Patent Publication Number: US-2006011337-A1

Title: Combined heat pump and air-conditioning apparatus and method

Description:
BACKGROUND OF THE INVENTION  
      This invention relates to heating and air-conditioning systems and, in particular, to combination heat pumps and air-conditioning systems.  
      Air-conditioning systems are conventionally installed in most vehicles, particularly in warmer climates. Usually the systems are only operational when the vehicle engine runs. However air-conditioning requirements may still exist when the engine is off. For example, it wastes a lot of fuel to maintain engine operation while the diesel vehicle is parked for a long period of time. However the operator of a tractor/trailer unit may require air-conditioning for the cab while he or she is resting. For this reason many diesel powered highway vehicles are equipped with auxiliary power units. These include a diesel engine which is relatively small compared with the main engine of the vehicle. Each auxiliary power unit (APU) conventionally includes a generator or alternator connected to the engine thereof. This provides electrical power to the vehicle while the main vehicle engine is off. The electrical power from the APU can be used to power an air-conditioner to maintain cooling of the cab while the vehicle is parked.  
      However, the vehicle may also require heating for the cab while the vehicle is parked. Theoretically this could be done by circulating liquid coolant from the APU engine through a heat exchanger in the cab. However this requires additional plumbing in the cab and it may be difficult to find space available for another heat exchanger. Also the engine of the APU may only provide sufficient heat if the engine is operating under a load. If no such load otherwise occurs, then it may be necessary to apply a load to the engine merely for purposes of generating sufficient heat. Obviously this wastes fuel.  
      An engine outputs energy in three different ways. Roughly one third of the energy goes to the mechanical, rotational output of the engine, which can be used for such purposes as running the APU generator. Another one third of the energy goes to exhaust. A final third is transferred to the engine coolant. Only this last third would normally be available for heating the cab of the vehicle.  
      Heat pumps have been used in the past to heat buildings and require a source of heat, for example heat obtained from the ground. Heat pumps are capable of transferring heat from a lower temperature body, such as the ground, to a higher temperature body, such as the interior of a building. This is done by applying energy, using a compressor, to compress a heat transfer medium such as a glycol/water mixture. Subsequently the heat transfer medium passes through a condenser where the medium is condensed by exchanging heat with the ambient air circulated through the condenser by a fan. Thus, the air in the building is heated. The liquefied heat transfer medium then passes through an expansion valve and flows through an evaporator where thermal energy is applied, by heat from the ground in the case of a conventional building-installed heat pump. The heated medium is then drawn into the compressor where it is compressed and the cycle continues.  
      Heat pumps have not been used traditionally in vehicles, in part because there is no obvious source of heat. Clearly vehicles move and accordingly connections to the ground are not possible.  
     SUMMARY OF THE INVENTION  
      According to one aspect of the invention, there is provided a combined heat pump and air-conditioning apparatus. There is a source of heat, a compressor having an input and an output, a heat exchanger, a condenser, an evaporator and first conduits for connecting the source of heat to the evaporator. There are heat transfer medium conduits interconnecting the heat exchanger, the condenser and the evaporator. A valve is operatively connected to the medium conduits and connects the output of the compressor to the condenser and connects the heat exchanger to the input of the compressor during an air-conditioning mode where the heat exchanger operates as an evaporator. The valve operatively connects the output of the compressor to the heat exchanger and connects the input of the compressor to the evaporator during a heat pump mode where the heat exchanger acts as a condenser.  
