Note: Descriptions are shown in the official language in which they were submitted.
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HEATER WITH RECIRCULATION AIR CONTROL MEANS
FIELD OF THE INVENTION
The present invention relates to a heater and in particular to a portable and
flameless air
heater.
BACKGROUND OF THE INVENTION
Remote industrial locations are often subject to extreme cold temperatures.
Heaters used
in such locations typically involve the burning of a fuel such as propane,
diesel or
kerosene in an open-flame boiler to provide heat input for a glycol heat
exchange system.
Such heating systems, however, result in the production of noxious fumes and
contaminating residual particulates. The use of an open flame also presents a
safety risk
in fire-hazardous areas such as fuel tank farms or gas compressor sites. In
addition, a
boiler-based system is often not portable, therefore, can only provide heat
within a
limited area.
Heaters based on the generation of heat by frictional means do not use an open
flame,
therefore, overcome the disadvantages of open-flame heater systems as
described above.
The frictional heaters currently available, however, are not suitable for use
as air heaters
in remote cold weather industrial applications. For example, US Patent No.
4,256,085
discloses a friction heater in which a heat exchanger imparts heat values to
liquid in a
heat transfer tank. The heater may be adapted to use a forced air system as
the method of
transfer of heat values from the exchanger, however, an enclosed air heating
system is not
provided such that it would be difficult to achieve air output of sufficiently
high
temperatures. While US Patent No. 4,312,322 does teach an enclosed air heating
system,
i
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it provides heated air batchwise, therefore, does not provide a continuous
source of
heated air. In addition, these and other frictional heaters, are generally
designed to be
operated by electrical power and so cannot be used in remote locations that
lack a source
of electricity. While it is possible to adapt such heaters for operation by a
fuel powered
engine, there are no means for removing exhaust and other fumes from the
output air.
Accordingly, there is a need in the art for a heater which is portable,
flameless, and
provides a continuous supply of pollution-free air of sufficiently high
temperatures for
use in cold weather industrial applications and for drying and curing
operations.
SUMMARY OF THE INVENTION
The present invention provides a portable and flameless heat-generating
device. The
device has a recycle system that permits the temperature of the air to be
driven up to
higher temperatures while providing a continuous flow of heated air. The
device can
produce a flow of substantially fume-free and particulate-free air. In one
embodiment,
the device also is capable of using the engine exhaust to further heat the
air, thereby
providing a more efficient heating system.
In accordance with one aspect of the present invention, there is provided a
heater for
heating a fluid including an enclosure having a fluid inlet and a fluid
outlet, a
heat-generating device for generating heat within the enclosure, a conduit
with one end
proximally located to the inlet and the other end proximally located to the
outlet for
conducting fluid from the outlet to the inlet, a fluid driving means for
drawing fluid into
the enclosure through the inlet and through the conduit and for forcing air
over the heat-
generating device; and a shutter that regulates the amount of fluid entering
the enclosure
through the inlet such that the amount of fluid passing through the inlet can
be controlled
to adjust the amount of fluid drawn from the conduit.
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BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1. is a sectional view along the length of a heater according to the
present invention.
Fig. 2 is a perspective view of a heater according to the present invention
with a side, an
end and the top removed to facilitate illustration.
Fig. 3 is a perspective view of a housing useful in a heater according to the
present
invention. A portion of an end and a side has been removed to facilitate
illustration.
Fig. 4 is a perspective view of a heater according to the present invention
showing air
flow patterns. A portion of an end and a side has been removed to facilitate
illustration.
Fig. 5 is a perspective view of an air flow control system useful in a heater
according to
the present invention.
Fig. 6 is an end view of the air flow control system shown in figure 5 with
the front
shutter removed.
Fig. 7 is a perspective view of an exhaust heat exchange unit useful in a
heater according
to the present invention.
Fig. 8 is a section along line 8 - 8 of Figure 7.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to Fig. 1, a heater according to one embodiment of the present
invention is
shown. The heater includes a heat generating device 2 and a fan 4 that are
contained
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within an enclosure 6. The enclosure has an air inlet 8 in front of the fan,
an opposing air
outlet 10 behind the heat generating device, and an air conduit 12 with one
end located
proximate the inlet and another end located proximate the outlet.
