.
FIG. 8 includes substantially the same piping arrangement as FIG. 7. In
addition,
FIG. 8 has a line with a drain valve connecting the condenser portion 530 to
the
suction of compressor 130. The refrigerant remaining in the second condenser
23
CA 02550277 2006-09-O1
Attorney Docket No.: ~" i 14-0045-O1
portion 530 after isolation valves 540 are closed may be stored in the second
condenser portion 530 or may be drawn into the refrigeration system 100 by
opening
drain valve 840 and permitting the refrigerant in condenser portion 530 to be
drawn
into the active system. Because the refrigerant from the isolated portion of
the
partitioned condenser 500 adds to the amount of refrigerant per unit volume of
the
refrigeration system 100, the pressure of the. refrigerant in increased.
Therefore, this
addition of refrigerant into the system from the isolated portion of the
partitioned
condenser 500 further assists in raising the system pressure.
[0059] FIG. 9 shows a refrigeration system 100 incorporating a partitioned
evaporator
200 and a partitioned condenser 500 according to the present invention. FIG. 9
shows
the refrigeration system including evaporator discharge line 145, blower 160,
compressor 130, compressor discharge line 135, partitioned condenser 500, fan
170,
condenser discharge line 140, and first heat transfer fluid 150, substantially
as
described above in the description of FIG. 7. In addition, FIG. 9 includes a 3-
way
valve 910 and a discharge line 310. The 3-way valve 910 connects to the first
discharge header 270 of the first evaporator portion 220, to the evaporator
discharge
line 145 and to the compressor discharge line 135. FIG. 9 also shows the
partitioned
evaporator 200 including first and second TXV valves 260 and 265, check valve
255,
first and second distributors 240 and 245, first and second discharge headers
270 and
275, arranged as discussed above in the description of FIG. 3. Heat transfer
fluid flow
710, preferably air, flows into the partitioned evaporator 200 substantially
evenly
across the first and second evaporator portions 220 and 230. A blower 160
moves
heat transfer fluid flow 710. Although, FIG. 9 depicts a blower, any fluid
moving
system is suitable for moving the fluid across the first and second evaporator
portions
220 and 230. The inlet flow 710 enters into a heat exchange relationship with
the first
and second evaporator portions 220 and 230 and exits the partitioned
evaporator as
outlet flow 715. During cooling mode, the refrigerant is circulated from the
partitioned condenser 500 to the partitioned evaporator 200, through the first
and
second evaporator portions 220 and 230 and to the compressor through
evaporator
discharge line 145 and 3-way valve 910. The inlet flow 710 of heat transfer
fluid is
cooled by both the first and second evaporator portions 220 and 230, providing
outlet
24
CA 02550277 2006-09-O1
Attorney Docket No.: ~,. ;14-0045-O 1
flow 715 of heat transfer fluid that has been cooled. During dehumidification
mode,
hot gas refrigerant from the discharge of the compressor flows into the 3-way
valve
910, which is opened to allow flow through the first discharge header
discharge line
310 and into the first discharge header 270 of the first evaporatorportion
220. One or
more controllers 720 facilitate the positioning of 3-way valve 910. The
controller 720
may receive inputs from pressure measuring or temperature measuring devices
and
position the 3-way valve 910. The hot gas refrigerant from the discharge of
the
compressor 130 enters the refrigerant circuits 210 of the first evaporator
portion 220
and at least partially condenses to a liquid. The condensing refrigerant heats
the first
evaporator portion 220 and warms the inlet flow 710 to produce a higher
temperature
outlet flow 715. The refrigerant, which is at least partially condensed,
travels through
the check valve 255 and combines with line 140 into the second evaporator
portion
230. The inlet flow 710 of heat transfer fluid is cooled and dehumidified by
the
second evaporator portion 230 and is heated by the isolated first evaporator
portion 220, as the refrigerant gas is at least partially condensed. The
outlet flow 715
is a mixture of the cooled, dehumidified air that flowed through the second
evaporator
portion 230 and the heated air that flowed though the first evaporator portion
220. To
summarize, the resultant outlet flow 715 is dehumidified air that is not
overcooled. In
cooling mode, first evaporator portion 220 and second evaporator portion 230
of
partitioned evaporator 200, act as evaporators. However, in dehumidification
mode,
first evaporator portion 220 acts as a condenser, while second evaporator
portion 230
acts as an evaporator. The partitioned condenser 500 shown in FIG. 9 operates
substantially as described above in the discussion of FIG. 7.
