JP6982272B2 - Heat pump type hot water supply device - Google Patents

Description

The present invention relates to a heat pump type hot water supply device, and more specifically, to a technique for avoiding low differential pressure operation (operation at a low compression ratio) of a compressor during boiling operation.

The heat pump type hot water supply device is provided with a refrigerant circuit in which a compressor, a heat exchanger on the user side, an expansion valve and a heat exchanger on the heat source side are sequentially connected via a refrigerant pipe, and a hot water storage tank as a basic configuration. For example, the heat exchanger on the user side has a configuration in which a refrigerant pipe is wound around the outer periphery of the hot water storage tank, and the heat exchanger on the user side is switched so that the heat exchanger acts as a condenser to heat the water in the hot water storage tank and the refrigerant. The water in the hot water storage tank is heated by replacement.

In such a heat pump type hot water supply device, a boiling operation is performed so that the water temperature in the hot water storage tank finally reaches the hot water temperature (target water temperature) to be reached. In the boiling operation, the high-temperature and high-pressure refrigerant discharged from the compressor flows into the heat exchanger on the user side, exchanges heat with the water in the hot water storage tank, and condenses. The condensed refrigerant is decompressed by the expansion valve, evaporates by heat exchange with the outside air in the heat source side heat exchanger, becomes a low-pressure gas refrigerant, and returns to the compressor.

Japanese Unexamined Patent Publication No. 2007-1183836

By the way, when the outside air temperature is high (for example, 30 ° C. or higher), the evaporation capacity in the heat source side heat exchanger becomes high, and the evaporation pressure rises in the low pressure side of the refrigerant circuit. On the other hand, at the start of the boiling operation, the water temperature in the hot water storage tank is low, so that the condensation pressure on the high pressure side of the refrigerant circuit is low.

When the pressure on the low pressure side is high and the pressure on the high pressure side is low, the compression ratio of the compressor may be low and fall below the lower limit of the performance of the compressor. However, if the rotation speed of the compressor is unnecessarily increased in order to secure the compression ratio, the operation efficiency during the boiling operation deteriorates.

In particular, immediately after the start of the boiling operation, that is, when the water temperature in the hot water storage tank is low and the temperature difference from the target water temperature is large, the number of revolutions of the compressor is increased to raise the temperature of the heat exchange part of the hot water storage tank. However, due to the large heat capacity of the water inside the hot water storage tank, the temperature of the water in the hot water storage tank that matches the temperature of the heat exchange unit cannot be obtained, and only the compression ratio becomes larger than necessary, resulting in higher operating efficiency. Getting worse.

Therefore, an object of the present invention is to set the compression ratio of the compressor to be equal to or higher than the lower limit of performance in the heat pump type hot water supply device without lowering the operation efficiency during the boiling operation.

In order to solve the above problems, the present invention sequentially connects a compressor, a flow path switching means, a user-side heat exchange unit for heat exchange between water and a refrigerant, and a heat source-side heat exchanger via a refrigerant pipe. It includes a refrigerant circuit, an outside temperature sensor that detects the outside air temperature, a pressure sensor that detects the condensation pressure of the refrigerant on the discharge side of the compressor, and a control means, and is detected by the outside temperature sensor by the control means. In a heat pump type hot water supply device in which the minimum rotation speed of the compressor is determined based on the outside air temperature and the condensation pressure of the refrigerant detected by the pressure sensor.
The control means has a table in which the minimum rotation speed of the compressor is determined according to the outside air temperature and the condensing pressure, and the table has at least one predetermined temperature To in which the outside air temperature is predetermined. The minimum rotation speed when the first outside air temperature Ta is higher and the minimum rotation speed when the second outside air temperature Tb is lower than the predetermined temperature To are defined, respectively, and correspond to the same value of the condensation pressure. The minimum rotation speed of the compressor is characterized in that the rotation speed at the time of the first outside air temperature Ta is higher than that at the time of the second outside air temperature Tb.

In the present invention, the minimum rotation speed is a rotation speed at which the compression ratio of the compressor does not fall below the lower limit of performance.

