JP2014109405A - Water heating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water heating system capable of shortening time necessary for defrosting and suppressing generation of residual unmelted frost.SOLUTION: A water heating system 10 includes: a first refrigerant circuit 20; a second refrigerant circuit 30; a water circuit 40; and a control unit 50. The first refrigerant circuit, which includes a first heat exchanger 22 and a second heat exchanger 32, is a circuit in which first refrigerant circulates. The first heat exchanger causes heat exchange between a heat source and the first refrigerant. The second heat exchanger causes heat exchange between the first refrigerant and second refrigerant. The second refrigerant circuit, which includes the second heat exchanger and a third heat exchanger 42, is a circuit in which the second refrigerant circulates. The third heat exchanger causes heat exchange between the second refrigerant and water. The water circuit, which includes the third heat exchanger, is a circuit through which the water passes. The control unit stops supply of the water to the third heat exchanger in the water circuit and supply of the second refrigerant to the second heat exchanger in the second refrigerant circuit before starting a defrosting operation.

Description

  The present invention relates to a water heating system.

  Conventionally, as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2001-108256), a hot water supply system that heats water using a heat pump and stores the generated hot water in a hot water storage tank is known. This hot water supply system includes a refrigerant circuit in which refrigerant circulates and a water circuit in which water flows. The refrigerant circuit is a circuit in which a compressor, a water-refrigerant heat exchanger, an expansion valve, and a refrigerant-air heat exchanger are connected. The refrigerant circuit constitutes a heat pump. The water circuit is a circuit in which a water supply pump, a water-refrigerant heat exchanger, and a hot water storage tank are connected. The refrigerant circuit and the water circuit share a water-refrigerant heat exchanger. The refrigerant circulating in the refrigerant circuit is heated by exchanging heat with the outside air in the refrigerant-air heat exchanger. The water flowing through the water circuit is heated by exchanging heat with the refrigerant circulating in the refrigerant circuit in the water-refrigerant heat exchanger.

  Further, as another hot water supply system, as disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 2004-132647), a hot water supply system including a dual refrigerant circuit including two refrigerant circuits and a water circuit is known. Yes. This hot water supply system includes a low-stage refrigerant circuit, a hot water supply refrigerant circuit, and a water circuit. The low stage side refrigerant circuit is a refrigerant circuit that constitutes a heat pump and includes a refrigerant-air heat exchanger and a refrigerant-refrigerant heat exchanger. The hot water supply refrigerant circuit is a refrigerant circuit that constitutes a heat pump and includes a refrigerant-refrigerant heat exchanger and a water-refrigerant heat exchanger. The low stage side refrigerant circuit and the hot water supply refrigerant circuit are cascade-connected via a refrigerant-refrigerant heat exchanger. The refrigerant circulating in the low-stage refrigerant circuit is heated by exchanging heat with the outside air in the refrigerant-air heat exchanger. The refrigerant circulating in the hot water supply refrigerant circuit is heated by exchanging heat with the refrigerant circulating in the low-stage refrigerant circuit in the refrigerant-refrigerant heat exchanger. The water flowing in the water circuit is heated by exchanging heat with the refrigerant circulating in the hot water supply refrigerant circuit in the water-refrigerant heat exchanger. This hot water supply system can achieve higher operating efficiency than the hot water supply system including the single refrigerant circuit disclosed in Patent Document 1.

  In a hot water supply system using a heat pump, frost may adhere to the refrigerant-air heat exchanger when the temperature of the outside air is low. Therefore, in order to suppress a decrease in operating efficiency of the hot water supply system, a defrost operation for removing frost attached to the refrigerant-air heat exchanger is performed. In the case of a hot water supply system having a single refrigerant circuit, the refrigerant-air heat exchanger uses the heat remaining in the water-refrigerant heat exchanger by reversing the refrigerant circulation direction in the refrigerant circuit from that during normal operation. To defrost.

  However, in a hot water supply system having a binary refrigerant circuit, the amount of heat remaining in the refrigerant-refrigerant heat exchanger of the low-stage refrigerant circuit is not sufficient, so that the time required for defrosting becomes longer, and the refrigerant-air heat Frost may remain on the exchanger.

  The objective of this invention is providing the water heating system which can shorten the time required for defrost and can suppress generation | occurrence | production of the unmelted frost.

  The water heating system according to the first aspect of the present invention includes a first refrigerant circuit, a second refrigerant circuit, a water circuit, and a control unit. The first refrigerant circuit has a first heat exchanger and a second heat exchanger, and is a circuit through which the first refrigerant circulates. The first heat exchanger exchanges heat between the heat source and the first refrigerant. The second heat exchanger exchanges heat between the first refrigerant and the second refrigerant. The second refrigerant circuit has a second heat exchanger and a third heat exchanger, and is a circuit through which the second refrigerant circulates. The second refrigerant circuit shares the first refrigerant circuit and the second heat exchanger. The third heat exchanger exchanges heat between the second refrigerant and water. The water circuit has a third heat exchanger and is a circuit through which water passes. The water circuit shares the second refrigerant circuit and the third heat exchanger. The control unit controls the first refrigerant circuit, the second refrigerant circuit, and the water circuit in order to perform the defrost operation of the first heat exchanger. The control unit stops the supply of water to the third heat exchanger in the water circuit and the supply of the second refrigerant to the second heat exchanger in the second refrigerant circuit before starting the defrost operation. The controller reverses the direction in which the first refrigerant circulates in the first refrigerant circuit and supplies the first refrigerant from the second heat exchanger to the first heat exchanger, thereby starting the defrost operation.

