JP4140625B2 - Heat pump water heater and control method of heat pump water heater - Google Patents

Description

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

  Conventionally, “composed of a compressor, a gas cooler, an internal heat exchanger, a throttle valve, an evaporator and a low-pressure refrigerant receiver connected in series to form a circuit and operated at supercritical pressure on the high side. In addition, the vapor compression circuit further comprises a detection means for detecting at least one operation state of the circuit and supercriticality by controlling the opening of the throttle valve as a function of the detected operating condition according to a predetermined high pressure set value. In order to adjust the pressure on the high side, a vapor compression circuit comprising the detection means and a control means connected to the throttle valve is disclosed (for example, see Patent Document 1).

  Since this vapor compression circuit has an internal heat exchanger corresponding to a high-low pressure heat exchanger, the refrigerant sucked into the compressor can be superheated and the reliability of the compressor can be improved. It has become. Further, in the supercritical vapor compression circuit corresponding to the refrigeration cycle, the throttle valve is adjusted based on the application of the detected actual circuit operating conditions and the corresponding optimum high side pressure value. .

  Further, “a refrigerant circulation circuit including a compressor, a radiator, a pressure reducing unit, and a heat absorber, a hot water supply circuit having a hot water storage tank, the radiator, and a flow rate adjusting unit, and a refrigerant discharge temperature of the compressor Discharge temperature control means for adjusting by controlling the pressure reducing means, the discharge temperature control means, the operating frequency of the compressor, the discharge temperature, the outside air temperature, the set hot water supply temperature, the inlet temperature of the radiator of the hot water supply circuit A heat pump hot water supply device that is controlled according to at least one value among them is disclosed (for example, see Patent Document 2).

  In this heat pump hot water supply apparatus, since the discharge temperature is controlled by the decompression means (expansion means), an excessive temperature rise of the compressor can be avoided and the reliability of the compressor can be improved. Yes. That is, the decompression means is controlled in accordance with at least one of the operating frequency of the compressor, the discharge temperature, the outside air temperature, the set hot water supply temperature, and the incoming water temperature of the radiator, and the refrigerant discharge temperature of the compressor is set to a predetermined temperature. It is supposed to be.

Japanese Patent No. 2931668 (page 2-3, FIG. 3) JP 2004-340535 A (page 4-6, FIG. 1)

  However, as a result of evaluating a refrigerant circuit that controls the discharge temperature with expansion means (expansion valve) using a high-low pressure heat exchanger in combination with the above technologies, when the discharge temperature is controlled to a target value, the same discharge temperature It is clear that there are multiple stable states. That is, there are a plurality of expansion valve openings at which the discharge temperatures are the same. And all the opening degrees of these expansion valves did not exhibit predetermined ability. Therefore, in the refrigerant circuit including the high / low pressure heat exchanger, when the discharge temperature is controlled by the expansion valve, there is a problem that a predetermined capacity cannot always be obtained.

  The present invention has been made to solve the above-described problems. In a heat pump water heater including a high-low pressure exchanger, the discharge temperature and the suction superheat degree are controlled by an expansion means, and the heat pump water heater corresponds to the installation location. The present invention provides a heat pump water heater capable of obtaining an optimum capacity.

A heat pump water heater according to the present invention includes a compressor that compresses a refrigerant to a supercritical pressure, a radiator that exchanges heat between the refrigerant discharged from the compressor and a load-side medium, a first expansion valve that depressurizes the refrigerant, and evaporation. The refrigerant pipe is branched between the refrigeration cycle in which the refrigerant is sequentially connected by the refrigerant pipe and the refrigerant circulates, and from the radiator to the first expansion valve, and reaches the evaporator from the first expansion valve. A high-low pressure heat exchanger for exchanging heat between the branch flow path reconnected to the refrigerant pipe, the high-pressure refrigerant flowing through the branch flow path and the low-pressure refrigerant sucked into the compressor, and the high-low pressure heat exchange A second expansion valve that is provided in the branch flow path from the evaporator to the evaporator, and decompresses the refrigerant; a suction temperature detector that measures and detects the temperature of the refrigerant sucked into the compressor; and the evaporation Evaporation temperature detection to measure and detect refrigerant temperature A stage and a discharge temperature detection means for measuring the detection temperature of the refrigerant discharged from the compressor, and a measurement control means for adjusting the opening degree of the first expansion valve and the second expansion valve, The measurement control means adjusts the opening of the second expansion valve according to temperature information from the discharge temperature detection means, and then receives temperature information from the suction temperature detection means and temperature information from the evaporation temperature detection means. And calculating the degree of intake superheat of the refrigerant from the difference, and adjusting the opening of the first expansion valve according to the intake superheat .

