WO2023062989A1

WO2023062989A1 - Heat medium circulation system

Info

Publication number: WO2023062989A1
Application number: PCT/JP2022/033866
Authority: WO
Inventors: 俊二森脇; 由樹山岡; 常子今川; 繁男青山; 和彦町田; 潤吉田; 泰彬坂東; 和人中谷
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2021-10-13
Filing date: 2022-09-09
Publication date: 2023-04-20

Abstract

This heat medium circulation system 100 comprises: a refrigerant circuit 110 that uses a combustible refrigerant and in which a compressor 111, a use-side heat exchanger 112, an expansion means 113, and a heat source-side heat exchanger 114 are connected in an annular manner; an air blowing device 117 circulating air to the heat source-side heat exchanger 114; a housing 140 incorporating at least the refrigerant circuit 110 and the air blowing device 117; an electric heating device 143 provided to a bottom plate 141 of the housing 140; and a control device 130. The control device 130 simultaneously starts the operation of the air blowing device 117 and the conduction of the electric heating device 143, and controls the power consumption of the electric heating device 143 so as to be lower than that at a stable time for a prescribed time from the start of conduction of the electric heating device 143, thereby stably operating the electric heating device 143, which suppresses freezing of drain water, and further improving safety.

Description

Heat medium circulation system

The present disclosure relates to a heat medium circulation system.

Patent Document 1 discloses an outdoor unit using a flammable refrigerant. This outdoor unit is provided with an electric heating device on the upper part of the bottom plate, and the electric heating device is energized after the outdoor fan rotates.

JP 2015-55455 A

The present disclosure provides a heat medium circulation system with improved safety by controlling power consumption while ventilating the atmosphere gas of the electric heating device.

In the heat medium circulation system according to the present disclosure, a compressor, a user-side heat exchanger, an expansion device, and a heat source-side heat exchanger are connected in a ring, a refrigerant circuit using a combustible refrigerant, and air in the heat source-side heat exchanger. A blower device for circulating the air blower, a housing containing at least the refrigerant circuit and the blower device, an electric heating device provided on the surface of the bottom plate of the housing, and a control device. The operation and the energization of the electric heating device are started at the same time, and the power consumption of the electric heating device is controlled to be lower than that in the stable state for a predetermined time after the start of energization of the electric heating device.

In the heat medium circulation system of the present disclosure, the surface temperature of the electric heating device is kept low until the atmosphere gas of the electric heating device is ventilated, so safety is further improved. Also, freezing of the bottom plate is prevented.

1 is a configuration diagram of a heat medium circulation system according to an embodiment of the present invention; Pressure-enthalpy diagram (Ph diagram) of the same heat medium circulation system Schematic diagram of the installation form of the electric heating device of the heat medium circulation system Configuration diagram of the control system of the same heat medium circulation system Correlation diagram between power density and heater surface temperature of the electric heating device of the same heat medium circulation system Flowchart for explaining the control operation of the air blower and the electric heating device of the same heat medium circulation system

(Knowledge, etc. on which this disclosure is based)
When the electric heating device is not energized until the combustible refrigerant is ventilated by the outdoor blower, the temperature of the bottom plate may drop and the moisture on the surface of the bottom plate may freeze. As a result, damage to the drain pipe or the like may occur.
Therefore, in the present disclosure, the operation of the blower device and the energization of the electric heating device are started at the same time, and the power consumption of the electric heating device is controlled to be lower than that in the stable state for a predetermined time after the start of energization of the electric heating device. As a result, even if the combustible refrigerant leaks, the amount of heat is suppressed so that the combustible refrigerant does not ignite. By doing so, it is possible to ventilate the electric heating device and exhaust the leaked refrigerant while suppressing the temperature drop of the bottom plate. As a result, it is possible to provide a heat medium circulation system with improved equipment reliability and improved safety.

Hereinafter, embodiments will be described in detail with reference to the drawings. However, more detailed description than necessary may be omitted. For example, detailed descriptions of well-known matters or redundant descriptions of substantially the same configurations may be omitted. This is to avoid the following description from becoming more redundant than necessary and to facilitate understanding by those skilled in the art.
It should be noted that the accompanying drawings and the following description are provided to allow those skilled in the art to fully understand the present disclosure and are not intended to limit the claimed subject matter thereby.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 5. FIG.

