Abstract:
A method and system for heating a space includes circulating refrigerant in a closed loop system having a first heat exchanger and a second heat exchanger. The circulating step includes pressurizing liquid refrigerant to a first pressure and heating the liquid refrigerant in a third heat exchanger to form a refrigerant vapor. The method further includes compressing refrigerant by a compressor to a second pressure, wherein the compressor is at least partially driven by refrigerant vapor received from the third heat exchanger, and supplying one of the first and second heat exchangers with refrigerant from the compressor. The method further includes supplying refrigerant from the other of the first and second heat exchangers to the compressor and selectively supercharging the refrigerant supplied to the compressor from the other of the first and second heat exchangers.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a new and improved heat pump system and method of cooling or heating a space. More particularly, the present invention relates to a method and apparatus for driving and controlling a heat pump system.  
       BACKGROUND  
       [0002]     High energy costs and environmental concerns over the generation of pollution require more energy efficient mechanisms for heating and cooling interior spaces. Utilizing renewable energy resources and, in some cases, waste heat from any number of sources improves energy efficiency. Mechanisms that use energy must be easily adapted to a number of different energy sources without the need for expensive or customized adaptors.  
         [0003]     The interior spaces that require heating and cooling are not limited to living and working environments, but also extend to spaces involved in transportation for humans and perishable commodities. The method of providing heating and cooling must be economical, efficient to manufacture, and inexpensive to maintain in order to be readily accessible for any number of applications in everyday life.  
         [0004]     The standard Carnot reversible heat pump cycle, which uses an expansion valve for expanding the refrigerant fluid and a mechanical compressor for the compression of the refrigerant vapor, has been in use for a wide variety of applications. Essentially, in the cooling mode, such systems pass saturated liquid refrigerant through an expansion valve to lower the refrigerant&#39;s pressure, and therefore the saturation temperature of the refrigerant correspondingly falls, and the cooled refrigerant is then directed to an evaporator where heat is absorbed from the atmosphere, thereby cooling the environmental space (or some other medium where cooling is desired).  
         [0005]     This cycle may be reversible, thus permitting the same system to operate as a heat pump. To provide heating of a space, energy is added to the system by a compressor and ambient air. Most of the prior art devices that accomplish this task are known to consume large amounts of energy (usually electrical energy), and are inefficient in both the cooling and heating modes.  
         [0006]     For example,  FIG. 1  depicts a conventional heat pump device. As illustrated, this conventional heat pump system requires a common compressor unit to be driven by direct electric motor energy input, or power transferred from a rotating shaft, as in a vehicle system.  
         [0007]     The benefits of heat powered heat pump devices designed for use in the home or office are well known. An example of a conventional heat powered heat pump is disclosed in U.S. Pat. No. 4,918,937.  
         [0008]     U.S. Pat. No. 4,918,937 provides an air conditioning system for an automobile that uses both a mechanical compressor and a refrigerant pump to motivate refrigerant through the system. The &#39;937 patent discloses an engine-driven mechanical compressor that compresses the vaporized refrigerant until the pressure of refrigerant flowing from the refrigerant pump through a heat exchanger and an ejector is high enough to sufficiently pressurize the vaporized refrigerant. Once the required pressure level is met, the mechanical compressor is disengaged and the refrigerant pump, heat exchanger and ejector motivate the refrigerant through the system. One drawback of the &#39;937 patent is that the system requires a mechanical compressor to compress the vaporized refrigerant being sent to the heat exchanger.  
         [0009]     The present invention provides a heat pump system that avoids some or all of the aforesaid shortcomings in the prior art.  
       SUMMARY OF THE INVENTION  
       [0010]     In accordance with one aspect of the invention, a method of heating a space includes circulating refrigerant in a closed loop system including a first heat exchanger and a second heat exchanger. The circulating step includes pressurizing liquid refrigerant to a first pressure, heating the liquid refrigerant in a third heat exchanger to form a refrigerant vapor, compressing refrigerant by a compressor to a second pressure, wherein the compressor is at least partially driven by refrigerant vapor received from the third heat exchanger, and supplying one the first and second heat exchangers with refrigerant from the compressor.  
         [0011]     According to another aspect of the present invention, a method of heating a space including circulating refrigerant in a closed loop system including a first heat exchanger and a second heat exchanger. The circulating step includes pressurizing liquid refrigerant to a first pressure, heating the liquid refrigerant in a third heat exchanger to form a refrigerant vapor. The method further includes compressing refrigerant by a compressor to a second pressure, wherein the compressor is at least partially driven by refrigerant vapor received from the third heat exchanger, and supplying one of the first and second heat exchangers with refrigerant from the compressor. Further steps include supplying refrigerant from the other of the first and second heat exchangers to the compressor, and selectively supercharging the refrigerant supplied to the compressor from the other of the first and second heat exchangers.  
         [0012]     According to yet another aspect of the present invention, a heat pump system includes a closed loop circuit having a liquid pump and a first heat exchanger located downstream of the liquid pump. The system further includes a refrigerant compressor driven by refrigerant flowing from the liquid pump through the first heat exchanger, a second heat exchanger fluidly coupled to the refrigerant compressor; and a third heat exchanger fluidly coupled to the refrigerant compressor. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a schematic representation of a conventional prior art heat pump device;  
         [0014]      FIG. 2  is a schematic representation of the novel heat powered heat pump system constructed in accordance with the present disclosure;  
         [0015]      FIG. 3  is a schematic representation of a switching valve controller circuit for the heat pump system constructed in accordance with the present disclosure;  
         [0016]      FIG. 4  is an enlarged partial schematic representation of the switching valve and piston assembly movement in accordance with the present disclosure;  
         [0017]      FIG. 5  is a further enlarged partial schematic representation of the switching valve and piston assembly movement in accordance with the present disclosure;  
         [0018]      FIG. 6  is yet a further enlarged partial schematic representation of the switching valve and piston assembly movement in accordance with the present disclosure;  
         [0019]      FIG. 7  is a schematic representation of a heat exchanger controller circuit for the heat pump system constructed in accordance with the present disclosure; and  
         [0020]      FIG. 8  is a cross-sectional side elevational view of the compressor unit component of the heat powered heat pump system constructed in accordance with the present disclosure. 
     
