US3896632A

US3896632A - Air cycle heating or cooling

Info

Publication number: US3896632A
Application number: US441406A
Authority: US
Inventors: Leslie E Huntley
Original assignee: Individual
Current assignee: Individual
Priority date: 1974-02-11
Filing date: 1974-02-11
Publication date: 1975-07-29
Anticipated expiration: 1992-07-29

Abstract

A method and apparatus for pumping heat utilizes air or other gas as the working fluid wherein a positive displacement compressor and a positive displacement expander are mechanically interlocked, the swept volume per unit time of the compressor relative to the swept volume per unit time of the expander being a function of absolute temperature of the air drawn into the compressor relative to the absolute temperature of the air provided for the expander. A heat exchanger is positioned between and connecting the compressor exhaust and the expander intake to purge heat from the compressed air flowing therethrough, the compressed air being released to ambient pressure through the expander to extract work from the air concurrent with cooling of the air through expansion and apply the extracted work to the compressor through the mechanical interlinking between the expander and the compressor, and means to provide supplemental heat when utilizing the heat pump to provide heat.

Description

United States Patent Huntley July 29, 1975 AIR CYCLE HEATING OR COOLING Primary Examiner-William J. Wye [76] Inventor: Leslie E. Huntley, Rt. 1, PO. Box 7,

Reubens, Idaho 83548 ABSTRACT [22] Filed: Feb. 11, 1974 A method and apparatus for pumping heat utilizes air [2]} Appl. No.: 441,406

or other gas as the working fluid wherein a positive displacement compressor and a positive displacement expander are mechanically interlocked, the swept volume per unit time of the compressor relative to the swept volume per unit time of the expander being a function of absolute temperature of the air drawn into the compressor relative to the absolute temperature of the air provided for the expander. A heat exchanger is positioned between and connecting the compressor exhaust and the expander intake to purge heat from the compressed air flowing therethrough, the compressed air being released to ambient pressure through the expander to extract work from the air concurrent with cooling of the air through expansion and apply the extracted work to the compressor through the mechanical interlinking between the expander and the compressor, and means to provide supplemental heat when utilizing the heat pump to provide heat.

12 Claims, 5 Drawing Figures PATENTEU JUL 2 9 i975 AIR CYCLE HEATING OR COOLING The present invention relates generally to heating- /cooling systems, and more particularly to heat pumping devices using air, gas or other working fluids which are adaptable for selective heating or cooling of a defined enclosed environment.

The desirability of providing air or gas at a temperature either above or below that of ambient temperature has long been recognized. Commonly, the provision of air at a temperature below the ambient temperature is provided by heat pumping wherein the heat extracted from the cooled air is exhausted outside of the enclosed environment. Liquid-vapor systems are commonly utilized to accomplish this. In such systems, the working fluid in vapor form is compressed to form a liquid at a relatively elevated temperature, the heat from the working fluid is transferred to another fluid and conducted outside of the enclosed environment, and the thus cooled liquid is then expanded to a lower pressure thereby providing a vapor at a much lower temperature which, in turn, is warmed through heat exchange with air conducted to the enclosed environment. Obviously, this process is reversible and the heat may be pumped to the interior rather than the exterior of the subject enclosed environment.

Instead of utilizing the conventional closed circuit liquid-vapor working fluid, air may be directly utilized as a working fluid and subjected to a roughly analogous process, i.e., compression to heat the working fluid, heat exchange to cool the compressed working fluid and expansion to lower pressure and temperature. There are certain simplifications, cost savings and safety factors to be gained through the use of air as a working fluid. For instance, the closed systems liquidvapor cycle requires a heat exchange step between the cooled vapor and air provided to the enclosed environment wherein a system utilizing air as the working fluid can directly exhaust the cooled air to the enclosed environment. No toxic working fluids are employed in air cycle apparatus. This provides an obvious safety factor while concurrently minimizing maintenance.