[1-1. composition]
[1-1-1. Configuration of heat medium circulation system]
In FIG. 1, the heat medium circulation system 100 includes a refrigerant circuit 110, a heat medium circuit 120, and a controller .

The refrigerant circuit 110 is a vapor compression refrigeration cycle, and is configured by sequentially connecting a compressor 111, a user-side heat exchanger 112, an expansion device 113, and a heat source-side heat exchanger 114 via pipes 116. . Propane, which is a flammable refrigerant, is used as the refrigerant.
The refrigerant circuit 110 is also provided with a four-way valve 115 for switching between a heating operation for generating hot water and a cooling operation for generating cold water.
The refrigerant circuit 110 is housed in a housing 140 outside the room. The housing 140 is provided with a blower 117 that circulates outdoor air to the heat source side heat exchanger 114 .
The heat medium circuit 120 is configured by sequentially connecting a use-side heat exchanger 112 , a use-side terminal 122 ,

switching valves

124 a and 124 b , and a carrier pump 121 through heat medium pipes 126 . The

switching valves

124a and 124b selectively switch the circuit of the heat medium. The conveying pump 121 is a heat medium conveying device. Water or antifreeze is used as a heat medium.
In addition, the heat medium circuit 120 is provided with a hot water storage tank 123 in parallel with the user terminal 122 . The hot water storage tank 123 is connected by a heat medium pipe 126 that branches from the switching valve 124b and merges with the switching valve 124a.

In the heat medium circuit 120, a water heating device 127 having a heater element is provided on the downstream side of the utilization side heat exchanger 112. As shown in FIG. At the highest position of the water heating device 127, a degassing device 128 capable of discharging the gas flowing through the heat medium circuit 120 to the outside is provided. The outlet of the deaerator 128 is open to the outdoor atmosphere.
In addition, in the heat medium circuit 120, a cutoff valve 129a is provided between the transfer pump 121 and the use side heat exchanger 112 to stop the flow of the heat medium. A cutoff valve 129b is provided between the utilization side heat exchanger 112 and the water heating device 127 .
In FIG. 1 , solid line arrows indicate the flow direction of the refrigerant during the heating operation, and dashed line arrows indicate the flow direction of the refrigerant during the cooling operation.

The state change of the refrigerant in the heating operation and the cooling operation will be described with reference to FIG.
During heating operation, the high-pressure refrigerant (point a) discharged from the compressor 111 flows into the user-side heat exchanger 112 via the four-way valve 115, and radiates heat to the heat medium flowing through the user-side heat exchanger 112. . The high-pressure refrigerant (point b) after radiating heat in the user-side heat exchanger 112 is depressurized and expanded by the expansion device 113 , and then flows into the heat source-side heat exchanger 114 . The low-pressure refrigerant (point c) flowing into the heat source side heat exchanger 114 absorbs heat from the outside air, evaporates, and returns to the suction side (point d) of the compressor 111 via the four-way valve 115 again.
On the other hand, during the cooling operation, the high-pressure refrigerant (point a) discharged from the compressor 111 flows into the heat source side heat exchanger 114 via the four-way valve 115, and the heat source side heat exchanger 114 radiates heat to the outside air. After radiating heat in the heat source side heat exchanger 114 , the high pressure refrigerant (point b) is depressurized and expanded in the expansion device 113 and then flows into the utilization side heat exchanger 112 . The low-pressure refrigerant (point c) flowing into the usage-side heat exchanger 112 absorbs heat from the heat medium flowing through the usage-side heat exchanger 112 and evaporates. point).