    
     DETAILED DESCRIPTION  
       [0021]     Reference will now be made in detail to the drawings. Wherever possible, the same reference numbers will be used to refer to the same or like parts.  
         [0022]      FIG. 2  depicts a heat powered heat pump system  10  in accordance with the present disclosure. As shown, the heat pump system  10  can cool an interior space, and by reversing the operation cycle, can also be used to heat an interior space. If the heat pump system  10  is used only for cooling or only for heating, certain components, such as a cooling/heating switch and a valve assembly can be altogether eliminated from the heat pump system  10 . Further, heat pump system  10  is readily scalable, making it applicable to cooling and heating uses in large spaces as well as smaller volumes. For example, heat pump system  10  can be readily carried on board vehicles with their associated space limitations.  
         [0023]     The heat pump system  10  will now be described by way of its operation. To initiate operation of heat pump system  10 , an electric motor driven pump unit  14  receives liquid refrigerant from valve  16  and pressurizes and delivers liquid refrigerant to heat exchanger  18 . The energy required to drive pump unit  14  is labeled Q 1 . Heat exchanger  18  receives the pressurized liquid refrigerant and adds available heat from an energy source Q S , discussed in greater detail below, which converts the liquid to a high pressure vapor. The high pressure vapor is then supplied to a switching valve  20  along high pressure vapor line  48 . It is noted that pump unit  14  can be any device that acts to pressurize liquid refrigerant, and pump unit  14  may operate continuously during the operation of heat pump system  10 .  
         [0024]     Heat pump system  10  further includes a relief/check valve assembly  60  interposed between heat exchanger  18  and the pump  14  for controlling the pressure of liquid traveling to the heat exchanger  18 .  
         [0025]     In the position shown in  FIG. 2 , switching valve  20  of heat pump system  10  directs high pressure vapor in line  48  to line  54  which forms an inlet to chamber A of a four chamber compressor unit  30 . Switching valve  20  also exposes chamber D of compressor unit  30  to output line  36  by way of line  28 .  
         [0026]     Compressor unit  30  may include a cylinder housing  22  and a double piston assembly  24  capable of reciprocation within the cylinder housing  22 . The two pistons of piston assembly  24  are connected by a piston rod  26 . The cylinder housing  22  includes a divider  32  at its midpoint having an opening for receiving the piston rod  26 . Housing  22  and piston assembly  24  together form four separate chambers of compressor unit  30 , and these compressor chambers are designated chambers A, B, C, and D. Chambers A and D will be referred to as external chambers, and chambers B and C will be referred to as internal chambers.  
         [0027]     When high pressure vapor is conducted through switching valve  20  into chamber A (and chamber D is exposed through switching valve  20  to output line  36 ), the piston assembly  24  will move to expand chamber A (a downward motion as shown in  FIG. 2 ). This motion of the piston assembly  24  will cause the volume of chamber B to decrease, having a resulting compression effect, while simultaneously causing the volume of chamber C to increase, having a resulting suction effect. Additionally, this motion of the piston assembly  24  expanding chamber A will cause vaporized refrigerant located in chamber D from a previous cycle to flow out line  28  through switching valve  20  and to output line  36 .  
         [0028]     The compression of the vapor in chamber B due to the movement of piston assembly  24  causes compressed vapor to be delivered through line  58  to valve  34 , and to output line  36 . Thus, pressurized refrigerant vapor is supplied to output line  36  from both chamber B and chamber D. The pressurized refrigerant in output line  36  then flows through a cooling/heating switching valve  12  and on to a heat exchanger  40 . Heat exchanger  40 , a condenser when cooling/heating switching valve  12  is in the cooling position (shown in  FIG. 2 ), is exposed to the atmosphere and the pressurized refrigerant releases and transfers heat to the atmosphere. This heat transfer transforms the pressurized vapor back to a liquid state (condensation) before returning to either heat exchanger  50  via expansion valve  52  or pump unit  14  via valve assembly  16 .  
