JP4269323B2 - Heat pump water heater - Google Patents

Description

The present invention relates to a heat pump water heater, and more particularly to a heat pump water heater that uses carbon dioxide (CO ₂ ) as a refrigerant.

A conventional refrigeration air conditioner uses CO ₂ as a refrigerant, and is provided with an accumulator that stores the refrigerant at the outlet of the evaporator, and the amount of refrigerant stored in the accumulator is controlled by adjusting the opening of the throttle valve. There is one that controls the operating high pressure of the apparatus to provide a predetermined cooling capacity (see, for example, Patent Document 1).

Japanese Patent Publication No. 7-18602 (page 3-5, Fig. 2)

  In the conventional refrigeration air conditioner, as described above, a container such as an accumulator for storing the refrigerant is necessary, and there is a problem that the cost of the refrigeration air conditioner increases.

Therefore, a compressor, a radiator, an expansion valve, and an evaporator are sequentially connected to the refrigeration cycle using CO ₂ as a refrigerant, and a cooler for cooling the heated fluid is provided so that the heat exchange amount of the cooler can be increased. The present applicant has proposed that an accumulator or other container can be made unnecessary by adjusting and processing the surplus refrigerant. In this case, heat exchange is performed for heat exchange with a heated fluid with poor heat transfer. There was a problem that a plurality of vessels were required and the device was large.

The present invention has been made in order to solve the above-described problems, and the control of the refrigerant amount distribution in the refrigeration cycle used in the heat pump water heater does not use a container having a volume for storing refrigerant, such as an accumulator, Furthermore, it aims at obtaining a low-cost heat pump water heater by implement | achieving, without increasing the heat exchanger which heat-exchanges with the to-be-heated fluid with bad heat transfer.
In addition, it is known that in the refrigeration cycle using CO ₂ , there is a refrigerant pressure value on the high-pressure side of the refrigeration cycle that maximizes the operating efficiency (COP) depending on the operating state. An object of the present invention is to obtain a heat pump water heater that realizes highly efficient operation by controlling the high-pressure side refrigerant pressure of the refrigeration cycle to a pressure that maximizes the COP by controlling the distribution.

A heat pump water heater according to the present invention includes a compressor that compresses a refrigerant to a supercritical pressure, a single radiator that exchanges heat between the refrigerant discharged from the compressor and a load-side medium, and a first expansion that depressurizes the refrigerant. A valve, an auxiliary heat exchanger for exchanging heat between the refrigerant and the outside air, a second expansion valve for decompressing the refrigerant , and a refrigeration cycle in which the refrigerant circulates by annularly connecting the single radiator A hot water supply circuit that stores a load-side medium heated by the circulating refrigerant in a tank, an auxiliary heat exchanger inlet temperature sensor provided on the refrigerant inlet side of the auxiliary heat exchanger, and the auxiliary heat exchanger inlet temperature sensor. that as the coolant temperature becomes a target temperature by controlling the opening degree of the first expansion valve, in which Ru and a high voltage control means for controlling the high-pressure side refrigerant pressure to a predetermined pressure.

According to the heat pump water heater of the present invention, the opening of the first expansion valve is controlled by the high pressure control means so that the refrigerant temperature detected by the auxiliary heat exchanger inlet temperature sensor becomes the target temperature. Since the side refrigerant pressure can be controlled, the operating state of the heat pump water heater can be controlled to a high pressure at which the COP is maximized. For this reason, the operation of a highly efficient heat pump water heater can be realized, a container or pressure sensor for controlling the refrigerant amount distribution is not required, and a heat exchanger for exchanging heat with a heated fluid with poor heat transfer is increased. And there is an effect that a low-cost heat pump water heater can be obtained.

Embodiment 1 FIG.
A first embodiment of the present invention is shown in FIG. FIG. 1 is a refrigerant circuit diagram of a heat pump water heater according to the present invention. In a heat pump unit 1, a compressor 3, a radiator 4, a first expansion valve 5, an auxiliary heat exchanger 6, a second expansion valve 7, The refrigerating cycle in which the evaporators 8 are sequentially connected in a ring, the fan 9 that blows outside air to the auxiliary heat exchanger 6 and the radiator 4, and water that is the load-side medium heated by the radiator 4 in the hot water supply circuit is fed On the other hand, in the tank unit 2, a tank 11 for storing hot water heated via the radiator 4 by water supply of the pump 10 is mounted. As the refrigerant of the heat pump water heater, carbon dioxide (CO ₂ ) is used which is in a supercritical state when the high pressure side in the refrigeration cycle is above the critical pressure (about 73 kg / cm ² ) and is easily available. The first expansion valve 5, the auxiliary heat exchanger 6, and the second expansion valve 7 constitute high pressure control means in the first embodiment.

  In the heat pump unit 1, a pressure sensor 12, which is a high pressure detecting means for detecting the refrigerant high pressure state of the refrigeration cycle, is provided in a pipe connecting the radiator 4 and the first expansion valve 5. The refrigerant pressure at the installation location on the high pressure side is measured. Further, in the hot water supply circuit, the water supply temperature sensor 13a is provided on the radiator 4 water inlet side, and the hot water discharge temperature sensor 13b is provided on the radiator 4 water outlet side, and measures the water temperature at the installation location. In addition, an outside air temperature sensor 13 c provided at or near the heat pump unit 1 measures the outside air temperature around the heat pump unit 1. In FIG. 1, the pressure sensor 12 is provided between the radiator 4 and the first expansion valve 5, but may be provided in a connection pipe between the compressor 3 and the radiator 4 on the upstream side of the radiator 4.