In operation, the fan continuously draws air into the enclosure from the inlet
and/or from
the conduit, then forces the air over the heating device. A shutter 14
controls the amount
of fresh air that is drawn from the inlet and, thereby, the amount of heated
air that exits
the enclosure from the outlet. As the shutter reduces the fresh air supply,
the fan draws
an increased amount of air from the conduit. This causes a greater amount of
air to be
recycled through the enclosure and conduit and less air to exit the enclosure
through the
outlet. This results in recirculation and further heating of air that has
already been passed
over the heat generating device such that increasingly higher air temperatures
are
achieved. A continuous output of heated air is provided by controlling the
shutter so as
to provide for both airflow out through outlet 10 and through air conduit 12
for air
recirculation.
The preferred embodiment of the present invention is shown in Figs. 2-7.
Referring to
Fig. 2, a fuel-powered engine 16 such as a diesel automobile engine provides
power to a
disc friction heater 18. The disc heater is of the type disclosed in US Patent
No.
4,256,085. In particular, the disc heater, in general, includes a rotatable
impellar within a
disc-shaped closed housing. The housing contains a heat transfer liquid. In
the present
invention, oil is used as the heat transfer liquid since this also acts to
lubricate the disc
and housing components such as bearing and rubber seals. It is preferable to
use an oil
such as Dextron IIITM that can sustain high temperatures and that contains an
antifoaming
agent.
In the present invention, the impeller is attached to a rotatable spline shaft
projecting
from the back of the engine. Rotation of the impeller by the spline shaft
during engine
operation generates heat as well as pressure within the system such that
circulation of the
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CA 02297715 2003-12-16
oil is readily effected through a closed conduit circuit to an oil to air heat
exchanger 20.
The closed conduit circuit includes a supply line 22 and a return line 24.
Heated oil from
the disc heater is passed to exchanger 20 through supply line 22 connected at
the bottom
of the exchanger. As air flows across the exchanger heat is transferred from
the oil to the
5 air. The oil travels upwards through the exchanger and exits into return
line 24 attached
to the top of the exchanger. The oil then passes through an oil filter 26 to
an oil holding
tank 28 where it is stored for re-use. Oil enters the disc unit from the
holding tank by
gravity feed through two inlets 30. All seals, lines and components of the
disc heater and
exchanger must be selected to accommodate elevated temperatures and pressures.
The
exchanger can, for example, have the structure of a standard automobile
radiator.
Airflow across the exchanger is generated by a fan 32. The fan is located on
the front of
and is driven by the engine. In a preferred embodiment, a ten blade, severe
pitch fan is
used that permits movement of very large air volumes. In one embodiment, a fan
capable
of moving 5,000 to 6,000 cubic feet of air per minute is used.
Preferably, fan 32 operates continuously when disc heater system is operating.
This
provides for more even and faster heating of air over a system using stagnant
air heating.
Referring to Figs. 2 and 3, the heater is constructed by placing the engine
and the disc
heater system described above on a skid 34. The skid is formed to define a
chamber that
can be used to act as a fuel tank 36 for supplying fuel such as, for example,
diesel to the
engine. A fuel spout 37 opens into tank 36.
Skid 34 also carries a front wall 38 and a back wall 40 between which is
formed an
engine chamber. Engine 16 is secured onto the skid by bolting onto mounting
platforms
42 on top of the fuel tank. An opening 44 on the front wall is provided in
front of the fan
and the heat exchanger is located over an opening 46 provided on the back
wall. A side
door (not shown) permits access to the engine control panel 48 which includes
a switch
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for starting and stopping the engine, throttles etc. The engine can be
controlled manually
or automatically, for example by computer or PLC control, as desired. The rpm
of the
engine can be controlled to control the rpm of the disc friction heater and
the rpm of the
fan.
The side door is normally closed so that air, driven by fan 32, passes through
the
enclosure by entering through opening 44 and exiting through opening 46. Heat
exchanger 20 is positioned relative to opening 46 so that all air passing
therethrough must
pass through the exchanger.
The skid is removably placed within an enclosure 49. The skid is centrally
located in the
enclosure. Referring to Figure 3, preferably sealing walls 50, 52, having
deformable
outer limits, extend between the top and sides of the skid and the walls of
enclosure 49 to
provide a seal therebetween. Walls 50, 52 can be carried by the skid or by the
enclosure.