Next, the state change of the heat medium in the heat medium circuit 120 will be described.
First, during the heating operation, the heat medium circulated by the conveying pump 121 is heated by the high-temperature refrigerant in the user-side heat exchanger 112 . After that, the heat medium is radiated to, for example, the air in the living space at the user terminal 122 and used to heat the user load. The heat medium whose temperature has been lowered by radiating heat at the user-side terminal 122 is heated again by the user-side heat exchanger 112 .
Here, when the amount of heat to be heated by the use-side heat exchanger 112 is less than the amount of heat that can sufficiently heat the use-side load, the heater element of the water heating device 127 is energized, and the heat medium flows into the water heating device 127. to heat directly.
Also, the high-temperature heat medium heated by the use-side heat exchanger 112 circulates in the hot water storage tank 123 by switching the

switching valves

124a and 124b. A high-temperature heat medium is introduced into the hot water storage tank 123 from the upper portion of the hot water storage tank 123 , and a low-temperature heat medium is led out from the lower portion of the hot water storage tank 123 and heated by the utilization side heat exchanger 112 .
On the other hand, during the cooling operation, the heat medium is cooled by the user-side heat exchanger 112 and circulated by the carrier pump 121 to absorb heat in the user-side terminal 122 and used to cool the user-side load. The heat medium whose temperature has been increased by absorbing heat in the utilization side terminal 122 is cooled again in the utilization side heat exchanger 112 .
Control device 130 is provided within housing 140 of heat medium circulation system 100 . The control device 130 controls the rotation speed of the compressor 111, the rotation speed of the conveying pump 121, the throttle amount of the expansion device 113, and the applied voltage of the water heating device 127, and switches the four-way valve 115 and switching

valves

124a and 124b. etc. By doing so, the efficiency of the vapor compression refrigeration cycle is increased.

Further, when the heating operation is performed, moisture in the air freezes in the heat source side heat exchanger 114 to form frost. As a result, the heat transfer performance of the heat source side heat exchanger 114 deteriorates, resulting in a reduction in heating capacity and a reduction in the coefficient of performance. In such a case, the degree of frost formation is determined from the outside air temperature, the operating time, the temperature of the heat source side heat exchanger 114, or the like, and a defrosting operation is performed in which the frost is melted and removed with the heat of the refrigerant.
Typical defrosting methods generally include reverse cycle defrosting and hot gas defrosting. In reverse cycle defrosting, the four-way valve 115 is switched to reverse the circulation direction of the refrigerant, the high-temperature and high-pressure gas refrigerant discharged from the compressor 111 is introduced into the heat source side heat exchanger 114, and the condensation heat of the gas refrigerant defrosts. to melt. Hot gas defrosting is performed by increasing the opening of the expansion device 113 without switching the four-way valve 115 and introducing the high-temperature and high-pressure gas refrigerant discharged from the compressor 111 into the heat source side heat exchanger 114 without reducing the pressure. , thaw the frost

Next, the flow of drain water during defrosting operation will be described with reference to FIG.
First, frost adheres to the surfaces of the heat transfer tubes and fins in the heat source side heat exchanger 114 during the heating operation. Here, the frost on the heat source side heat exchanger 114 is heated and melted by the defrosting operation. The melted drain water runs along the fin surfaces of the heat source side heat exchanger 114 and falls from below the heat source side heat exchanger 114 to the bottom plate 141 of the outdoor housing 140 . Drain water flows out of the housing 140 through a drain hole 142 provided in the bottom plate 141 .
A certain amount of drain water that falls on the bottom plate 141 during the defrosting operation is drained from the drain hole 142. However, due to variations in the installation of the housing 140 and structural restrictions of the bottom plate 141, etc., the slope to the drain hole 142 is small. part of the drain water stays in the Therefore, the accumulated drain water may freeze during the heating operation under environmental conditions below the freezing point.
If the defrosting operation and the heating operation are repeated in such a state, ice will accumulate on the bottom plate 141 . In the worst case, the accumulated ice and the fan blades of the blower 117 come into contact with each other, causing the blower 117 to malfunction. In addition, problems such as breakage of the refrigerant pipe due to contact of the ice with the refrigerant pipe occur. Therefore, reliability and safety may not be ensured.
Therefore, in general, an electric heating device 143 is installed on the surface of the bottom plate 141 to heat the bottom plate 141 and prevent the drain water from freezing.
The electric heating device 143 is composed of, for example, a sheathed heater, a silicon rubber heater, or a PTC heater. It is desirable that the electric heating device 143 is arranged at an appropriate position with a heater length corresponding to the area of the bottom plate 141 so that the temperature of the bottom plate 141 can be sufficiently increased.
In addition, in this embodiment, the electric heating device 143 uses a heater having a power density of 2 W/cm ² when a rated voltage is applied.