According to the present invention, the same condensation pressure is used when the outside air temperature is higher than the predetermined outside air temperature (at the time of the first outside air temperature Ta) and when the outside air temperature is lower than the predetermined outside air temperature (at the time of the second outside air temperature Tb). However, the minimum rotation speed of the compressor is set to a different value, specifically, when the outside air temperature is higher than the predetermined outside air temperature, the outside air temperature is set higher than when the outside air temperature is lower than the predetermined outside air temperature. By increasing the minimum rotation speed when the outside air temperature is high as compared with when the outside air temperature is low, it is possible to prevent the compression ratio from falling below the lower limit of performance. In addition, when the outside air temperature is low, the compression ratio is unlikely to fall below the lower limit of performance. Therefore, by lowering the minimum rotation speed compared to when the outside air temperature is high, the operating efficiency during boiling operation should be improved. Can be done.

The schematic diagram which shows the structure of the heat pump type hot water supply apparatus by this invention. The schematic diagram which shows the table provided in the control means.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. As an embodiment, a heat pump type hot water supply device having a hot water storage tank which is a hot water supply terminal and heating water stored in the hot water storage tank by heat exchange with a refrigerant will be described as an example. The present invention is not limited to the following embodiments, and various modifications can be made without departing from the gist of the present invention.

FIG. 1 shows the configuration of a heat pump type hot water supply device according to the present invention. This heat pump type hot water supply device 100 is configured by winding a part of a refrigerant pipe 11 described later around the outer periphery of a compressor 1 having a variable capacity, a four-way valve 2 which is a flow path switching means, and a hot water storage tank 70, and heat on the user side. It has a refrigerant circuit 10 in which a switching unit 3, an expansion valve 4, a heat source side heat exchanger 5, and an accumulator 6 are connected in order by a refrigerant pipe 11, and the circulation direction of the refrigerant can be switched by switching the four-way valve 2. It has become like.

In the refrigerant circuit 10, the refrigerant pipe 11 near the refrigerant discharge port of the compressor 1 is provided with a discharge temperature sensor 51 for detecting the temperature of the refrigerant discharged from the compressor 1. Further, in the refrigerant pipe 11 between the heat exchange unit 3 and the expansion valve 4, the temperature of the refrigerant flowing out from the heat exchange unit 3 when the heat exchange unit 3 is functioning as a condenser, or heat exchange. A refrigerant temperature sensor 53 is provided to detect the temperature of the refrigerant flowing into the heat exchange unit 3 when the unit 3 functions as an evaporator.

Further, in the refrigerant pipe 11 between the expansion valve 4 and the heat source side heat exchanger 5, the temperature of the refrigerant flowing into the heat source side heat exchanger 5 when the heat source side heat exchanger 5 is functioning as an evaporator Or, the heat exchange temperature sensor 54, which is a heat exchange temperature detecting means, detects the temperature of the refrigerant flowing out from the heat source side heat exchanger 5 when the heat source side heat exchanger 5 is functioning as a condenser. It is prepared.

Further, the refrigerant pipe 11 on the discharge side of the compressor 1 (between the four-way valve 2 and the heat exchange unit 3) exchanges heat during the boiling operation, that is, when the heat exchange unit 3 functions as a condenser. A pressure sensor 50 for detecting the condensation pressure of the refrigerant in the unit 3 is provided. Further, an outside air temperature sensor 52, which is an outside air temperature detecting means, is provided in the vicinity of the heat source side heat exchanger 5.

In the vicinity of the heat source side heat exchanger 5, a fan 7 that takes in outside air into a housing (not shown) of the heat pump type hot water supply device 100 and circulates the outside air to the heat source side heat exchanger 5 is arranged. The fan 7 is attached to an output shaft (rotational shaft) of a motor (not shown) whose rotation speed can be varied. Further, the expansion valve 4 is capable of pulse control of the valve opening degree by using a stepping motor.

The heat exchange unit 3 is included in a part of the refrigerant pipe 11. In the present embodiment, the heat exchange unit 3 is configured by spirally winding a part of the refrigerant pipe 11 around the lower side of the outer peripheral surface of the hot water storage tank 70, and exchanges heat with the water in the hot water storage tank 70. The heat exchange unit 3 may be arranged in the hot water storage tank 70. Further, although not shown, the heat exchange unit 3 causes the water in the hot water storage tank 70 to flow into the heat exchange unit 3 and becomes a refrigerant, like a double tube heat exchanger having a refrigerant side flow path and a water side flow path. It may be one that exchanges heat.