An example of an advanced system utilizing air as the working fluid is to be found in United States letters Patent No. 2,496,602. This patent discloses the use of turbine-type compressors and expanders, the two being linked to extract work from the expansion and apply it to the compressor. However, since the expansion and compression steps are most efficiently conducted in an adiabatic manner, and since the turbines inherently compromise adiabatic compression and expansion, certain drawbacks exist with regard to this prior art system. Also, turbines tend to be inefficient at modest flow rates.

Other prior art references, which are believed to be less pertinent than the above-discussed patent, include United States letters Patent Nos. 1,966,938, 2,586,002, 2,971,343, and 3,623,332.

The present invention which provides heretofore unavailable improvements in efficiency, simplicity and versatility over previous air working fluid heat pumps, comprises a method and device for reversibly providing either heated or cooled air in a simplified and efficient manner. The method and apparatus utilizes positive displacement compressor and expander components, such as piston and cylinder arrangements, vane pumps such as the Roots, or Pappenheim devices, or other similar or analogous positive displacement rotary,

swash plate or reciprocating pumps and motors. After air is brought to an elevated pressure by the compressor and, accordingly, the temperature raised appreciably, the air is conducted through a heat exchanger to withdraw heat therefrom. Because of the relatively elevated-temperature of the compressed air, it is not difficult to maintain the temperature differential necessary for such heat exchange, since even the ambient temperatures will be at a substantially lower temperature than the compressed air. Preferably, the heat exchange is concurrent with exhaust air from the subject enclosed environment providing the lower temperature medium.

After cooling, the compressed air is expanded through the expander which extracts work therefrom. Expansion concurrently induces a marked cooling of the air as it returns to ambient pressure. The expanded working medium then may be exhausted directly into the enclosed environment. Alternatively, as will be discussed below, the heat extracted from the compressed air by heat exchange can be directed into the enclosed environment.

To enhance efficiency, the work extracted by expansion of the compressed air through the expander is mechanically applied to the compressor. This greatly alleviates the necessity for energy to be supplied to the system, although, of course, the work available from the expander is not alone adequate to operate the compresv sor. Accordingly, additional energy is supplied either directly to the compressor, or, as will be described below, through an auxiliary compressor.

In the event heating is desired, the relationship between the compressor and expander may be reversed, i.e., with the gas exhausted through the expander being vented to the exterior and the heat exchange medium to which heat is transferred from the compressed air being directed to the enclosed environment. Since the efficiency of providing heated air, as opposed to cooled air, may be less depending upon the heating range required and thus require a more substantial apparatus, it is often more advantageous to provide additional heat directly into the hot air output rather than to size the apparatus for heating while providing greatly excess capacity for cooling.

Also, heat may be provided while the apparatus is operated in a cooling mode but with the exhaust air being heated substantially beforebeing conducted through the heat exchanger in order that heat is transferred to the compressed" air rather than extracted therefrom. In this situation, upon expansion, the air will not be cooled below the ambient temperature but instead will be warmer than the air introduced into the compressor. This approach has the advantage of having substantial power available through the expander which may be utilized to run auxiliary equipment in addition to the compressor.

Accordingly, an object of the present invention is to provide a new and improved method and apparatus for pumping'heat using air as the working medium with substantially adiabatic compression and expansion.

Another object of the-present invention is to provide a new and improved method and apparatus for pumping heat utilizing air as the working medium which is readily reversible from a cooling to a heating mode.

Yet another object of the present invention is to provide a new and improved method and apparatus for providing air cycle heat pumping wherein the compressor and expander drives are mechanically connected whereby the expander functions as a motor and provides an auxiliary drive to the compressor.

Still another object of the present invention is to provide a device of the above-described nature wherein the pumping capacities of the compressor and the expander are sized to provide high efficiency with optimum compression of the working medium.

These and other objects and features of the present invention will become apparent from the following description.

FIG. 1 is a simplified, partially-sectioned illustration of an embodiment of the present invention;

FIG. 2 is a simplified, partially-sectioned illustration of another embodiment of the present invention.

