JP2007093100A - Control method of heat pump water heater, and heat pump water heater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method of a heat pump water heater capable of controlling the distribution of a refrigerant quantity in a refrigerating cycle used in the heat pump water heater without using a container having a volume to store a refrigerant such as an accumulator, and performing high outside air and high temperature boiling-up operation without increasing the withstand pressure of a refrigerant circuit and elemental components in the heat pump water heater. <P>SOLUTION: This heat pump water heater comprises a refrigerating cycle constituted by connecting a compressor, a radiator, a first expansion valve and an evaporator by refrigerant piping, a branch flow channel branching the refrigerating piping at a place from the radiator to the first expansion valve, and reconnecting the refrigerant piping at a place from the first expansion valve to the evaporator, and a high and low pressure heat exchanger for exchanging heat between a high-pressure refrigerant flowing in the branch flow channel and a low-pressure refrigerant sucked to the compressor, and an opening of the first expansion valve is adjusted to be reduced when discharge pressure is higher than prescribed pressure. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

  Conventionally, “a compressor that compresses refrigerant to a supercritical pressure, a radiator that exchanges heat between the refrigerant discharged from the compressor and the fluid to be heated, an expansion valve that reduces the refrigerant below the critical pressure, and an evaporator are connected in sequence. A heat pump system comprising a basic refrigerant circuit through which refrigerant circulates and a cooler that cools the heated fluid flowing into the radiator, and adjusting a heat exchange amount of the cooler. '' (For example, refer to Patent Document 1).

  The heat pump system includes a compressor that compresses the refrigerant to a supercritical pressure, a radiator that exchanges heat between the refrigerant discharged from the compressor and the fluid to be heated, an expansion valve that reduces the refrigerant to a critical pressure or less, and an evaporator. Are connected to each other to form a refrigerant circuit, and a cooler that cools the heated fluid flowing into the radiator, and the cooling amount of the heated fluid is adjusted by the cooler from the radiator. Excess refrigerant is processed by controlling the outlet temperature of the refrigerant below a predetermined temperature.

Japanese Unexamined Patent Publication No. 2004-003825 (page 4-6, FIG. 1)

  However, in the case of the above heat pump system, a container such as an accumulator is not necessary, but there is a problem that a plurality of heat exchangers for exchanging heat with a heated fluid with poor heat transfer are required, resulting in a large apparatus. In addition, when the boiling temperature is high, the high-pressure side pressure becomes high, and when the outside air temperature becomes high, the high-pressure side pressure becomes even higher. Therefore, it is necessary to increase the pressure resistance of the refrigerant circuit and component parts, leading to an increase in cost. There was also. Furthermore, in order not to increase the pressure resistance of the refrigerant circuit and the component parts, it is necessary to operate with a reduced capability, resulting in a problem of insufficient capability.

  The present invention has been made to solve the above-described problems, and controls the refrigerant amount distribution in the refrigeration cycle used in the heat pump water heater without using a container having a volume for storing refrigerant such as an accumulator. The present invention provides a control method for a heat pump water heater to be realized. Moreover, the control method of the heat pump water heater which implement | achieves high external air and a high temperature boiling operation, without raising the pressure | voltage resistance of the refrigerant circuit in a heat pump water heater, or component parts is provided.

  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 passage reconnected to the refrigerant pipe while reaching the condenser, and a high-low pressure heat exchanger for exchanging heat between the high-pressure refrigerant flowing through the branch passage and the low-pressure refrigerant sucked into the compressor A control method for a heat pump water heater, wherein the discharge pressure of the refrigerant discharged from the compressor is measured, and when the discharge pressure is greater than a predetermined pressure, the opening of the first expansion valve is reduced. It is characterized by adjusting to.

  The control method of the 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 pressure reducing the refrigerant. The refrigerating cycle in which the refrigerant is circulated by sequentially connecting the expansion valve and the evaporator with a refrigerant pipe, and the refrigerant pipe is branched between the radiator and the first expansion valve, and the first expansion valve A branch flow path reconnected to the refrigerant pipe while reaching the evaporator, and 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 method for controlling a heat pump water heater provided, wherein the discharge pressure of the refrigerant discharged from the compressor is measured, and when the discharge pressure is higher than a predetermined pressure, the drive frequency of the compressor is increased. It is characterized by adjusting .