  Further, in the heat pump unit 1, the discharge temperature sensor 13 d is in the outlet pipe of the compressor 3, the radiator refrigerant outlet temperature sensor 13 e is in the refrigerant outlet pipe of the radiator 4, and the auxiliary heat exchanger inlet temperature sensor 13 f is in auxiliary heat. Refrigerant inlet pipes of the exchanger 6 are respectively provided so that the refrigerant temperature at each temperature sensor installation place in the refrigerant circuit can be measured.

  A measurement control device 14 is provided in the heat pump unit 1. The measurement control device 14 is based on the measurement information from the pressure sensor 12 and each temperature sensor 13 and the content of the operation command information instructed by the user of the heat pump water heater, and the first expansion valve. 5, the heat exchange amount of the auxiliary heat exchanger 6, the opening of the second expansion valve 7, the operation method of the pump 10, and the like.

  Next, the operation of the heat pump water heater will be described. In the refrigeration cycle of the heat pump unit 1, the temperature of the high-temperature and high-pressure gas refrigerant discharged from the compressor 3 decreases while radiating heat to the hot water supply circuit side by the radiator 4. At this time, if the high-pressure side refrigerant pressure is equal to or higher than the critical pressure, the refrigerant radiates heat at a reduced temperature without undergoing a gas-liquid phase transition in a supercritical state. If the high-pressure side refrigerant pressure is equal to or lower than the critical pressure, the refrigerant radiates heat while liquefying. Hot water supply heating is performed by applying heat radiated from the refrigerant to a load side medium such as water on the load side (hot water supply water circuit). The high-pressure and low-temperature refrigerant flowing out of the radiator 4 through hot water heating passes through the first expansion valve 5 and is decompressed here, and then flows into the auxiliary heat exchanger 6 to exchange heat with the outside air. At that time, when the refrigerant temperature flowing into the auxiliary heat exchanger 6 is higher than the outside air temperature, the refrigerant is cooled or condensed, and when the refrigerant temperature is lower than the outside air temperature, it is heated or evaporated. Then, after the pressure is reduced to a low-pressure gas-liquid two-phase state by the second expansion valve 7 connected between the heat exchanger 6 and the evaporator 8, it flows into the evaporator 8, where it absorbs heat from outside air, Evaporated gas. The low-pressure gas refrigerant exiting the evaporator 8 is sucked into the compressor 3 and circulates to form a refrigeration cycle.

  On the hot water supply circuit side, the heat radiated from the refrigerant by the radiator 4 is guided from the lower part of the tank 11 by the pump 10 provided on the inflow side of the radiator 4 to the hot water supply circuit side of the radiator 4. It is given to a load side medium such as water to be conveyed. The heated load-side medium flows in from the upper part of the tank 11 and is stored in the tank 11.

Next, the operation control operation in this heat pump water heater will be described. In the refrigeration cycle in which the high pressure side is operated in a supercritical state such as CO ₂ as the refrigerant, there is a high pressure side refrigerant pressure value that maximizes the operation efficiency as described above. FIG. 2 is a PH diagram showing a refrigeration cycle when the refrigerant pressure at the high-pressure side is changed so that the refrigerant temperature at the outlet of the radiator 4 is the same. The vertical axis represents pressure P and the horizontal axis represents enthalpy H. I'm taking it. In FIG. 2, as the high-pressure side refrigerant pressure value in the refrigeration cycle increases in the order of P1, P2, and P3, the enthalpy difference ΔHg in the radiator 4 increases, and the heating capacity increases accordingly. On the other hand, when the high-pressure side refrigerant pressure value increases, the enthalpy difference ΔHc in the compressor 3 corresponding to the compressor input also increases. FIG. 3 shows the tendency of ΔHg and ΔHc at this time to change according to the high-pressure side refrigerant pressure value of the refrigeration cycle. In FIG. 3, the horizontal axis represents the pressure on the high pressure side in the refrigeration cycle, the vertical axis represents the ratio, the dotted line represents the enthalpy difference ΔHg in the radiator 4, the alternate long and short dash line represents the enthalpy difference ΔHc in the compressor 3, and the solid line represents COP (operating efficiency). ). In FIG. 3, in the region where the increase rate of ΔHg corresponding to the capacity accompanying the increase in the high-pressure side refrigerant pressure exceeds the increase rate of ΔHc corresponding to the input (range from P1 to P2), the refrigeration cycle represented by ΔHg / ΔHc In the region where the increase rate of ΔHg corresponding to the capacity is lower than the increase rate of ΔHc corresponding to the input (range from P2 to P3), the COP decreases. Therefore, there is a high-pressure side refrigerant pressure value at which COP is maximum, and this corresponds to the point P2 in FIG.

