JP2009162403A - Air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To minimize heat loss in a refrigerant-fluid heat exchanger for exchanging heat between a primary side refrigerating cycle and a secondary side liquid fluid cycle. <P>SOLUTION: This air conditioner 10 heats and cools a room by heat exchange between: the refrigerating cycle 20 provided with successively connecting a compressor 21, a four-way valve 22, an outdoor side heat exchanger 23, an expansion device 25 and a refrigerant-fluid heat exchanger 40, and using hydrocarbons refrigerant as a refrigerant; and the liquid fluid cycle 30 constituted by successively connecting a liquid pump 11, the refrigerant-fluid heat exchanger 40, and an indoor side heat exchanger 32 by the refrigerant-fluid heat exchanger 40. The air conditioner is further provided with: an internal heat exchanger 24 exchanging heat between a suction side of the compressor 21 and an intermediate part between the outdoor side heat exchanger 23 and the expansion device 25; and a control portion 50 performing the control so that the refrigerant of the refrigerating cycle is not in a superheated state in the refrigerant-fluid heat exchanger 40 and is in a superheated state in the internal heat exchanger 24 in a cooling operation. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an air conditioner such as a home air conditioner, and more particularly to a combustible refrigerant used as a refrigerant.

HC refrigerants such as R290 (propane) and R600a (isobutane) are used in refrigerators and the like as alternative refrigerants for fluorocarbon refrigerants that have been used in refrigeration cycles. However, since the HC refrigerant is a flammable refrigerant, the amount of the refrigerant is large, and there are many restrictions for flowing into the indoor side of the air conditioner connected to the pipe. For this reason, a primary side refrigeration cycle using HC refrigerant is disposed on the outdoor side, and a secondary side liquid fluid cycle that performs heat transfer using sensible heat fluid such as water or brine is disposed on the indoor side. -What is performing heat exchange with a fluid heat exchanger is known (for example, refer to patent documents 1).
JP 2006-3679 A

  The air conditioner described above has the following problems. That is, in the above-described refrigerant-fluid heat exchanger for exchanging heat between the primary-side refrigeration cycle and the secondary-side liquid-fluid cycle, heat loss is likely to occur, and refrigeration efficiency may be reduced. .

  Accordingly, an object of the present invention is to provide an air conditioner that can minimize heat loss in a refrigerant-fluid heat exchanger that performs heat exchange between a primary-side refrigeration cycle and a secondary-side liquid-fluid cycle. Yes.

  In order to solve the problems and achieve the object, the air conditioner of the present invention is configured as follows.

  A compressor, a four-way switching valve, an outdoor heat exchanger, an expansion device, a refrigerant-fluid heat exchanger are sequentially connected, and a refrigeration cycle using a hydrocarbon-based refrigerant as a refrigerant, a liquid pump, a refrigerant-fluid heat exchanger In an air conditioner that performs heat exchange with a liquid-fluid cycle formed by sequentially connecting indoor heat exchangers with the refrigerant-fluid heat exchanger to perform indoor air conditioning, the suction side of the compressor, and the chamber An internal heat exchanger that exchanges heat between the outer heat exchanger and the expansion device, and a control that controls the refrigerant in the refrigeration cycle to be in a superheat state in the internal heat exchanger during cooling operation And a portion.

  According to the present invention, it is possible to minimize heat loss in the refrigerant-fluid heat exchanger that performs heat exchange between the primary-side refrigeration cycle and the secondary-side liquid fluid cycle.

  FIG. 1 is an explanatory view showing the structure of an air conditioner 10 according to an embodiment of the present invention. The air conditioner 10 includes a refrigeration cycle 20, a liquid-fluid cycle 30, a refrigerant-fluid heat exchanger 40 shared by these cycles, and a control unit 50 that controls each unit in a coordinated manner. In FIG. 1, a solid line arrow R indicates the flow direction of the refrigerant during cooling, and a broken line arrow D indicates the flow direction of the refrigerant during heating.

  In the refrigeration cycle 20, a compressor 21, a four-way valve 22, an outdoor heat exchanger 23, an internal heat exchanger 24, an expansion valve 25, a refrigerant-fluid heat exchanger 40, and the compressor 21 are sequentially connected. In FIG. 1, 26 indicates a temperature sensor (output value: Ta), 27 indicates a temperature sensor (output value: Tb), and 28 indicates a temperature sensor (output value: Tc). An HC refrigerant is used as the refrigerant.

  In the liquid fluid cycle 30, a liquid pump 31, a refrigerant-fluid heat exchanger 40, and an indoor heat exchanger (FCU) 32 are sequentially connected. In FIG. 1, reference numeral 33 denotes a reservoir tank. As the liquid fluid, water or brine (calcium chloride aqueous solution, sodium chloride aqueous solution, etc.) is usually used.