[0060) FIG. 10 shows a refrigeration system 100 incorporating a partitioned
evaporator 200 according to the present invention. FIG. 10 further shows the
refrigeration system 100 including evaporator discharge line 145, blower 160,
compressor 130, compressor discharge line 135, partitioned condenser 500, fan
170,
condenser discharge line 140, and first heat transfer fluid 150, substantially
as
described above in the description of FIG. 7. In addition, FIG. 10 includes
one or
both of a bypass valve 440, and a flow restriction valve 430 on bypass line
410.
Bypass line 410 connects the compressor discharge line 135 of the compressor
130 to
CA 02550277 2006-09-O1
Attorney Docket No.: ~ _ i 4-0045-O 1
the inlet of the first evaporator portion 220 between the first TXV valve 260
and the
first distributor 240. One or more controllers 720 facilitate the positioning
of isolation
valves 540 and of the bypass valve 440. The controller 720 may receive inputs
from
pressure measuring or temperature measuring devices and position the isolation
valves 540 and bypass valve 440, e.g., open or closed: FIG. 10 shows the
partitioned
evaporator 200, including first and second TXV valves 260 and 265, isolation
valve
250, first and second distributors 240 and 245, and first and second discharge
headers
270 and 275, arranged as discussed above in the description of FIG. 4. Inlet
flow 710,
preferably air, flows into the partitioned evaporator 200 substantially evenly
across
the first and second portions 220 and 230. The inlet flow 710 enters into a
heat
exchange relationship with the first and second evaporator portions 220 and
230 and
exits the partitioned evaporator as outlet flow 715. During cooling mode, the
refrigerant is circulated from the partitioned condenser 500 to the
partitioned
evaporator 200, through the first and second evaporator portions 220 and 230
and to
the compressor 130 through evaporator discharge line 145. The bypass valve 440
and
the flow restriction valve 430 are set to prevent flow of refrigerant through
the bypass
line 410. The inlet flow 710 of heat transfer fluid is cooled by both the
first and
second evaporator portions 220 and 230, providing outlet flow 715 of heat
transfer
fluid that has been cooled. During dehumidification mode, isolation valve 250
is
closed, preventing flow of refrigerant into the first evaporator portion 220.
The
bypass valve 440 is opened and the flow restriction valve 430 is set to allow
flow of
refrigerant. Although FIG. 10 is shown with both a bypass valve 440 and a flow
restriction valve 430, either the bypass valve 440 or flow restriction valve
430 may be
removed from the bypass line 410, so long as the flow of the refrigerant may
be
stopped during cooling mode and permitted during dehumidification mode. Hot
gas
refrigerant from the discharge of the compressor 130 is then allowed to flow
from the
compressor discharge line 135 through the bypass line 410 into the first
distributor
240 and the first evaporator portion 220. The hot gas refrigerant from the
discharge
of the compressor 130 heats the first evaporator portion 220 and combines with
the
outlet flow from the second evaporator portion 230 into the evaporator
discharge line
145. The inlet flow 710 of heat transfer fluid is cooled and dehumidified by
the
26
CA 02550277 2006-09-O1
Attorney Docket No.: ~_ ~4-0045-O1
second evaporator portion 230 and is heated by the hot gas from the discharge
of the
compressor in the isolated first evaporator portion 220. The outlet flow 715
is a
mixture of the cooled, dehumidified air that flowed through the second
evaporator
portion 230 and the heated air that flowed though the first evaporator portion
220.
The resultant outlet flow 71 S is dehumidified air that is not overcooled. The
partitioned condenser S00 shown in FIG. 10 operates substantially as described
above
in the discussion of FIG. 7.