  The water heating system according to the first aspect includes a binary refrigerant circuit in which a first refrigerant circuit and a second refrigerant circuit are cascade-connected via a second heat exchanger. This water heating system is used as, for example, hot water supply equipment. The first refrigerant circuit is a low-stage refrigerant circuit, and the second refrigerant circuit is a high-stage refrigerant circuit. The first refrigerant circulating in the first refrigerant circuit is heated by exchanging heat with a heat source in the first heat exchanger, and is cooled by exchanging heat with the second refrigerant circulating in the second refrigerant circuit in the second heat exchanger. The The heat source that exchanges heat in the first heat exchanger is, for example, outside air. The second refrigerant circulating in the second refrigerant circuit is heated by exchanging heat with the first refrigerant circulating in the first refrigerant circuit in the second heat exchanger, and exchanges heat with water flowing in the water circuit in the third heat exchanger. And cooled. The water flowing through the water circuit is heated by exchanging heat with the second refrigerant circulating in the second refrigerant circuit in the third heat exchanger. In this water heating system, frost may adhere to the first heat exchanger when the temperature of the outside air that is a heat source is low. In this case, this water heating system performs the defrost operation which removes the frost adhering to the 1st heat exchanger. Specifically, by performing reverse cycle operation in which the circulation direction of the first refrigerant in the first refrigerant circuit is reversed from that during normal operation, the first heat is utilized using the heat remaining in the second heat exchanger. Defrost the exchanger.

  This water heating system stops the flow of water in the water circuit and the circulation of the second refrigerant in the second refrigerant circuit before performing the defrost operation of the first heat exchanger by the reverse cycle operation of the first refrigerant circuit. The heat exchange in the second heat exchanger and the third heat exchanger is suppressed. Next, this water heating system performs a positive cycle operation in which the first refrigerant is circulated in the same direction as in the normal operation in the first refrigerant circuit, and raises the temperature of the second heat exchanger. Thereafter, the water heating system starts reverse cycle operation of the first refrigerant circuit, and defrosts the first heat exchanger using heat remaining in the second heat exchanger. That is, in this water heating system, before the first heat exchanger is defrosted by the reverse cycle operation of the first refrigerant circuit, the first refrigerant circuit is previously operated in the forward cycle to heat the second heat exchanger. Accumulate. Since the first refrigerant circuit is a refrigerant circuit on the lower stage side of the binary refrigerant circuit, the amount of heat remaining in the second heat exchanger at the start of the reverse cycle operation may not be sufficient for defrosting the first heat exchanger. There is sex. Therefore, before performing the reverse cycle operation of the first refrigerant circuit, the flow of water in the water circuit and the circulation of the second refrigerant in the second refrigerant circuit are stopped, and further the forward cycle operation of the first refrigerant circuit is performed. Thus, this water heating system causes the second heat exchanger to accumulate heat sufficient for defrosting the first heat exchanger. Therefore, this water heating system can shorten the time required for defrosting and can suppress the occurrence of unmelted frost.

  A water heating system according to a second aspect of the present invention is the water heating system according to the first aspect, wherein the first refrigerant circuit has a first compressor that compresses the first refrigerant, and the second refrigerant circuit is And a second compressor for compressing the second refrigerant. The control unit increases the operating frequency of the first compressor for the first operating time and stops the operation of the second compressor before starting the defrost operation.

  In the water heating system according to the second aspect, before performing the defrost operation of the first heat exchanger by the reverse cycle operation of the first refrigerant circuit, the operation frequency of the first compressor is increased from the normal operation time, The first cycle operation of the first refrigerant circuit is performed for the first operation time. By increasing the operating frequency of the first compressor, heat is effectively accumulated in the second heat exchanger. Therefore, this water heating system can effectively shorten the time required for defrosting.

  The water heating system according to the third aspect of the present invention is the water heating system according to the first aspect or the second aspect, and the controller is configured such that the temperature of the first refrigerant supplied to the second heat exchanger is the first. When the temperature is reached, defrost operation is started.

  In the water heating system according to the third aspect, the control unit passes, for example, the second heat exchanger while performing the positive cycle operation of the first refrigerant circuit before the start of the defrost operation of the first heat exchanger. The temperature of the first refrigerant to be monitored is monitored. And when the temperature of the 1st refrigerant | coolant which passes a 2nd heat exchanger reaches 1st temperature, the control part is that the heat sufficient for the defrost of the 1st heat exchanger was accumulate | stored in the 2nd heat exchanger. Judgment is made and defrost operation of the first heat exchanger is started. Therefore, by setting the first temperature in advance, this water heating system can effectively shorten the time required for defrosting.

  The water heating system according to a fourth aspect of the present invention is the water heating system according to any one of the first to third aspects, wherein the control unit further circulates the second refrigerant in the second refrigerant circuit. The defrosting operation is started by reversing the direction and supplying the second refrigerant from the third heat exchanger to the second heat exchanger.

  In the water heating system according to the fourth aspect, the defrost operation of the first heat exchanger is performed by performing the reverse cycle operation of both the first refrigerant circuit and the second refrigerant circuit. Due to the reverse cycle operation of the second refrigerant circuit, the heat remaining in the third heat exchanger moves to the second heat exchanger, so that a large amount of heat is accumulated in the second heat exchanger. In the water heating system, when hot water remains in the water circuit at the start of the defrosting operation of the first heat exchanger, the heat of the hot water in the water circuit is transferred to the first heat exchanger via the second refrigerant circuit. Can be used for defrosting. Therefore, by performing the reverse cycle operation of the second refrigerant circuit, this water heating system can effectively shorten the time required for defrosting.

  The water heating system which concerns on a 1st viewpoint can shorten the time required for defrost, and can suppress generation | occurrence | production of the unmelted frost.

  The water heating system according to the second aspect to the fourth aspect can effectively shorten the time required for defrosting.

It is a circuit block diagram at the time of the normal driving | operation of the water heating system which concerns on embodiment. It is a circuit block diagram before the defrost operation | movement start of the water heating system which concerns on embodiment. It is a circuit block diagram at the time of the defrost driving | operation of the water heating system which concerns on embodiment. It is a circuit block diagram at the time of the defrost driving | operation of the water heating system which concerns on the modification B.