  Furthermore, the control method of the heat pump water heater according to the present invention includes 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, and a first pressure reducing the refrigerant. The refrigerating cycle in which the refrigerant is circulated by sequentially connecting the expansion valve and the evaporator with a refrigerant pipe, and the refrigerant pipe is branched between the radiator and the first expansion valve, and the first expansion valve A branch flow path reconnected to the refrigerant pipe while reaching the evaporator, and 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 method of controlling a heat pump water heater provided, wherein the discharge pressure of the refrigerant discharged from the compressor is measured, the outside air temperature is higher than a predetermined temperature, and the boiling temperature of the load-side medium is higher than a predetermined temperature The outside air temperature is the same As compared with the case boiling temperature of the load-side medium is lower than a predetermined temperature, and adjusting to increase the frequency of the compressor.

  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 branch passage reconnected to the refrigerant pipe, a high-low pressure heat exchanger for exchanging heat between the high-pressure refrigerant flowing in the branch passage and the low-pressure refrigerant sucked into the compressor, and discharging from the compressor A pressure detecting means for measuring and detecting the pressure of the refrigerant, and adjusting the opening of the first expansion valve when the refrigerant pressure measured and detected by the pressure detecting means is greater than a predetermined pressure. Measurement control means to And butterflies.

  The 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 valve that depressurizes the refrigerant. And a refrigerating cycle in which the refrigerant circulates by sequentially connecting the evaporator with a refrigerant pipe, and the refrigerant pipe is branched between the radiator and the first expansion valve, and the evaporator is connected to the evaporator from the first expansion valve. A high-low pressure heat exchanger that exchanges 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 compressor And a pressure detection means for measuring and detecting the pressure of the refrigerant discharged from the refrigerant, and when the refrigerant pressure measured and detected by the pressure detection means is greater than a predetermined pressure, the drive frequency of the compressor is adjusted to be increased With measurement control means And wherein the door.

  Furthermore, the heat pump water heater according to the present invention includes 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, and a first expansion valve that depressurizes the refrigerant. And a refrigerating cycle in which the refrigerant circulates by sequentially connecting the evaporator with a refrigerant pipe, and the refrigerant pipe is branched between the radiator and the first expansion valve, and the evaporator is connected to the evaporator from the first expansion valve. A high-low pressure heat exchanger that exchanges 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 compressor Pressure detection means for measuring and detecting the pressure of the refrigerant discharged from the refrigerant, and when the outside air temperature is higher than the predetermined temperature and the boiling temperature of the load side medium is higher than the predetermined temperature, the outside air temperature is the same and the load side The boiling temperature of the medium is a predetermined temperature Ri than when low, is characterized in that a measurement control unit for adjusting so as to increase the driving frequency of the compressor.

  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. A refrigeration cycle in which a refrigerant is circulated by sequentially connecting a valve and an evaporator with a refrigerant pipe, a high-low pressure heat exchanger provided between the evaporator and the compressor, and a refrigerant circulated in the refrigeration cycle In order to lead to the high-low pressure heat exchanger, the refrigerant pipe is branched between the radiator and the first expansion valve, and the refrigerant pipe is reused between the high-low pressure heat exchanger and the evaporator. A branch flow path to be connected; pressure detection means for measuring and detecting the pressure of the refrigerant discharged from the compressor; and measurement control means for controlling the compressor and the expansion valve. Measured and detected by pressure detection means When the refrigerant pressure is higher than a predetermined pressure, the opening of the first expansion valve is adjusted to be small, so that the heat pump hot water supply is controlled while controlling the refrigerant amount distribution existing in the refrigerant circuit of the refrigeration cycle. The operating state of the machine can be controlled to a high pressure that maximizes the COP. In addition, a highly efficient heat pump water heater can be operated, and a container for controlling the refrigerant amount distribution is not required, and a low-cost heat pump water heater can be provided. Furthermore, there is an effect that a high-temperature outdoor air and high-temperature boiling operation can be realized at low cost without increasing the pressure resistance of the heat pump water heater, and a heat pump water heater having a predetermined capacity can be obtained.

