JP2006300343A - Refrigerating cycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enlarge a temperature range of a heat-exchanged fluid in a radiator and a heat sink that can maximize COP by preventing the abnormal rise of a discharge temperature caused by the intake temperature rise of a compressor. <P>SOLUTION: This refrigerating cycle comprises a refrigerant circulating circuit with the compressor, the radiator, a pressure reducing means and the heat sink connected in annular shape, and a cycle heat exchanger for exchanging heat between a refrigerant between the radiator and pressure reducing means, and a refrigerant between the pressure reducing means and heat sink. The refrigerating cycle further comprises a heat exchange quantity adjusting means for adjusting the heat exchange quantity of the cycle heat exchanger. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention includes a refrigeration cycle using a supercritical fluid as a refrigerant, and in particular, a cycle heat exchanger that exchanges heat with each other between a high-pressure refrigerant between a radiator and a decompression unit and a low-pressure refrigerant between the decompression unit and a heat absorber. Related to the refrigeration cycle.

  The background art of the present invention will be described below with reference to the drawings shown in Patent Document 1. In FIG. 5, the refrigerant circuit 5 includes a compressor 1 that compresses the refrigerant, a radiator 2 that cools the refrigerant, an internal heat exchanger 6 that exchanges heat between the high-pressure side line and the low-pressure side line, and a reduced pressure that depressurizes the refrigerant. It comprises means 3 and a heat absorber 4 for evaporating and evaporating the refrigerant.

  This refrigerant circuit 5 is connected to the high-pressure side passage 17a of the internal heat exchanger 6 from the discharge side of the compressor 1 via the radiator 2, and the outflow side of the high-pressure side passage 17a is connected to the decompression means 3 to compress the refrigerant circuit 5. From the machine 1 to the inflow side of the decompression means 3. The outflow side of the decompression means 3 is connected to the heat absorber 4, and the outflow side of the heat absorber 4 is connected to the low pressure passage 17 b of the internal heat exchanger 6. The outflow side of the low-pressure passage 17b is connected to the suction side of the compressor 1.

  That is, the internal heat exchanger 6 performs heat exchange between the high pressure line extending from the outflow side of the radiator 2 to the decompression unit 3 and the low pressure side line extending from the outflow side of the heat absorber 4 to the compressor 1.

  In the refrigerant circuit 5, carbon dioxide is used as the refrigerant, and the refrigerant compressed by the compressor 1 enters the radiator 2 as a high-temperature and high-pressure supercritical refrigerant, where it dissipates heat and cools it. Thereafter, the internal heat exchanger 6 exchanges heat with the low-temperature refrigerant in the low-pressure side line, further cools, and is sent to the decompression means 3 without being liquefied. Then, the pressure is reduced in the pressure reducing means 3 to become low-temperature and low-pressure wet steam, and heat is exchanged with air in the heat absorber 4 to evaporate and flow into the internal heat exchanger 6. In the internal heat exchanger 6, the high-pressure side line After the heat exchange with the high-temperature refrigerant, it is returned to the compressor 1.

  Further, on the low pressure side line of the refrigerant circuit 1, a heat exchange amount adjusting means 7 b that bypasses the internal heat exchanger 6 and adjusts the heat exchange amount of the internal heat exchanger 6 is provided. That is, the heat exchange amount adjusting means 7 b has one end connected between the decompression means 3 and the internal heat exchanger 6 and the other end connected between the internal heat exchanger 6 and the compressor 1.

The control device 16 inputs a pressure signal from the discharge pressure sensor 18 that detects the discharge pressure of the compressor 1 and a signal from the discharge temperature sensor 19 that detects the discharge temperature of the compressor 1, and performs COP based on these signals. The optimum pressure to be maximized is calculated, and whether or not the high pressure has risen to the dangerous area, whether or not the discharge temperature has risen to the dangerous temperature, etc. are determined, and based on this, the heat exchange amount adjusting means 7b is opened. The degree of driving is controlled.
JP 11-193967 A

  However, in the above configuration, the heat exchange by the internal heat exchanger 6 causes the intake temperature of the compressor 1 to rise, so the discharge temperature also rises. If the heat exchange amount is increased with the aim of improving COP, the suction temperature further rises and the discharge temperature also rises.

  If the heat exchange amount is reduced by the heat exchange amount adjusting means 7b in order to avoid an abnormal increase in the discharge temperature, an abnormal increase in the discharge temperature can be avoided, but the COP will not be an optimum value but will decrease.