The method for controlling a heat pump water heater according to the present invention includes a compressor that compresses a refrigerant to a supercritical pressure, a radiator that exchanges heat between the refrigerant discharged from the compressor and a load-side medium, and a first expansion that depressurizes the refrigerant. The refrigerant pipe is branched between the refrigeration cycle in which the refrigerant circulates by sequentially connecting the valve and the evaporator with the refrigerant pipe, and the refrigerant reaches the first expansion valve, and the evaporation from the first expansion valve. A branch flow path reconnected to the refrigerant pipe while reaching the compressor, a high-low pressure heat exchanger for exchanging heat between the high-pressure refrigerant flowing through the branch flow path and the low-pressure refrigerant sucked into the compressor, A control method of a heat pump water heater provided in the branch flow path from a low pressure heat exchanger to the evaporator and having a second expansion valve for decompressing the refrigerant, and is sucked into the compressor Measure the refrigerant suction temperature and cool the evaporator. The evaporation temperature is measured, the discharge temperature of the refrigerant discharged from the compressor is measured, after adjusting the opening degree of the second expansion valve by the temperature information from said discharge temperature detecting means, the suction temperature detecting Calculating the degree of refrigerant superheating from the difference between the temperature information from the means and the temperature information from the evaporating temperature detecting means, and adjusting the opening of the first expansion valve according to the degree of suction superheat. .

A heat pump water heater according to the present invention includes a compressor that compresses a refrigerant to a supercritical pressure, a radiator that exchanges heat between the refrigerant discharged from the compressor and a load-side medium, a first expansion valve that depressurizes the refrigerant, and evaporation. The refrigerant pipe is branched between the refrigeration cycle in which the refrigerant is sequentially connected by the refrigerant pipe and the refrigerant circulates, and from the radiator to the first expansion valve, and reaches the evaporator from the first expansion valve. A high-low pressure heat exchanger for exchanging heat between the branch flow path reconnected to the refrigerant pipe, the high-pressure refrigerant flowing through the branch flow path and the low-pressure refrigerant sucked into the compressor, and the high-low pressure heat exchange A second expansion valve that is provided in the branch flow path from the evaporator to the evaporator, and decompresses the refrigerant; a suction temperature detector that measures and detects the temperature of the refrigerant sucked into the compressor; and the evaporation Evaporation temperature detection to measure and detect refrigerant temperature A stage and a discharge temperature detection means for measuring the detection temperature of the refrigerant discharged from the compressor, and a measurement control means for adjusting the opening degree of the first expansion valve and the second expansion valve, The measurement control means adjusts the opening of the second expansion valve according to temperature information from the discharge temperature detection means, and then receives temperature information from the suction temperature detection means and temperature information from the evaporation temperature detection means. Since the refrigerant intake superheat degree is calculated from the difference between the two and the opening degree of the first expansion valve is adjusted based on the intake superheat degree, the optimum capacity can be exhibited according to the environmental load of the installation location.