[0061] FIG. 11 illustrates a flow chart detailing a method of the present
invention
relating to head pressure control in a HVAC system for use with the systems
shown in
FIGS. 7-10. The method includes a determination of the minimum system head
pressure, Pf, at step 1101. The minimum head pressure is set to the desired
operating
pressure of the refrigeration system 100. The minimum head pressure is
preferably
greater than the pressure corresponding to temperature of evaporator icing.
Evaporator icing may occur when the surface temperature of the evaporator and
suction piping is less than 32°F. Pf is preferably the system high side
pressure that
results in saturated suction temperatures above freezing under most load
conditions.
For R22 refrigerant, a typical value of Pf is 180 psig. Subsequent to
determining the
minimum system head pressure, Pf, the actual system head pressure, Pm, is
measured
at step 1103. Any suitable pressure measurement method can be used for
determining
Pm. Preferably, the measurement takes place on a line between the TXV valve
265
and the compressor 130. Subsequent to the measurement taken at step 1103, a
determination of whether the measured refrigerant pressure is less than the
minimum
system head pressure, Pf, at step 1105. If the measured pressure of the
refrigerant,
Pm, is less than the pressure for evaporator freezing, which corresponds to
Pf, (i.e.,
"YES" on the flowchart show in FIG. 11), isolation valves) 540 are closed and
refrigerant flow is blocked to one or more of the refrigerant circuits inside
of the
partitioned condenser 500 in step 1107. If the measured pressure of the
refrigerant,
Pm, is greater than the minimum system head pressure, Pf, (i.e., "NO" on the
flowchart shown in FIG. 11), a determination of whether the measure head
pressure,
Pm, is less than the system reset pressure, Pr as shown in step 1110. If the
measured
pressure, Pm, is greater than the system reset Pressure, Pr, (i.e., "YES" on
the
27
CA 02550277 2006-09-O1
Attorney Docket No.: io ;14-0045-O1
flowchart shown in FIG. 11 ), the isolation valves 540, if closed, will be
opened. If the
measured pressure, Pm, is less than the system reset pressure, Pr, (i.e. "NO"
on the
flowchart shown in FIG. 11), then no action will be taken regarding the
isolation
valves 540. If open, the isolation valves 540 will remain open. If closed, the
isolation
valves 540 will remain closed. The value Pr-Pf represents a pressure buffer
for the
system so that the isolation valves 540 will not be inclined to open and close
rapidly.
The opening of the isolation valves 540 in step 1109 allows refrigerant to
flow to all
refrigerant circuits within the condenser. When the refrigerant flows through
all the
refrigerant circuits 510 of the condenser, the heat transfer to the first heat
transfer
fluid 150 from the refrigerant is at a maximum. If the isolation valves 540
are closed
in step 1107, the refrigerant is only permitted to flow through a portion of
the
partitioned condenser 500. Each portion has a predetermined heat transfer
surface
area. Because the refrigerant is only permitted to flow into a portion of the
condenser
and some portions are isolated, the heat transfer area and the corresponding
amount of
heat transfer is reduced. Therefore, less heat is removed from the
refrigerant.
Likewise, less heat is transferred to the first heat transfer fluid 150,
thereby
maintaining a higher refrigerant temperature. Additionally, because the
temperature
of the refrigerant is higher, the corresponding pressure of the refrigerant is
also
higher. Therefore, the refrigerant pressure of the system is increased.
[0062] In the HVAC system according to the present invention, when the head
pressure in the suction line 145 to the compressor 130 decreases, the
temperature of
the refrigerant in the evaporator 110 likewise decreases. When the head
pressure has
decreased to a certain level, the partitioned evaporator 200 operates at
temperatures
that may result in icing of the partitioned evaporator 200. Icing is a
condition when
the temperature at the exterior of the refrigerant circuits of the evaporator
is
sufficiently low to freeze water present in the heat transfer fluid. In
particular, in a
residential system, the heat transfer fluid is typically air and the water
that freezes is
humidity present in the air. The ice formed by the water frozen on the surface
of the
refrigerant circuits eventually prevents the proper operation of the HVAC
system by
inhibiting heat transfer and/or damaging system components. This icing
generally
begins at refrigerant saturated suction temperatures from about 25°F to
about 32°F.