  The control method of the 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 pressure reducing the refrigerant. A refrigerating cycle in which refrigerant is circulated by sequentially connecting expansion valves and an evaporator through refrigerant piping, a high-low pressure heat exchanger provided between the evaporator and the compressor, and a refrigerant circulating in the refrigerating cycle In order to guide the refrigerant to the high-low pressure heat exchanger, the refrigerant pipe is branched between the radiator and the first expansion valve, and between the high-low pressure heat exchanger and the evaporator, the refrigerant pipe is branched. A branch flow path that is reconnected to the pressure sensor, a pressure detection means that measures and detects the pressure of the refrigerant discharged from the compressor, and a measurement control means that controls the compressor and the expansion valve. , Measured by the pressure detection means If the pressure of knowledge refrigerant is greater than a predetermined pressure, so adjusted as to increase the frequency of the compressor, the same effect as described above can be obtained.

  Furthermore, the control method of the heat pump water heater according to the present invention includes 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, and a first pressure reducing the refrigerant. A refrigerating cycle in which refrigerant is circulated by sequentially connecting expansion valves and an evaporator through refrigerant piping, a high-low pressure heat exchanger provided between the evaporator and the compressor, and a refrigerant circulating in the refrigerating cycle In order to guide the refrigerant to the high-low pressure heat exchanger, the refrigerant pipe is branched between the radiator and the first expansion valve, and between the high-low pressure heat exchanger and the evaporator, the refrigerant pipe is branched. A branch flow path that is reconnected to the pressure sensor, a pressure detection means that measures and detects the pressure of the refrigerant discharged from the compressor, and a measurement control means that controls the compressor and the expansion valve. , Outside temperature is a predetermined temperature When the boiling temperature of the load-side medium is higher than the predetermined temperature, the outside air temperature is the same, and the frequency of the compressor is higher than when the boiling temperature of the load-side medium is lower than the predetermined temperature. Since the adjustment is performed to increase the value, the same effect as described above can be obtained.

  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 the refrigerant pipe is reconnected to the evaporator. Measures the pressure of the refrigerant discharged from the compressor, and the connected branch channel, the high- and low-pressure heat exchanger that exchanges heat between the high-pressure refrigerant flowing through the branch channel and the low-pressure refrigerant sucked into the compressor Pressure detecting means for detecting, and measurement control means for adjusting the opening of the first expansion valve to be small when the refrigerant pressure measured and detected by the pressure detecting means is greater than a predetermined pressure. The refrigerant cycle of the refrigeration cycle While controlling the amount of refrigerant distributions existing within the operating conditions of the heat pump water heater can be controlled to a high pressure as the COP maximum. In addition, a highly efficient heat pump water heater can be operated, and a container for controlling the refrigerant amount distribution is not required, and a low-cost heat pump water heater can be provided. Furthermore, there is an effect that a high-temperature outdoor air and high-temperature boiling operation can be realized at low cost without increasing the pressure resistance of the heat pump water heater, and a heat pump water heater having a predetermined capacity can be obtained.

  The 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 valve that depressurizes the refrigerant. And a refrigerating cycle in which the refrigerant is circulated by sequentially connecting the evaporator with a refrigerant pipe, and the refrigerant pipe is branched between the radiator and the first expansion valve, and between the refrigerant and the evaporator. A high-low pressure heat exchanger for exchanging heat between the branch flow path reconnected to the low-pressure refrigerant, the high-pressure refrigerant flowing through the branch flow path, and the low-pressure refrigerant sucked into the compressor, and the pressure of the refrigerant discharged from the compressor A pressure detection means for measuring and detecting the pressure, and a measurement control means for adjusting the frequency of the compressor to be increased when the refrigerant pressure measured and detected by the pressure detection means is greater than a predetermined pressure. The same effect as above It is.

  Furthermore, the heat pump water heater according to the present invention includes 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, and a first expansion valve that depressurizes the refrigerant. And a refrigerating cycle in which the refrigerant is circulated by sequentially connecting the evaporator with a refrigerant pipe, and the refrigerant pipe is branched between the radiator and the first expansion valve, and between the refrigerant and the evaporator. A high-low pressure heat exchanger for exchanging heat between the branch flow path reconnected to the high-pressure refrigerant, the high-pressure refrigerant flowing through the branch flow path, and the low-pressure refrigerant sucked into the compressor, and the pressure of the refrigerant discharged from the compressor When the outside air temperature is higher than the predetermined temperature and the boiling temperature of the load side medium is higher than the predetermined temperature, the outside air temperature is the same, and the boiling temperature of the load side medium is Compared to when the temperature is lower than the specified temperature , Since a measurement control unit for adjusting so as to increase the frequency of the compressor, the same effect as described above can be obtained.