The method for controlling a heat pump water heater according to the present invention includes a compressor that compresses a refrigerant to a supercritical pressure, a radiator that exchanges heat between the refrigerant discharged from the compressor and a load-side medium, and a first expansion that depressurizes the refrigerant. The refrigerant pipe is branched between the refrigeration cycle in which the refrigerant circulates by sequentially connecting the valve and the evaporator with the refrigerant pipe, and the refrigerant reaches the first expansion valve, and the evaporation from the first expansion valve. A branch flow path reconnected to the refrigerant pipe while reaching the compressor, a high-low pressure heat exchanger for exchanging heat between the high-pressure refrigerant flowing through the branch flow path and the low-pressure refrigerant sucked into the compressor, A control method of a heat pump water heater provided in the branch flow path from a low pressure heat exchanger to the evaporator and having a second expansion valve for decompressing the refrigerant, and is sucked into the compressor Measure the refrigerant suction temperature and cool the evaporator. The evaporation temperature is measured, the discharge temperature of the refrigerant discharged from the compressor is measured, after adjusting the opening degree of the second expansion valve by the temperature information from said discharge temperature detecting means, the suction temperature detecting Calculating the degree of refrigerant superheating from the difference between the temperature information from the means and the temperature information from the evaporating temperature detecting means, and adjusting the opening of the first expansion valve by the suction superheat degree. The optimum ability can be demonstrated according to the environmental load.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing a refrigerant circuit configuration of a heat pump water heater 100 according to an embodiment of the present invention. The heat pump water heater 1 is roughly composed of a heat pump unit 1 and a tank unit 2. The heat pump unit 1 is equipped with a refrigeration cycle 20 in which a compressor 3, a radiator 4, a first expansion valve 5, and an evaporator 6 are sequentially connected in an annular manner by a refrigerant pipe 15.

  The refrigeration cycle 20 is generally called a heat pump cycle, and has a function of heating water to hot water by circulating a refrigerant. The compressor 3 compresses the refrigerant into a high-temperature and high-pressure refrigerant. The radiator 4 is generally called a heat exchanger, and heats water by exchanging heat between the high-temperature and high-pressure refrigerant discharged from the compressor 3 and hot water. The first expansion valve 5 is used to depressurize the refrigerant after being heated to obtain a low-temperature and low-pressure refrigerant. The evaporator 6 is generally called an outdoor heat exchanger, and causes the refrigerant to absorb heat from the air.

The refrigerant pipe 15 circulates the refrigerant in the refrigeration cycle 20. The refrigerant pipe 15 branches from the radiator 4 to the first expansion valve 5 and is connected to the evaporator 6 from the first expansion valve 5. The branched refrigerant pipe 15 is referred to as a branch flow path 8. As the refrigerant, carbon dioxide (CO ₂ ), which is in a supercritical state at the high pressure side in the refrigeration cycle 20 and reaches a critical pressure (about 73 kg / cm ² ) or more and is easily available, is used.

  The heat pump unit 1 is equipped with a fan 7, a high / low pressure heat exchanger 9, a second expansion valve 10, and a pump 11. The fan 7 functions to blow outside air to the evaporator 6. The high-low pressure heat exchanger 9 is disposed between the evaporator 6 and the compressor 3, and is connected to the refrigerant pipe 15 and the branch flow path 8. In FIG. 1, the case where the high-low pressure heat exchanger 9 is a double pipe heat exchanger is shown as an example. This high / low pressure heat exchanger 9 shows a case where the outer pipe side is a high pressure side flow path and the inner pipe side is a low pressure side flow path, but the outer pipe side is a low pressure side flow path and the inner pipe side is a high pressure side. It is good also as a side channel. In addition, as for the flow direction of the refrigerant | coolant which flows through the inner pipe side and the outer pipe side, it is desirable that it is a counterflow, and shall be a counterflow here.

  The second expansion valve 10 is disposed in the branch flow path 8 from the high-low pressure heat exchanger 9 to the refrigerant pipe 15. The second expansion valve 10 serves to depressurize the refrigerant cooled by heat exchange with the low-pressure refrigerant in the high-low pressure heat exchanger 9 to obtain a low-temperature and low-pressure refrigerant. The pump 11 constitutes a hot water supply circuit 30 and functions to supply water as a load-side medium from the tank 12 to the radiator 4 and supply hot water heated by the radiator 4 to the tank 12.

  The tank unit 2 is equipped with a tank 12 for storing hot water heated via the radiator 4 by water supplied from the pump 11. In addition, the tank 12 in the tank unit 2 and the radiator 4 in the heat pump unit 1 are connected by a water pipe 16 to constitute a hot water supply water circuit 30. The water pipe 16 circulates water and hot water that are load-side media in the hot water supply circuit 30. That is, the hot water supply circuit 30 heats the water that is the load-side medium in the tank 12 by the radiator 4 and stores the hot water in the tank 12 by the pump 11.

