JP2008032273A - Refrigerant circuit and hot water supply system using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerant circuit capable of introducing water to a water heat exchanger after a water temperature is surely lowered by a sub-heat exchanger even if an outside air temperature is high, and surely lowering the water temperature by the sub-heat exchanger in the refrigerant circuit operated by supercritical pressure, in the refrigerant circuit for producing hot water by the water heat exchanger. <P>SOLUTION: In this refrigerant circuit constituted by successively connecting a compressor, the water heat exchanger, a pressure reducing mechanism and an air heat exchanger, operated by supercritical pressure at a high pressure side, and introducing the water of which the heat is collected at a low pressure side to the water heat exchanger to heat the water, the sub-heat exchanger for collecting the heat at the low pressure side is disposed at the upstream side of the air heat exchanger and the downstream side of the pressure reducing mechanism. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a refrigerant circuit suitable for a refrigerant having a low critical temperature, and a hot water supply system.

  A heat pump using a general vapor compression refrigeration cycle has a refrigerant circuit that circulates refrigerant in the order of a compressor, a condenser, an expansion valve, and an evaporator. The refrigerant evaporates and collects heat in the process of passing through the evaporator, and condenses and dissipates heat in the process of passing through the condenser. The condenser constitutes a water heat exchanger together with a flow passage for water for hot water supply and a heating medium (fluid) for heating. In this water heat exchanger, water and a heat medium can be warmed by the heat radiation of the refrigerant and used for hot water supply or heating.

  In recent years, it has been desired to employ a substance that does not destroy the ozone layer as a refrigerant for a heat pump. Typical examples of such substances include R410A and carbon dioxide, and many hot water supply systems using them have been proposed.

  The characteristics of these refrigerants include that R410A has a larger global warming potential than carbon dioxide, and that the critical temperature of carbon dioxide is as low as about 31 ° C compared to about 72 ° C of R410A. In addition, in a hot water supply system that uses a refrigerant that operates in a transcritical cycle, such as carbon dioxide, if the high-temperature and high-pressure refrigerant is not sufficiently cooled, the radiative enthalpy difference cannot be obtained and the amount of heat released during the heat release process is reduced. , COP (= heat dissipation / compressor work) decreases. This tendency becomes more prominent as the temperature of the feed water increases.

Therefore, the temperature of water introduced into the water heat exchanger is adjusted to reduce the temperature of water entering the water heat exchanger, thereby increasing the heat dissipation amount in the radiator and maintaining high capacity and COP during operation. There has been proposed a hot water supply system that is previously lowered by a heat exchanger.
JP 2002-98429 A. Japanese Patent Application Laid-Open No. 2004-132658.

However, in a refrigerant circuit having a conventional water heat exchanger, the auxiliary heat exchanger is disposed downstream of the air heat exchanger in which the refrigerant that has exchanged heat with air flows or is cooled by a fan. Yes. Therefore, the water circuit that exchanges heat in the auxiliary heat exchanger exchanges heat with the refrigerant heated by the air heat exchanger or directly exchanges heat with the outside air. There may be a case where heat absorption is not sufficiently performed.
In particular, when the outside air temperature is high, heat absorption in the auxiliary heat exchanger is not sufficiently performed, so that the temperature of the water flowing into the water heat exchanger is not sufficiently lowered, and there is a problem that further improvement of COP cannot be expected.

Therefore, in the refrigerant circuit of claim 1, the compressor, the water heat exchanger, the pressure reducing mechanism, and the air heat exchanger are sequentially connected, and the high pressure side is operated at supercritical pressure, and the low pressure side auxiliary heat is In the refrigerant circuit for introducing and heating water recovered by the exchanger to the water heat exchanger,
The auxiliary heat exchanger is provided between the air heat exchanger and the pressure reducing mechanism.

  A hot water supply system according to a second aspect is a hot water supply system using the refrigerant circuit, wherein water introduced into the water heat exchanger is stored in a hot water storage tank.

  In the refrigerant circuit according to claim 1, since the auxiliary heat exchanger for recovering heat to the low pressure side is provided on the upstream side of the air heat exchanger and the downstream side of the pressure reducing mechanism, the water heat exchanger has a certain low value. The temperature of the refrigerant that flows to the expansion valve inlet after radiating heat from the water heat exchanger is between 30 and 40 degrees Celsius, which has a low utility value stored in warm water or hot water storage tanks in summer. Since it is difficult to be affected by hot water or the like, the refrigerant circuit can be operated efficiently. In addition, carbon dioxide, whose ozone depletion coefficient and global warming coefficient are much smaller than alternative refrigerants, can be used as the refrigerant, preventing problems such as ozone depletion, environmental pollution, and global warming. be able to.