Between the enclosure and wall 38 is formed a front air chamber 54 and between
enclosure 49 and wall 40 is formed a back air chamber 56. Walls 50 prevent
communication between the front air chamber and the engine chamber, defined
between
walls 38 and 40, except through opening 44. Walls 50 also prevent
communication
between back air chamber 56 and the engine chamber except through opening 46.
Walls
52 form two air channels 58 between the skid and the enclosure that are openly
disposed
to the front and back chambers. Communication between front air chamber 54 and
back
air chamber 56 is effected through opening 44, the engine chamber and opening
46 and
also through channels 58.
The use of a skid allows the interior heater components to be assembled
outside of the
skid and then mounted therein. However, other constructions that provide for
an air
channel between the front and back openings to the inner chamber may
alternately be
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used. In one embodiment, the skid and walls 38, 40 are connected to the walls
of the
enclosure. In such an embodiment, skid is not removable from the enclosure.
The heater is made easily transportable by providing wheels or skis on the
enclosure.
Alternatively, the heater may be transported on a trailer.
The airflow in the heater construction described above is illustrated in Fig.
4. The fan,
when operating, continuously draws air into the engine chamber between front
and back
walls 38, 40 from front chamber 54 through the front opening 44. Air is drawn
into the
front chamber through an inlet 60. The air drawn by the fan is heated by being
forced
through heat exchanger 20 out opening 46 and into back chamber 56. The heated
air in
the back chamber may then exit through an enclosure outlet 62 or recirculate
to the front
chamber through channels 58, as will be described in more detail hereinafter.
To enhance the recirculation of air, a shutter 66 is located over enclosure
inlet 60 and
flaps 68 are located over the front opening of each of channels 58. The
shutter is attached
by brackets 69 to the front wall of the skid and projects forward from the
skid to fit
sealingly into enclosure inlet 60. This shutter mounting arrangement
facilitates electrical
connection between the shutter and the skid, as the shutter moves with the
skid. Other
shutter mounting arrangements are within the scope of the invention.
Flaps 68 are pivotally attached to the skid and are pivotable between a closed
position
sealing the channels and an open position. Recirculation of heated air is
achieved by
opening the flaps so as to permit air to flow through the channels from the
back chamber
to the front chamber while closing the shutter so as limit the amount of fresh
air entering
the enclosure through inlet 60. Since the fan continues to draw a steady
amount of air,
reducing the amount of air drawn from the outside will increase the amount of
air drawn
from back air chamber 56 through channels 58. This will reduce the amount of
air
exiting the enclosure. Since this mode of operation passes much of the air
repeatedly
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across the heat exchanger, higher air temperatures can be achieved than with a
continuous
flow of fresh air through the heater. Once the desired temperature is reached,
as
measured by a temperature sensor 70 in the back air chamber, air can be forced
out of the
enclosure by opening the shutter and closing the flaps. Alternately, to
maintain a
continuous flow of heated air out of the enclosure, shutter 66 can remain
partially open so
as to allow some recirculation of the heated air while some air exits the
enclosure.
While the shutter and flaps can be controlled manually, referring to Figs. 5
and 6, the
shutter and flaps are preferably operated by a set of electronic controllers
72, 74 in
communication with temperature sensor 70. Temperature sensor 70 is positioned
in back
air chamber 56 and is set, as is known, to a selected temperature. Sensor 70
communicates with controller 72 by a line 75a and controller 72 communicates
with
controller 74 through line 75b. Sensor 70 and controller 72 can be any
commercially
available high temperature thermostat. Controller 74 is a shutter controller
such as, for
example, a BellimoT"~ actuator model no. AF24-SR95. Control arm 76 extends
from
controller 74 to drive rotation of the louvers of shutter 66. Another control
arm 77
extends to drive the opening and closing of flaps 68.
The flaps and the shutters can be driven to open and close in any desired way.