  In the heat pump unit 1, a feed water temperature sensor 13 a is provided on the water inlet side of the radiator 4, and a tapping temperature sensor 13 b is provided on the water outlet side of the radiator 4. The feed water temperature sensor 13a and the tapping temperature sensor 13b serve to measure the temperature of the water flowing in the water pipe 16 at each installation location. In addition, in the heat pump unit 1, an outside air temperature sensor 13c for measuring the temperature of outside air is provided. The outside air temperature sensor 13 c may be provided anywhere within the heat pump unit 1. For example, the outside air temperature sensor 13c may be provided in a place that comes into contact with outside air.

  Further, in the heat pump unit 1, the discharge temperature sensor 13 d is on the refrigerant outlet side of the compressor 3, the suction temperature sensor 13 e is on the refrigerant inlet side of the compressor, and the evaporation temperature sensor 13 f is from the inlet of the evaporator 6 to the middle part. Are provided respectively. The discharge temperature sensor 13d, the suction temperature sensor 13e, and the evaporation temperature sensor 13f function to measure the temperature (discharge temperature, suction temperature, evaporation temperature) of the refrigerant flowing through the refrigerant pipe 15 at each installation location.

  Note that a measurement control device 14 is provided in the heat pump unit 1. The measurement control device 14 includes temperature information measured by the feed water temperature sensor 13a, the tapping temperature sensor 13b, the outside air temperature sensor 13c, the discharge temperature sensor 13d, the suction temperature sensor 13e, and the evaporation temperature sensor 13f, and the user of the heat pump water heater 100. From the operation command information instructed through the operation unit (not shown), the operation method of the compressor 3, the opening of the first expansion valve 5, the opening of the second expansion valve 10, the pump 11 It has a function to control the driving method.

  Next, the operation of the heat pump water heater 100 will be described. In the refrigeration cycle 20 of the heat pump unit 1, the high-temperature and high-pressure gas refrigerant discharged from the compressor 3 decreases in temperature while radiating heat (heats water) to the hot water supply circuit 30 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. Further, if the high-pressure side refrigerant pressure is equal to or lower than the critical pressure, the refrigerant radiates heat while being liquefied.

  That is, hot water heating is performed by applying heat radiated from the refrigerant to a load-side medium (water flowing through the hot water supply circuit 30). The high-pressure and low-temperature refrigerant flowing out of the radiator 4 by heating with hot water is branched into one that passes through the first expansion valve 5 and one that flows into the branch flow path 8. Here, the refrigerant passing through the first expansion valve 5 is decompressed to a low-pressure gas-liquid two-phase state. On the other hand, the refrigerant flowing into the branch flow path 8 passes through the high pressure side flow path of the high and low pressure heat exchanger 9 and flows through the low pressure side flow path of the high and low pressure heat exchanger 9 flowing out of the evaporator 6. Used for heat exchange.

  The refrigerant flowing into the branch channel 8 is cooled by applying heat to the low-pressure refrigerant that passes through the low-pressure side channel in the high-low pressure heat exchanger 9, and then passes through the second expansion valve 10 and passes through the low-pressure gas-liquid. Depressurized to a two-phase state. The refrigerant that has passed through the first expansion valve 5 and the refrigerant that has passed through the second expansion valve 10 merge before entering the evaporator 6 and flow into the evaporator 6. Then, the refrigerant absorbs heat from outside air and is evaporated and gasified. The low-pressure refrigerant that has exited the evaporator 6 passes through the high-low pressure heat exchanger 9 to exchange heat with the high-pressure refrigerant that passes through the high-pressure channel, and is heated and gasified. Then, it is sucked into the compressor 3. In this way, the refrigeration cycle 20 is formed by circulating the refrigerant.