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. The expansion valve inlet temperature sensor 13g is provided at the inlet of the second expansion valve 10, respectively. The discharge temperature sensor 13d, the suction temperature sensor 13e, the evaporation temperature sensor 13f, and the expansion valve inlet temperature sensor 13g have a function of measuring the temperature of the refrigerant flowing through the refrigerant pipe 15 and the branch flow path 8 at the respective installation locations. Fulfill.

  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.

  A pressure sensor 25 is provided in the heat pump unit 1. The pressure sensor 25 is provided between the radiator 4 and the first expansion valve 5, and fulfills the function of measuring the refrigerant pressure at an installation location on the high pressure side of the refrigeration cycle 20. Here, the case where the pressure sensor 25 is provided between the radiator 4 and the first expansion valve 5 is illustrated, but between the compressor 3 and the radiator 4 on the upstream side of the radiator 4. You may make it provide in.

  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 (outer pipe) of the high and low pressure heat exchanger 9 and flows out from the evaporator 6, and then flows through the low pressure side flow path (inside This is used for heat exchange with the low-pressure refrigerant passing through the pipe.

  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.

Next, the operation control operation in the heat pump water heater 100 will be described.
FIG. 2 is an explanatory diagram (PH diagram) showing the relationship between the pressure of the refrigeration cycle 20 and enthalpy when the high pressure is changed so that the temperature of the refrigerant at the outlet of the radiator 4 becomes the same. In the refrigeration cycle 20 in which the high pressure side is operated in a supercritical state such as CO ₂ as a refrigerant, there is a high pressure at which the operation efficiency is maximized as is well known.

  In FIG. 2, the vertical axis represents pressure (P) and the horizontal axis represents enthalpy (H). Here, as the high pressure of the refrigeration cycle 20 increases in the order of P1, P2, and P3, the enthalpy difference ΔHg in the radiator 4 increases, and the heating capacity increases accordingly. Further, the enthalpy difference ΔHc in the compressor 3 corresponding to the input of the compressor 3 increases as the high pressure of the refrigeration cycle 20 increases in the order of P1, P2, and P3.

  FIG. 3 is an explanatory diagram showing a relationship between a change due to high pressure of the refrigeration cycle 20 and COP (operation efficiency), ΔHg, and ΔHc. That is, the tendency of change due to the high pressure of the refrigeration cycle 20 in ΔHg and ΔHc explained in FIG. 2 is shown. In FIG. 3, the horizontal axis represents the high-pressure side pressure in the refrigeration cycle 20, and the vertical axis represents the ratio. Line B represents the enthalpy difference ΔHg in the radiator 4, line B represents the enthalpy difference ΔHc in the compressor 3, and line A represents the COP.

  In FIG. 3, in the region where the increase rate of ΔHg corresponding to the capacity accompanying the increase in high pressure exceeds the increase rate of ΔHc corresponding to the input (range from P1 to P2), the COP of the refrigeration cycle 20 represented by ΔHg / ΔHc. Can be seen to rise. On the other hand, it can be seen that COP decreases in a region (in the range of P2 to P3) where the increase rate of ΔHg corresponding to the capacity accompanying the increase in high pressure is lower than the increase rate of ΔHc corresponding to the input. That is, there is a high pressure at which COP is maximized. This corresponds to the point P2 shown in FIG.

The high pressure in the refrigeration cycle 20 in the heat pump water heater 100 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, so the amount of refrigerant in the radiator 4 when operating in the high pressure state P3 shown in FIG. 2 is operated in the high pressure state P1. The amount of refrigerant in the radiator 4 is larger than that when the operation is performed.

  That is, if the operation is adjusted so that the amount of refrigerant existing in the radiator 4 is increased, the high pressure is increased, and conversely, the operation is adjusted so that the amount of refrigerant existing in the radiator 4 is decreased. In this case, the high pressure will decrease. Therefore, by operating so as to control the amount of refrigerant present in the radiator 4, the high pressure can be set to be the pressure that maximizes the COP. By doing so, the capability of the heat pump water heater 100 can be greatly exerted.

  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.