28
CA 02550277 2006-09-O1
Attorney Docket No.: 2~ ~ 14-0045-O1
In order to prevent the freezing of the evaporator, the pressure in the
suction line 145
is preferably maintained above the temperature that corresponds to the
freezing point
of the partitioned evaporator 200.
(0063] In one method according to the invention, the pressure of the
refrigerant is
measured and compared to a predetermined pressure. The pressure measurement
may
be taken from any point in the refrigeration system 100. However, the
preferred point
of measurement of refrigerant pressure is on the evaporator discharge line 145
to the
compressor. The evaporator discharge line 145 to the compressor also
corresponds to
the outlet of the partitioned evaporator 200. The outlet of the partitioned
evaporator
200 represents a low pressure point in the refrigeration system 100, due to
the phase
change of the refrigerant to a vapor resulting from the heat exchange
relationship
existing between the refrigerant and the second heat transfer fluid 155 in the
partitioned evaporator 200. The predetermined pressure is preferably a
pressure that
is greater than or equal to the pressure that corresponds to a temperature
that results in
icing at the partitioned evaporator 200.
(0064] FIG. 12 shows a control method according to one embodiment of the
present
invention for use with the system shown in FIGS. 7-8. The method includes a
mode
determination step 1210 where the operational mode of the system is determined
or
selected. The operational mode can be provided by the controller and/or user,
where
the mode can either be cooling only or require dehumidification. Examples of
control
systems for determination of the operational mode are described in further
detail
below in the discussion of Figures 15 and 16. The method then includes a
decisional
step 1220 wherein it is determined whether dehumidification is required or
not. If the
determination in step 1220 is "NO" (i.e., no dehumidification required), then
the
method proceeds to opening step 1230 wherein the valve to the first evaporator
portion 220 is opened or remains open in step 1230. The opening of the first
evaporator portion 220 to the flow of refrigerant permits both the first and
second
evaporator portions 220 and 230 to provide cooling to the inlet flow 710. If
the
decisional step 1220 is a "YES" (i.e., dehumidification is required), then the
valve to
the first evaporator portion 220 is closed or remains closed in step 1240. The
closing
29
CA 02550277 2006-09-O1
Attorney Docket No.: ~" ~ 14-0045-O1
of the first evaporator portion 220 to the flow of refrigerant allows the
first evaporator
portion 220 to equilibrate at a temperature substantially equal to the
temperature of
the heat transfer fluid entering the partitioned evaporator 200. After either
the
opening step 1230 or the closing step 1240, the method returns to the
determination
step 1210 and the method repeats.
(0065] Although FIG. 12 shows that the decisional step 1220 provides a "YES"
or
"NO" to steps 1230 or 1240, the method is not limited to an open or closed
isolation
valve 250. A flow-restricting valve may also be used. The use of a flow-
restricting
valve allows the amount of flow into the first evaporator portion 220 to be
varied. For
example, the flow restricting valve may be used in an operational mode that is
open to
full flow, partially restricted flow or closed to flow, depending on the
signal from a
controller. Controller 720, using inputs, such as refrigerant temperature,
heat transfer
fluid temperatures, and humidity readings, provides a signal to the
restricting valve to
determine the amount of refrigerant flow permitted through the isolation valve
250.