  On the other hand, on the hot water supply circuit 30 side, the heat radiated by the radiator 4 is given to a load side medium such as water. This load-side medium is guided from the lower part of the tank 12 by the pump 11 provided on the inflow side of the radiator 4 and is sent to the radiator 4. The load-side medium heated here is fed to the upper part of the tank 12 by the pump 11. Thus, the load side medium flows in from the upper part of the tank 12 and is stored in the tank 12 so as to store heat.

  FIG. 2 is an explanatory diagram showing changes in the state of the refrigerant in each part when the opening degree of the second expansion valve 10 is changed. FIG. 2A shows the relationship between the second expansion valve 10 and the suction superheat degree. FIG. 2B shows the relationship between the second expansion valve 10 and the discharge temperature. FIG. 2C shows the relationship between the second expansion valve 10 and the radiator outlet temperature and suction temperature. FIG. 2D shows the relationship between the second expansion valve 10 and the high pressure side pressure. FIG. 2E shows the relationship between the second expansion valve 10 and the heating capacity. Note that A, B, and X shown in FIG. 2 indicate the opening degree of the second expansion valve 10 (hereinafter referred to as opening degree A, opening degree B, and opening degree X).

  In FIG. 2A, the horizontal axis represents the second expansion valve opening, and the vertical axis represents the intake superheat (deg). The degree of suction superheat is obtained from the difference between the temperature information from the suction temperature sensor 13e and the temperature information from the evaporation temperature detection sensor 13f. As shown in FIG. 2A, it can be seen that the suction superheat degree increases as the opening degree of the second expansion valve 10 increases. That is, when the opening degree X and the opening degree B are set to the opening degree A of the second expansion valve 10, the suction superheat degree of the refrigerant sucked into the compressor 3 is increased. .

  In FIG. 2B, the horizontal axis represents the second expansion valve opening, and the vertical axis represents the discharge temperature (° C.). This discharge temperature is the temperature of the refrigerant detected by the discharge temperature sensor 13d when discharged from the compressor 3. In FIG. 2B, a target value of the discharge temperature is set. In addition, it turns out from FIG.2 (b) that it does not become discharge temperature more than a target value according to the magnitude | size of the opening degree of the 2nd expansion valve 10. FIG. That is, when the second expansion valve 10 is set to the opening A, the discharge temperature is about the same as the target value. However, when the second expansion valve 10 is set to the opening X, the discharge is lower than the target value. When the second expansion valve 10 is set to the opening B, the discharge temperature is equal to or higher than the target value.

  In FIG. 2C, the horizontal axis represents the second expansion valve opening, and the vertical axis represents the radiator outlet temperature and the suction temperature (° C.). The radiator outlet temperature is the refrigerant temperature at the outlet of the radiator 4, and the suction temperature is the refrigerant temperature detected by the suction temperature sensor 13e when sucked into the compressor 3. It is. As shown in FIG. 2 (c), it can be seen that at any temperature, the temperature increases as the opening of the second expansion valve 10 increases. That is, the radiator outlet temperature and the suction temperature rise when the opening degree X and the opening degree B are set compared to when the second expansion valve 10 is set to the opening degree A.

  In FIG. 2D, the horizontal axis represents the second expansion valve opening, and the vertical axis represents the high-pressure side pressure (MPa). This high-pressure side pressure is the pressure on the high-pressure side of the refrigerant compressed by the compressor 3. As shown in FIG. 2D, it can be seen that the high pressure side pressure decreases as the opening of the second expansion valve 10 increases. That is, the high pressure side pressure of the refrigerant is lower when the opening degree X and the opening degree B are set than when the second expansion valve 10 is set to the opening degree A.

  In FIG. 2E, the horizontal axis represents the second expansion valve opening, and the vertical axis represents the heating capacity (kW). This heating capability is the capability that the refrigerant compressed by the compressor 3 heats the load-side medium (water). As shown in FIG. 2 (e), the heating capacity does not substantially change until the opening degree of the second expansion valve 10 reaches a predetermined opening degree, but decreases as the opening degree becomes larger than the predetermined opening degree. I understand. That is, the heating capacity of the second expansion valve 10 does not change much from the opening A to the opening X, but when the opening is equal to or higher than the opening X, the heating capacity is rapidly reduced.