  The high pressure Ph of the refrigeration cycle 20 when operated in this state is measured by the pressure sensor 15. And from the heating capacity set by the user of the heat pump water heater 100, the feed water temperature measured and detected by the feed water temperature sensor 13a, the outside air temperature measured and detected by the outside air temperature sensor 13c, the operating capacity of the compressor 3, etc. The optimum high pressure that maximizes the COP is calculated using a predetermined arithmetic expression, and the target pressure that is the optimum high pressure is compared with the detected high pressure Ph. In this way, if the current high pressure is lower than the optimum high pressure, the amount of refrigerant in the radiator 4 may be adjusted to increase. On the contrary, if the current high pressure is higher than the optimum high pressure, the amount of refrigerant in the radiator 4 may be adjusted to be small.

  Control of the amount of refrigerant in the radiator 4 is performed by adjusting the opening degree of the first expansion valve 5 and the second expansion valve 10. Here, the operation 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 through the branch flow path 8 is reduced, and the heat exchange amount of the high / low pressure heat exchanger 9 is reduced. On the other hand, when the opening degree of the first expansion valve 5 is reduced, the amount of refrigerant flowing through the branch flow path 8 is increased, and the heat exchange amount of the high-low pressure heat exchanger 9 is increased.

  FIG. 4 is an explanatory diagram (PH 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. 4, the vertical axis represents pressure (P), and the horizontal axis represents enthalpy (H). Further, the solid line represents the case where the heat exchange amount in the high / low pressure heat exchanger 9 is small, and the broken line represents 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. 4, 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.

  If the refrigerant state at the inlet of the evaporator 6 is a lower dryness, the volume occupied by the liquid refrigerant increases at least near the inlet of the evaporator 6. As a result, when the evaporator 6 is viewed as a whole, the amount of refrigerant existing here increases. Therefore, when the amount of heat exchange in the high / low pressure heat exchanger 9 is large, and the amount of cooling there increases, the refrigerant temperature detected by the expansion valve inlet temperature sensor 13g decreases, and the refrigerant state at the inlet of the evaporator 6 becomes more. The degree of dryness is low and the amount of refrigerant present in the evaporator 6 increases in a two-phase state with a large amount of liquid refrigerant.

  On the other hand, when the amount of heat exchange in the high / low pressure heat exchanger 9 is small and the amount of cooling is reduced, the refrigerant temperature detected by the expansion valve inlet temperature sensor 13g rises, and the refrigerant state at the inlet of the evaporator 6 is dry. Remains in a high state, a two-phase state with a large amount of gas refrigerant, and the amount of refrigerant present in the evaporator 6 decreases. As described above, the amount of refrigerant existing in the evaporator 6 can be changed by changing the heat exchange amount in the high-low pressure heat exchanger 9 by controlling the flow rate in the first expansion valve 5.

  That is, when 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 amount of refrigerant existing in the evaporator 6 is reduced and the first expansion valve 5 is opened. When the degree is reduced, the amount of refrigerant existing in the evaporator 6 increases because the heat exchange amount of the high-low pressure heat exchanger 9 increases. Also, measurement information such as the feed water temperature sensor 13a, the hot water temperature sensor 13b, the outside air temperature sensor 13c, the discharge temperature sensor 13d, the suction temperature sensor 13e, the evaporation temperature sensor 13f, the expansion valve inlet temperature sensor 13g, etc., and the user of the heat pump water heater 100 If the correspondence with the high pressure is known in advance based on the content of the operation command information instructed from the above, if a map or function is incorporated in the measurement control device 14, the high pressure side pressure of the refrigeration cycle 20 is detected. There is no need to provide the pressure sensor 25.

  By doing so, the pressure sensor 25 is not required, and thus it is possible to realize a more efficient operation of the heat pump water heater 100 without cost. In that case, for example, the first expansion valve 5 and the second expansion valve 10 may be combined, and new control may be added such as controlling the discharge temperature and the suction superheat degree. In addition, you may make it provide the sensor etc. which measure the refrigerant | coolant state of the refrigerating cycle 20 required for that.

Next, the operation control operation of the heat pump water heater 100 will be described.
FIG. 5 is a flowchart showing the flow of operations for controlling the discharge temperature and the suction superheat degree by adjusting the opening degree 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). Then, the measurement control device 14 controls the second expansion valve 10 so that the refrigerant discharge temperature measured and detected by the discharge temperature sensor 13d becomes 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 high pressure of the refrigerant is measured and detected by the pressure sensor 25 (step S105). And the measurement control apparatus 14 determines whether the high pressure of the refrigerant | coolant measured and detected by the pressure sensor 25 is a preset value (step S106). That is, when the high pressure of the refrigerant has reached the set value (step S106; N), the opening degree of the first expansion valve 5 is decreased (step S107). By reducing the opening degree of the first expansion valve 5, the heat exchange amount of the high / low pressure heat exchanger 9 is increased.