  A water heating system according to an embodiment of the present invention will be described with reference to the drawings. The water heating system according to the present embodiment is used as, for example, hot water supply equipment.

(1) Configuration of Water Heating System FIG. 1 is a circuit configuration diagram during normal operation of the water heating system 10 according to the present embodiment. FIG. 2 is a circuit configuration diagram of the water heating system 10 according to the present embodiment before starting the defrost operation. FIG. 3 is a circuit configuration diagram of the water heating system 10 according to the present embodiment during the defrost operation. The water heating system 10 mainly includes a first refrigerant circuit 20, a second refrigerant circuit 30, a water circuit 40, and a control unit 50. The water heating system 10 includes a binary refrigerant circuit in which a first refrigerant circuit 20 and a second refrigerant circuit 30 are cascade-connected. The first refrigerant circuit 20 is a low-stage refrigerant circuit. The second refrigerant circuit 30 is a high-stage refrigerant circuit. The first refrigerant circuit 20 and the second refrigerant circuit 30 each constitute a heat pump. Next, the 1st refrigerant circuit 20, the 2nd refrigerant circuit 30, the water circuit 40, and the control part 50 are each demonstrated.

(1-1) First Refrigerant Circuit The first refrigerant circuit 20 mainly includes a first heat exchanger 22, a first compressor 24, a first expansion valve 26, a first four-way switching valve 28, and a second. The refrigerant circuit is connected to the heat exchanger 32. In the first refrigerant circuit 20, the first refrigerant circulates. The first refrigerant is R410A. The first refrigerant circuit 20 performs the first normal cycle operation or the first reverse cycle operation according to the circulation direction of the first refrigerant. In FIG. 1, the direction of circulation of the first refrigerant during the first positive cycle operation is indicated by an arrow. In FIG. 3, the circulation direction of the first refrigerant during the first reverse cycle operation is indicated by an arrow. The first forward cycle operation is performed during normal operation of the water heating system 10, and the first reverse cycle operation is performed during defrost operation of the water heating system 10. The normal operation of the water heating system 10 is an operation for heating water flowing through the water circuit 40. The defrosting operation of the water heating system 10 is an operation for removing frost attached to the first heat exchanger 22.

  The first heat exchanger 22 is a refrigerant-air heat exchanger. In the first heat exchanger 22, heat exchange is performed between the first refrigerant circulating in the first refrigerant circuit 20 and the heat source. The heat source is, for example, outside air and geothermal heat, but in this embodiment, the heat source is outside air. The first heat exchanger 22 is, for example, a plate fin coil heat exchanger. A fan 22 a is installed in the vicinity of the first heat exchanger 22. The fan 22 a blows outside air to the first heat exchanger 22, and discharges the outside air heat-exchanged with the first refrigerant in the first heat exchanger 22.

  The first compressor 24 is a compressor that sucks and compresses the low-pressure first refrigerant flowing through the first refrigerant circuit 20 and discharges the high-temperature and high-pressure first refrigerant. The first compressor 24 is, for example, a rotary compressor.

  The first expansion valve 26 is an electric valve for adjusting the flow rate and pressure of the first refrigerant circulating in the first refrigerant circuit 20.

  The first four-way switching valve 28 is a switching valve for switching the first normal cycle operation and the first reverse cycle operation to reverse the direction of circulation of the first refrigerant in the first refrigerant circuit 20. The first four-way switching valve 28 has a first port 28a, a second port 28b, a third port 28c, and a fourth port 28d. The first four-way switching valve 28 is in the first communication state or the second communication state. In the first communication state, as shown in FIG. 1, the first port 28a and the second port 28b communicate with each other, and the third port 28c and the fourth port 28d communicate with each other. In the second communication state, as shown in FIG. 1, the first port 28a and the third port 28c communicate with each other, and the second port 28b and the fourth port 28d communicate with each other. When the first refrigerant circuit 20 performs the first positive cycle operation, the first four-way switching valve 28 is in the first communication state. When the first refrigerant circuit 20 performs the first reverse cycle operation, the first four-way switching valve 28 is in the second communication state.

  The second heat exchanger 32 is a refrigerant-refrigerant heat exchanger. In the second heat exchanger 32, heat exchange is performed between the first refrigerant circulating in the first refrigerant circuit 20 and the second refrigerant circulating in the second refrigerant circuit 30. The first refrigerant circuit 20 and the second refrigerant circuit 30 share the second heat exchanger 32. The second heat exchanger 32 includes a first heat exchange part 32a through which the first refrigerant circulating in the first refrigerant circuit 20 passes and a second heat exchange part 32b through which the second refrigerant circulating through the second refrigerant circuit 30 passes. And have. The second heat exchanger 32 is, for example, a plate heat exchanger that is covered with a heat insulating member.

  The discharge side of the first compressor 24 is connected to the first port 28 a of the first four-way switching valve 28. The second port 28 b of the first four-way switching valve 28 is connected to the first heat exchange part 32 a of the second heat exchanger 32. The first heat exchange part 32 a of the second heat exchanger 32 is connected to the first expansion valve 26. The first expansion valve 26 is connected to the first heat exchanger 22. The first heat exchanger 22 is connected to the third port 28 c of the first four-way switching valve 28. The fourth port 28 d of the first four-way switching valve 28 is connected to the suction side of the first compressor 24.