  First, the state change of the refrigerant when the opening degree of the second expansion valve 10 is changed will be described. When the second expansion valve 10 is made larger than the opening degree X, the radiator outlet temperature suddenly rises (FIG. 2 (c)). As described above, in the high-low pressure heat exchanger 9, the high-pressure refrigerant (outer pipe side) and the low-pressure refrigerant (inner pipe side) are opposed to each other. That is, since the refrigerant flowing out of the radiator 4 flows into the outer pipe of the high / low pressure heat exchanger 9, the radiator outlet temperature is equal to the high pressure side inlet temperature of the high / low pressure heat exchanger 9, and from the evaporator 6 Since the refrigerant that has flowed out flows into the inner pipe of the high-low pressure heat exchanger 9, the temperature of the refrigerant sucked into the compressor 3 is equal to the low-pressure side outlet temperature of the high-low pressure heat exchanger 9.

  Therefore, as the radiator outlet temperature rises, the suction temperature rises (FIG. 2 (c)), and the suction superheat degree of the compressor 3 also rises (FIG. 2 (a)). As the suction temperature rises, the discharge temperature of the compressor 3 rises (FIG. 2B). When the opening degree of the second expansion valve 10 is increased, the discharge temperature of the compressor 3 is increased and then increased. That is, when the second expansion valve 10 is set to the opening A, the discharge temperature is about the same as the target value. However, when the second expansion valve 10 is set from the opening A to the opening X, the target The discharge temperature is lower than the value, and when the second expansion valve 10 is set to the opening degree B, the discharge temperature is equal to or higher than the target value.

  When the second expansion valve 10 is set to the opening A and the opening B, the discharge temperature of the compressor 3 is almost equal to the target value, but the heating capacity is set to the opening A. The direction when it is set to the opening degree B is decreasing (FIG. 2 (e)). Therefore, it can be seen that it is difficult to ensure a predetermined heating capacity only by adjusting the refrigerant discharge temperature by controlling the second expansion valve 10. That is, in addition to adjusting the discharge temperature of the refrigerant, it is also necessary to control the suction superheat degree.

  Next, the refrigerant state change when the opening degree of the first expansion valve 5 is changed will be described. When the opening degree of the first expansion valve 5 is increased, the amount of refrigerant flowing into the branch flow path 8 is reduced, and the amount of heat exchange in the high / low pressure heat exchanger 9 is also reduced. On the other hand, if the opening degree of the first expansion valve 5 is reduced, the amount of refrigerant flowing into the branch flow path 8 increases, and the amount of heat exchange in the high-low pressure heat exchanger 9 also increases.

  FIG. 3 is an explanatory diagram showing the relationship between the pressure of the refrigeration cycle 20 and the enthalpy when the amount of heat exchange in the high / low pressure heat exchanger 9 varies. In FIG. 3, the vertical axis represents pressure (P) and the horizontal axis represents enthalpy (H). The solid line indicates the case where the heat exchange amount in the high / low pressure heat exchanger 9 is small, and the broken line indicates the case where the heat exchange amount in the high / low pressure heat exchanger 9 is large. Further, point C shows a state in which the refrigerant flowing out of the high and low pressure heat exchanger 9 is decompressed by the second expansion valve 10, and point D shows that the refrigerant at the outlet of the radiator 4 is the first expansion valve. 5 shows a state where the pressure is reduced.

  Point E indicates the state of the refrigerant at the inlet of the evaporator 6 where point C and point D merge. The refrigerant flow rate flowing through the branch circuit 8 and the refrigerant flow rate passing through the first expansion valve 5 Determine by ratio. As shown in FIG. 3, when the amount of heat exchange in the high / low pressure heat exchanger 9 increases, the temperature of the refrigerant at the inlet of the second expansion valve 10 decreases and the amount of cooling increases. That is, the refrigerant state at the inlet of the evaporator 6 has a low enthalpy and a low dryness. The refrigeration cycle 20 in this case follows a path indicated by a broken line in the figure.