         [0029]     Heat exchanger  50  receives liquid refrigerant from heat exchanger  40  through expansion valve  52 , located on valve assembly  16 . It is noted that expansion valve  52  may include any type of structure that lowers the pressure of the flowing liquid refrigerant (e.g., a flow orifice, a capillary tube, a sophisticated modulating device that adjusts for dynamic operating loads). The liquid refrigerant in heat exchanger  50  is then vaporized due to exposure with available heat from the interior space. The transfer of heat from the interior space to the liquid refrigerant in heat exchanger  50  acts to cool the interior space.  
         [0030]     While the heat exchanger  50  receives liquid refrigerant from heat exchanger  40 , the movement of piston assembly  24  causes chamber C to draw vaporized refrigerant in from a heat exchanger  50  via line  51  and line  56 . The vaporized refrigerant flowing through line  51  travels though cooling/heating switching valve  12 , and, as will be described in more detail below, through either a supercharger  21  or check valve  29 . The refrigerant will also pass through check valve  42  as it travels to line  56  and into chamber C.  
         [0031]     Vaporized refrigerant flowing to chamber C will flow through supercharger  21  when the supercharger  21  is operating. Otherwise, the vaporized refrigerant will flow through check valve  29  on its way to chamber C. A pressure switch  27  may be included in heat pump system  10  to control the actuation of supercharger  21  based on the outlet pressure of supercharger  21 . When supercharger  21  is operating, supercharger  21  pressurizes the vapor refrigerant flowing from heat exchanger  50  to chamber C. Supercharger  21  may continue to pressurize refrigerant toward chamber C even when chamber C is at its maximum volume. During operation of compressor unit  30 , it is understood that the pressure of refrigerant in output line  36  is higher than the discharge pressure of supercharger  21 , thus preventing the flow of refrigerant vapor from supercharger  21  to output line  36 .  
         [0032]     The flow rate of the supercharger  21  can be selected or adjusted so that it equals the rate required to fill chamber C as chamber C expands. With such a matched flow rate, the power required to operate the supercharger  21  is relatively low when chamber C is expanding. Once chamber C stops expanding—corresponding to the piston assembly  24  reaching a maximum position—the supercharger  21  may continue to supercharge chamber C. During this supercharge period, the pressure in chamber C increases, along with the power Q A  required to operate the supercharger  21 . Accordingly, the supercharge period is the only time that the supercharger  21  demands any substantial power.  
         [0033]     In the operation described above, supercharger  21  acts to supercharge chamber C and supplement the energy received by the heat pump system  10 . Thus, supercharger  21  acts as a backup energy source that is only used when the system demands call for it. Thus, supercharger  21  is only required for relatively short periods of time to provide supercharging of chamber C, and therefore requires only a relatively small amount of “purchased external” energy. During low heat transfer requirements of the system, the supercharger is not required, and the amount of “purchased external” energy is zero.  
         [0034]     It is understood that supercharger  21  may operate as a typical mechanical compressor when there is no waste heat to power Q S  or when the operating load of the heat pump system  10  is relatively low and the system  10  does not require operation of compressor unit  30 . For example, if Q S  receives its power from solar energy during the day, at night, there will be a relatively small amount of power supplied to heat exchanger  18 . Further, there may also be a relatively low demand for cooling from the system  10 . In this example, the supercharger  21  may operate as a compressor to carry the low system load. In this operation, supercharger  21  moves refrigerant through check valves  38  and  42 , valve  34 , output line  36  to heat exchangers  40 ,  50  and back to supercharger  21  through line  51 .  
         [0035]     The above described operation of heat pump system  10  has detailed the movement of the piston assembly  24  to expand chamber A. When this operation is complete, switching valve  20  may be switched such that high pressure vapor is now delivered to chamber D of compressor unit  30 , and simultaneously chamber A is exposed to output line  36  thru switching valve  20 . This action causes the piston assembly  24  to move to expand chamber D (an upward motion as shown in  FIG. 2 ). This movement of piston assembly  24  also causes chamber C to compress vapor and deliver vapor through line  56  to valve  34 . Thus, output line  36  now receives high pressure vapor from both chamber C and chamber A. This high pressure vapor in output line  36  then travels through cooling/heating switching valve  12 , and then on to heat exchanger  40 .  