  In the hot water supply system according to the second aspect, since water introduced into the water heat exchanger is stored in the hot water storage tank, an efficient hot water supply system can be configured.

  The hot water supply system of the present invention includes a compressor, a water heat exchanger that radiates heat from a high-pressure refrigerant to water, a decompression mechanism (such as an expansion valve), an air heat exchanger in which low-pressure refrigerant absorbs heat from the air, and the air heat exchanger A refrigerant circuit comprising a sub heat exchanger disposed between the pressure reducing mechanism and the low pressure refrigerant absorbing heat from water, a water supply pipe for supplying water to be heat exchanged by the water heat exchanger, a hot water storage tank, a sub heat A water circulation circuit consisting of a circulation pump that circulates in the flow passage that communicates the exchanger and the water heat exchanger, other detectors that detect refrigerant temperature, water temperature, hot water temperature, etc. (not shown) and the detection results of each element It consists of a control device that performs control.

  Hereinafter, specific embodiments will be described with reference to the drawings. First, FIG. In this embodiment, the compressor 31, the water heat exchanger 11 that dissipates heat from the high-pressure refrigerant to the water, the decompression mechanism (expansion valve or the like) 33, and the low-pressure refrigerant decompressed by the decompression mechanism absorbs heat from the water. The refrigerant circuit 10 includes a heat exchanger 12 and an air heat exchanger 34 in which a low-pressure refrigerant absorbs heat from the air.

  Further, the tap water stored in the hot water storage tank 20 by the water supply pipe 21 is sent from the lower part of the hot water storage tank 20 by the water circulation pump 42 and heat-exchanged with the refrigerant in the auxiliary heat exchanger 12, and then from the water heat exchanger inlet passage 40a. It has the flow path 40 which introduce | transduces into the water heat exchanger 11, heats with a refrigerant | coolant, returns to the upper part of the hot water storage tank 20 from a water heat exchanger exit flow path, and supplies warm water from the hot water supply port 24 as needed.

  Here, in the auxiliary heat exchanger 12, the low-temperature and low-pressure refrigerant absorbs heat from water. In the water heat exchanger 11, water is heated by a high-temperature and high-pressure refrigerant. At this time, the adjustment of the heat absorption amount may be handled by the water circulation amount, the rotation number of the blower fan 35, or the refrigerant circulation amount by changing the frequency of the compressor 31. Note that the auxiliary heat exchanger 12 and the water heat exchanger 11 both use refrigerant and water as counterflows. Further, the hot water storage tank 20 forms a layer due to the temperature difference so that high temperature water and low temperature water are indicated by broken lines.

  According to this, since the auxiliary heat exchanger 12 is arranged on the downstream side of the decompression mechanism 33 and on the upstream side of the air heat exchanger 34, water and the refrigerant are cooled before the temperature of the refrigerant rises in the air heat exchanger 34. The heat exchange can be performed. Therefore, even when the outside air temperature is high and the temperature of the refrigerant that has passed through the air heat exchanger 34 is the same as or higher than the temperature of the water, the temperature of the water introduced into the water heat exchanger 11 can be kept low. Thus, the water heat exchanger 11 can be heated by the refrigerant.

  Next, FIG. In this embodiment, the compressor 31, the water heat exchanger 11 that dissipates heat from the high-pressure refrigerant to the water, the decompression mechanism (expansion valve or the like) 33, and the low-pressure refrigerant decompressed by the decompression mechanism absorbs heat from the water. The refrigerant circuit 10 includes a heat exchanger 12 and an air heat exchanger 34 in which a low-pressure refrigerant absorbs heat from the air.

  Further, the tap water stored in the hot water storage tank 20 by the water supply pipe 21 is sent out from the lower part of the hot water storage tank 20 by the water circulation pump 42, absorbed by the auxiliary heat exchanger 12, heated by the water heat exchanger 11, and placed in the upper part of the hot water storage tank 20. Returning, it has the flow path 40 which supplies warm water from the hot water supply port 24 as needed.

  According to this, since the auxiliary heat exchanger 12 is installed inside the hot water storage tank 20 and directly absorbs heat from the water supplied by the water supply pipe 21, the lower heat storage tank 20 absorbs heat by the auxiliary heat exchanger 12 and cools it. The stored water is stored. The cooled water is sent to the water heat exchanger 11 by the water circulation pump 42, receives heat from the high-temperature and high-pressure refrigerant, converts it to hot water, returns it to the upper part of the hot water storage tank 20, and stores the hot water.