The high-pressure side refrigerant pressure in the refrigeration cycle in this heat pump water heater using CO ₂ as the refrigerant is determined by the amount of refrigerant present in the radiator 4. When the refrigerant state is supercritical, the density of the refrigerant increases as the pressure increases. Therefore, the refrigerant amount in the radiator 4 when operating in the high pressure P3 state shown in FIG. It becomes larger than the refrigerant amount in the radiator 4 when operating in the P1 state. That is, if it is operated so that the amount of refrigerant present in the radiator 4 increases, the high-pressure side refrigerant pressure value increases, and conversely, if it is operated so that the amount of refrigerant present in the radiator 4 decreases, the high pressure side refrigerant pressure value increases. The side refrigerant pressure value decreases. Therefore, by controlling the amount of refrigerant present in the radiator 4, it is possible to control the high-pressure side refrigerant pressure value so as to become a COP maximum pressure.

  Next, the control operation of this heat pump water heater will be described. The operating capacity of the compressor 3 controlled by the rotational speed and the rotational speed of the pump 10 are information on the ambient outside air temperature T0 measured and detected by the outside air temperature sensor 13c and the feed water temperature Twi measured and detected by the feed water temperature sensor 13a. The water temperature Two at the water outlet 4 of the radiator 4 measured and detected by the heating capacity Q and the temperature sensor 13b is used as a predetermined target value, for example, target heating capacity Qm = 4.5 kW, target water outlet temperature Twom = 65 It is controlled to be at ° C. The second expansion valve 7 is controlled so that the refrigerant discharge temperature Td at the outlet of the compressor 3 measured and detected by the discharge temperature sensor 13d becomes a predetermined target value. The first expansion valve 5 is controlled to a predetermined initial opening. The heat exchange amount of the evaporator 8 is controlled by operating the fan 9 for conveying air as a heat transfer medium in a predetermined state.

  The high pressure side refrigerant pressure Ph of the refrigeration cycle when operated in this state is measured by the pressure sensor 12. And from the heating capacity Q set by the user of the heat pump water heater, the feed water temperature Twi measured and detected by the feed water temperature sensor 13a, the outside air temperature T0 measured and detected by the outside air temperature sensor 13c, the operating capacity of the compressor 3, etc. Then, the optimum high-pressure side refrigerant pressure value that maximizes the COP is calculated using a predetermined arithmetic expression, and the target pressure that is the optimum high-pressure side refrigerant pressure value is compared with the detected high-pressure side refrigerant pressure Ph. If the current high-pressure side refrigerant pressure is lower than the optimum high-pressure side refrigerant pressure value, the current high-pressure side refrigerant pressure is higher than the optimum high-pressure side refrigerant pressure value so that the amount of refrigerant in the radiator 4 increases. The amount of refrigerant in the radiator 4 is controlled to be small.

  Control of the amount of refrigerant in the radiator 4 is performed by opening control of the first expansion valve 5. FIG. 4 is a PH diagram showing the state change of the heat pump water heater when the opening degree control of the first expansion valve 5 is performed. The vertical axis represents pressure P and the horizontal axis represents enthalpy H. Yes. The refrigeration cycle indicated by the solid line in FIG. 4 represents the operating state when the opening degree of the first expansion valve 5 is reduced and the flow resistance is increased, while the refrigeration cycle indicated by the dotted line is the opening degree of the first expansion valve 5. Represents the operating condition when the flow resistance is decreased. ΔP1 is a refrigerant pressure difference due to the first expansion valve 5, and ΔP2 is a refrigerant pressure difference due to the second expansion valve 7. When the opening degree of the first expansion valve 5 is controlled, the second expansion valve 7 reduces the pressure from the intermediate pressure to the low pressure at the outlet of the first expansion valve 5, so that the refrigeration indicated by the solid line in FIG. In the cycle, the opening degree is increased so that ΔP2 becomes smaller and the flow resistance is reduced. In the refrigeration cycle indicated by the dotted line in FIG. 4, the opening degree is reduced so that ΔP2 becomes larger. Is driven to become larger.

The refrigerant state in the auxiliary heat exchanger 6 between the first expansion valve 5 and the second expansion valve 7 becomes a state indicated by a point A in FIG. 4 by controlling the opening degree of the first expansion valve 5. In the refrigeration cycle indicated by the solid line in FIG. 4, the refrigerant present in the auxiliary heat exchanger 6 becomes a two-phase refrigerant close to the low-pressure side refrigerant pressure, and in the refrigeration cycle indicated by the dotted line in FIG. 4, the refrigerant present in the auxiliary heat exchanger 6. Becomes a refrigerant in a supercritical state close to the high-pressure side refrigerant pressure. Therefore, in the auxiliary heat exchanger 6, there is a refrigerant in a state close to high-pressure liquid in the dotted refrigeration cycle and the amount of refrigerant increases, whereas in the solid refrigeration cycle, refrigerant exists in a gas-liquid two-phase state. The amount of refrigerant present in the auxiliary heat exchanger 6 is reduced by the amount of gas refrigerant present. This situation is expressed as a correlation between the pressure P of the auxiliary heat exchanger 6 and the refrigerant amount M when the auxiliary heat exchanger 6 has the same enthalpy difference, as shown in FIG.
In FIG. 5, the vertical axis represents the refrigerant amount M, the horizontal axis represents the pressure P, and a line representing the saturation pressure is indicated by a dotted line. When the pressure is higher than the saturation pressure, the amount of refrigerant existing in the auxiliary heat exchanger 6 gradually increases according to the pressure. However, when the pressure is lower than the saturation pressure, gas is present, and at a pressure close to the saturation pressure, the volume ratio of the gas increases rapidly as the pressure decreases, so the amount of refrigerant present in the auxiliary heat exchanger 6 increases rapidly. To decrease. And if it falls to the pressure close | similar to a low pressure side refrigerant | coolant pressure, the increase in the volume ratio of the gas accompanying pressure reduction will also become substantially constant, and the refrigerant | coolant amount which exists in the auxiliary heat exchanger 6 will also reduce gradually. Since such a refrigerant amount change occurs, the amount of refrigerant existing in the auxiliary heat exchanger 6 can be controlled by controlling the pressure in the auxiliary heat exchanger 6 by controlling the opening degree of the first expansion valve 5.