[1-1-2. Configuration of control device]
Next, the configuration of the control device 130 will be described with reference to FIG.
The control device 130 includes a controller 131, a user interface 132, a high pressure side pressure sensor 133, a discharge temperature sensor 134, a heat source side heat exchange temperature sensor 135, an outside air temperature sensor 136, an incoming water temperature sensor 137, and an outgoing water temperature. It is composed of a sensor 138 and a gas sensor 139 . The controller 131 is equipped with a microcomputer, memory, and the like. A user interface 132 is used to input the operation stop of the device, the temperature setting of the heat medium to be generated, and the like. The high pressure side pressure sensor 133 is provided in the discharge side pipe of the compressor 111 and detects the discharge side pressure. A discharge temperature sensor 134 detects the temperature of the discharged refrigerant. The heat source side heat exchanger temperature sensor 135 is provided in the refrigerant pipe of the heat source side heat exchanger 114 and detects the saturation temperature of the refrigerant flowing through the heat source side heat exchanger 114 . The outside air temperature sensor 136 is provided on the outer surface of the housing 140 of the heat medium circulation system 100 and detects the outside air temperature. The incoming water temperature sensor 137 detects the temperature of the heat medium flowing into the utilization side heat exchanger 112 provided in the heat medium circuit 120 . The outgoing water temperature sensor 138 detects the temperature of the heat medium flowing out from the utilization side heat exchanger 112 . A gas sensor 139 is provided in the lower part of the housing 140 and detects the concentration of combustible gas.

[1-2. motion]
The operation of the heat medium circulation system 100 configured as described above will be described below.

[1-2-1. Cooling and heating operation]
The controller 131 performs heating operation or cooling operation based on input information of the user interface 132 . During operation, the compressor 111 is controlled at a rotation speed determined based on the detection value of the outside air temperature sensor 136 , the detection value of the water temperature sensor 138 , and the water temperature set value of the user interface 132 . While comparing with the detection value of the discharge temperature sensor 134 so that the discharge temperature target value determined based on the detection value of the high pressure side pressure sensor 133 and the detection value of the heat source side heat exchanger temperature sensor 135, the expansion device 113 Controls the amount of aperture.
Further, during operation, the rotation speed of the conveying pump 121 is controlled so that the difference between the detected value of the outgoing water temperature sensor 138 and the detected value of the incoming water temperature sensor 137 becomes a predetermined temperature difference.
Furthermore, during the heating operation, the voltage applied to the heater element of the water heating device 127 is controlled so that the detected value of the water temperature sensor 138 becomes the water temperature setting value.

[1-2-2. Operation of electric heating device]
The operation of the electric heating device 143 in heating operation and defrosting operation will be described.
When the heating operation is input to the user interface 132, the opening of the expansion device 113 is set to the initial value, the carrier pump 121 is operated, and the heat medium in the heat medium circuit 120 is circulated. After that, the air blower 117 is operated, and the air that has passed through the heat source side heat exchanger 114 passes through the housing 140 and is discharged to the outside. At the same time as the operation of the air blower 117, the electrical heating device 143 is started to be energized, and the bottom plate 141 is heated. However, the applied voltage is controlled below the rated voltage so that the power density is 1 W/cm ² , keeping the surface temperature of the electric heating device 143 lower than normal and operating the electric heating device 143 .
Then, when the rotational speed of the air blower 117 reaches a predetermined air volume, the applied voltage is increased to the rated voltage to further increase the temperature of the bottom plate 141 .
Further, when the heat source side heat exchanger 114 is frosted due to the heating operation, the defrosting operation is started, but the air blower 117 is stopped when the reverse cycle defrosting is executed.
At this time, the voltage applied to the electric heating device 143 is lowered so that the power density is reduced from 2 W/cm ² to 1 W/cm ² to keep the surface temperature low. Then, the defrosting operation is finished and the heating operation is started. When the number of rotations of the blower 117 reaches a predetermined air volume, the applied voltage is raised to the rated voltage to keep the surface temperature of the electric heating device 143 high.
Furthermore, during the heating operation, when the concentration detected by the gas sensor 139 reaches or exceeds a predetermined concentration, the power supply to the electric heating device 143 is stopped and the surface temperature of the electric heating device 143 is lowered.