  The air conditioner 10 configured as described above operates as follows. That is, during cooling, the compressor 21 and the liquid pump 31 are operated, and the refrigerant and liquid fluid flow along the solid arrow C in FIG. In the refrigeration cycle 20, the high-temperature and high-pressure refrigerant vapor exiting the compressor 21 passes through the four-way valve 22 and flows into the outdoor heat exchanger 23, where heat is taken away by the outside air, and condensed and liquefied. The high-pressure liquid refrigerant that has exited the outdoor heat exchanger 23 passes through the internal heat exchanger 24, flows into the expansion valve 25, is decompressed, becomes a low-pressure gas-liquid two-phase refrigerant, and enters the refrigerant-fluid heat exchanger 40. Inflow. Then, while flowing through the refrigerant flow path in the refrigerant-fluid heat exchanger 40, it is heated by the brine flowing in the brine flow path, and most of the low-pressure liquid refrigerant becomes vapor and flows out of the refrigerant-fluid heat exchanger 40. . This low-pressure refrigerant passes through the four-way valve 22 and is sucked into the compressor 21 again.

  On the other hand, in the liquid fluid cycle 30, the brine discharged by the liquid pump 31 flows into the indoor heat exchanger 32 via the refrigerant-fluid heat exchanger 40, exchanges heat with indoor air, and cools the room. . The brine heated by the room air and having a raised temperature flows into the refrigerant-fluid heat exchanger 40. And while flowing in the brine flow path in the refrigerant-fluid heat exchanger 40, it is cooled by the refrigerant flowing in the refrigerant flow path, and the brine temperature decreases. The brine that has left the refrigerant-fluid heat exchanger 40 flows into the liquid pump 31 again. In this way, the refrigerant-fluid heat exchanger 40 is configured to have a parallel flow that flows in the same direction of the refrigerant and the brine during the cooling operation.

  Next, control by the control unit 50 will be described. In the refrigeration cycle 20, the refrigerant-fluid heat exchanger 40 functions as an evaporator during the cooling operation, but the liquid refrigerant is not completely evaporated in the refrigerant-fluid heat exchanger 40, and control is performed so as not to cause superheat. I do. Specifically, the temperature Ta of the temperature sensor 26 at the inlet of the refrigerant-fluid heat exchanger 40 and the temperature Tc of the temperature sensor 28 on the outlet side of the internal heat exchanger 24 are Ta> Tb and Ta <Tc (+ β ) Is adjusted so as not to be superheated in the refrigerant-fluid heat exchanger 40 by adjusting the opening of the expansion valve 25 or the operating frequency of the compressor 21 so as to satisfy.

  As shown in FIG. 2, the refrigerant is allowed to flow out of the outlet without being superheated in the refrigerant-fluid heat exchanger 40. As a result, the temperature difference ΔT between the refrigerant temperature Tr and the water temperature Tw can be ensured also at the outlet of the refrigerant-fluid heat exchanger 40.

  On the other hand, if the refrigerant that has flowed out of the refrigerant-fluid heat exchanger 40 returns to the compressor 21 in a liquid mixture state without being superheated, the reliability of the compressor 21 is impaired. Heat is exchanged with the refrigerant at the outlet of the exchanger (condenser) 23 to superheat the refrigerant.

  For comparison, FIG. 3 shows control when the refrigerant superheats in the refrigerant-fluid heat exchanger 40. That is, the difference between the temperature Ta of the temperature sensor 26 on the inlet side of the refrigerant-fluid heat exchanger 40 and the temperature Tb of the temperature sensor 27 on the outlet side during evaporation is controlled so that Ta <Tb (+ α). Thus, control is performed so that the refrigerant superheats in the refrigerant-fluid heat exchanger 40. As a result, the refrigerant causes superheat on the outlet side of the refrigerant-fluid heat exchanger 40, the temperature Tr rises, and the temperature difference ΔT ′ from the water temperature Tw decreases.

  Therefore, in the case of the present invention shown in FIG. 2, when a heat exchange amount equivalent to the conventional one shown in FIG. 3 is obtained, the evaporation temperature (evaporation pressure) can be increased to Tr ′, and compression The load on the machine 21 can be reduced, and the refrigeration cycle efficiency (cycle COP) can be increased.

  Note that α and β are variables that take a fixed value or a refrigerant flow rate into consideration.