      According to another aspect of the invention, a combined heat pump and air-conditioning apparatus comprises a heat exchanger, a condenser, an evaporator, an internal combustion engine, and a compressor operatively connected to the engine. The compressor has an input port and an output port. There is also a valve, a first conduit connected to the output port of the compressor, a second conduit connected to the heat exchanger, a third conduit connected to the heat exchanger, a fourth conduit connecting the third conduit to the evaporator, a fifth conduit connected to the evaporator, a sixth conduit connected to the condenser, a seventh conduit connected to the input port of the compressor, an eighth conduit connected to the sixth conduit and the fifth conduit and a ninth conduit connected to the condenser and to the third conduit. Coolant conduits connect the engine to the evaporator for supplying heated engine coolant to the evaporator. There is a valve having a first port, a second port, a third port, a fourth port and a movable valve member for interconnecting the ports, the first port being connected to the seventh conduit, the second port being connected to the second conduit, the third port being connected to the first conduit and the fourth port being connected to the eighth conduit. The apparatus has an air-conditioning mode where the valve member connects the second port to the first port and connects the third port to the fourth port, whereby a heat transfer medium compressed by the compressor flows to the condenser through the first conduit, the eighth conduit and the sixth conduit. The heat transfer medium flows from the condenser to the heat exchanger through the ninth conduit and the third conduit and flows from the heat exchanger to the input port of the compressor through the second conduit and the seventh conduit. The apparatus has a heat pump mode where the valve member connects the third port to the second port and the fourth port to the first port, whereby the heat transfer medium compressed by the compressor flows to the heat exchanger through the first conduit and the second conduit, and flows from the heat exchanger to the evaporator through the third conduit and the fourth conduit. The heat transfer medium flows from the evaporator to the input port of the compressor through the fifth conduit, the eighth conduit and the seventh conduit.  
      According to a further aspect of the invention, there is provided a vehicle having an interior, an internal combustion engine and a combined heat pump and air-conditioning apparatus. The apparatus has a compressor with an input and an output, a heat exchanger communicating with the interior of the vehicle, a condenser, an evaporator and heat transfer medium conduits for a heat transfer medium. The medium conduits interconnect the heat exchanger, the condenser and the evaporator. Coolant conduits interconnect the evaporator and the engine for carrying coolant heated by the engine. A valve is operatively connected to the medium conduits and connects the output of the compressor to the condenser and connects the heat exchanger to the input of the compressor during an air-conditioning mode where the heat exchanger operates as an evaporator. The valve operatively connects the output of the compressor to the heat exchanger and connects the input of the compressor to the evaporator during a heat pump mode where the heat exchanger acts as a condenser.  
      According to a still further aspect of the invention, there is provided a method of heating and cooling a space having a heat exchanger and a fan for directing air over the heat exchanger into the space. The method comprises cooling the space during an air-conditioning mode by connecting an output of a heat transfer medium compressor to a condenser, connecting the condenser to the heat exchanger and connecting the heat exchanger to an input of the compressor, whereby the heat exchanger and fan act as an evaporator for cooling the space. The space is heated during a heat pump mode by connecting the output of the compressor to the heat exchanger, connecting the heat exchanger to an evaporator and connecting the evaporator to the input of the compressor.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic diagram of a combined air-conditioner and heat pump apparatus for a vehicle, according to an embodiment of the invention, showing the apparatus in an air-conditioning mode;  
       FIG. 2  is a diagram similar to  FIG. 1  showing the apparatus in a heat pump mode; and  
       FIG. 3  is a partly diagrammatic, isometric view of the apparatus of  FIGS. 1 and 2 . 
    
    
     DETAILED DESCRIPTIONS OF THE PREFERRED EMBODIMENTS  
      Referring to the drawings, these show a combined heat pump and air-conditioning apparatus  10  according to an embodiment of the invention. The apparatus includes a heat exchanger  12  which, as detailed below, acts alternatively as an evaporator or condenser depending upon the mode of operation of the apparatus. Air driven past the heat exchanger  12  by a fan  16 , adjacent to the heat exchanger, is discharged into interior  20  of cab  22  of a vehicle. The heat exchanger in this particular example may be a conventional or pre-existing heat exchanger and fan which normally function as an evaporator for an air-conditioning system powered by an auxiliary power unit for the vehicle. In one particular embodiment the heat exchanger may comprise a second coil in a pre-existing evaporator installed in the vehicle for the conventional air-conditioning system powered by the vehicle engine, as disclosed in the co-pending patent application entitled AUXILIARY AIR-CONDITIONING APPARATUSES AND METHODS FOR VEHICLES and assigned to Teleflex Canada Incorporated.  