  Depending on the temperature of the heat exchange fluid of the radiator 2 or the heat absorber 4, the amount of heat exchange that can avoid the abnormal discharge temperature cannot be set while maximizing the COP. The temperature range of the heat exchange fluid of the radiator 2 and the heat absorber 4 that can be supported is narrow.

  An object of the present invention is to widen the temperature range of the heat exchange fluid of the radiator 2 and the heat absorber 4 that can maximize COP by preventing an abnormal increase in discharge temperature due to an increase in the intake temperature of the compressor 1. It is aimed.

  In order to achieve this object, the refrigeration cycle of the present invention includes a cycle heat exchanger that exchanges heat with each other between the refrigerant between the radiator and the decompression unit and the refrigerant between the decompression unit and the heat absorber.

  As a result, it is possible to prevent an increase in the discharge temperature caused by heating the refrigerant sucked in the compressor and increasing the suction temperature, and to optimally adjust the COP.

  The refrigeration cycle of the present invention has a refrigeration cycle in which the temperature range of the heat exchange fluid of the heat sink and the heat sink that can maximize COP is prevented by preventing an abnormal increase in discharge temperature due to an increase in the suction temperature of the compressor. Can be provided.

  The first invention includes a cycle heat exchanger that exchanges heat with each other between the refrigerant between the radiator and the decompression unit and the refrigerant between the decompression unit and the heat absorber.

  As a result, it is possible to prevent an increase in discharge temperature by heating the refrigerant sucked in the compressor and raising the suction temperature, and a refrigeration cycle having a wider temperature range of the heat exchange fluid of the heat sink and the heat sink that can maximize COP Can provide.

  The second aspect of the invention is particularly the first aspect of the invention, and is provided with heat exchange amount adjusting means for adjusting the heat exchange amount of the cycle heat exchanger.

  As a result, the adjustment range of the heat exchange amount at which the COP is optimal can be broadened, so that it is possible to provide a refrigeration cycle in which the temperature range of the heat exchange fluid of the heat sink and the heat absorber that can maximize the COP is wider.

  The third invention is the first and second inventions, in particular, by adjusting the heat exchange amount using the heat exchange amount adjusting means, thereby adjusting the high pressure and bringing about a predetermined cycle efficiency.

  As a result, the adjustment range of the high pressure can be expanded by adjusting the heat exchange amount at which the COP is optimal, so that the temperature range of the heat exchange fluid of the radiator and the heat sink that can maximize the COP is wider. Can provide.

  The fourth invention is particularly the first to third inventions, wherein the heat exchange amount adjusting means is provided in the refrigerant circuit on the high pressure side.

  As a result, the flow amount of the high-pressure side refrigerant to the cycle heat exchanger can be adjusted. Therefore, the adjustment range of the high-pressure pressure can be broadened by adjusting the heat exchange amount at which the COP is optimal. In addition, a refrigeration cycle having a wider temperature range of the heat exchange fluid of the heat absorber can be provided.

  The fifth invention is particularly the first to fourth inventions, wherein the heat exchange amount adjusting means is provided in the refrigerant circuit on the low pressure side.

  As a result, the flow amount of the low-pressure side refrigerant to the cycle heat exchanger can be adjusted. Therefore, the adjustment range of the high-pressure pressure can be broadened by adjusting the heat exchange amount at which the COP is optimal. In addition, a refrigeration cycle having a wider temperature range of the heat exchange fluid of the heat absorber can be provided.

  In the sixth invention, in particular, in the first to fifth inventions, a refrigerant whose pressure is increased to a critical pressure or higher is used in the heat pump.

  As a result, the water is heated by the refrigerant whose pressure has been increased to the critical pressure or higher, so that the refrigerant is pressurized to the critical pressure or higher by the compressor. Even if it does not condense. Therefore, it becomes easy to form a temperature difference between the flow path on the refrigerant side and the flow path on the water side over the entire heat exchanger that heats the water with the refrigerant, so that hot water can be obtained and the heat exchange efficiency can be increased.

(Embodiment 1)
Hereinafter, a refrigeration cycle according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram of a refrigeration cycle in an embodiment of the present invention.