  The operation of the first refrigerant circuit 20 that performs the first positive cycle operation will be described. The first positive cycle operation is performed during the normal operation of the water heating system 10. The first refrigerant is sucked into the first compressor 24 as a low-pressure gas refrigerant and compressed. The compressed first refrigerant is discharged from the first compressor 24 as a high-temperature and high-pressure gas refrigerant, passes through the first port 28a and the second port 28b of the first four-way switching valve 28, and passes through the second heat exchanger 32. Sent to. In the second heat exchanger 32, the first refrigerant passes through the first heat exchange part 32a, and the second refrigerant passes through the second heat exchange part 32b. In the second heat exchanger 32, heat is transferred between the first refrigerant and the second refrigerant by transferring heat from the high temperature first refrigerant to the low temperature second refrigerant. Thereby, in the 2nd heat exchanger 32, the 1st refrigerant | coolant which is a high-temperature / high pressure gas refrigerant condenses and turns into a high voltage | pressure liquid refrigerant. The first refrigerant is depressurized by passing through the first expansion valve 26, and becomes a low-pressure gas-liquid two-phase refrigerant. The first refrigerant in the low-pressure gas-liquid two-phase state is evaporated by heat exchange with the outside air in the first heat exchanger 22 to become a low-pressure gas refrigerant. Then, the first refrigerant passes through the third port 28 c and the fourth port 28 d of the first four-way switching valve 28 and is sent to the first compressor 24. The 1st refrigerant circuit 20 which performs the 1st regular cycle operation supplies the heat of outside air to the 2nd refrigerant circulating through the 2nd refrigerant circuit 30 via the 1st refrigerant by repeating the above process.

  The first refrigerant circuit 20 performs a first reverse cycle operation during the defrost operation of the water heating system 10. The operation of the first refrigerant circuit 20 that performs the first reverse cycle operation will be described later.

(1-2) Second Refrigerant Circuit The second refrigerant circuit 30 mainly includes a second heat exchanger 32, a second compressor 34, a second expansion valve 36, a second four-way switching valve 38, and a third. The refrigerant circuit is connected to the heat exchanger. In the second refrigerant circuit 30, the second refrigerant circulates. The second refrigerant is R134a. The second refrigerant circuit 30 performs the second normal cycle operation or the second reverse cycle operation according to the circulation direction of the second refrigerant. In FIG. 1, the direction of circulation of the second refrigerant during the second positive cycle operation is indicated by an arrow. In FIG. 4 described later, the circulation direction of the second refrigerant during the second reverse cycle operation is indicated by an arrow. The second forward cycle operation is performed during the normal operation of the water heating system 10, and the second reverse cycle operation is performed during the defrost operation of the water heating system 10.

  The second heat exchanger 32 is a refrigerant-refrigerant heat exchanger. As described above, in the second heat exchanger 32, heat exchange is performed between the first refrigerant circulating in the first refrigerant circuit 20 and the second refrigerant circulating in the second refrigerant circuit 30.

  The second compressor 34 is a compressor that sucks and compresses the low-pressure second refrigerant flowing through the second refrigerant circuit 30 and discharges the high-temperature and high-pressure second refrigerant. The second compressor 34 is, for example, a rotary compressor.

  The second expansion valve 36 is an electric valve for adjusting the flow rate and pressure of the second refrigerant circulating in the second refrigerant circuit 30.

  The second four-way switching valve 38 is a switching valve for switching the second forward cycle operation and the second reverse cycle operation to reverse the circulation direction of the second refrigerant in the second refrigerant circuit 30. The second four-way switching valve 38 has a fifth port 38a, a sixth port 38b, a seventh port 38c, and an eighth port 38d. The second four-way switching valve 38 is in the third communication state or the fourth communication state. In the third communication state, as shown in FIG. 1, the fifth port 38a and the sixth port 38b communicate with each other, and the seventh port 38c and the eighth port 38d communicate with each other. In the fourth communication state, as shown in FIG. 1, the fifth port 38a and the seventh port 38c communicate with each other, and the sixth port 38b and the eighth port 38d communicate with each other. When the second refrigerant circuit 30 performs the second positive cycle operation, the second four-way switching valve 38 is in the third communication state. When the second refrigerant circuit 30 performs the second reverse cycle operation, the second four-way switching valve 38 is in the fourth communication state.

  The third heat exchanger 42 is a water-refrigerant heat exchanger. In the third heat exchanger 42, heat exchange is performed between the second refrigerant circulating in the second refrigerant circuit 30 and the water flowing in the water circuit 40. The second refrigerant circuit 30 and the water circuit 40 share the third heat exchanger 42. The third heat exchanger 42 includes a third heat exchange part 42 a through which the second refrigerant circulating in the second refrigerant circuit 30 passes and a fourth heat exchange part 42 b through which water flowing through the water circuit 40 passes. In the third heat exchanger 42, for example, a refrigerant pipe as the third heat exchange part 42a is spirally wound around the outer circumference of the water pipe as the fourth heat exchange part 42b, and a groove is formed inside the water pipe. It is a tornado-type heat exchanger having the configuration described above.

  The discharge side of the second compressor 34 is connected to the fifth port 38 a of the second four-way switching valve 38. The sixth port 38 b of the second four-way switching valve 38 is connected to the third heat exchange part 42 a of the third heat exchanger 42. The third heat exchange part 42 a of the third heat exchanger 42 is connected to the second expansion valve 36. The second expansion valve 36 is connected to the second heat exchange part 32 b of the second heat exchanger 32. The second heat exchange part 32 b of the second heat exchanger 32 is connected to the seventh port 38 c of the second four-way switching valve 38. The eighth port 38 d of the second four-way switching valve 38 is connected to the suction side of the second compressor 34.