FIG. 3 is a simplified, partially-sectioned illustration of yet another embodiment of the instant invention; and

FIGS. 4 and 5 are simplified, partially-sectioned illustrations of embodiments of the instant invention particularly adapted for generating substantial amounts of heat.

Turning now to the drawings, wherein like components are designated by like reference numerals throughout the various figures, a device for pumping heat utilizing an air cycle is illustrated in FIG. 1 and generally designated by reference numeral 10. Heat pump includes positive displacement compressor 12 and positive displacement expander 13. A typical posifive-displacement compressor 12 is comprised, as illustrated, of cylinder 15 having piston 16 sealingly and slidingly disposed therein. Connecting rod 17 is pivotally attached to piston 16. Intake valve 18 and exhaust valve 19 are positioned in cylinder head 20 at an upper portion of cylinder 15. Intake valve 18 and exhaust valve 19 may be flap or reed valves actuated by pressure difference, or, for instance, poppet valves positively operated by cams (not shown) in a conventional synchronized manner.

Compressor 12 operates on a two-stroke cycle with intake valve 18 open as piston 16 moves downward and, exhaust valve 19 selectively advanced to an open position as piston 16 moves upward. Accordingly, air is drawn into cylinder 15 through intake valve 18 as piston 16 moves downward and expelled therefrom through exhaust valve 19 as piston 16 moves upward.

Expander 13 is, as illustrated, similar to compressor 12 in construction. Expander cylinder 21 contains piston 22 sealingly and slidingly disposed therein. Connecting rod 23 is pivotally attached to piston 22. Intake valve 24 and exhaust valve 25, which are positively actuated by means not shown, are disposed in the cylinder head at the upper end of cylinder 21.

Since heat pump 10 operates to provide heated or cooled air to the interior of an enclosed environment, wall 27 is schematically indicated to establish such inner and outer relationship. Dependent upon operation of heat pump 10 in a cooling or in a heating function, differing sides of wall 27 may be considered as being the enclosed environment. Compressor l2 and expander 13 are in communication through wall 27 by means of heat exchanger 28, and, more specifically, by means of pressurized passage 29 of heat exchanger 28. Pressurized passage 29 is in communication with exhaust valve 19 of compressor 12 and intake valve 24 of expander 13. Further, pressurized passage 29 is sealed from exhaust passage 30 but includes a substantial wall area in common to provide a heat exchange relationship between the air in pressure passage 29 and cooler air in exhaust passage 30.

Connecting rod 17 of compressor 12 is connected in an eccentric manner to compressor pulley 32. Connecting rod 23 of expander 13 is connected in the same manner to variable diameter expander pulley 33. It will be noted that expander pulley 33 may vary in diameter from that of compressor pulley 32, the ratio of pulley diameters being approximately equal to the ratio of temperatures, and for instance one or both

pulleys

32 and 33 may be variable pitch V-belt pulleys. Another motor-driven pulley 34 is connected to both compressor pulley 32 and expander 33 by means of belt 35. Accordingly, as a result of the difference in the diameters of compressor pulley 32 and expander pulley 33, the rate at which compressor 32 pumps a given volume of air will differ from the rate at which expander 13 permits the volume of air to be exhausted. This relationship is necessary since a given mass of air occupies differing volumes as pressure and temperature change. More specifically, the volume varies inversely proportional to changes in the absolute pressure and directly proportional to changes in the absolute temperature. As a result, the air ingested into compressor 12 is determined by the swept volume, or effective swept volume, of compressor 12 and the temperature and pressure of the air at intake valve 18. Similarly, the volume of air used to drive expander 13 is determined by the temperature and pressure of the air at intake valve 24. Since the air in pressurized passage 29 of exchanger 28 is, in general, at a higher pressure and temperature than the ambient air, these offsetting factors must be taken into account in sizing expander 13. Further, the effective swept volume of expander 13 may be less than the displacement thereof since it may be desirable to close intake valve 24 before piston 22 reaches bottom deadcenter. Obviously, if intake valve 24 were in the open position when piston 22 is at bottom dead-center, the pressures within cylinder 21 would be the same as that within pressurized passage 29 and this pressure would, upon the opening of exhaust valve 25, vent to ambient pressure without doing reclaimable work. For this reason, closure of intake valve 24 before piston 22 reaches bottom dead-center establishes an effective swept volume and the pressure in cylinder 21 will be rather closer to ambient temperature upon opening of exhaust valve 25.