  In FIG. 1, a refrigerant circuit 5 includes a compressor 1 for compressing refrigerant, a radiator 2 for cooling the refrigerant, a cycle heat exchanger 20 for exchanging heat between the refrigerant on the high-pressure side line and the low-pressure side line, and decompression means for decompressing the refrigerant. 3. It is comprised by the heat absorber 4 which evaporates and evaporates a refrigerant | coolant.

  The refrigerant circuit 5 is connected from the radiator 3 on the discharge side of the compressor 1 to the high pressure side passage 17 a of the cycle heat exchanger 20, and the outflow side of the high pressure side passage 17 a is connected to the decompression means 3. To the inflow side of the decompression means 3. The outflow side of the decompression means 3 is connected to the low pressure side passage 17 b of the cycle heat exchanger 20, and the outflow side of the low pressure side passage 17 b is connected to the intake side of the compressor 1 through the heat absorber 4. .

  That is, the cycle heat exchanger 20 performs heat exchange between the high pressure line extending from the outflow side of the radiator 2 to the decompression unit 3 and the low pressure side line extending from the outflow side of the decompression unit 3 to the heat absorber 4.

  In the refrigerant circuit 5, carbon dioxide is used as the refrigerant, and the refrigerant compressed by the compressor 1 enters the radiator 2 as a high-temperature and high-pressure supercritical refrigerant, where it dissipates heat and cools it.

  Thereafter, heat is exchanged with the low-temperature refrigerant in the low-pressure side line in the cycle heat exchanger 20 to further cool it, and it is sent to the decompression means 3 without being liquefied. Then, the pressure is reduced in the pressure reducing means 3 to become low-temperature and low-pressure wet steam, and flows into the cycle heat exchanger 20. After heat exchange with the high-temperature refrigerant in the high-pressure side line in the cycle heat exchanger 20, Heat exchange is performed to evaporate and return to the compressor 1.

  Further, heat exchange amount adjusting means 7 a and 7 b for bypassing the cycle heat exchanger 20 and adjusting the heat exchange amount of the cycle heat exchanger 20 are provided on the high pressure side line and the low pressure side line of the refrigerant circuit 1, respectively. ing. That is, the heat exchange amount adjusting means 7 a has one end connected between the decompression means 3 and the cycle heat exchanger 6 and the other end connected between the cycle heat exchanger 6 and the radiator 2. The heat exchange amount adjusting means 7 b has one end connected between the decompression means 3 and the cycle heat exchanger 6 and the other end connected between the cycle heat exchanger 6 and the heat absorber 4.

  The control device 16 includes a radiator fluid temperature sensor 8 that detects the temperature of the heat exchange fluid with the refrigerant flowing in the radiator 2, and a heat absorber that detects the temperature of the heat exchange fluid with the refrigerant flowing in the heat absorber 4. Based on the signal from the fluid temperature sensor 9, the opening degree that is the optimum heat exchange amount of the heat exchange adjusting means 7 a, 7 b that maximizes the COP is calculated and driven and controlled. Note that the heat exchange fluid here may be liquid or gas.

  FIG. 2 is a cycle diagram of the present invention, in which the horizontal axis represents specific enthalpy and the vertical axis represents pressure. The curve in the figure shows the saturation curve of carbon dioxide.

  A and A 'are discharge points of the compressor 1, B and E are outlets of the radiator 2, C is an inlet of the heat absorber 4, and D is an intake point of the compressor 1, respectively. Point B 'represents the outlet of the high-pressure cycle heat exchanger 20, and point C1 represents the inlet of the low-pressure cycle heat exchanger 20.

  Furthermore, when the heat exchange amount of the cycle heat exchanger 20 is zero, the cycle state can be represented by A-B-C-D.

  Here, when the amount of heat exchange in the cycle heat exchanger 20 is increased, the refrigerant at the point B becomes a point B ′ due to heat exchange, flows into the decompression means 3 and is decompressed to the point C ′. The The refrigerant at the point C ′ absorbs heat from the high-pressure refrigerant at the cycle heat exchanger 20 and is sent to the heat absorber 4 as a point C.

  At this time, in the figure, for example, 800 kg / m3 at the B 'point, 500 kg / m3 at the B point, the refrigerant density is different at the B' point and the B point, and the refrigerant density at the B 'becomes large.

  Therefore, since the refrigerant density at the point B ′ becomes larger than the refrigerant density at the point B, the refrigerant hold amount on the high pressure side increases, the high pressure decreases, and the state of the refrigerant discharged from the compressor 1 becomes the point A ′. .