  The state that requires the largest amount of refrigerant in the refrigerant circuit is when the pressure on the high pressure side is high and the refrigerant temperature at the outlet of the gas cooler (equivalent to a radiator) is low. The specific environmental conditions corresponding to this are the ambient temperature. Is high and / or the feed water temperature is low. Here, the operation when the outside air temperature decreases will be described. When the outside air temperature decreases, the evaporation temperature decreases accordingly. That is, the refrigerant pressure on the low-pressure side is lowered, and the amount of refrigerant existing in the auxiliary heat exchanger 6 and the evaporator 8 is reduced in theory, but the total amount of refrigerant in the refrigeration cycle of this heat pump water heater does not change, so the radiator 4 The amount of refrigerant present in the refrigerant will increase. Accordingly, the high-pressure side refrigerant pressure rises, resulting in an inefficient operation state. Therefore, when the pressure in the auxiliary heat exchanger 6 is increased by controlling the valve opening degree of the first expansion valve 5 in order to keep the high-pressure side refrigerant pressure optimal, the amount of refrigerant existing in the auxiliary heat exchanger 6 increases. In addition, since the dryness at the inlet of the evaporator 8 is also reduced, the gas refrigerant in the evaporator 8 is reduced and the amount of refrigerant existing in the evaporator 8 is increased. Therefore, the amount of refrigerant in the radiator 4 is reduced, and the optimum high pressure can be controlled. This operation is shown in the P-H diagram of FIG. 6, in which the vertical axis represents pressure P, the horizontal axis represents enthalpy H, the solid line represents the normal refrigeration cycle operation, and the dotted line represents the case where the outside air is low. The refrigeration cycle operation is shown.

  Next, an operation when the feed water temperature Twi measured and detected by the feed water temperature sensor 13a is increased will be described. When the feed water temperature Twi rises, the radiator 4 outlet refrigerant temperature Te detected by the radiator refrigerant outlet temperature sensor 13e provided in the refrigerant outlet side pipe of the radiator 4 rises, and the dryness of the auxiliary heat exchanger 6 inlet also increases. In theory, the amount of refrigerant present in the radiator 4 and the auxiliary heat exchanger 6 decreases, but the total refrigerant amount in the refrigeration cycle of the heat pump water heater does not change. An increase in the amount of refrigerant present in the vessel 4 results in an inefficient operating state. In order to keep the high-pressure side refrigerant pressure optimal, by increasing the pressure in the auxiliary heat exchanger 6, the amount of refrigerant present in the auxiliary heat exchanger 6 increases, so the amount of refrigerant present in the radiator 4 decreases, It can be controlled to the optimum high pressure. This operation is shown in the P-H diagram of FIG. 7, where the vertical axis represents pressure P, the horizontal axis represents enthalpy H, the solid line represents normal refrigeration cycle operation, and the dotted line represents a high water supply temperature. The refrigeration cycle operation is shown.

  Therefore, as shown in FIG. 4, when the opening degree is increased by the opening degree control of the first expansion valve 5 provided between the radiator 4 and the auxiliary heat exchanger 6, the amount of refrigerant present in the radiator 4. Decreases, the high-pressure side refrigerant pressure decreases. When the opening degree is reduced, the amount of refrigerant existing in the radiator 4 increases, so the high-pressure side refrigerant pressure increases. Thus, by controlling the opening of the first expansion valve 5 so that the high-pressure side refrigerant pressure of the refrigeration cycle becomes the pressure that maximizes the COP, an efficient heat pump water heater according to the environmental load condition Can be realized.

  Compared with the case where a container having a predetermined volume is provided on the refrigerant circuit and the refrigerant is stored therein to increase or decrease the amount of refrigerant existing in the container, the amount of refrigerant existing in the radiator 4 is increased or decreased as described above. This is because the amount of refrigerant is changed while changing the state in a state where the refrigerant is constantly flowing in the radiator 4, so that the state of the refrigerant circulating in the refrigeration cycle in the radiator 4 is quickly changed. To be implemented. Accordingly, when the opening degree of the first expansion valve 5 is controlled by feedback control so that the high-pressure side refrigerant pressure becomes the optimum high-pressure side refrigerant pressure value, the optimum high-pressure side refrigerant pressure value changes depending on the change in operating conditions. Even so, the high-pressure side refrigerant pressure can be quickly brought close to the changed optimum high-pressure side refrigerant pressure value, operation control can be stably performed, and more efficient operation of the heat pump water heater can be realized.