In order to compensate for the different volumes passing through compressor 12 and expander 13 as a result of differing temperatures, the size of compressor pulley 32 and expander pulley 33 differ. Further, once the apparatus has reached a steady-state operation, the pressure in passage 29 may be monitored and maintained at a predetermined optimum value. For instance, pressure sensor 38 within pressure passage 29 of heat exchanger 28, in conjunction with controller 39, produces an output signal which varies the diameter of, for instance. expander pulley 33 to maintain the pressure at the desired level. When the pressure exceeds the desired value. the diameter of expander pulley 33 decreases thereby increasing the swept volume per unit time of expander 13. The converse occurs when the pressure is below the desired level.

Another variant of the same general type of apparatus is illustrated in FIG. 2 wherein the diameters of compressor cylinder 15 and expander cylinder 21 differ. Accordingly, though piston 16 of compressor 12 and piston 22 of expander 13 may move linearly at identical rates. the swept volume per unit time will, of course, vary as the square of the diameters. Piston 16 is rigidly attached to piston 22 by means of link member 44 which extends sealingly through compressor cylinder head 42 and expander cylinder head 43. Expander piston 22 is connected eccentrically to crank shaft 45 by means of connecting rod 23. Crank shaft 45, in turn, is driven by motor 46. Accordingly, rotation of crank shaft 45 moves piston 22 reciprocally in cylinder 21 and, in unison, also moves piston 16 and cylinder by means of link member 44. Since the diameters of compressor cylinder 15 and expander cylinder 21 cannot be varied during operation, the sizes thereof are determined for steady-state operating conditions.

An apparatus somewhat similar to that of FIG. 2 is illustrated in FIG. 3. Expander piston 22, which is of a diameter identical to that of compressor piston 16, is linked to undriven flywheel 48 by connecting rod 23. Energy is supplied to the system by auxiliary compressor 49 which provides compressed air to pressurized passage 29. In order to initiate and maintain move ment, auxiliary expander cylinder 50 with auxiliary expander piston 51 disposed therein is linked through auxiliary expander linkage 52 to link member 44. Since auxiliary expander piston 51 is in communication with pressurized passage 29, a force imbalance is exerted upon the combined expander end of the system and causes movement of the linked auxiliary expander piston 51, expander piston 22 and compressor piston 16.

As with any of the embodiments of the instant invention, it is to be understood that the apparatus may be run in a reversed configuration with the illustrated expander functioning as a compressor and the illustrated compressor functioning as an expander. Thus, a fully balanced system would have auxiliary expanders being selectively engaged and disengaged depending upon the desired mode of operation.

An example of an apparatus run in the reversed or heating mode is schematically illustrated in FIG. 4 wherein compressor 12 is considered to be within the enclosed environment and expander 13 outside of the enclosed environment. Therefore, the air exiting from exhaust passage 30 will be heated as a result of heat exchange between the compressed air in pressure passage 29 and the lower temperature air drawn into exhaust passage 30 from outside the environment. However, since the air drawn into exhaust passage 30 is often quite cool in instances requiring operation in the heating mode, the apparatus operates in a less efficient manner. and in the case of extreme heating ranges would be greatly oversized for the normal cooling demand. For this reason, an auxiliary heating element 55 is provided in heat exchanger passage 30 to further heat the air provided to the enclosed environment.

Still another embodiment is shown in FIG. 5 wherein compressor 12 and expander 13 are operated in the cooling" mode, but a burner 58 is provided to heat the air through exhaust passage 30. Thus, the air in exhaust passage 30 will be at an elevated temperature and transfer heat into the air in pressure passage 29, even though the compressed air in pressurized passage 29 is heated to a substantial degree by compression to a higher level. For this reason, the air is exhausted from pressure passage 29 through expander 13 and will be heated above ambient temperature even though substantial amounts of work may be provided to auxiliary power unit 60 by expander 13.