  The operation of the second refrigerant circuit 30 that performs the second positive cycle operation will be described. The second positive cycle operation is performed during the normal operation of the water heating system 10. The second refrigerant is sucked into the second compressor 34 as a low-pressure gas refrigerant and compressed. The compressed second refrigerant is discharged from the second compressor 34 as a high-temperature and high-pressure gas refrigerant, passes through the fifth port 38a and the sixth port 38b of the second four-way switching valve 38, and passes through the third heat exchanger 42. Sent to. In the third heat exchanger 42, the second refrigerant passes through the third heat exchange part 42a, and the water passes through the fourth heat exchange part 42b. In the third heat exchanger 42, heat is transferred between the second refrigerant and water by transferring heat from the high-temperature second refrigerant to the low-temperature water. Thereby, in the 3rd heat exchanger 42, the 2nd refrigerant | coolant which is a high-temperature / high pressure gas refrigerant condenses and turns into a high voltage | pressure liquid refrigerant. The second refrigerant is depressurized by passing through the second expansion valve 36, and becomes a low-pressure gas-liquid two-phase refrigerant. The second refrigerant in the low-pressure gas-liquid two-phase state is evaporated by heat exchange with the first refrigerant in the second heat exchanger 32 to become a low-pressure gas refrigerant. Then, the second refrigerant passes through the seventh port 38 c and the eighth port 38 d of the third four-way switching valve 38 and is sent to the second compressor 34. The second refrigerant circuit 30 that performs the second positive cycle operation repeats the above steps, so that the heat of the first refrigerant circulating in the first refrigerant circuit 20 flows through the water circuit 40 via the second refrigerant. To supply.

  Note that the second refrigerant circuit 30 may perform the second reverse cycle operation during the defrost operation of the water heating system 10. The operation of the second refrigerant circuit 30 that performs the second reverse cycle operation will be described later.

(1-3) Water Circuit The water circuit 40 is a circuit in which a third heat exchanger 42, a water supply pump 44, a water supply line 46, and a hot water line 48 are mainly connected. In the water circuit 40, water flows. In FIG. 1, the direction of water flow is indicated by arrows. Water flowing through the water circuit 40 is taken from the water supply line 46, passes through the water supply pump 44, is heated by the third heat exchanger 42, and is sent to the hot water supply line 48. The water supply pump 44 and the water supply line 46 are piping outside the casing of the water heating system 10.

  The feed water pump 44 is a pump for taking water from the feed water line 46 and sending it to the third heat exchanger 42. For example, the water supply line 46 is connected to a water receiving tank installed outside the water heating system 10. A pressure reducing valve for reducing the pressure of the water supplied from the water supply line 46 may be attached to the pipe connecting the water supply line 46 and the water supply pump 44. The third heat exchanger 42 is a water-refrigerant heat exchanger. As described above, in the third heat exchanger 42, heat exchange is performed between the second refrigerant circulating in the second refrigerant circuit 30 and the water flowing in the water circuit 40. The hot water line 48 is connected to, for example, a hot water storage tank installed outside the water heating system 10.

  The operation of the water circuit 40 will be described. Water taken from the water supply line 46 by the water supply pump 44 is sent to the third heat exchanger 42. In the third heat exchanger 42, heat is transferred between the second refrigerant and water by transferring heat from the high-temperature second refrigerant to the low-temperature water. Thereby, in the 3rd heat exchanger 42, water is heated. The water heated by the third heat exchanger 42 is sent to the hot water line 48 as hot water.

(1-4) Control Unit The control unit 50 is a computer for controlling each component of the water heating system 10. The control unit 50 is connected to the first compressor 24, the first expansion valve 26, the first four-way switching valve 28, the second compressor 34, the second expansion valve 36, the second four-way switching valve 38, and the water supply pump 44. Yes. The control unit 50 controls, for example, the operating frequencies of the first compressor 24 and the second compressor 34, the opening degrees of the first expansion valve 26 and the second expansion valve 36, and the rotation speed of the water supply pump 44. For example, the control unit 50 is installed in an electrical component unit (not shown) in the water heating system 10.

  The control unit 50 can control the first four-way switching valve 28 to switch between the first communication state and the second communication state. The controller 50 can switch the third communication state and the fourth communication state by controlling the second four-way switching valve 38. That is, during operation of the water heating system 10, the control unit 50 can control the first four-way switching valve 28 to switch between the first normal cycle operation and the first reverse cycle operation, and the second four-way The switching valve 38 can be controlled to switch between the second normal cycle operation and the second reverse cycle operation.

(2) Operation of Water Heating System The operation of the water heating system 10 will be described. The water heating system 10 performs normal operation or defrost operation. FIG. 1 is a circuit configuration diagram of the water heating system 10 during normal operation. During normal operation of the water heating system 10, the first refrigerant circuit 20 performs a first positive cycle operation, and the second refrigerant circuit 30 performs a second positive cycle operation. In this case, as shown in FIG. 1, the first four-way switching valve 28 of the first refrigerant circuit 20 is in the first communication state, and the second four-way switching valve 38 of the second refrigerant circuit 30 is the third communication valve. In communication. In the water circuit 40, the water taken from the water supply line 46 by the water supply pump 44 is heated in the third heat exchanger 42, and hot water is supplied to the hot water line 48.

  During normal operation of the water heating system 10, the first heat exchanger 22 of the first refrigerant circuit 20 performs heat exchange in which heat is transferred from outside air to the first refrigerant that circulates through the first refrigerant circuit 20. That is, the outside air blown by the fan 22 a is deprived of heat in the first heat exchanger 22. Therefore, frost may adhere to the first heat exchanger 22 under conditions where the temperature of the outside air is low, such as in a cold district and in winter. When frost adheres to the first heat exchanger 22, the efficiency of heat exchange in the first heat exchanger 22 decreases compared to a state where frost does not adhere to the first heat exchanger 22, and the water heating system 10. The driving efficiency will be reduced. Therefore, the water heating system 10 needs to periodically perform a defrost operation for removing frost attached to the first heat exchanger 22 in order to suppress a decrease in operation efficiency under a condition where the temperature of the outside air is low. . The defrosting operation of the water heating system 10 is performed by melting frost attached to the first heat exchanger 22 with heat. Next, the operation | movement at the time of the defrost driving | operation of the water heating system 10 is demonstrated.

  The defrosting operation of the water heating system 10 includes a defrost preparation process and a reverse cycle defrost process. The defrost preparation process is a process performed before defrosting the first heat exchanger 22. The reverse cycle defrost process is a process of defrosting the first heat exchanger 22 by performing the first reverse cycle operation of the first refrigerant circuit 20. FIG. 2 is a circuit configuration diagram of the water heating system 10 in the defrost preparation process. FIG. 3 is a circuit configuration diagram of the water heating system 10 in the reverse cycle defrost process.