[0066] FIG. 13 shows another control method according to the present invention
for
use with the system shown in FIG. 9. The method includes a mode determination
step
1310 where the operational mode of the system is determined. As in the method
shown in FIG. 12, the operational mode can be provided by the controller
and/or user,
where the mode can either be cooling only or dehumidification. Examples of
control
systems for determination of the operational mode are described in further
detail
below in the discussion of FIGS. 15 and 16. The method then includes a
decisional
step 1320 wherein it is determined whether dehumidification is required or
not. If the
determination in step 1320 is "NO" (i.e., no dehumidification required), then
the
method proceeds to step 1330 wherein the 3-way valve 910 is set to provide
refrigerant flow from the discharge line 310 of the evaporator portion 220 to
the
compressor suction line 145. The setting of the 3-way valve 910 allows the
flow of
refrigerant to both the first and second evaporator portions 220 and 230 to
provide
cooling to the inlet flow 710. If the decisional step 1320 is a "YES" (i.e.,
dehumidification is required), then the 3-way valve 910 is set to provide
refrigerant
flow from the discharge of the compressor to the discharge line 310 of the
evaporator
CA 02550277 2006-09-O1
Attorney Docket No.: ~" ~ 14-0045-O1
portion 220. The hot gas refrigerant from the discharge of the compressor 130
flows
into the first evaporator portion 220 and provides heat to the first
evaporator portion
220. The directing of hot gas refrigerant to the first evaporator portion 220
allows the
first evaporator portion 220 to exchange heat with the heat transfer fluid 155
entering
the partitioned evaporator 200. The inlet flow 155 of heat transfer fluid is
cooled and
dehumidified by the second evaporator portion 230 and is heated by heat
exchange
with the hot gas from the discharge of the compressor 130 in the isolated
first
evaporator portion 220. The outlet flow 71 S is a mixture of the cooled,
dehumidified
air that flowed through the second evaporator portion 230 and the heated air
that
flowed though the first evaporator portion 220. The resultant outlet flow 715
is
dehumidified air that is not overcooled. After either the 3-way valve 910
directing
steps 1330 or 1340, the method returns to the determination step 1310 and the
method
repeats.
[0067] Although FIG. 13 shows that the decisional step 1320 provides a "YES"
or
"NO" to steps 1330 or 1340, the method is not limited to an open or closed
isolation
valve 250. A flow restriction valve may also be used. The use of a flow
restriction
valve allows the amount of flow into the first evaporator portion 220 to be
varied. For
example, the flow restriction valve may be used in an operational mode that is
open to
full flow, partially restricted flow or closed to flow, depending on the
signal from
controller 720. Alternatively, the flow into the first evaporator portion 220
from the
discharge of the compressor 130 in dehumidification mode may be varied through
use
of the 3-way valve 910, depending on the signal from a controller. The 3-way
valve
910 may also include flow restriction abilities that allow the flow of
refrigerant to be
varied. A controller, using inputs, such as refrigerant temperature, heat
transfer fluid
temperatures, and humidity readings, provides a signal to the restriction
valve or the
3-way valve 910 to determine the amount of refrigerant flow permitted through
the
isolation valve 250 or the amount of hot gas refrigerant permitted through the
first
evaporator portion 220.
[0068] FIG. 14 shows a control method according to the present invention for
use
with the system shown in FIG. 10. The method includes a mode determination
step
31
CA 02550277 2006-09-O1
Attorney Docket No.: ~,. . ~4-0045-Ol
1410 where the operational mode of the system is determined. As in the method
shown in FIG. 12 and 13, the operational mode can be provided by controller
720
and/or user, where the mode can either be cooling only or dehumidification.
The
method then includes a decisional step 1420 wherein it is determined whether
dehumidification is required or not. If the determination in step 1420 is "NO"
(i.e., no
dehumidification required), then the method proceeds to step 1430 wherein the
valve
250 to the first evaporator portion 220 is opened or remains open. After or
concurrently with step 1430, a bypass line 410 is closed from refrigerant flow
in step
1340. The opening of the first evaporator portion 220 and the closing of the
bypass
line 410 allow the flow of refrigerant to both the first and second evaporator
portions
220 and 230 to provide cooling to the inlet flow 710. If the decisional step
1420 is a
"YES" (i.e., dehumidification is required), then the valve to the first
evaporator
portion 220 is closed or remains closed. After or concurrently with step 1450,
the
bypass line 410 is opened to flow of refrigerant in step 1460. Hot gas
refrigerant from
the discharge of the compressor 130 flows through the bypass 410 and into the
first
evaporator portion 220 and provides heat to the first evaporator portion 220.