  Further, when the amount of refrigerant existing in the auxiliary heat exchanger 6 is controlled by controlling the opening degree of the first expansion valve 5, the auxiliary heat exchanger 6 is provided by the temperature sensor 13f provided in the inlet pipe of the auxiliary heat exchanger 6. The refrigerant temperature Tf flowing into the engine may be measured and detected, and the opening degree control of the first expansion valve 5 may be performed based on the detected temperature Tf. For example, when the volume of the radiator 4 is known, the high pressure change accompanying the change in the refrigerant amount can be estimated in advance, and the correlation between the refrigerant amount and the pressure existing in the auxiliary heat exchanger 6 shown in FIG. 5 is known. The amount of refrigerant present in the radiator 4 and the amount of refrigerant in the auxiliary heat exchanger 6 that realizes the amount of change are estimated from the deviation between the current high-pressure side refrigerant pressure and the optimum high-pressure side refrigerant pressure value, A target temperature Tfm at the inlet of the heat exchanger 6 that realizes the refrigerant amount is set. Then, the opening degree control of the first expansion valve 5 is performed such that the refrigerant temperature Tf at the inlet of the auxiliary heat exchanger 6 becomes the target temperature Tfm. By controlling in this way, the pressure sensor 12 for detecting the high-pressure side refrigerant pressure in the refrigeration cycle is not necessary, so that a more efficient operation of the heat pump water heater can be realized at low cost.

  FIG. 8 is a diagram showing a refrigerant flow path configuration of the evaporator 8 and the auxiliary heat exchanger 6 in the present invention. As shown in FIG. 8, the auxiliary heat exchanger 6 having a high temperature of the refrigerant flowing through the refrigerant circuit is disposed below the evaporator 8 connected to the downstream side of the refrigerant circuit. Since frost formation is difficult and the number of defrosts can be reduced, a more efficient heat pump water heater can be realized. In addition, it has the effect of preventing the formation of root ice.

  Further, as shown in FIG. 9, when the auxiliary heat exchanger 6 having a high refrigerant temperature is arranged upstream of the evaporator 8 with respect to the air flow, condensation occurs when the saturation temperature in the auxiliary heat exchanger 6 is higher than the outside air. Since the heat released by the auxiliary heat exchanger 6 on the side can be recovered by the evaporator 8, more efficient operation of the heat pump water heater can be realized.

Embodiment 2. FIG.
The second embodiment of the present invention will be described below with reference to FIG. FIG. 10 is a refrigerant circuit diagram of the heat pump water heater in the second embodiment. 10, except for the first high / low pressure heat exchanger 15 and the expansion valve 16 for bypass, is basically the same as in FIG. 1, and the function and effect thereof are also the same as those in the first embodiment. Are denoted by the same reference numerals, and the description thereof is omitted. The first high / low pressure heat exchanger 15 is, for example, a double pipe heat exchanger, and the outer pipe side is a main side flow path and the inner pipe side is a bypass side flow path, but the outer pipe side is a bypass side flow path, The inner pipe side may be used as the main channel. A branch pipe is connected between the radiator 4 and the first expansion valve 5, and the branched pipe is connected to the suction side pipe of the compressor 3 through the bypass expansion valve 16 and the first high / low pressure heat exchanger 15. Has been. Further, a first expansion valve inlet temperature sensor 13 g is disposed between the first high / low pressure heat exchanger 15 and the first expansion valve 5. The bypass expansion valve 16 and the first high / low pressure heat exchanger 15 constitute high pressure control means in the second embodiment.

  First, the operation of the first high / low pressure heat exchanger 15 and the bypass expansion valve 16 in the second embodiment will be described. The low-temperature and high-pressure refrigerant that has flowed out of the radiator 4 passes through the main-side flow path of the first high- and low-pressure heat exchanger 15. In the bypass side flow path of the first high / low pressure heat exchanger 15, a part of the refrigerant in the main side flow path exiting the first high / low pressure heat exchanger 15 passes through the first expansion valve 5 and the evaporator 8. After being bypassed and passing through the bypass expansion valve 16 and being reduced in pressure to the low-pressure two-phase refrigerant, the refrigerant flows into the bypass-side flow path of the first high-low pressure heat exchanger 15. In the first high / low pressure heat exchanger 15, the high-pressure main-side refrigerant and the low-pressure bypass-side refrigerant exchange heat, and the main-side refrigerant passes through the bypass-side refrigerant. Heat transfer. Along with this, the refrigerant in the main-side refrigerant channel is further cooled and flows into the first expansion valve 5 downstream thereof. On the other hand, the refrigerant in the bypass-side flow path absorbs heat, evaporates, and is sucked into the compressor 3.

  The amount of heat exchange in the first high / low pressure heat exchanger 15 increases / decreases depending on the refrigerant flow rate of the bypass side flow path serving as a cold heat source, and the flow rate of refrigerant flowing through the bypass side flow path is small (opening of the bypass expansion valve 16). If the degree is reduced, the amount of heat exchange decreases, and the amount of heat exchange increases as the flow rate of refrigerant flowing through the bypass-side flow path increases (the degree of opening of the bypass expansion valve 16 increases). FIG. 11 shows a PH diagram of the refrigeration cycle when the amount of heat exchange in the first high / low pressure heat exchanger 15 varies. In FIG. 11, the vertical axis indicates pressure P, the horizontal axis indicates enthalpy H, the solid line indicates a small heat exchange amount in the first high / low pressure heat exchanger 15, and the broken line indicates the large heat exchange amount. . Point B in the figure is the state of the refrigerant flowing out of the main flow path in the first high-low pressure heat exchanger 15 and decompressed by the first expansion valve 5, that is, the refrigerant state at the inlet of the evaporator 8. When the amount of heat exchange in the first high / low pressure heat exchanger 15 increases, the temperature detected by the first expansion valve inlet temperature sensor 13g decreases, the refrigerant state at the inlet of the evaporator 8 is further cooled, and the enthalpy is low. The refrigerant state is low in dryness, and the refrigeration cycle follows a path indicated by a broken line in FIG. On the other hand, when the amount of heat exchange decreases, the temperature detected by the first expansion valve inlet temperature sensor 13g increases, the cooling amount decreases, the enthalpy is high, and the dryness remains large. Follow the path of the refrigeration cycle indicated by the solid line.