  In the defrost preparation step, first, the control unit 50 stops the operation of the second compressor 34 of the second refrigerant circuit 30 and simultaneously stops the operation of the water supply pump 44 of the water circuit 40. That is, the control unit 50 stops the circulation of the second refrigerant in the second refrigerant circuit 30 and simultaneously stops the flow of water in the water circuit 40. Thereby, heat exchange between the first refrigerant and the second refrigerant in the second heat exchanger 32 and heat exchange between the second refrigerant and water in the third heat exchanger 42 are suppressed.

  Next, in the defrost preparation process, the controller 50 performs the first positive cycle operation of the first refrigerant circuit 20 for a predetermined time. At this time, the control unit 50 performs control to make the operating frequency of the first compressor 24 of the first refrigerant circuit 20 higher than the operating frequency of the first compressor 24 during normal operation of the water heating system 10. For example, in the defrost preparation process, the control unit 50 performs the first positive cycle operation of the first refrigerant circuit 20 for 5 minutes in a state where the operation frequency of the first compressor 24 is 10% higher than the operation frequency during normal operation. I do. The control unit 50 may perform the first positive cycle operation of the first refrigerant circuit 20 by gradually increasing the operation frequency of the first compressor 24 from the operation frequency during normal operation. The first high-temperature refrigerant discharged from the first compressor 24 is supplied to the second heat exchanger 32 by the first positive cycle operation of the first refrigerant circuit 20. As described above, heat exchange in the second heat exchanger 32 is suppressed, and the flow rate of the first refrigerant supplied to the second heat exchanger 32 increases due to the increase in the operating frequency of the first compressor 24. In the second heat exchanger 32, the heat of the high-temperature first refrigerant discharged from the first compressor 24 is accumulated. As a result, the temperature of the second heat exchanger 32 increases.

  After the defrost preparation process is completed, a reverse cycle defrost process is performed. In the reverse cycle defrost process, the control unit 50 switches the first four-way switching valve 28 from the first communication state to the second communication state, and starts the first reverse cycle operation of the first refrigerant circuit 20. The circulation direction of the first refrigerant in the first reverse cycle operation is opposite to the circulation direction of the first refrigerant in the first normal cycle operation. Specifically, in the first reverse cycle operation, the first refrigerant is the first compressor 24, the first four-way switching valve 28 (the first port 28a and the third port 28c), the first heat exchanger 22, the first The expansion valve 26, the second heat exchanger 32, the first four-way switching valve 28 (the second port 28b and the fourth port 28d), and the first compressor 24 are circulated in order. In the reverse cycle defrost process, the heat of the high-temperature first refrigerant discharged from the first compressor 24 and the heat accumulated in the second heat exchanger 32 in the defrost preparation process are supplied to the first heat exchanger 22. Is done. Thereby, the frost adhering to the 1st heat exchanger 22 melts, and the 1st heat exchanger 22 is defrosted.

(3) Features The water heating system 10 includes a dual refrigerant circuit in which the first refrigerant circuit 20 and the second refrigerant circuit 30 are cascade-connected via the second heat exchanger 32. The first refrigerant circuit 20 is a low-stage refrigerant circuit, and the second refrigerant circuit 30 is a high-stage refrigerant circuit. The first refrigerant that circulates in the first refrigerant circuit 20 is heated by exchanging heat with outside air that is a heat source in the first heat exchanger 22, and is circulated through the second refrigerant circuit 30 in the second heat exchanger 32. It is cooled by exchanging heat with it. The second refrigerant circulating in the second refrigerant circuit 30 is heated by exchanging heat with the first refrigerant circulating in the first refrigerant circuit 20 in the second heat exchanger 32, and the water circuit 40 in the third heat exchanger 42. It is cooled by exchanging heat with flowing water. The water flowing through the water circuit 40 is heated by exchanging heat with the second refrigerant circulating in the second refrigerant circuit 30 in the third heat exchanger 42. Thus, the water heating system 10 is a system that heats water using two heat pumps.

  The water heating system 10 including a binary refrigerant circuit has a maximum temperature of the first refrigerant that is a refrigerant that exchanges heat with the outside air, as compared with a water heating system including a single refrigerant circuit that includes one refrigerant circuit and one water circuit. Is low. Thereby, after stopping the normal operation of the water heating system 10, immediately after the first reverse cycle operation of the first refrigerant circuit 20 is performed and the defrost of the first heat exchanger 22 is started, the second heat exchange is performed. Due to the first refrigerant passing through the vessel 32, the heat stored in the second heat exchanger 32 may not be sufficient to defrost the first heat exchanger 22. Therefore, even if the first reverse cycle operation of the first refrigerant circuit 20 is started immediately after stopping the normal operation of the water heating system 10, it takes a long time to defrost the first heat exchanger 22, There is a risk that the frost adhered to the first heat exchanger 22 will remain unmelted.

  The water heating system 10 according to the present embodiment is used for defrosting the first heat exchanger 22 by performing a defrost preparation process before starting the reverse cycle defrost process in which the defrost of the first heat exchanger 22 is performed. The generated heat is accumulated in the second heat exchanger 32. In the defrost preparation step, the operation of the second compressor 34 and the feed water pump 44 is stopped so that the heat is efficiently accumulated in the second heat exchanger 32, and the second heat exchanger 32 and the third heat exchanger. In a state where the heat exchange of 42 is suppressed, the first positive cycle operation of the first refrigerant circuit 20 is performed for a predetermined time. Thereby, since the high temperature 1st refrigerant | coolant compressed with the 1st compressor 24 is sent to the 2nd heat exchanger 32 by which heat exchange was suppressed, the 2nd heat exchanger 32 is heated and 2nd heat exchange is carried out. Heat is stored in the vessel 32. In the defrost preparation step, the first positive cycle operation of the first refrigerant circuit 20 is performed by setting the operation frequency of the first compressor 24 higher than the operation frequency during normal operation. Thereby, since the flow rate of the first refrigerant sent from the first compressor 24 to the second heat exchanger 32 can be increased, heat is efficiently accumulated in the second heat exchanger 32.