The upper part of the hot water storage tank 70 is provided with a hot water supply port 73 for supplying hot water stored inside the hot water storage tank 70 to a bathtub, a washbasin faucet, or the like. Further, a water inlet 72 for supplying water to the inside of the hot water storage tank 70 is provided in the lower portion of the hot water storage tank 70, and a water pipe (not shown) is connected to the water inlet 72.

Further, a water temperature sensor 58 for detecting the temperature of hot water staying in the hot water storage tank 70 is provided in a substantially central portion of the inside of the hot water storage tank 70 in the vertical direction.

In addition to the configuration described above, the heat pump type hot water supply device 100 has a control means 60. The control means 60 takes in the temperature detected by the temperature sensors 51, 52, 53, 54, 58 and the condensing pressure of the refrigerant during the boiling operation detected by the pressure sensor 50, or from a user using a remote control (not shown) or the like. Various controls related to the operation of the heat pump type hot water supply device 100, such as drive control of the compressor 1 and fan 7, switching control of the four-way valve 2, opening control of the expansion valve 4, etc. conduct.

Although not shown, the control means 60 has a timer unit for measuring time, a storage unit for storing values detected by various sensors, a control program of the heat pump type hot water supply device 100, and the like.

Next, the flow of the refrigerant and the operation of each part in the refrigerant circuit 10 included in the heat pump type hot water supply device 100 of the present embodiment will be described.

The heat pump type hot water supply device 100 of the present embodiment uses the refrigerant circuit 10 as a heating cycle to boil water stored in the hot water storage tank 70, and a cooling cycle for the refrigerant circuit 10 during the boiling operation. The reverse cycle defrosting operation for defrosting the heat source side heat exchanger 5 can be performed.

During the boiling operation, the refrigerant flows in the direction of the solid arrow 80 in FIG. 1, whereas in the reverse cycle defrosting operation, the four-way valve 2 is switched and the refrigerant flows in the direction of the broken arrow 81 in FIG. Since the reverse cycle defrosting operation is not particularly characterized in the above, the detailed description thereof will be omitted, and the operation of the heat pump type hot water supply device 100 during the boiling operation will be described below.

<Boiling operation>
When the user operates a remote controller or the like (not shown) to instruct the start of the boiling operation, the control means 60 switches the four-way valve 2 so that the refrigerant circuit 10 becomes a heating cycle. Specifically, the control means 60 is such that the discharge side of the compressor 1 and the heat exchange unit 3 are connected, and the suction side of the compressor 1 and the heat source side heat exchanger 5 are connected. Switch the four-way valve 2. As a result, the heat exchange unit 3 functions as a condenser, and the heat source side heat exchanger 5 functions as an evaporator.

Next, the control means 60 starts the compressor 1 and the fan 7 to start the boiling operation of the heat pump type hot water supply device 100. The control means 60 determines the temperature difference stored in the storage unit and the number of revolutions of the compressor 1 according to the temperature difference between the current water temperature in the hot water storage tank 70 and the boiling target temperature detected by the water temperature sensor 58. The number of revolutions of the compressor 1 is determined with reference to the associated table (not shown), and the compressor 1 is driven by this number of revolutions.

When the compressor 1 is driven, as shown by the solid line arrow 80 in FIG. 1, the high-temperature and high-pressure refrigerant discharged from the compressor 1 passes through the four-way valve 2 and exchanges heat with water in the heat exchange unit 3 to condense. Further, the pressure is reduced by the expansion valve 4, heat is exchanged with the outside air by the heat source side heat exchanger 5, the air is evaporated, the gas and liquid are separated by the accumulator 6, and then sucked into the compressor 1 and compressed again by the compressor 1. Repeat the process.

In this way, the water in the hot water storage tank 70 is heated by the high-temperature and high-pressure refrigerant flowing through the heat exchange unit 3, and when the water temperature in the hot water storage tank 70 boils up and reaches the target temperature, the control means 60 uses the compressor 1 and the fan. Stop the operation of 7.

The control means 60 constantly monitors the water temperature in the hot water storage tank 70 detected by the water temperature sensor 58, and when the water temperature drops from the boiling target temperature to a preset predetermined temperature (for example, 5 ° C.), it boils. Restart the raising operation.