Here, FIG. 5 is a graph showing the relationship between the power density and the surface temperature of the heater (electric heating device). Until a sufficient amount of air passes through the electric heating device 143, the electric heating device 143 is operated at a voltage applied to the heater of 1 W/cm ^{2 ,} which is a heater surface temperature well below the flash point of propane, 432°C. Then, after a sufficient air volume is secured, the electric heating device 143 is operated at a voltage applied to the heater of 2 W/cm ² which is lower than the flash point of propane and a surface temperature sufficient to heat the bottom plate 141 . Thus, the heater applied voltage is controlled.

The operation at this time will be described in more detail with reference to the flowchart shown in FIG. First, the user instructs to start the heating operation by operating the user interface 132 (step S1). Then, according to the instruction, control device 130 operates blower device 117 and simultaneously applies a voltage having a power density of 1 W/cm ² to electric heating device 143 (step S2). Then, the compressor 111 and the conveying pump 121 are operated to control their rotation speeds, and the opening degree of the expansion device 113 is adjusted (step S3). Next, the control device 130 detects the refrigerant concentration Cr in the housing 140 with the gas sensor 139 (step S4). Then, the refrigerant concentration Ca and the refrigerant concentration Cr set in advance are compared to determine whether the refrigerant concentration Cr is equal to or higher than the refrigerant concentration Ca (step S5).

When the refrigerant concentration Cr is equal to or higher than the refrigerant concentration Ca (YES in step S5), it is determined that the refrigerant is leaking from the refrigerant circuit 110. Then, while the air blower 117 continues to operate, the electric heating device 143 is de-energized (step S6). At the same time, the operations of the compressor 111 and the transport pump 121 are stopped (step S7). Next, the

shutoff valves

129a and 129b are energized to operate in the closing direction to stop the flow of the heat medium (step S8).

On the other hand, when the refrigerant concentration Cr is less than the refrigerant concentration Ca (NO in step S5), it is determined that the combustible refrigerant is not leaking from the refrigerant circuit 110, and the operation is continued. Then, it is determined whether or not the blower 117 has been operated for a predetermined time (step S9). Then, when it is determined that a sufficient air volume has been secured after operating for a predetermined time (YES in step S9), the voltage is increased so that the power density of the electric heating device 143 becomes 2 W/cm ² (step S10). .
Thereafter, the preset defrosting operation start temperature Tds is compared with the detected temperature Te of the heat source side heat exchanger temperature sensor 135 to determine whether or not the detected temperature Te, which is the heat exchanger temperature, is less than the defrost operation start temperature Tds. Determine (step S11). When the heat exchanger temperature Te is equal to or higher than the defrosting operation start temperature Tds (NO in step S11), it is determined that the amount of frost on the heat source side heat exchanger 114 is small and the defrosting operation is not necessary, and the heating operation is started. continue.

On the other hand, if the heat exchanger temperature Te is less than the defrosting operation start temperature Tds (YES in step S11), it is determined that the heat source side heat exchanger 114 has a large amount of frost due to the heating operation and that defrosting is necessary. do. Then, the four-way valve 115 is switched to the cooling side, and the blower 117 is stopped to start the defrosting operation (step S12).
At this time, the applied voltage is lowered so that the power density of the electric heating device 143 becomes 1 W/cm ² at the same time as the air blower 117 is stopped (step S13).
Then, the preset defrosting operation end temperature Tde is compared with the temperature Te detected by the heat source side heat exchanger temperature sensor 135, and it is determined whether or not the heat exchanger temperature Te is equal to or higher than the defrosting operation end temperature Tde (step S14). When the heat exchanger temperature Te is lower than the defrosting operation end temperature Tde (NO in step S14), it is determined that frost remains in the heat source side heat exchanger 114, and the defrosting operation is continued.

On the other hand, if the heat exchanger temperature Te is equal to or higher than the defrosting operation end temperature Tde (YES in step S14), it is determined that the frost on the heat source side heat exchanger 114 has completely melted and the defrosting is completed. Then, the four-way valve 115 is switched to the heating side, and the air blower 117 is operated to start the heating operation (step S15).