  When the refrigerant state at the inlet of the evaporator 8 is a lower dryness, the volume occupied by the liquid refrigerant is increased at least near the inlet of the evaporator 8. As a result, the amount of refrigerant existing here increases as viewed in the evaporator 8 as a whole. Therefore, when the amount of heat exchange in the first high / low pressure heat exchanger 15 is large, and the amount of cooling there increases, the temperature detected by the first expansion valve inlet temperature sensor 13g decreases, and the temperature at the inlet of the evaporator 8 decreases. The refrigerant state is lower in dryness and becomes a two-phase state with a large amount of liquid refrigerant, and the amount of refrigerant present in the evaporator 8 increases. On the other hand, when the amount of heat exchange in the first high / low pressure heat exchanger 15 is small and the amount of cooling is reduced, the temperature detected by the first expansion valve inlet temperature sensor 13g rises, and the temperature at the inlet of the evaporator 8 increases. The refrigerant state remains in a high dryness state, becomes a two-phase state with a large amount of gas refrigerant, and the amount of refrigerant present in the evaporator 8 decreases. Thus, the amount of refrigerant existing in the evaporator 8 can be changed by changing the heat exchange amount in the first high / low pressure heat exchanger 15 by controlling the flow rate in the bypass expansion valve 16.

  Therefore, when the heat pump water heater is operated, the control for setting the high-pressure side refrigerant pressure of the refrigeration cycle to an optimum high pressure is performed as follows. First, when the high-pressure side refrigerant pressure is lower than the optimum high pressure at which the COP is maximum, the first expansion valve inlet is used to increase the amount of refrigerant in the radiator 4 and increase the high pressure as described with reference to FIG. Bypass expansion valve so that the temperature detected by the temperature sensor 13g rises, that is, the refrigerant state at the inlet of the evaporator 8 becomes a two-phase state with a lot of gas refrigerant and the amount of refrigerant in the evaporator 8 is reduced. The opening degree of 16 is reduced, the bypass flow rate is reduced, and the heat exchange amount in the first high / low pressure heat exchanger 15 is reduced. Conversely, when the high pressure is higher than the optimum high pressure at which the COP is maximum, the temperature detected by the first expansion valve inlet temperature sensor 13g in order to reduce the amount of refrigerant in the radiator 4 and lower the high pressure. So that the refrigerant state at the inlet of the evaporator 8 becomes a two-phase state with a lot of liquid refrigerant and the amount of refrigerant in the evaporator 8 is increased. The amount of heat exchange in the first high / low pressure heat exchanger 15 is increased by increasing the flow rate. Thus, by controlling the opening degree of the bypass expansion valve 16, the high-pressure side refrigerant pressure in the refrigeration cycle can be controlled to the maximum COP pressure, and an efficient operation of the heat pump water heater can be realized.

Embodiment 3 FIG.
Hereinafter, Embodiment 3 of the present invention will be described with reference to FIG. FIG. 12 is a refrigerant circuit diagram of the heat pump water heater in the third embodiment. In FIG. 12, except for the second high / low pressure heat exchanger 17 and the third expansion valve 18, it is basically the same as FIG. 1, and the function and effect thereof are also the same as those of the first embodiment. The same reference numerals are given to the portions, and the description thereof is omitted. The second high / low pressure heat exchanger 17 is, for example, a double pipe heat exchanger, and the inner pipe side is a low pressure side flow path and the outer pipe side is a high pressure side flow path. The outer pipe side may be a low pressure side flow path. Further, the second high / low pressure heat exchanger 17 and the third expansion valve 18 are disposed on the branch flow path 19. The branch channel 19 branches from the radiator 4 to the first expansion valve 5, and the branched channel (pipe) passes through the second high / low pressure heat exchanger 17 and the third expansion valve 18. It is connected to a pipe from the first expansion valve 5 to the evaporator 8. Further, a second expansion valve inlet temperature sensor 13 h is disposed between the second high / low pressure heat exchanger 17 and the third expansion valve 18. The second high / low pressure heat exchanger 17 and the third expansion valve 18 constitute high pressure control means in the third embodiment.

  First, the operation of the second high / low pressure heat exchanger 17 and the third expansion valve 18 in this embodiment will be described. The low-pressure two-phase or low-pressure gas refrigerant that has flowed out of the evaporator 8 passes through the low-pressure channel of the second high-low pressure heat exchanger 17. In the high-pressure side flow path of the second high-low pressure heat exchanger 17, a part of the high-pressure and low-temperature refrigerant exiting the radiator 4 bypasses the first expansion valve 5 and passes through the third expansion valve 18. And flows into the evaporator 8. In the second high-low pressure heat exchanger 17, the refrigerant in the high-pressure channel and the refrigerant in the low-pressure channel exchange heat, and heat is transferred from the refrigerant in the high-pressure channel to the refrigerant in the low-pressure channel. Along with this, the refrigerant in the high-pressure side refrigerant flow path is further cooled and flows into the evaporator 8 downstream thereof. On the other hand, the refrigerant in the low-pressure side channel absorbs heat, evaporates, and is sucked into the compressor 3.