         [0036]     The motion of the piston assembly  24  to expand chamber D further causes chamber B of the compressor unit  30  to increase in volume. This movement of piston assembly  24  draws refrigerant vapor from heat exchanger  50  in the same manner described above with respect to the expansion of chamber C.  
         [0037]     The movement of piston assembly  24  in the direction to expand chamber D produces the same effect at the heat exchangers  40  and  50  as the motion to expand chamber A. Namely, heat is rejected at the heat exchanger  40  (condenser), and at the same time heat is absorbed at heat exchanger  50  (evaporator).  
         [0038]     The switching time period on switching valve  20  is variable to adjust the heat transfer rate of the system. Control of switching valve  20  may be obtained by a conventional control system, such as the control circuit  70  and  71  detailed below. In operation, when the system  10  is functioning with a short switching time period for switching valve  20 , this causes faster cycling rates of the piston assembly  24  of compressor unit  30 , and therefore, a higher heat transfer rate at the respective heat exchangers  40  and  50 . When no heat transfer is required of heat exchangers  40  and  50 , cycling of switching valve  20  is stopped and compressor unit  30  halts.  
         [0039]      FIG. 3  shows the switching valve  20  wired to a controlling circuit  70 . Switching valve  20  is a conventional three-position, electrically actuated, spring centered, four-way fluid diverter valve. Switching valve  20  has three positions, namely, a straight diversion position  72 , a center “off” position  74 , and a crossed diversion position  76 . The center position  74  of switching valve  20  has the configuration of “blocked flow” on the fluid input and return ports of the valve  20 , and the “working ports” supplying the compressor unit  30  are in fluid communication with the selected chambers of the compressor unit  30 .  
         [0040]     The cycling and frequency of the cycling between positions  72 ,  74 , and  76  of switching valve  20  is controlled by an electrical control circuit  70 . Electrical power, designated P, is switched and alternately supplied to output wires  82  and  84 . The cycling of the electrical signals traveling to switching valve  20  from the control circuit  70  via output wires  82  and  84  is regulated by a control signal  73  acting on control circuit  70 .  
         [0041]     As depicted in  FIG. 3 , an input/output device  71  may receive signals from a thermostat  19 , the piston assembly position sensors  23  and  25 , and pressure switch  27 . The device  71  may then provide the control signal  73  to electrical control circuit  70 , thus regulating the frequency at which power is applied to output wires  82  and  84 . Further, the device  71  may also provide a signal to the supercharger  21  and switching valve  20 , thus regulating the operation of both the supercharger  21  and switching valve  20 .  
         [0042]     The circuit controller  70  may include a delay in timing, or “dead time,” after the signal to output wire  82  is removed and before the signal to output wire  84  is applied, and conversely, when a signal is removed from output wire  84  and before a signal is applied to output wire  82 . This “dead time” feature allows switching valve  20  to remain in the center position for a predetermined amount of time, the advantages of which are described in greater detail below.  
         [0043]     Referring now to  FIGS. 4-6 , there is shown in greater detail the three positions of switching valve  20 , namely the dynamics of the heat pump system  10  during the cycling of switching valve  20  through each of the three positions of the switch.  
         [0044]     Beginning with  FIG. 4 , switching valve  20  receives a signal from output wire  82  and consequently is in the straight open position  72 . In this position  72 , high pressure vapor is supplied to compressor unit chamber A and evacuated from chamber D along lines  54  and  28 , respectively. This causes the piston assembly  24  to move downwardly (as shown), thereby exhausting vapor out of chamber D and chamber B, while simultaneously receiving vapor into chamber C by the movement action of the piston assembly  24 .  