  In addition, since the auxiliary heat exchanger 12 can be arranged inside the hot water storage tank, the hot water supply system can be downsized, and the water cooled by the auxiliary heat exchanger 12 can be sent directly to the water heat exchanger 11. The water flow passage 40 can be simplified.

  FIG. In the embodiment shown in FIG. 1, the compressor 31, the water heat exchanger 11 that radiates heat from the high-pressure refrigerant to the water, the decompression mechanism (expansion valve or the like) 33, and the low-pressure refrigerant decompressed by the decompression mechanism absorbs heat from the water. The refrigerant circuit 10 includes the auxiliary heat exchanger 12 and an air heat exchanger 34 in which a low-pressure refrigerant absorbs heat from the air.

  Further, the tap water stored in the hot water storage tank 20 by the water supply pipe 21 is circulated from the approximate center of the hot water storage tank 20 to the auxiliary heat exchanger 12 by the second water circulation pump 42a and then absorbed, and then returned to the lower part of the hot water storage tank 20. It has a flow passage 40 that is fed from the lower part of the hot water storage tank 20 by the water circulation pump 42, heated by the water heat exchanger 11 and returned to the upper part of the hot water storage tank 20, and supplies hot water from the hot water supply port 24 as necessary.

According to this embodiment, the heat is recovered from the medium temperature water generated by mixing the upper high temperature water and the lower low temperature water, and the heat absorption amount of the refrigerant is increased on the upstream side of the air heat exchanger 34. The suction temperature of 31 can be increased, and the work of the compressor 31 can be reduced.
Next, the operation efficiency of the refrigerant circuit will be described based on examples. According to the refrigerant circuit shown in FIGS. 1 to 3, the amount of heat absorbed by the auxiliary heat exchanger 12 can be increased, so that the water supplied to the water medium heat exchanger 11 from the water heat exchanger inlet channel 40a has a low temperature, Therefore, the heat dissipation amount Q of the refrigerant that exchanges heat with water in the water heat exchanger 11 increases.
Moreover, since the heat radiation amount in the water heat exchanger 11 increases, the temperature of the refrigerant that has exited the water heat exchanger 11 can be lowered, and the refrigerant temperature at the inlet of the expansion valve decreases.

  Further, on the low pressure side after passing through the decompression mechanism 33 in the refrigeration cycle, the refrigerant temperature rises in the process of heat absorption of the refrigerant in the auxiliary heat exchanger 12, so that the suction pressure and the suction temperature of the compressor 31 rise. Therefore, the work W of the compressor 31 for obtaining the same discharge pressure can be reduced.

  By constructing the refrigerant circuit as described above, the sub heat exchanger 12 absorbs heat from the water, and the heat radiation amount in the water heat exchanger 11 is increased, thereby improving COP (= heat radiation amount / compressor work). It becomes possible.

  Further, as a feature of this system, the water temperature hardly changes as much as the outside air temperature, and stable operation can be performed by absorbing heat from the water even when the outside air temperature is below freezing. In addition, cold water production may be performed by introducing a four-way valve into the system and reversing the cycle.

It is a cycle diagram which shows Example 1 by this invention. It is a cycle diagram which shows Example 2 by this invention. It is a cycle diagram which shows Example 3 by this invention. It is a cycle diagram which shows a prior art.

Explanation of symbols

10 Refrigerant circuit (heat pump)
11 Water Heat Exchanger 12 Sub Heat Exchanger 20 Hot Water Storage Tank 21 Water Supply Pipe 24 Hot Water Supply Port 31 Compressor 33 Pressure Reduction Mechanism (Expansion Valve)
34 Air heat exchanger 35 Blower fan 40 Flow path 40a Water heat exchanger inlet flow path 40b Water heat exchanger outlet flow path 42 Circulation pump 42a Second water circulation pump

Claims (2)

A compressor, a water heat exchanger, a pressure reducing mechanism, and an air heat exchanger are sequentially connected, and the high pressure side is operated at a supercritical pressure, and the water recovered by the low pressure side sub heat exchanger is recovered. In the refrigerant circuit for introducing and heating the water heat exchanger,
A refrigerant circuit in which the auxiliary heat exchanger is provided between the air heat exchanger and the pressure reducing mechanism. A hot water supply system using the refrigerant circuit according to claim 1,
A hot water supply system characterized in that water introduced into the water heat exchanger is stored in a hot water storage tank.