  Next, during heating, in the refrigeration cycle 20, the high-temperature and high-pressure refrigerant vapor that has exited the compressor 21 flows into the refrigerant-fluid heat exchanger 40 through the four-way valve 22. The refrigerant that has flowed into the refrigerant flow path in the refrigerant-fluid heat exchanger 40 is cooled, condensed, and liquefied by the brine flowing in the brine flow path. The high-pressure liquid refrigerant that has exited the refrigerant-fluid heat exchanger 40 flows into the expansion valve 25 and is depressurized to become a low-pressure gas-liquid two-phase refrigerant that passes through the internal heat exchanger 24 and operates as an outdoor heat exchanger. Flows into the vessel 23. This low-pressure gas-liquid two-phase refrigerant takes heat from the outside air in the outdoor heat exchanger 23 and evaporates to become a low-pressure vapor refrigerant and flows out of the outdoor heat exchanger 23. This low-pressure vapor refrigerant passes through the four-way valve 22 and is sucked into the compressor 21 again.

  In the liquid fluid cycle 30, the brine discharged by the liquid pump 11 flows into the indoor heat exchanger 32 through the refrigerant-fluid heat exchanger 40, exchanges heat with indoor air, and heats the room. . The brine whose heat has been taken away by the room air and whose temperature has been lowered flows into the refrigerant-fluid heat exchanger 40. And while flowing in the brine flow path in the refrigerant-fluid heat exchanger 40, it is heated by the refrigerant flowing in the refrigerant flow path, and the brine temperature rises. The brine that has left the refrigerant-fluid heat exchanger 40 flows into the indoor heat exchanger 32 again. Thus, at the time of heating operation, it becomes a counterflow which flows through the refrigerant | coolant-fluid heat exchanger 40 in the reverse direction of a refrigerant | coolant and a brine.

  As described above, in the air conditioner 10 according to the present embodiment, the refrigeration cycle efficiency is ensured by sufficiently ensuring the temperature difference ΔT between the refrigerant and water on the outlet side of the refrigerant-fluid heat exchanger 40 during the cooling operation. Can be improved.

  FIG. 4 is a graph showing the relationship between the suction temperature (suction temperature) of the compressor 21 and the cycle COP and the high-pressure side outlet temperature of the internal heat exchanger 24 when a puff pan is used as the refrigerant of the refrigeration cycle 20. is there. When the amount of heat exchange in the internal heat exchanger 24 is increased, the outlet temperature of the high-pressure side internal heat exchanger 24 is lowered, and the suction temperature of the compressor 21 is raised. And the cycle COP is rising with the rise in suction temperature. As described above, when propane is used as a refrigerant, the system efficiency can be improved by increasing the heat exchange amount of the internal heat exchanger 24 and increasing the suction temperature, as long as the system does not interfere with the discharge temperature.

  The present invention is not limited to the above embodiment. For example, the temperature sensor 25 may be provided at an arbitrary location in the refrigerant-fluid heat exchanger 40, and the temperature sensor 26 may be provided at the inlet side of the internal heat exchanger 24. Of course, various modifications can be made without departing from the scope of the present invention.

Explanatory drawing which shows the structure of the air conditioner which concerns on one embodiment of this invention. The graph which shows the temperature change of the refrigerant | coolant and water in the refrigerant | coolant-fluid heat exchanger at the time of incorporating and controlling in the air conditioner. The graph which shows the temperature change of the refrigerant | coolant and water in the refrigerant | coolant-fluid heat exchanger in the case of not incorporating control in the air conditioner. The graph which showed the relationship between the suction temperature (suction temperature) of a compressor at the time of using a blow pan as a refrigerant | coolant of a refrigerating cycle, cycle COP, and the high temperature side exit temperature of an internal heat exchanger.

Claims (3)

A refrigeration cycle in which a compressor, a four-way switching valve, an outdoor heat exchanger, an expansion device, a refrigerant-fluid heat exchanger are sequentially connected, and a hydrocarbon-based refrigerant is used as a refrigerant;
A liquid fluid cycle in which a liquid pump, a refrigerant-fluid heat exchanger, and an indoor heat exchanger are sequentially connected,
In the air conditioner that performs heat exchange with the refrigerant-fluid heat exchanger to cool and heat the room,
An internal heat exchanger that exchanges heat at the suction side of the compressor and an intermediate portion between the outdoor heat exchanger and the expansion device;
An air conditioner comprising: a control unit that performs control so that the refrigerant of the refrigeration cycle is in a superheat state in the internal heat exchanger during cooling operation.   The air conditioner according to claim 1, wherein the refrigerant-fluid heat exchanger is configured such that the refrigerant and the fluid flow in parallel during a cooling operation.   The air conditioner according to claim 1 or 2, wherein the refrigerant is propane.

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