Preferably, control arm 76 is pivotally connected to the louvers of shutter in
a
conventional way to drive the louvers to rotate in unison. In the illustrated
embodiment,
flaps 68 are opened and closed by a drive mechanism including a rotatable
plate 78 and a
pair of rod arms 79 extending between the plate and the flaps. Control arm 77
is
pivotally connected at connection 80 to plate 78 such that movement of arm 77
causes
rotation of the plate, as shown by the arrow. The rod arms 79 are also
pivotally
connected to plate 78 such that any rotation of the plate causes the rod arms
to be driven
outwardly or inwardly to pivot flaps to cover or open, respectively, channels
58. As an
example, referring to Figure 6, driving plate 78 in a clockwise direction will
close flaps
68 over the openings of channels 58.
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Generally, controller 74 will function to ensure that shutter 66 is partially
closed (1/2"
gaps between louvers) when flaps 68 are open. When a selected temperature is
reached,
as determined by controller 72 and temperature sensor 70, controller 74 will
open the
shutters and close the flaps. It will be understood that flaps 68 need not be
included to
obtain some amount of recycling. However, the flaps, when closed, prevent air
from
passing through channels 58, thus, maximizing the output of heated air. While
not as
useful as a heater providing a continuous flow of heated air, the heater can
be used in a
batch mode by closing shutter 66 entirely. Operating the fan during batch mode
heating
ensures that even and faster heating occurs over a stagnant air system.
The engine is preferably located in the engine chamber and, as such, also acts
as a heat
source. Air is heated as it passes over the engine and across the engine
radiator 81
located adjacent the front skid opening 60. An additional source of heat is
preferably
provided by an engine exhaust heat exchanger system, as illustrated in Figs. 7
and 8. A
front exchanger 82 and a back exchanger 84 in communication with the engine
and
positioned such that air passing through the heater will pass therethrough. In
particular,
the front exchanger is positioned in front air chamber 54 over opening 44 and
back
exchanger 84 is positioned in the engine chamber over opening 46. The
exchangers are
positioned over the wall openings such that air flowing into the skid is
heated by the front
exchanger and air flowing into the back chamber is heated by the back
exchanger.
Exhaust flows from the engine, shown schematically at 16a, through a feed pipe
86 into
the back exchanger. After passing through the back exchanger, the exhaust
gases are
then conveyed through a cross pipe 88 into front exchanger 82 before being
ducted away
from the enclosure through pipe 92. In use, the end having enclosure outlet 62
will be
positioned in an area requiring an input of heated air while the end having
inlet 60 therein
will be open to the unheated surroundings. Therefore, pipe 92 preferably opens
outside
the enclosure on inlet 60 end.
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Exchangers 82, 84 are each formed by two main pipes 82a, 84a interconnected by
a series
of cross pipes 82b, 84b. In back exchanger 84, both vertical pipes include
caps 84c at
their bottom ends thereby forcing the exhaust through the cross pipes 84b and
upwards
5 through cross pipe 88. In front exchanger, a stop plate 90 is positioned
midway down the
first vertical pipe to force exhaust through the horizontal pipes above the
plate to the
second vertical pipe. Caps 82c at the top and bottom of that pipe forces
exhaust
downward and across the cross pipes 82b below the plate. The exhaust then
flows down
the lower section of the first pipe and out of the enclosure through pipe 92
where the
10 exhaust is directed away from the working environment. Preferably pipe 92
is distanced
as much as possible from enclosure inlet 60 to avoid exhaust from being drawn
into the
system. To direct the exhaust output to a location away from the heater, hoses
such as
ducting hoses may be attached to pipe 92.
To increase the efficiency of heat transfer by the exhaust exchangers,
residence time of
the exhaust in the exchangers is preferably increased. This can be achieved by
creating
backpressure within the system. In one embodiment, cross pipes, for example
82b, are
inserted as far as possible into vertical pipes, for example 82a. In this
embodiment, the
effective opening from the cross pipes 82b to the vertical pipes is reduced in
size over
mounting the cross pipes to open just inside the vertical pipe.
To prevent other fumes generated by the engine, such as engine off gases, from
contaminating the air within the heater, a relay vent (not shown) connecting
the engine
tappet cover to the exhaust system is preferably provided. Off gases are
thereby vented
to the exhaust system rather than being released into the engine chamber.
To maximize heat retention in the heater as well as to reduce noise heard
outside of the
heater, the skid compartment may be insulated with a heat-resistant material
such as foil-
backed foam.
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Numerous modifications, variations and adaptations may be made to the
particular
embodiments of the invention described above without departing from the scope
of the
invention as defined in the claims.