  On the other hand, when the amount of heat exchange in the high / low pressure heat exchanger 9 decreases, the temperature of the refrigerant at the inlet of the second expansion valve 10 increases and the amount of cooling decreases. That is, the refrigerant state at the inlet of the evaporator 6 has a high enthalpy and a high dryness. The refrigerant cycle in this case follows a path indicated by a solid line in the figure. That is, if the opening degree of the first expansion valve 5 is increased, the heat exchange amount of the high / low pressure heat exchanger 9 is reduced, so that the suction superheat degree is reduced and the opening degree of the first expansion valve 5 is reduced. Since the heat exchange amount of the high / low pressure heat exchanger 9 increases, the suction superheat degree increases.

  Next, the operation control operation of the heat pump water heater 100 will be described. First, the operating capacity of the compressor 3 controlled by the rotational speed and the rotational speed of the pump 11 are information on the ambient outside temperature measured and detected by the outside temperature sensor 13c and the feed water temperature measured and detected by the feed water temperature sensor 13a. It is adjusted based on etc. That is, based on such information, adjustment control is performed so that the temperature of water at the outlet of the radiator 4 measured and detected by the heating capacity and the temperature sensor 13b becomes a predetermined target value. For example, the rotation speeds of the compressor 3 and the pump 11 are controlled so that the target heating capacity is 4.5 kW and the target water outlet temperature is 65 ° C. Further, the heat exchange amount of the evaporator 6 is controlled by operating the rotational speed of the fan 7 that conveys the air as the heat transfer medium in a predetermined state.

  FIG. 4 is a flowchart showing a flow of operations for controlling the opening degrees of the first expansion valve 5 and the second expansion valve 10. First, the refrigerant temperature at the outlet of the compressor 3 is measured and detected by the discharge temperature sensor 13d (step S101). And the measurement control apparatus 14 controls the 2nd expansion valve 10 so that the discharge temperature of the refrigerant | coolant measured and detected by the discharge temperature sensor 13d may become a predetermined target value (step S102). That is, when the discharge temperature has reached the target value (step S102; N), the opening degree of the second expansion valve 10 is increased (step S103). On the other hand, when the discharge temperature is less than the target value (step S102; Y), the opening degree of the second expansion valve 10 is decreased (step S104).

  Next, the refrigerant temperature at the inlet of the compressor 3 is measured and detected by the suction temperature sensor 13e (step S105). Then, the refrigerant temperature in the evaporator 6 is measured and detected by the evaporation temperature sensor 13f (step S106). Based on the measured suction temperature and evaporation temperature, the measurement control device 14 calculates the suction superheat degree (step S107). The measurement control device 14 determines whether or not the calculated suction superheat degree is a predetermined target value (step S108).

  That is, when the suction superheat degree has reached the target value (step S108; N), the opening degree of the first expansion valve 5 is increased (step S109). By increasing the opening degree of the first expansion valve 5, the amount of heat exchange in the high / low pressure heat exchanger 9 is decreased. Thereafter, returning to the beginning of the control operation, the discharge temperature is detected. On the other hand, when the suction superheat degree is less than the target value (step S108; Y), the opening degree of the first expansion valve 5 is decreased (step S110). The amount of heat exchange in the high / low pressure heat exchanger 9 is increased by decreasing the opening degree of the first expansion valve 5. Thereafter, returning to the beginning of the control operation, the discharge temperature is detected.

  As described above, by controlling the opening degrees of the first expansion valve 5 and the second expansion valve 10, the discharge temperature and the suction superheat degree of the refrigeration cycle 20 can be brought close to predetermined target values. It is. That is, the heat pump water heater 100 can adjust and control the first expansion valve 5 and the second expansion valve 10 according to the load conditions of the environment in which the heat pump water heater 100 is installed. Therefore, the predetermined capacity of the refrigeration cycle 20 can be exhibited and maintained.