The
closing of the first evaporator portion 220 to the flow of refrigerant from
the
condenser 130 and the directing of hot gas refrigerant to the first evaporator
portion
220 allows the first evaporator portion 220 to exchange heat with the
refrigerant
circuits 510 entering the partitioned evaporator 200. The inlet flow 710 of
heat
transfer fluid is cooled and dehumidified by the second evaporator portion 230
and is
heated by heat exchange with the hot gas from the discharge of the compressor
in the
isolated first evaporator portion 220. The outlet flow 71 S is a mixture of
the cooled,
dehumidified air that flowed through the second evaporator portion 230 and the
heated air that flowed though the first evaporator portion 220. The resultant
outlet
flow 715 is dehumidified air that is not overcooled. After either the bypass-
closing
step 1440 or the bypass-opening step 1460, the method returns to the
determination
step 1410 and the method repeats.
[0069] Although FIG. 14 shows that the decisional step 1420 provides a "YES"
or
"NO" to steps 1430 or 1450, the method is not limited to an open or closed
isolation
valve 250. A flow restriction valve may also be used. The use of a flow
restriction
32
CA 02550277 2006-09-O1
Attorney Docket No.: ~_ . r4-0045-Ol
valve allows the amount of flow into the first evaporator portion 220 to be
varied. For
example, the flow restriction valve may be used in an operational mode that is
open to
full flow, partially restricted flow or closed to flow, depending on the
signal from
controller 720. Additionally, the flow through the bypass line 410 may be
varied
through use of the bypass valve 440 and/or flow restriction valve 430,
depending on
the signal from controller 720. Controller 720, using inputs, such as
refrigerant
temperature, heat transfer fluid temperatures, and humidity readings, provides
a signal
to isolation valve 250, bypass valve 440 and flow restriction valve 430 to
determine
the amount of refrigerant flow permitted through the flow restriction valve
430 in
place of isolation valve 250 and the amount of hot gas refrigerant permitted
through
the first evaporator portion 220.
[0070] FIG. 1 S illustrates a control method according to the present
invention that
determines the operation mode of the partitioned evaporator 200. The
determination
of the operational mode is made through the use of controller 720. This
determination
may be used in steps 1210, 1310 and 1410 of FIGS. 12, 13 and 14, respectively.
The
determination takes place by first sensing temperature and/or humidity in an
enclosed
space in step 1 S 10. The temperature and/or humidity measurements are made
for a
controller to determine whether the enclosed space requires cooling or
dehumidification. The inputs from temperature sensors and humidity sensors are
provided to controller 720 in step 1520, where the controller uses the sensed
temperatures and/or humidity to determine the operational mode. In step 1520,
the
controller determines whether cooling is required and whether dehumidification
is
required. In a first decisional step 1530, it is determined whether the
controller has
determined that cooling is required. If the first decisional step 1530
determines
"YES", cooling mode is required, the partitioned evaporator 200 in the
refrigeration
system 100 is set to allow flow into all of the refrigerant circuits 210 in
the partition
evaporator 200 and cool across both the first and second evaporator portions
220 and
230 in step 1540. In addition to cooling, cooling mode also performs
dehumidification. However, in a cooling mode, the second heat transfer fluid
is only
cooled and is not heated to increase the temperature of the second heat
transfer fluid
155 once the second heat transfer fluid 155 travels through the partitioned
evaporator
33
CA 02550277 2006-09-O1
Attorney Docket No.: i~ , i4-0045-O1
200. If the first decisional step 1530 determines "NO", then a second
decisional step
1550 is made. The second decisional step 1550 determines whether the
controller has
determined that dehumidification mode (i.e., dehumidification without
overcooling) is
required. If the second decisional step 1550 determines "YES",
dehumidification
mode is required, the operational mode is set to dehumidification in step
1560. If the
second decisional step 1550 determines "NO", dehumidification mode is not
required,
the operational mode is set to inactive and the system operates neither a
cooling nor a
dehumidification cycle in step 1570.