By the way, as described above, when the outside air temperature is high, the evaporation capacity of the heat source side heat exchanger 5 is high, and the evaporation pressure is high on the low pressure side of the refrigerant circuit 10. On the other hand, at the start of the boiling operation, the water temperature in the hot water storage tank 70 is low, so that the condensation pressure of the refrigerant circuit 10 is low.

When the pressure on the low pressure side is high and the pressure on the high pressure side is low, the compression ratio of the compressor 1 may be low and fall below the lower limit of the performance of the compressor 1. The lower limit of the compression ratio is, for example, 1.2. However, if the rotation speed of the compressor 1 is unnecessarily increased in order to secure the compression ratio, the operation efficiency during the boiling operation deteriorates.

In particular, immediately after the start of the boiling operation, that is, when the water temperature in the hot water storage tank is low and the temperature difference from the target water temperature is large, the rotation speed of the compressor 1 is increased to raise the temperature of the heat exchange unit 3 of the hot water storage tank. However, due to the large heat capacity of the water inside the hot water storage tank, the temperature of the water in the hot water storage tank that matches the temperature of the heat exchange unit cannot be obtained, and only the compression ratio becomes larger than necessary for operation. Efficiency deteriorates.

Therefore, in the heat pump type hot water supply device 100, the control means 60 determines the minimum rotation speed of the compressor 1 based on the outside air temperature detected by the outside air temperature sensor 52 and the condensation pressure of the refrigerant detected by the pressure sensor 50. It is provided with a desired table (hereinafter referred to as table T). FIG. 2 schematically shows an example of the table T.

In this example, on the table T, the first outside air temperature Ta on the high temperature side of the outside air temperature of 30 ° C. or higher and the low temperature side of the outside air temperature of less than 30 ° C. are set on the table T. The second outside air temperature of Tb is set.

The minimum rotation speed of the compressor 1 selected according to the condensation pressure is set for each of the first outside air temperature Ta on the high temperature side and the second outside air temperature Tb on the low temperature side. Here, the threshold value at the time of pressure increase is 2.5 and 3.2, while the threshold value at the time of pressure decrease is 2.3 and 3.0 at each outside air temperature Ta and Tb. This is to prevent chattering of the rotation speed control of the compressor 1.

With the condensed pressure detected by the pressure sensor 50 as Cp, the control means 60 refers to the first outside air temperature Ta on the table T when the outside air temperature detected by the outside air temperature sensor 52 is 30 ° C. or higher. If the condensed pressure Cp detected by the pressure sensor 50 is less than 2.5 MPa (Cp <2.5) when the pressure rises, select the minimum rotation speed of 35 rps, and the condensed pressure Cp is 2.5 MPa or more and less than 3.2 MPa. If (2.5 ≦ Cp <3.2), select the minimum rotation speed of 30 rps, and if the condensation pressure Cp is 3.2 MPa or more (3.2 ≦ Cp), select the minimum rotation speed of 25 rps, and select these minimum rotation speeds. The compressor 1 is driven at a rotation speed of several or more.

When the outside air temperature detected by the outside air temperature sensor 52 is 30 ° C. or higher, the control means 60 refers to the first outside air temperature Ta on the table T, and is detected by the pressure sensor 50 when the pressure drops. If the condensation pressure Cp is less than 2.3 MPa (Cp <2.3), select the minimum rotation speed of 35 rps, and if the condensation pressure Cp is 2.3 MPa or more and less than 3.0 MPa (2.3 ≤ Cp <3.0). For example, the minimum rotation speed of 30 rps is selected, and if the condensation pressure Cp is 3.0 MPa or more (3.0 ≦ Cp), the minimum rotation speed of 25 rps is selected, and the compressor 1 is driven at these minimum rotation speeds or more.

When the outside air temperature detected by the outside air temperature sensor 52 is less than 30 ° C., the control means 60 refers to the second outside air temperature Tb in the table T, and is detected by the pressure sensor 50 when the pressure rises. If the condensation pressure Cp is less than 2.5 MPa (Cp <2.5), select the minimum rotation speed of 30 rps, and if the condensation pressure Cp is 2.5 MPa or more and less than 3.2 MPa (2.5 ≦ Cp <3.2). For example, the minimum rotation speed of 25 rps is selected, and if the condensation pressure Cp is 3.2 MPa or more (3.2 ≦ Cp), the minimum rotation speed of 20 rps is selected, and the compressor 1 is driven at these minimum rotation speeds or higher.