  The amount of heat exchange in the second high / low pressure heat exchanger 17 increases or decreases depending on the flow rate of the refrigerant flowing through the branch flow path 19, and the flow rate of the refrigerant flowing through the branch flow path 19 is small (the opening degree of the third expansion valve 18 is reduced). When it is reduced, the amount of heat exchange decreases, and when the flow rate of the refrigerant flowing through the branch flow path 19 increases (the opening degree of the third expansion valve 18 increases), the amount of heat exchange increases. FIG. 13 shows a PH diagram of the refrigeration cycle when the amount of heat exchange in the second high / low pressure heat exchanger 17 varies. In FIG. 13, when the pressure P is plotted on the vertical axis and the enthalpy H is plotted on the horizontal axis, and the solid line indicates a small amount of heat exchange in the second high / low pressure heat exchanger 17, the broken line indicates the heat in the second high / low pressure heat exchanger 17. The case of a large exchange amount is shown. Point C in the figure is a state in which the refrigerant that has exited the second high-low pressure heat exchanger 17 has been decompressed by the third expansion valve 18. Further, a point D in the figure is a state where the refrigerant at the outlet of the radiator 4 is decompressed by the first expansion valve 5. Point E in the figure is the refrigerant state at the inlet of the evaporator 8 where point C and point D merge, and is determined by the refrigerant flow rate through the branch circuit 19 and the refrigerant flow rate ratio through the first expansion valve 5. When the amount of heat exchange in the second high / low pressure heat exchanger 17 increases, the temperature detected by the second expansion valve inlet temperature sensor 13h decreases, the refrigerant state at the inlet of the evaporator 8 is further cooled and the enthalpy is low, The refrigerant state is low in dryness, and the refrigeration cycle follows a path indicated by a broken line in FIG. On the other hand, when the amount of heat exchange decreases, the temperature detected by the second expansion valve inlet temperature sensor 13h increases, the cooling amount decreases, the enthalpy is high, and the dryness remains large. Follow the path of the refrigeration cycle indicated by the solid line.

  When the refrigerant state at the inlet of the evaporator 8 is a lower dryness, the volume occupied by the liquid refrigerant is increased at least near the inlet of the evaporator 8. As a result, when the evaporator 8 is viewed as a whole, the amount of refrigerant existing here increases. That is, when the amount of heat exchange in the second high / low pressure heat exchanger 17 is large and the amount of cooling there increases, the temperature detected by the second expansion valve inlet temperature sensor 13h decreases, and the temperature at the inlet of the evaporator 8 decreases. The refrigerant state is lower in dryness and becomes a two-phase state with a large amount of liquid refrigerant, and the amount of refrigerant present in the evaporator 8 increases. On the other hand, when the amount of heat exchange in the second high / low pressure heat exchanger 17 is small and the amount of cooling is reduced, the temperature detected by the second expansion valve inlet temperature sensor 13h rises, and the temperature at the inlet of the evaporator 8 increases. The refrigerant state remains in a high dryness state, becomes a two-phase state with a large amount of gas refrigerant, and the amount of refrigerant present in the evaporator 8 decreases. Thus, the amount of refrigerant existing in the evaporator 8 can be changed by changing the heat exchange amount in the second high / low pressure heat exchanger 17 by controlling the flow rate in the third expansion valve 18.

  Therefore, by controlling the opening of the third expansion valve 18 so that the refrigerant temperature detected by the second expansion valve inlet temperature sensor 13h becomes the target temperature, the high-pressure side refrigerant pressure in the refrigeration cycle is set to the COP maximum. Therefore, the heat pump water heater can be operated efficiently.

It is a refrigerant circuit figure of the heat pump water heater which concerns on Embodiment 1 of this invention. It is a PH diagram showing the driving | running state of the heat pump water heater at the time of the high pressure side refrigerant | coolant pressure fluctuation which concerns on Embodiment 1 of this invention. It is a figure which shows the correlation with the high pressure side refrigerant | coolant pressure which concerns on Embodiment 1 of this invention, and driving | operation efficiency COP. It is a PH diagram showing the change of the operating condition of the heat pump water heater at the time of the 1st expansion valve opening degree control concerning Embodiment 1 of the present invention. It is a figure which shows the correlation of the pressure and refrigerant | coolant amount of the auxiliary heat exchanger which concern on Embodiment 1 of this invention. It is a PH diagram showing the operating condition of the heat pump water heater when the outside air according to Embodiment 1 of the present invention is low. It is a PH diagram showing the driving | running state of the heat pump water heater when the feed water temperature which concerns on Embodiment 1 of this invention is high. It is a figure which shows the path | pass structure of the auxiliary heat exchanger and evaporator which concern on Embodiment 1 of this invention. It is a figure which shows the modification of the path | pass structure of the auxiliary heat exchanger and evaporator which concerns on Embodiment 1 of this invention. It is a refrigerant circuit figure of the heat pump water heater which concerns on Embodiment 2 of this invention. It is a PH diagram showing the change of the operating condition of the heat pump water heater at the time of heat exchange amount control of the high and low pressure heat exchanger concerning Embodiment 2 of the present invention. It is a refrigerant circuit figure of the heat pump water heater which concerns on Embodiment 3 of this invention. It is a PH diagram showing the change of the operating condition of the heat pump water heater at the time of heat exchange amount control of the high and low pressure heat exchanger concerning Embodiment 3 of the present invention.