[0071] FIG. 16 shows an alternate control method according to the present
invention
that determines the operation mode of a multiple refrigerant circuit system.
In the
system controlled in FIG. 16, multiple refrigerant systems 100 are utilized
and one or
more of the refrigerant systems 100 include a partitioned evaporator 200
according to
the invention. The control method shown in FIG. 16 operates in a similar
manner to
FIG. 15 in that the controller receives inputs from temperature and/or
humidity
sensors in step 1610 and determines the operational mode of the system in step
1620.
Likewise, if the first decisional step 1630 determines "NO", then a second
decisional
step 1650 is performed. The second decisional step 1670 determines whether the
controller has determined that a dehumidification mode (i.e., dehumidification
without overcooling) is required. If the second decisional step 1670
determines
"YES", dehumidification mode is required, the operational mode is set to
dehumidification in step 1680. If multiple refrigerant systems 100 are
present, the
controller 720 independently determines which of the refrigerant systems 100
are
active or inactive, based upon temperature and/or humidity measurements. When
multiple refrigeration systems 100 are present, at least one refrigerant
system 100
includes a partitioned evaporator 200. The controller 720 independently
determines
which partitioned evaporator 200 is subject to isolation of the first
evaporator portion
220, based upon temperature and/or humidity measurements. However, if the
second
decisional step 1670 determines "NO", dehumidification is not required, the
operational mode is set to inactive and the system operates neither a cooling
nor a
dehumidification cycle in step 1690. If the first decisional step 1630
determines
"YES", cooling is required, a third decisional step 1640 is performed. In the
third
34
CA 02550277 2006-09-O1
Attorney Docket No.: ~. . i4-0045-Ol
decisional step 1640, a determination is made as to the number of stages to be
activated in order to provide the cooling. Each stage has an evaporator
capable of
providing cooling to the second heat transfer fluid 155. The greater the
number of
stages activated, the greater the amount of cooling provided. At least one of
the
multiple refrigerant circuits includes a partitioned evaporator 200. If the
controller
determines that the cooling demand only requires one refrigerant system 100 to
be
active, one refrigerant system 100 will be used to cool second heat transfer
fluid 155
in step 1650. When the partitioned evaporator 200 is used to operate in
cooling mode,
the partitioned evaporator 200 is configured to allow flow into all of the
refrigerant
circuits 210 in the partition evaporator 200 and cool across both the first
and second
evaporator portions 220 and 230 in step 1660. If multiple partitioned
evaporators 200
are present, all of the refrigerant circuits 210 in each of the partition
evaporators 200
allow flow of refrigerant into both the first and second evaporator portions
220 and
230 and cool the second heat transfer fluid 155.
[0072] The present invention is not limited to the control methods shown in
FIGS. 11-
16. The partitioned evaporator 200 and the partitioned condenser S00 may be
used in
one or more refrigerant circuits of multiple refrigerant circuit systems,
where the
control of the repeating capabilities within the first evaporator portion 220
of the
partitioned evaporator 200 and the head pressure control within the first
condenser
portion 520 may each be independently controlled to provide the desired
temperature
and/or humidity within the conditioned space and the desired refrigerant
pressure
within the system. Any combination of cooling, repeating, or modulation of
combinations of cooling and repeating may be used with the present invention.
In
addition, operational modes controlling the refrigerant pressure may be used
in
conjunction with the cooling and dehumidification modes of operation.
[0073] While the invention has been described with reference to a preferred
embodiment, it will be understood by those skilled in the art that various
changes may
be made and equivalents may be substituted for elements thereof without
departing
from the scope of the invention. In addition, many modifications may be made
to
adapt a particular situation or material to the teachings of the invention
without
CA 02550277 2006-09-O1
Attorney Docket No.: L_ . i4-0045-O1
departing from the essential scope thereof. Therefore, it is intended that the
invention
not be limited to the particular embodiment disclosed as the best mode
contemplated
for carrying out this invention, but that the invention will include all
embodiments
falling within the scope of the appended claims.
36