         [0045]      FIG. 5  depicts the piston assembly  24  as having reached its maximum downward stroke. At this point, the electric signal along output wire  82  has been discontinued, and removed from switching valve  20  by circuit controller  70  and input/output device  71 , thereby allowing switching valve  20  to move to its center position. Input/output device  71  receives signals from the piston position sensor devices  23  and  25  to facilitate the switching sequence of switching valve  20 . This allows the pressurized vapor in compressor unit  30  chamber A to communicate through switching valve  20  and move into chamber D and pressurize chamber D. This sequence of events improves the operating efficiency of the overall system  10  since the vapor pressure in chamber A is not completely exhausted to condenser  40  (not shown, see  FIG. 2 ) through switching valve  20 .  
         [0046]      FIG. 6  shows the last cycle of piston movement in the heat powered heat pump system  10 . Here, after a pre-determined time, the “dead time,” circuit controller  70  applies an electrical current along output wire  84  to switching valve  20  that causes switching valve  20  to supply high pressure vapor to chamber D of compressor unit  30 . As a result, the piston assembly  24  moves to expand chamber D. When the piston assembly  24  reaches its maximum upward stroke, the cycle begins again.  
         [0047]      FIG. 7  shows an alternative embodiment of the present disclosure. In this embodiment, a power control system  80  controls heat pump system  10 . Control system  80  enables the amount of power Q S  supplied to heat exchanger  18  to be controlled and limited depending upon the rejection temperature of the acting condenser unit ( 40  or  50 ) within the system.  
         [0048]     As will be described in more detail below, heat exchangers  40  and  50  can act as a condenser or an evaporator depending upon the position of cooling/heating switching valve  12 . Therefore, the power Q S  supplied to heat exchanger  18  is proportional to the rejection power of the system&#39;s condenser heat exchanger at the time, whether it be heat exchanger  40  or heat exchanger  50 .  FIG. 7  depicts a power control system  80  that monitors the rejection temperature of the “condenser” heat exchanger, designated X, and monitors the temperature, designated Y, of the high-pressure vapor leaving heat exchanger  18 . Depending upon the physical thermodynamic characteristics of the refrigerant fluid used in the system, a circuit controller  78  maintains a differential relationship between temperature X and temperature Y by supplying a signal along output wire  86  to modulate the amount of power supplied to heat exchanger  18 . Signals traveling along output  86  could energize a flow valve  88  when the system is powered by hot fluid (such as solar powered hot water generation). Alternatively, signals traveling along output  86  could energize a power relay (not shown) that would be located directly in substitution of flow valve  88 , in the case where electrical power is employed to power an electrical heating element to heat the refrigerant in heat exchanger  18 .  
         [0049]      FIG. 8  shows an enlarged cross-sectional illustration of the compressor unit  30 , including the presence and location of sealing elements  62 ,  64 , and  66 . These sealing elements  62 ,  64 , and  66  represent the sliding seals within compressor unit  30 . The sealing elements  62 ,  64 , and  66  can be constructed from metallic materials, alloys, or elastomer sealing materials. The elastomer sealing material is chosen for compatibility with refrigerant fluids and the anticipated system operating temperature extremes. It is noted that sealing elements  62  and  66  act as piston rings being centrally located at the piston heads  44  and  46 , respectfully. Sealing element  64 , located in compressor housing  22  and divider  32 , acts to seal the piston rod  26 . Overall, the sealing elements  62 ,  64 , and  66  act to insure that each compressor unit  30  chamber A, B, C, and D do not come into fluid communication with one another.  
         [0050]     Additionally,  FIG. 8  depicts the different cross-sectional surface areas of piston assembly  24 . In particular, the internal chambers B and C have smaller surface areas  33  than the external chamber surface areas  31 .  
         [0051]     As previously mentioned above, heat pump system  10  may include a cooling/heating switching valve  12  that allows the system to switch between an interior cooling mode and an interior heating mode. This is accomplished by activating cooling/heating switching valve  12  to supply highly pressurized refrigerant vapor to one of the heat exchanger  40  or the heat exchanger  50 .  
         [0052]     As the system has been described, in the interior cooling mode, and if we denote heat or energy transfer as positive “+” when put into the system, and as negative “−” when energy is transferred out of the system, we can write an energy balance equation as follows (based on an ideal system with no energy losses): 
 