  Therefore, in the water heating system 10, heat sufficient for defrosting the first heat exchanger 22 in the reverse cycle defrost process is efficiently accumulated in the second heat exchanger 32 in the defrost preparation process. After completion of the defrost preparation process, the water heating system 10 starts a reverse cycle defrost process. In the reverse cycle defrost process, the water heating system 10 performs the first reverse cycle operation of the first refrigerant circuit 20 to transfer the heat accumulated in the second heat exchanger 32 to the first refrigerant via the first refrigerant. Supply to heat exchanger 22. Thereby, the water heating system 10 heats the first heat exchanger 22 and defrosts the first heat exchanger 22.

  As described above, the water heating system 10 performs the first forward cycle operation of the first refrigerant circuit 20 in advance before starting the defrost of the first heat exchanger 22 by the first reverse cycle operation of the first refrigerant circuit 20. The heat is accumulated in the second heat exchanger 32. Since the first refrigerant circuit 20 is a low-stage refrigerant circuit of the binary refrigerant circuit, the highest temperature of the first refrigerant circulating through the first refrigerant circuit 20 is circulated through the refrigerant circuit of the water heating system including the single refrigerant circuit. Lower than the maximum temperature of the refrigerant. Therefore, during the normal operation of the water heating system 10, the amount of heat stored in the second heat exchanger 32 may not be sufficient for defrosting the first heat exchanger 22. Therefore, the water heating system 10 stops the flow of water in the water circuit 40 and the circulation of the second refrigerant in the second refrigerant circuit 30 before starting the first reverse cycle operation of the first refrigerant circuit 20. By performing the first positive cycle operation of the first refrigerant circuit 20 for a predetermined time, heat sufficient for defrosting the first heat exchanger 22 is efficiently accumulated in the second heat exchanger 32. Therefore, the water heating system 10 can shorten the time required for defrosting the first heat exchanger 22 and can suppress the occurrence of unmelted frost.

  In addition, the water heating system 10 is configured so that the first refrigerant circuit 20 is in a state where the operation frequency of the first compressor 24 is higher than the operation frequency during normal operation before the first reverse cycle operation of the first refrigerant circuit 20 is started. Twenty first positive cycle operations are performed. By making the operating frequency of the first compressor 24 higher than usual, the flow rate of the first refrigerant discharged from the first compressor 24 can be increased. Accordingly, the flow rate of the high-temperature first refrigerant supplied to the second heat exchanger 32 can be increased before defrosting of the first heat exchanger 22 is started, so that the second heat exchanger 32 is heated. Is effectively accumulated. Therefore, the water heating system 10 can effectively shorten the time required for defrosting.

(4) Modifications The specific configuration of the embodiment of the present invention can be changed without departing from the gist of the present invention. Hereinafter, modified examples applicable to the embodiment of the present invention will be described.

(4-1) Modification A
The water heating system 10 according to the present embodiment first performs the first positive cycle operation of the first refrigerant circuit 20 in a state where the operation frequency of the first compressor 24 is increased from the normal operation in the defrost preparation step. Perform for a predetermined time. Next, the water heating system 10 starts the first reverse cycle operation of the first refrigerant circuit 20 and defrosts the first heat exchanger 22 in the reverse cycle defrost process. However, in the defrost preparation step, the water heating system 10 does not perform the first positive cycle operation of the first refrigerant circuit 20 for a predetermined time, but passes the first heat exchange unit 32a of the second heat exchanger 32. The first positive cycle operation may be performed until the temperature of the refrigerant reaches a predetermined temperature. That is, the water heating system 10 may end the defrost preparation process and start the reverse cycle defrost process when the temperature of the first refrigerant passing through the second heat exchanger 32 reaches a predetermined temperature. .

  In the present modification, the second heat exchanger 32 is provided with a temperature sensor (not shown) for measuring the temperature of the first refrigerant passing through the first heat exchange unit 32a. The temperature sensor is attached to, for example, the outer peripheral surface of the pipe through which the first refrigerant flows, which is the first heat exchange unit 32a. The temperature sensor is connected to the control unit 50. The controller 50 receives the temperature of the first refrigerant measured by the temperature sensor. For example, when the temperature of the first refrigerant passing through the first heat exchange unit 32a reaches 46 ° C., the control unit 50 ends the defrost preparation process and starts the reverse cycle defrost process.

  In the water heating system 10 according to this modification, the control unit 50 monitors the temperature of the first refrigerant passing through the second heat exchanger 32, and the temperature of the first refrigerant passing through the second heat exchanger 32 is predetermined. When this temperature is reached, it is determined that the heat necessary for defrosting the first heat exchanger 22 has been accumulated in the second heat exchanger 32, and the defrost preparation process is terminated. When the minimum amount of heat necessary for defrosting the first heat exchanger 22 can be calculated, by setting in advance the temperature of the first refrigerant, which is the end condition of the defrost preparation step, based on the calculated amount of heat. The control unit 50 can reduce the time required for the defrost preparation process. Therefore, the water heating system 10 according to the present modification can shorten the time required for the defrost preparation process for accumulating heat in the second heat exchanger 32, and effectively shortens the time required for defrosting. be able to.

(4-2) Modification B
In the water heating system 10 according to the present embodiment, the control unit 50 performs the first reverse cycle operation of the first refrigerant circuit 20 in the reverse cycle defrost process. However, the controller 50 may further perform the second reverse cycle operation of the second refrigerant circuit 30 in the reverse cycle defrost process. FIG. 4 is a circuit configuration diagram at the time of defrosting operation of the water heating system 10 according to the present modification.