Further, when the outside air temperature detected by the outside air temperature sensor 52 is less than 30 ° C., the control means 60 refers to the time of the second outside air temperature Tb in the table T, and detects it by the pressure sensor 50 when the pressure drops. If the condensed pressure Cp to be formed is less than 2.3 MPa (Cp <2.3), select the minimum rotation speed of 30 rps, and if the condensed pressure Cp is 2.3 MPa or more and less than 3.0 MPa (2.3 ≦ Cp <3.0). If, select the minimum rotation speed of 25 rps, select the minimum rotation speed of 20 rps if the condensation pressure Cp is 3.0 MPa or more (3.0 ≦ Cp), and drive the compressor 1 at these minimum rotation speeds or higher. do.

In this way, the minimum rotation speed of the compressor for the same value of condensation pressure is the first on the high temperature side, Ta on the lower temperature side, regardless of whether the pressure rises or falls. 2 In this embodiment, the temperature is set higher than Tb at the outside air temperature by 5 rps.

As described above, the minimum rotation speed of the compressor 1 is determined with reference to the table T in FIG. 2, that is, when the outside air temperature is high (30 ° C. or higher), when the outside air temperature is low (less than 30 ° C.). By increasing the minimum rotation speed as compared with the case, it is possible to prevent the compression ratio from falling below the lower limit of the performance when the outside air temperature is high and the possibility of falling below the lower limit of the performance of the compression ratio is high.

On the other hand, when the outside air temperature is low (less than 30 ° C), the compression ratio is less likely to fall below the lower limit of performance, so by lowering the minimum rotation speed compared to when the outside air temperature is high (30 ° C or higher), It is possible to improve the operation efficiency during boiling operation.

In the above embodiment, the table T includes two outside air temperatures Ta and Tb, but the outside air temperature is, for example, two outside air temperatures of 30 ° C. and 25 ° C., and three outside air temperatures (30 ° C. or higher). , 25 ° C or higher and lower than 30 ° C, and lower than 25 ° C).

In that case, under the condition that the minimum rotation speed of the compressor for the same value of condensation pressure is higher at the outside air temperature on the high temperature side than at the outside air temperature on the lower temperature side, how is the rotation speed difference? It may be arbitrarily decided whether or not the value should be set.

100 Heat pump type hot water supply device 1 Compressor 2 Four-way valve 3 Heat exchanger (heat exchanger on the user side)
4 Expansion valve 5 Heat source side heat exchanger 6 Cumulator 7 Fan 10 Refrigerant circuit 11 Refrigerant piping 51 Discharge temperature sensor 52 Outside air temperature sensor 53 Refrigerant temperature sensor 58 Water temperature sensor 60 Control means 70 Hot water storage tank

Claims (2)

A compressor circuit that sequentially connects a compressor, a flow path switching means, a heat exchange section on the user side that exchanges heat between water and a refrigerant, and a heat exchanger on the heat source side via a refrigerant pipe, and an outside temperature that detects the outside air temperature. It includes a sensor, a pressure sensor that detects the condensed pressure of the refrigerant on the discharge side of the compressor, and a control means, and is detected by the outside air temperature detected by the outside temperature sensor and the pressure sensor by the control means. In a heat pump type hot water supply device in which the minimum number of revolutions of the compressor is determined based on the condensation pressure of the refrigerant.
The control means has a table in which the minimum rotation speed of the compressor is determined according to the outside air temperature and the condensation pressure, and the table has at least one predetermined temperature To in which the outside air temperature is predetermined. The minimum rotation speed when the first outside air temperature Ta is higher and the minimum rotation speed when the second outside air temperature Tb is lower than the predetermined temperature To are defined, respectively, and correspond to the same value of the condensation pressure. The heat pump type hot water supply device is characterized in that the minimum rotation speed of the compressor is determined to be higher at the first outside air temperature Ta than at the second outside air temperature Tb. The heat pump type hot water supply device according to claim 1, wherein the minimum rotation speed is a rotation speed at which the compression ratio of the compressor does not fall below the lower limit of performance.

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