 Q   A   +Q   1   +Q   S   +Q   50   −Q   40 =0 
 
         [0053]     where 
        Q A =Supercharger     Q 1 =Pump Input Power     Q S =Energy From Heat Source     Q 50 =Interior Heat Transfer     Q 40 =Atmosphere Heat Transfer        
 
         [0059]     or 
 
 Q   A   +Q   1   +Q   S   +Q   50   =Q   40  
 
         [0060]     Therefore, all heat/power is rejected to the atmosphere when the heat powered heat pump system  10  is in the cooling mode.  
         [0061]     If the system is used to supply heat to the interior space, cooling/heating switching valve  12  is switched to the heating position, which in effect switches (reverses) the functions of the heat exchanger  40  and heat exchanger  50 . Now, in this heating functioning mode, heat exchanger  40  has become an evaporator and heat exchanger  50  has become a condenser. The condenser function, to reject heat, is now in the interior space and will now heat the interior space. The heat exchanger functioning as an evaporator, here heat exchanger  40 , is now located outside the interior space and has the ability to absorb heat from the atmosphere.  
         [0062]     The energy balance equation now becomes (based on an ideal system with no energy losses): 
 
 Q   A   +Q   1   +Q   S   +Q   40   −Q   50 =0 
 
         [0063]     where 
        Q A =Supercharger     Q 1 =Pump Input Power     Q S =Energy From Heat Source     Q 50 =Interior Heat Transfer     Q 40 =Atmosphere Heat Transfer        
 
         [0069]     or 
 
 Q   A   +Q   1   +Q   S   +Q   40   =Q   50  
 
         [0070]     Therefore, during the heating mode of the system, Q 50  (interior heat transfer) is equal to the total energy input to the system  10 , including the large heat input Q 40 , from the atmosphere. For example, when the system  10  is used to heat an electric car that is powered by fuel cells, Q 1  is consumed from the battery, Q S  is provided by the waste heat from the fuel cells, and Q 40  is provided from the atmosphere. This results in a decreased consumption of battery power for the same amount of energy to heat the car&#39;s interior, adding up to less energy required to operate the system  10 , and much greater efficiency overall. If there is insufficient waste heat to power Q S , as during the beginning operation of the car, the battery may be used to provide the initial power for Q S , and after sufficient waste heat from the fuel cells is generated, the battery will no longer provide power for Q S .  
         [0071]     Efficiency of the heat pump system  10  is greatly enhanced by the available heat input to heat exchanger  18 . To illustrate this point, energy, in the form of heat, is applied to heat exchanger  18  in many forms. This available heat might be generated by direct electrical power from a power grid, photovoltaic cells, wind power generators, and fuel cell technology, including proton exchange membrane fuel cells, and fuel cells designed for electric car power plants, such as zinc pellet fuel cells. Alternatively, the heat passed on to the heat exchanger  18  may be derived from hot water sources. This hot water may have been generated using all of the above systems, or directly through the use of solar power hot water generation (e.g., direct exposure panels, etc.). All of these methods that provide generated heat and/or waste heat from mechanical heat creation (e.g., engine waste heat) are factors in the overall greater operating efficiency realized with the subject heat powered heat pump system  10 . As used in this disclosure, waste heat includes any source of heat energy that is expelled from a device and would otherwise be emitted to the atmosphere.  
         [0072]     As an alternative arrangement of heat pump system  10 , high pressure refrigerant vapor from heat exchanger  18  could be alternatingly supplied to chambers B and C rather than chambers A and D of compressor unit  30 . Accordingly, in this arrangement, chambers A and D would supply and receive refrigerant vapor from heat exchangers  40  and  50 .  
         [0073]     It should be understood, however, that even though these numerous characteristics and advantages of the invention that have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, chemistry and arrangement of parts within the principal of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.