Summarily, it will be seen that the present invention, as described and illustrated, provides an efficient manner for providing either heated or cooled air. By using positive displacement compressors and expanders, and by utilizing the power produced by exhausting the compressed air through the expander to drive, at least in part, the compressor, efficiency is substantially enhanced and the requirement for a complicated closed system and toxic working fluid is avoided. The additional power required can be provided by a motor driving the compressor, by an auxiliary driven compressor or by heat added to the system. In these latter two cases, the expanders may function to drive the compressor without an additional motor drive to the compressor.

Although several embodiments of the present invention have been illustrated and described, it is anticipated that various changes and modifications beyond the illustrated embodiments will be apparent to those skilled in the art and that such changes may be made without departing from the scope of the invention, as defined by the following claims.

What is claimed is:

1. A method for transferring heat between a first environment and a second environment, comprising: substantially adiabatically compressing gaseous working medium from the first environment by means of a positive displacement compressor, conducting the compressed and, accordingly, heated gaseous working medium from the compressor through a pressure passage of a heat exchanger to a positive displacement expander, conducting exhaust gaseous working medium from the second environment through a second passage of the heat exchanger to the first environment, transferring heat from the heated, compressed gaseous working medium to the exhaust gaseous working medium, adiabatically expanding the compressed gaseous working medium from which heat has been transferred through the positive displacement expander and into the second environment to extract work. from and cool the expanded gaseous working medium, applying the work obtained from the expansion of the compressed gaseous working medium from the expander to the compressor, and varying the ratio of the effective swept volume per unit time of the compressor relative to the effective swept volume per unit time of the expander directly as the absolute temperature of the first environment varies, whereby cool gaseous working medium is provided from the expander to the second environment, heated exhaust gaseous working medium is supplied from the heat exchanger to the first environment and energy is conserved by the application of work from the expander to the compressor and by the substantially adiabatic compression and expansion of the compressed gaseous working medium.

2. A method as set forth in claim 1 wherein the ratio of the effective swept volume per unit time of the compressor and the effective swept volume per unit time of the expander is maintained at a predetermined value at a predetermined operational pressure of the compressed gaseous working medium in the heat exchanger and increased when the pressure of the compressed gaseous working medium in the heat exchanger falls below the predetermined value and decreased as the pressure of the compressed gaseous working medium of the heat exchanger exceeds the predetermined value.

3. A method as set forth in claim 1 wherein heat is added to the exhaust air in the heat exchanger before heat exchange between the exhaust gaseous working medium and the compressed gaseous working medium, and in which the gaseous working medium exhausted from the expander is at a temperature higher than the ambient temperature in the first environment.

4. A method as set forth in claim 1 wherein heat is added to the exhaust gaseous working medium in the heat exchanger after heat exchange of such gaseous working medium with the compressed gaseous working medium and the quantity of heat supplied to the first environment by the exhaust gaseous working medium is accordingly increased.

5. Apparatus for transferring heat between a first environment and a second environment, comprising: means separating the first environment from the second environment, a positive displacement compressor ingesting a gaseous working medium from the first environment, a heat exchanger having at least two passages defined therethrough, one of the heat exchanger passages comprising a pressure passage communicating with the exhaust port of the compressor at one end and with an intake port of a positive displacement expander at the other end thereof, the other passage of the heat exchanger being in a heat-exchange relationship with the pressure passage and communicating with the first environment at one end and the second environment at the other end, means interlinking the compressor and expander for transferring work between the drive of the expander and the drive of the compressor, means for applying energy to said compressor and said expander, and means for controlling said energy applying means for varying the ratio of the effective swept volume per unit of time of said compressor to the effective swept volume per unit of time of said expander.

6. An apparatus as set forth in claim 5 wherein the means interlinking the expander and compressor is a belt, the means for supplying energy to the apparatus is a drive motor bearing upon the belt by means of a pulley, and said controlling means includes a variable diameter ratio pulley whereby the relative operating speeds of the compressor and the expander can be var ied.