  And the measurement control apparatus 14 determines whether the opening degree of the 1st expansion valve 5 is 0 (fully closed state) (step S108). When the opening degree of the first expansion valve 5 is not 0 (step S108; N), the discharge temperature is detected at the beginning of the control operation. On the other hand, when the opening degree of the first expansion valve 5 is 0 (step S108; Y), the frequency of the compressor 3 is further increased (step S109). That is, the amount of heat exchange in the high-low pressure heat exchanger 9 is increased by increasing the frequency of the compressor 3. Thereafter, returning to the beginning of the control operation, the discharge temperature is detected.

  On the contrary, when the high pressure of the refrigerant is less than the set value (step S106; Y), the suction temperature of the refrigerant sucked into the compressor 3 is measured and detected by the suction temperature sensor 13e (step S110). Further, the evaporating temperature of the refrigerant in the evaporator 4 is measured and detected by the evaporating temperature sensor 13f (step S111). Based on the measured suction temperature and evaporation temperature, the measurement controller 14 calculates the suction superheat degree (step S112). The measurement control device 14 determines whether or not the calculated suction superheat degree is a predetermined target value (step S113).

  That is, when the suction superheat degree has reached the target value (step S113; N), the opening degree of the first expansion valve 5 is increased (step S114). 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 S113; 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.

  FIG. 6 is an explanatory diagram (PH diagram) showing the state of the refrigerant when the frequency of the compressor 3 is increased. In FIG. 6, the vertical axis represents pressure (P) and the horizontal axis represents enthalpy (H). In the figure, the solid line indicates a state where the boiling temperature is high, the first expansion valve 5 is set to 0 (full closed state), and the compressor 3 is set to a low frequency. The state is shown in which the temperature is high, the opening of the first expansion valve 5 is fully closed, and the compressor 3 is set to a high frequency. Further, Ta1 and Tb1 indicate the refrigerant temperature at the outlet of the radiator 4 (radiator outlet refrigerant temperature), and Ta2 and Tb2 indicate the temperature of the refrigerant drawn into the compressor 3 (compressor intake temperature), respectively.

  Generally, when the boiling temperature is increased, the high pressure of the refrigerant is increased. Therefore, when the first expansion valve 5 is at the opening degree 0 (fully closed state) and exceeds the upper limit pressure, if the frequency of the compressor 3 is increased, the radiator outlet refrigerant temperature rises. Note that the high and low pressure heat exchanger 9 has a high pressure channel and a low pressure channel that are opposed to each other, and the high pressure side inlet temperature of the high and low pressure heat exchanger 9 is equal to the radiator outlet refrigerant temperature, and the low pressure side outlet The temperature is equal to the compressor intake temperature. Therefore, when the radiator outlet refrigerant temperature rises from Ta1 to Tb1, the compressor suction temperature also rises from Ta2 to Tb2. Therefore, if it is going to control discharge temperature only with the 2nd expansion valve 10, when the frequency of the compressor 3 is increased, the high pressure of a refrigerant | coolant will fall.

  From the above, not only the opening degree of the second expansion valve 10 but also the opening degree of the first expansion valve 5 is adjusted to set the discharge temperature of the refrigeration cycle 20 to a predetermined target. It can be close to the value. That is, the heat pump water heater 100 adjusts the distribution of the amount of refrigerant existing in the refrigeration cycle 20 by reducing the opening of the first expansion valve 5 when the high pressure of the refrigerant is larger than the target value. The operating state is controlled to a high pressure that maximizes the COP. If no high-pressure sensor is installed, if the outside air temperature is higher than the predetermined value and the boiling temperature is higher than the predetermined value, the boiling temperature of the same outside air temperature is compressed as compared with the case where the boiling temperature is lower than the predetermined value. A map that increases the frequency of the machine 3 may be created.