      The apparatus also includes an air-conditioning condenser  24  with a fan  25 , a heat pump evaporator  26  and a compressor  28  driven by engine  30  which, in this example, is an auxiliary engine for the vehicle forming part of an auxiliary power unit for the vehicle. The evaporator heats a heat transfer medium flowing through conduits  54  and  55  with engine coolant flowing through coolant conduits  96  and  98 . In this example a continuous belt  32  operatively connects sheave  34  of the engine, shown in  FIG. 3 , to sheave  36  of the compressor. There is a valve  40 , in this particular example a 4-way, 2 position valve, which is used to select an air-conditioning mode or a heat pump mode as described in more detail below. An expansion valve  42 , in this case a capillary tube, acts as an expansion device.  
      There is a first conduit  51  connected to output port  60  of the compressor, a second conduit  52  connected to a first port  62  of the heat exchanger, a third conduit  53  connected to port  64  of the heat exchanger and a fifth conduit  55  connected to port  68  of the evaporator. There are a sixth conduit  56 , a seventh conduit  57  and an eighth conduit  58 . Conduit  56  connects port  66  of the condenser to the fifth conduit  55  and to the eighth conduit  58 . The seventh conduit  57  is connected to input port  70  of the compressor.  
      The valve  40  has four ports  81 ,  82 ,  83  and  84 . Port  81  is connected to the seventh conduit  57 . Port  82  is connected to second conduit  52 . Third port  83  is connected to conduit  51 , while fourth port  84  is connected to eighth conduit  58 .  
      The valve has a valve member or spool  90  which is movable to two different positions, shown in  FIGS. 1 and 2 , by means of an actuator  92 , in this case a solenoid. In the air-conditioning mode, shown in  FIG. 1 , the valve member connects second port  82  to the first port  81  and connects the third port  83  to the fourth port  84 . Alternatively, in the heat pump mode shown in  FIG. 2 , the valve member connects the third port  83  to the second port  82  and connects the fourth port  84  to the first port  81 .  
      The coolant conduits  96  and  98  extend from the engine  30  to the evaporator  26  for providing hot coolant from the engine to the evaporator and for returning the coolant to the engine.  
      There is a first one-way valve  100  positioned along ninth conduit  59  which prevents a flow of fluid toward the condenser  24 . A second one-way valve  102  is located along fifth conduit  55  and prevents a flow of fluid toward the evaporator  26 .  
      During the air-conditioning mode, as shown in  FIG. 1 , heat transfer medium is fed into input port  70  of the compressor  28  through the seventh conduit  57  and is compressed by the compressor, discharged through port  60  and passes through the first conduit  51  to third port  83  of the valve  40 . The heat transfer medium then passes from port  84  of the valve through conduits  58  and  56  to condenser  24 . The medium cannot flow into the evaporator  26  due to the action of one-way valve  102 . The medium is condensed in the condenser and then passes through capillary tube  42  where the medium is depressurized and passes through heat exchanger  12  which acts as an evaporator during the air-conditioning mode. The fan  16  forces air through the heat exchanger  12 , thereby cooling the air for the interior  20  of the vehicle.  
      Referring to  FIG. 2 , this shows the apparatus  10  in the heat pump mode. Here the valve  40  connects port  83  to port  82  and connects port  84  to port  81 . Heat transfer medium compressed by the compressor exits through output port  60  of the compressor and enters port  62  of the heat exchanger  12  via conduits  51  and  52 . In this mode, the heat exchanger acts as a condenser. The fan  16  forces air through the heat exchanger  12 , thereby heating the cab and cooling the medium to condense the medium. The condensed medium passes through capillary tube  42 , via conduit  53 , where it is depressurized and enters port  67  of the evaporator  26  via conduit  54 . The medium is prevented from entering the condenser  24  by one-way valve  100 . In the evaporator, the heat transfer medium is heated by hot coolant from the engine  30  circulated through the evaporator by conduits  96  and  98 . The evaporated medium is drawn into the input port  70  of the compressor via conduits  55 ,  58  and  57  and ports  84  and  81  of the valve  40 . The medium does not enter the condenser through conduit  56  due to higher pressure on the opposite side of the condenser. Thus it may be seen that the interior of the vehicle is heated by energy transferred from the engine  30 , both from coolant flowing through the evaporator  26  and by the energy applied to the compressor  28  by the engine  30 .  
      It will be understood by someone skilled in the art that many of the details provided above are by way of example only and can be varied or deleted without departing from the scope of the invention which is to be interpreted with reference to the following claims.