  At this time, the cycle heat exchanger 20 exchanges heat between E-B 'and C-C' and the heat exchange amount becomes equal, but the state of the refrigerant sucked in the compressor 1 does not change greatly.

  The efficiency COP is COP0 = Δhg ÷ Δhc when the heat exchange amount is zero, and COP1 = Δhg ÷ Δhc ′ when the heat exchange amount is zero when the heat exchange amount is zero, and Δhc> Since Δhc ′, COP0 <COP1.

  FIG. 3 is a diagram showing the relationship between the high pressure and the heat exchange amount of the cycle heat exchanger 20.

  When the heat exchange amount of the cycle heat exchanger 20 is increased, the density of the refrigerant flowing into the decompression means 3 can be increased, so that the high pressure can be reduced.

  FIG. 4 is a diagram showing the relationship between the high pressure and the COP, in which the refrigerant temperature at the radiator outlet is constant.

  When the amount of heat exchange in the cycle heat exchanger 20 is increased and the high pressure is lowered, the COP is improved. However, if the pressure drops below a certain high pressure, the density of the refrigerant flowing into the pressure reducing means becomes excessively large, causing a shortage of the refrigerant gas in the refrigerant circuit 5 and reducing the COP.

  Thus, by adjusting the heat exchange amount of the cycle heat exchanger 20, the COP can be optimally adjusted by adjusting the high pressure.

  Further, since there is no heat exchange with the suction refrigerant of the compressor 1 and the suction refrigerant is not heated, the suction temperature of the compressor 1 does not depend on the amount of heat exchange of the cycle heat exchanger 20, so that the compressor It is possible to prevent the discharge temperature from rising due to heating the suction refrigerant and raising the suction temperature, and to adjust the COP optimally to widen the temperature range of the heat exchange fluid of the radiator 2 and the heat absorber 4.

  In the above-described embodiment, the high-pressure side pressure using carbon dioxide as the refrigerant is equal to or higher than the critical pressure of the refrigerant. However, these embodiments are not limited to this, and the high-pressure side pressure is It can also be applied to those that are less than the critical pressure. In the above-described embodiment, the air conditioner is dedicated to heating, but the present invention is not limited to this, such as an air conditioner that can be switched between heating and cooling, a hot water heater that heats hot water using a heat pump operation, and the like. In particular, the present invention can be applied to multifunctional water heaters such as floor heating and bath drying devices.

  As described above, in the refrigeration cycle according to the present invention, the temperature range of the heat exchange fluid of the heat sink and the heat sink that can maximize the COP by preventing the abnormal increase in the discharge temperature due to the increase in the suction temperature of the compressor. Is useful as a wider refrigeration cycle.

Circuit diagram of refrigeration cycle in an embodiment of the present invention Cycle diagram of refrigeration cycle in an embodiment of the present invention Relationship diagram between high pressure and heat exchange amount of cycle heat exchanger 20 in an embodiment of the present invention Relationship diagram between high pressure and COP in an embodiment of the present invention Circuit diagram of conventional refrigeration cycle

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Compressor 2 Radiator 3 Pressure reducing means 4 Heat absorber 5 Refrigerant circuit 7a, 7b Heat exchange amount adjusting means 20 Cycle heat exchanger

Claims (6)

A refrigerant circulation circuit having a compressor, a radiator, a decompression unit, and a heat absorber; a high-pressure refrigerant between the radiator and the decompression unit; and a low-pressure refrigerant between the decompression unit and the heat absorber; A refrigeration cycle equipped with a cycle heat exchanger that exchanges heat with each other. The refrigeration cycle according to claim 1, further comprising heat exchange amount adjusting means for adjusting a heat exchange amount of the cycle heat exchanger. 3. The refrigeration cycle according to claim 2, wherein the high pressure is adjusted by adjusting the heat exchange amount using the heat exchange amount adjusting means, thereby providing a predetermined cycle efficiency. The refrigeration cycle according to claim 2 or 3, wherein the heat exchange amount adjusting means is provided in the refrigerant circuit on the high pressure side. The refrigeration cycle according to any one of claims 2 to 4, wherein the heat exchange amount adjusting means is provided in the refrigerant circuit on the low pressure side. The refrigeration cycle according to any one of claims 1 to 5, wherein a refrigerant whose pressure is increased to a critical pressure or higher is used.

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