Explanation of symbols

1 heat pump unit, 2 tank unit, 3 compressor, 4 radiator, 5 first expansion valve (expansion valve), 6 heat exchanger, 7 second expansion valve, 8 evaporator, 9 fan, 10 pump, 11 Tank, 12 Pressure sensor (high pressure detection means), 13 Temperature sensor, 14 Measurement control device, 15 First high / low pressure heat exchanger, 16 Bypass expansion valve, 17 Second high / low pressure heat exchanger, 18 3rd Expansion valve, 19 branch flow path.

Claims (8)

A compressor that compresses the refrigerant to a supercritical pressure, a single radiator that exchanges heat between the refrigerant discharged from the compressor and the load-side medium, a first expansion valve that decompresses the refrigerant, and heat exchange between the refrigerant and the outside air A refrigeration cycle in which the auxiliary heat exchanger, the second expansion valve for decompressing the refrigerant , and the evaporator are connected in an annular manner to circulate the refrigerant,
A hot water supply circuit for storing a load-side medium heated by a refrigerant flowing through the single radiator in a tank;
An auxiliary heat exchanger inlet temperature sensor provided on the refrigerant inlet side of the auxiliary heat exchanger;
High-pressure control means for controlling the high-pressure side refrigerant pressure to a predetermined pressure by controlling the opening of the first expansion valve so that the refrigerant temperature detected by the auxiliary heat exchanger inlet temperature sensor becomes a target temperature. the heat pump water heater, characterized in that Ru with and. The heat pump water heater according to claim 1, characterized in that arranged the auxiliary heat exchanger in the lower part of the evaporator. The heat pump water heater according to claim 1, characterized in that arranged the auxiliary heat exchanger on the downstream side of the air heat exchanger the evaporator. A compressor that compresses the refrigerant to a supercritical pressure, a single radiator that exchanges heat between the refrigerant discharged from the compressor and the load-side medium, an expansion valve that decompresses the refrigerant, and an evaporator are connected in an annular shape, A refrigeration cycle in which the refrigerant circulates;
A hot water supply circuit for storing a load-side medium heated by a refrigerant flowing through the single radiator in a tank;
A bypass expansion valve provided in the bypass passage connected to the suction side of the compressor is branched from between the radiator and the expansion valve,
A first high-low pressure heat exchanger disposed on the downstream side of the bypass expansion valve of the bypass channel and exchanging heat between the low-pressure refrigerant in the bypass channel and the high-pressure refrigerant in the main channel; ,
A first expansion valve inlet temperature sensor provided on the refrigerant inlet side of the expansion valve in the refrigeration cycle;
High pressure control means for controlling the high pressure side refrigerant pressure to a predetermined pressure by controlling the opening of the bypass expansion valve so that the refrigerant temperature detected by the first expansion valve inlet temperature sensor becomes a target temperature. the heat pump water heater, characterized in that Ru with and. A compressor that compresses the refrigerant to a supercritical pressure, a single radiator that exchanges heat between the refrigerant discharged from the compressor and the load-side medium, an expansion valve that decompresses the refrigerant, and an evaporator are connected in an annular shape, A refrigeration cycle in which the refrigerant circulates;
A hot water supply circuit for storing a load-side medium heated by a refrigerant flowing through the single radiator in a tank;
High pressure control means for controlling the high pressure side refrigerant pressure to a predetermined pressure,
The high-pressure control means includes
Between the refrigerant of the branch flow path, which is provided in a branch flow path branched from between the radiator and the expansion valve and connected to the inlet side of the evaporator, and the low pressure side refrigerant of the main flow path A second high and low pressure heat exchanger for exchanging heat at
A third expansion valve disposed on the downstream side of the second high / low pressure heat exchanger of the branch flow path;
The heat pump water heater characterized by comprising. A high pressure detecting means for detecting a refrigerant high pressure state is provided in the refrigeration cycle, a water supply temperature sensor for detecting a water supply temperature is provided on the radiator inflow side of the hot water supply circuit, and an outside air temperature sensor for detecting an ambient temperature is further provided.
The high-pressure control means includes
The pressure detected by the high-pressure detecting means includes a feed water temperature detected by the feed water temperature sensor, an outside air temperature detected by the outside air temperature sensor, a target heating capacity in the hot water supply circuit, and a target boiling in the hot water supply circuit. The heat pump water heater according to claim 5 , wherein the opening degree of the second high / low pressure heat exchanger is controlled so as to be a target pressure calculated from the raised temperature. A second expansion valve inlet temperature sensor is provided on the refrigerant inlet side of the third expansion valve in the branch flow path;
The high-pressure control means includes
According to claim 5, wherein the refrigerant temperature detected by the second expansion valve inlet temperature sensor is configured to control an opening degree of the third expansion valve so that the target temperature Heat pump water heater. The heat pump water heater according to any one of claims 1 to 7 , wherein the refrigerant used in the refrigeration cycle is carbon dioxide.

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