7. An apparatus as set forth in claim 6 wherein a pressure sensor is provided in the pressure passage and includes means to vary the diameter of the variable diameter pulley in response to changes in pressure within the pressure passage.

8. An apparatus as set forth in claim 5 wherein a heat-producing means is positioned within one of the heat exchange passages between the first and second environment at a position adjacent the second environment.

9. An apparatus as set forth in claim 5 wherein a heat-producing means is positioned within one of the heat exchange passages between the first and second environment at a position adjacent the first environment.

10. Apparatus for transferring heat between a first environment and a second environment comprising: means separating the first environment from the second environment, a positive displacement compressor ingesting a gaseous working medium from the first environment and having a piston mechanism, a positive displacement expander having a piston mechanism of an effective working surface greater than that of said compressor piston, a heat exchanger having at least two passages defined therethrough, one of said passages being a pressure passage communicating with the exhaust port of said compressor and the intake port of said expander, the other said passage being in heatexchange relationship with the said pressure passage and communicating between the first and second environments, means interlinking said compressor and expander pistons, and means for introducing pressure into said pressure passage, whereby the said compressor piston will drive the apparatus and work will be transferred between said compressor and expander via said interlinking means.

11. An apparatus as set forth in claim 10 wherein the compressor and expander each have piston devices of the same diameter, the interlinking means is a link rod commonly attached to the piston in the compressor and the piston in the expander, said introducing means includes an auxiliary-driven compressor communicating with the pressure passage of the heat exchanger, and said compressor also includes an auxiliary expander of a piston device type attached by means of an auxiliary linkage between the auxiliary expander piston and the link rod to both the expander and compressor.

12. Apparatus in accordance with claim 11 wherein the intake and exhaust ports for said auxiliary expander piston both communicate with said pressure passage.

Claims

1. A method for transferring heat between a first environment and a second environment, comprising: substantially adiabatically compressing gaseous working medium from the first environment by means of a positive displacement compressor, conducting the compressed and, accordingly, heated gaseous working medium from the compressor through a pressure passage of a heat exchanger to a positive displacement expander, conducting exhaust gaseous working medium from the second environment through a second passage of the heat exchanger to the first environment, transferring heat from the heated, compressed gaseous working medium to the exhaust gaseous working medium, adiabatically expanding the compressed gaseous working medium from which heat has been transferred through the positive displacement expander and into the second environment to extract work from and cool the expanded gaseous working medium, applying the work obtained from the expansion of the compressed gaseous working medium from the expander to the compressor, and varying the ratio of the effective swept volume per unit time of the compressor relative to the effective swept volume per unit time of the expander directly as the absolute temperature of the first environment varies, whereby cool gaseous working medium is provided from the expander to the second environment, heated exhaust gaseous working medium is supplied from the heat exchanger to the first environment and energy is conserved by the application of work from the expander to the compressor and by the substantially adiabatic compression and expansion of the compressed gaseous working medium.

6. An apparatus as set forth in claim 5 wherein the means interlinking the expander and compressor is a belt, the means for supplying energy to the apparatus is a drive motor bearing upon the belt by means of a pulley, and said controlling means includes a variable diameter ratio pulley whereby the relative operating speeds of the compressor and the expander can be varied.

10. Apparatus for transferring heat between a first environment and a second environment comprising: means separating the first environment from the second environment, a positive displacement compressor ingesting a gaseous working medium from the first environment and having a piston mechanism, a positive displacement expander having a piston mechanism of an effective working surface greater than that of said compressor piston, a heat exchanger having at least two passages defined therethrough, one of said passages being a pressure passage communicating with the exhaust port of said compressor and the intake port of said expander, the other said passage being in heat-exchange relationship with the said pressure passage and communicating between the first and second environments, means interlinking said compressor and expander pistons, and means for introducing pressure into said pressure passage, whereby the said compressor piston will drive the apparatus and work will be transferred between said compressor and expander via said interlinking means.