CA2297715C

CA2297715C - Heater with recirculation air control means

Info

Publication number: CA2297715C
Application number: CA002297715A
Authority: CA
Inventors: Lorne Gordon Norton
Original assignee: ARTIC THERM INTERNATIONAL Ltd
Current assignee: ARTIC THERM INTERNATIONAL Ltd
Priority date: 2000-01-31
Filing date: 2000-01-31
Publication date: 2005-04-12
Anticipated expiration: 2020-01-31
Also published as: CA2480705C; CA2297715A1; CA2480705A1

Abstract

A heater for heating a fluid is taught 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. The heater can generate a continuous flow of heated fluid at extremely high temperatures.

Description

v i;

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 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.

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 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 DMSL.egal\044964\00001\1685991v1 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 DMSLegal\044964\00001 \1685991v 1 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 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 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.

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.

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.

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.

Claims

1. A heater for heating a fluid comprising:
(a) an enclosure including a fluid inlet and a fluid outlet and formed to accommodate a fluid flow therethrough from the inlet to the outlet;
(b) a heat-generating device for generating heat within the enclosure;
(c) a conduit including one end opening proximal to the inlet and an opposite end opening proximal to the outlet, the conduit capable of recirculating therethrough at least some fluid from the outlet to the inlet in a fluid flow reverse from that through the enclosure;
(d) a fluid driving means for moving fluid into the enclosure through the inlet and through the conduit and for forcing the fluid over the heat-generating device; and (e) 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.

2. The heater as defined in claim 1 wherein the heat-generating device is a disc friction heater.

3. The heater as defined in claim 2 wherein the disc friction heater is driven by an engine contained within the enclosure.

4. The heater as defined in claim 3 further comprising an exhaust heat exchange for accepting the engine's exhaust and the exhaust heat exchange positioned such that the fluid moves therethrough when passing through the enclosure.

5. The heater as defined in claim 3 wherein the engine includes a vent to conduct engine off gases away from the engine and out of the enclosure without entering the fluid.

6. The heater as defined in claim 1 wherein the shutter actuation to open or close is controlled by a thermostat.

7. The heater as defined in claim 6 wherein the thermostat is positioned adjacent the outlet.

8. The heater as defined in claim 1 wherein the fluid driving means is a fan.

9. The heater as defined in claim 1 wherein the fluid is air.

10. The heater as defined in claim 1 wherein the conduit includes a gate for regulating the amount of fluid passing therethrough.

11. The heater as defined in claim 1 wherein the heat generating device is removable from the enclosure.

12. The heater as defined in claim 1 wherein the shutter is disposed over the inlet.

13. The heater as defined in claim 1 wherein the enclosure defines an upstream fluid chamber, a fluid heating chamber configured to receive fluid passing from the upstream fluid chamber and a downstream fluid chamber to receive fluid passing from the fluid heating chamber and the conduit is formed to extend between the upstream fluid chamber and the downstream fluid chamber to pass fluid from the downstream fluid chamber to the upstream fluid chamber to pass again through the fluid heating chamber.

14. The heater as defined in claim 1 wherein the enclosure is formed of material and the material of the enclosure defines at least in part the conduit, which extends alongside the enclosure.

15. A heater for heating a fluid comprising:
(a) an enclosure including a fluid inlet and a fluid outlet, the enclosure defining a first conduit between the inlet and the outlet;
(b) a heat-generating device for generating heat within the enclosure;
(c) a recycle conduit including a first end opening proximal to the inlet and an opposite end opening proximal to the outlet to permit recycling of at least some fluid from the outlet back to the inlet;
(d) a fluid driving means for moving fluid into the enclosure through the inlet and through the recycle conduit and for forcing the fluid over the heat-generating device; and (e) 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 recycle conduit.

16. The heater as defined in claim 15 wherein the heat-generating device includes a disc friction heater.

17. The heater as defined in claim 16 wherein the disc friction heater is driven by an engine positioned within the enclosure.

18. The heater as defined in claim 17 further comprising an exhaust heat exchange for accepting the engine's exhaust and the exhaust heat exchange positioned such that the fluid moves therethrough when passing through the enclosure.

19. The heater as defined in claim 16 wherein the engine includes a vent to conduct engine off gases away from the engine and out of the enclosure without entering the fluid.

20. The heater as defined in claim 15 wherein the shutter actuation to open or close is controlled by a thermostat.

21. The heater as defined in claim 20 wherein the thermostat is positioned adjacent the outlet.

22. The heater as defined in claim 15 wherein the fluid driving means includes a fan.

23. The heater as defined in claim 15 wherein the fluid is air.

24. The heater as defined in claim 15 wherein the conduit includes a gate for regulating the amount of fluid passing therethrough.

25. The heater as defined in claim 15 wherein the heat generating device is removable from the enclosure.

26. The heater as defined in claim 15 wherein the shutter is disposed over the inlet.

27. The heater as defined in claim 15 wherein the enclosure defines an upstream fluid chamber, a fluid heating chamber configured to receive fluid passing from the upstream fluid chamber and a downstream fluid chamber to receive fluid passing from the fluid heating chamber and the conduit is formed to extend between the upstream fluid chamber and the downstream fluid chamber to pass fluid from the downstream fluid chamber to the upstream fluid chamber to pass again through the fluid heating chamber.

28. The heater as defined in claim 27 further comprising a thermostat for controlling operation of the shutter, the thermostat positioned to operate based on fluid temperature in the downstream fluid chamber.

29. The heater as defined in claim 15 wherein the enclosure is formed of material and the material of the enclosure defines at least in part the conduit, the conduit extending alongside the enclosure.

30. A heater for heating a fluid comprising:
(a) an enclosure including a fluid inlet and a fluid outlet and the enclosure being formed to accommodate a fluid flow therethrough from the inlet to the outlet;
(b) a heat-generating device for generating heat within the enclosure;
(c) a conduit including a first end opening proximal to the inlet and an opposite end opening proximal to the outlet for conducting fluid from the outlet to the inlet;
(d) a fluid driving means for moving fluid into the enclosure through the inlet and through the conduit and for forcing the fluid over the heat-generating device; and (e) a shutter positioned over the inlet to regulate the amount of fluid entering the enclosure through the inlet and spaced from the first end of the conduit such that fluid passing through the conduit is unobstructed by the shutter.

31. The heater as defined in claim 30 wherein the shutter actuation to open or close is controlled by a thermostat.

32. The heater as defined in claim 31 wherein the thermostat is positioned adjacent the outlet.

33. The heater as defined in claim 30 wherein the fluid driving means includes a fan.

34. The heater as defined in claim 30 wherein the fluid is air.

35. The heater as defined in claim 30 wherein the conduit includes a gate for regulating the amount of fluid passing therethrough.

36. The heater as defined in claim 30 wherein the heat generating device is mounted on a skid and the shutter is mounted on a bracket to extend out from the skid to its position covering the inlet, such that the components of the heat generating device and shutter can be removed from the enclosure with the skid.