It is a schematic block diagram which shows the refrigerant circuit structure of the heat pump water heater which concerns on embodiment. It is explanatory drawing which shows the state change of the refrigerant | coolant in each site | part at the time of changing the opening degree of a 2nd expansion valve. It is explanatory drawing which shows the relationship between the pressure of a refrigerating cycle when the heat exchange amount in a high-low pressure heat exchanger fluctuates, and enthalpy. 3 is a flowchart showing a flow of an operation for controlling the opening degrees of the first expansion valve 5 and the second expansion valve 10.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heat pump unit, 2 Tank unit, 3 Compressor, 4 Heat radiator, 5 1st expansion valve, 6 Evaporator, 7 Fan, 8 Branch flow path, 9 High-low pressure heat exchanger, 10 2nd expansion valve, 11 Pump, 12 tank, 13a Feed water temperature sensor, 13b Hot water temperature sensor, 13c Outside air temperature sensor, 13d Discharge temperature sensor, 13e Suction temperature sensor, 13f Evaporation temperature sensor, 14 Measurement control device, 15 Refrigerant piping, 16 Water piping, 20 Refrigeration Cycle, 30 hot water supply circuit, 100 heat pump water heater.

Claims (4)

A compressor that compresses the refrigerant to a supercritical pressure, a radiator that exchanges heat between the refrigerant discharged from the compressor and the load-side medium, a first expansion valve that depressurizes the refrigerant, and an evaporator are sequentially connected by a refrigerant pipe. A refrigeration cycle in which the refrigerant circulates;
A branch flow path branched from the radiator to the first expansion valve and reconnected to the refrigerant pipe from the first expansion valve to the evaporator;
A high-low pressure heat exchanger for exchanging heat between the high-pressure refrigerant flowing through the branch flow path and the low-pressure refrigerant sucked into the compressor;
A second expansion valve that is provided in the branch flow path from the high-low pressure heat exchanger to the evaporator and depressurizes the refrigerant;
Suction temperature detection means for measuring and detecting the temperature of refrigerant sucked into the compressor;
Evaporating temperature detecting means for measuring and detecting the temperature of the refrigerant in the evaporator;
Discharge temperature detection means for measuring and detecting the temperature of the refrigerant discharged from the compressor;
Measurement control means for adjusting the opening of the first expansion valve and the second expansion valve;
The measurement control means includes
After adjusting the opening of the second expansion valve based on temperature information from the discharge temperature detecting means, the refrigerant is sucked from the difference between the temperature information from the suction temperature detecting means and the temperature information from the evaporation temperature detecting means. A heat pump water heater characterized by calculating a degree of superheat and adjusting an opening degree of the first expansion valve according to the degree of suction superheat . The high / low pressure heat exchanger is:
The heat pump water heater according to claim 1, wherein a refrigerant pipe in which the low-pressure side refrigerant flows and a branch flow path in which the high-pressure side refrigerant flows are opposed to each other in the high-low pressure heat exchanger. The heat pump water heater according to claim 1 or 2, wherein the refrigerant used in the refrigeration cycle is carbon dioxide. A compressor that compresses the refrigerant to a supercritical pressure, a radiator that exchanges heat between the refrigerant discharged from the compressor and the load-side medium, a first expansion valve that depressurizes the refrigerant, and an evaporator are sequentially connected by a refrigerant pipe. A refrigeration cycle in which the refrigerant circulates;
A branch flow path branched from the radiator to the first expansion valve and reconnected to the refrigerant pipe from the first expansion valve to the evaporator;
A high-low pressure heat exchanger for exchanging heat between the high-pressure refrigerant flowing through the branch flow path and the low-pressure refrigerant sucked into the compressor;
A control method for a heat pump water heater provided in the branch flow path from the high-low pressure heat exchanger to the evaporator, and comprising a second expansion valve for decompressing the refrigerant,
Measure the suction temperature of the refrigerant sucked into the compressor,
Measure the refrigerant evaporation temperature in the evaporator,
Measure the discharge temperature of the refrigerant discharged from the compressor,
After adjusting the opening of the second expansion valve based on temperature information from the discharge temperature detecting means, the refrigerant is sucked from the difference between the temperature information from the suction temperature detecting means and the temperature information from the evaporation temperature detecting means. A control method for a heat pump water heater , wherein the degree of superheat is calculated, and the opening degree of the first expansion valve is adjusted by the suction superheat degree .

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