  In the present modification, the control unit 50 switches the second four-way switching valve 38 from the third communication state to the fourth communication state at the start of the reverse cycle defrost process, and performs the second reverse cycle operation of the second refrigerant circuit 20. Start. The circulation direction of the second refrigerant in the second reverse cycle operation is opposite to the circulation direction of the second refrigerant in the second forward cycle operation. Specifically, in the second reverse cycle operation, the second refrigerant is the second compressor 34, the second four-way switching valve 38 (the fifth port 38a and the seventh port 38c), the second heat exchanger 32, the second The expansion valve 36, the third heat exchanger 42, the second four-way switching valve 38 (the sixth port 38b and the eighth port 38d), and the second compressor 34 are sequentially passed through and circulated.

  In the present modification, the heat stored in the third heat exchanger 42 is transferred to the second heat via the second refrigerant by performing the second reverse cycle operation of the second refrigerant circuit 30 in the reverse cycle defrost process. It is supplied to the exchanger 32. Thereby, heat is accumulated in the second heat exchanger 32. As in the present embodiment, the heat accumulated in the second heat exchanger 32 is transferred to the first heat exchanger 22 via the first refrigerant by the first reverse cycle operation of the first refrigerant circuit 30. Supplied. That is, since the amount of heat supplied to the first heat exchanger 22 is increased by performing the second reverse cycle operation of the second refrigerant circuit 30 in the reverse cycle defrost process, the time required for the defrost is shortened.

  In this modification, the water heating system 10 uses the second refrigerant to exchange the heat of the hot water in the water circuit 40 via the second refrigerant when hot water remains in the water circuit 40 at the start of the reverse cycle defrost process. By supplying to the vessel 32, the heat of the hot water in the water circuit 40 can be used for defrosting of the first heat exchanger 22. Therefore, in the reverse cycle defrosting process, the water heating system 10 can effectively reduce the time required for defrosting by performing the second reverse cycle operation of the second refrigerant circuit 30 together with the first reverse cycle operation of the first refrigerant circuit 20. Can be shortened.

  In this modification, when the second reverse cycle operation of the second refrigerant circuit 30 is performed in the reverse cycle defrost process, the operation frequency of the second compressor 34 is set to be higher than the operation frequency during the normal operation of the water heating system 10. Is preferably set to a low value.

  The water heating system according to the present invention can shorten the time required for defrosting, and can suppress the occurrence of unmelted frost.

DESCRIPTION OF SYMBOLS 10 Water heating system 20 1st refrigerant circuit 22 1st heat exchanger 24 1st compressor 30 2nd refrigerant circuit 32 2nd heat exchanger 34 2nd compressor 40 Water circuit 42 3rd heat exchanger 50 Control part

JP 2001-108256 A JP 2004-132647 A

The water heating system according to the first aspect of the present invention includes a first refrigerant circuit, a second refrigerant circuit, a water circuit, and a control unit. The first refrigerant circuit has a first heat exchanger and a second heat exchanger, and is a circuit through which the first refrigerant circulates. The first heat exchanger exchanges heat between the heat source and the first refrigerant. The second heat exchanger exchanges heat between the first refrigerant and the second refrigerant. The second refrigerant circuit has a second heat exchanger and a third heat exchanger, and is a circuit through which the second refrigerant circulates. The second refrigerant circuit shares the first refrigerant circuit and the second heat exchanger. The third heat exchanger exchanges heat between the second refrigerant and water. The water circuit has a third heat exchanger and is a circuit through which water passes. The water circuit shares the second refrigerant circuit and the third heat exchanger. The control unit controls the first refrigerant circuit, the second refrigerant circuit, and the water circuit in order to perform the defrost operation of the first heat exchanger. The control unit stops the supply of water to the third heat exchanger in the water circuit and the supply of the second refrigerant to the second heat exchanger in the second refrigerant circuit before starting the defrost operation . In the refrigerant circuit, the first refrigerant is circulated in the same direction as during normal operation. The controller reverses the direction in which the first refrigerant circulates in the first refrigerant circuit and supplies the first refrigerant from the second heat exchanger to the first heat exchanger, thereby starting the defrost operation.

Claims (4)

A first heat exchanger (22) that exchanges heat between the heat source and the first refrigerant; and a second heat exchanger (32) that exchanges heat between the first refrigerant and the second refrigerant. A first refrigerant circuit (20) in which
A second refrigerant that has the second heat exchanger shared with the first refrigerant circuit and a third heat exchanger (42) that exchanges heat between the second refrigerant and water, and in which the second refrigerant circulates. A circuit (30);
A water circuit (40) having the third heat exchanger shared with the second refrigerant circuit and through which water passes;
A controller (50) for controlling the first refrigerant circuit, the second refrigerant circuit and the water circuit in order to perform a defrost operation of the first heat exchanger;
With
The control unit supplies water to the third heat exchanger in the water circuit and starts supplying the second refrigerant to the second heat exchanger in the second refrigerant circuit before starting the defrost operation. Shut off the supply,
The controller reverses the direction in which the first refrigerant circulates in the first refrigerant circuit, and supplies the first refrigerant from the second heat exchanger to the first heat exchanger, whereby the defrosting is performed. Start driving,
Water heating system (10). The first refrigerant circuit has a first compressor (24) for compressing the first refrigerant,
The second refrigerant circuit has a second compressor (34) for compressing the second refrigerant,
The control unit increases the operating frequency of the first compressor for a first operating time before starting the defrost operation, and stops the operation of the second compressor.
The water heating system according to claim 1. The controller starts the defrost operation when the temperature of the first refrigerant supplied to the second heat exchanger reaches a first temperature.
The water heating system according to claim 1 or 2. The controller further reverses the direction in which the second refrigerant circulates in the second refrigerant circuit, and supplies the second refrigerant from the third heat exchanger to the second heat exchanger, Starting the defrost operation,
The water heating system according to any one of claims 1 to 3.

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