It is a schematic block diagram which shows the refrigerant circuit structure of the heat pump water heater which concerns on embodiment of this invention. It is a PH diagram which shows the relationship between the pressure of a refrigerating cycle, and enthalpy when changing a high voltage | pressure so that a radiator exit refrigerant | coolant temperature may become the same. It is explanatory drawing which shows the relationship with the change by the high voltage | pressure of a refrigerating cycle, and COP, (DELTA) Hg, and (DELTA) Hc. It is a PH diagram which shows the relationship between the pressure of a refrigerating cycle when the amount of heat exchange in a high-low pressure heat exchanger fluctuates, and enthalpy. It is a flowchart which shows the flow of operation | movement which adjusts the opening degree of a 1st expansion valve and a 2nd expansion valve, and controls discharge temperature and suction | inhalation superheat degree. It is a PH diagram which shows the state of the refrigerant | coolant at the time of increasing the frequency of a compressor.

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, 13g Expansion valve inlet temperature sensor, 14 Measurement control device, 15 Refrigerant piping , 16 water piping, 20 refrigeration cycle, 25 pressure sensor, 30 hot water supply circuit, 100 heat pump water heater.

Claims (8)

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 control method for a heat pump water heater comprising a high-low pressure heat exchanger for exchanging heat between a high-pressure refrigerant flowing through the branch flow path and a low-pressure refrigerant sucked into the compressor,
Measure the discharge pressure of the refrigerant discharged from the compressor,
When the discharge pressure is higher than a predetermined pressure, the opening degree of the first expansion valve is adjusted to be small. A method for controlling a heat pump water heater. 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 control method for a heat pump water heater comprising a high-low pressure heat exchanger for exchanging heat between a high-pressure refrigerant flowing through the branch flow path and a low-pressure refrigerant sucked into the compressor,
Measure the discharge pressure of the refrigerant discharged from the compressor,
When the discharge pressure is larger than a predetermined pressure, adjustment is made to increase the drive frequency of the compressor. 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 control method for a heat pump water heater comprising a high-low pressure heat exchanger for exchanging heat between a high-pressure refrigerant flowing through the branch flow path and a low-pressure refrigerant sucked into the compressor,
Measure the discharge pressure of the refrigerant discharged from the compressor,
When the outside air temperature is higher than the predetermined temperature and the boiling temperature of the load side medium is higher than the predetermined temperature, compared to the case where the outside air temperature is the same and the boiling temperature of the load side medium is lower than the predetermined temperature, A control method for a heat pump water heater, wherein the drive frequency of the compressor is adjusted to be increased. A second expansion valve is provided in the branch passage between the high-low pressure heat exchanger and the evaporator, and decompresses the refrigerant;
The method for controlling a heat pump water heater according to any one of claims 1 to 3, wherein the second expansion valve is also adjusted together with the first expansion valve and the compressor. The high-low pressure heat exchanger is
The control method for a heat pump water heater according to any one of claims 1 to 3, wherein the branch flow path through which the high-pressure refrigerant flows and the refrigerant pipe through which the low-pressure refrigerant sucked into the compressor flow are opposed to each other. . 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 that exchanges heat between the high-pressure refrigerant flowing through the branch flow path and the low-pressure refrigerant sucked into the compressor;
Pressure detection means for measuring and detecting the pressure of the refrigerant discharged from the compressor;
A heat pump comprising: a measurement control means for adjusting the opening of the first expansion valve when the pressure of the refrigerant measured and detected by the pressure detection means is greater than a predetermined pressure. Water heater. 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 that exchanges heat between the high-pressure refrigerant flowing through the branch flow path and the low-pressure refrigerant sucked into the compressor;
Pressure detection means for measuring and detecting the pressure of the refrigerant discharged from the compressor;
A heat pump water heater comprising: a measurement control unit configured to adjust the drive frequency of the compressor to be increased when the refrigerant pressure measured and detected by the pressure detection unit is greater than a predetermined pressure. 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 that exchanges heat between the high-pressure refrigerant flowing through the branch flow path and the low-pressure refrigerant sucked into the compressor;
Pressure detection means for measuring and detecting the pressure of the refrigerant discharged from the compressor;
When the outside air temperature is higher than the predetermined temperature and the boiling temperature of the load side medium is higher than the predetermined temperature, the outside air temperature is the same, compared with the case where the boiling temperature of the load side medium is lower than the predetermined temperature. And a measurement control means for adjusting so as to increase the driving frequency of the compressor.

Images