[1-3. effects, etc.]
As described above, in the present embodiment, the heat medium circulation system 100 includes the refrigerant circuit 110, the heat medium circuit 120, the control device 130, the blower device 117, the bottom plate 141, and the electric heating device 143. . Refrigerant circuit 110 is a combustible refrigerant vapor compression refrigeration cycle. A compressor 111 , a user-side heat exchanger 112 , an expansion device 113 , and a heat source-side heat exchanger 114 are annularly connected to the refrigerant circuit 110 . Heat medium circuit 120 circulates a liquid heat medium that heats and cools the load on the user side. The blower 117 circulates outdoor air to the heat source side heat exchanger 114 . The electric heating device 143 is provided on the surface of the bottom plate 141 and electrically heats the bottom plate 141 .
The electric heating device 143 is energized at the same time as the air blower 117 is operated, and is controlled to be lower than the stable power consumption for a predetermined time after the start of energization.
As a result, the electric heating device 143 is energized simultaneously with the operation of the blower device 117 . Therefore, the temperature of the bottom plate 141 is prevented from lowering due to air blowing, and the temperature of the bottom plate 141 rises quickly.
Also, if gas leaks and stays on the bottom plate 141 while the operation is stopped, the wind speed is low immediately after the operation of the blower 117 and the gas that stays is difficult to diffuse. Since the temperature is controlled to be low, the power density of the electric heating device 143 is low for a predetermined time after the operation of the blower 117, and the surface temperature of the electric heating device 143 is kept low until the atmosphere gas of the electric heating device 143 is ventilated.
Therefore, it is possible to achieve both more reliable prevention of ignition of the leaked refrigerant due to heat generation of the electric heating device 143 and prevention of freezing of the bottom plate 141 . Therefore, safety regarding leakage of the combustible refrigerant is further improved.

As in this embodiment, the power density of the electric heating device 143 is 2 W or less, and the power density may be controlled to be less than 1 W/cm 2 for a predetermined time after the start of energization.
As a result, the power density of the electric heating device 143 is low and the surface temperature is kept at a temperature sufficiently lower than the ignition temperature of propane in the time period when the wind speed is low after the blower device 117 starts operating. Therefore, even if combustible gas remains, it will not ignite.
Therefore, it is possible to achieve both more reliable prevention of ignition of the leaked refrigerant due to heat generation of the electric heating device 143 and prevention of freezing of the bottom plate 141 . Therefore, safety against leakage of combustible refrigerant is further improved.

As in the present embodiment, the predetermined time for controlling the power consumption of the electric heating device 143 to be low may be set to the time until the air volume of the blower device 117 reaches a predetermined air volume that can sufficiently exhaust the stagnant gas. good.
As a result, the combustible gas that has leaked from the refrigerant circuit 110 and has accumulated in the vicinity of the electric heating device 143 is diffused by the wind generated by the blower device 117 . Until the combustible gas is exhausted to the outside of the housing 140, the surface temperature of the electric heating device 143 is maintained at a temperature sufficiently lower than the ignition temperature of propane. do not.

As in this embodiment, when the gas concentration detection value of the gas sensor 139 becomes higher than the preset gas concentration, the operation of the air blower 117 is continued and the power supply to the electric heating device 143 is cut off. good.
This makes it possible to reliably determine that the combustible refrigerant has leaked. At the time of gas leakage, the exhaust of the combustible gas by the air blower 117 and the stoppage of power supply to the electric heating device 143 quickly lower the surface temperature. Therefore, safety is further improved.

As in this embodiment, the combustible refrigerant may be propane or a mixed refrigerant containing propane.
As a result, the global warming potential (GWP) is low, and adverse effects on the environment can be suppressed even when the refrigerant leaks. Therefore, environmental performance is improved.

(Other embodiments)
As described above, the present embodiment has been described as an example of the technology disclosed in the present application. However, the technology in the present disclosure is not limited to this, and can also be applied to embodiments with modifications, replacements, additions, omissions, and the like. Further, it is also possible to combine the constituent elements described in the above embodiments to form a new embodiment.
Therefore, other embodiments will be exemplified below.

In the present embodiment, the cooling/heating water heater has been described as an example of the heat medium circulation system 100 . The heat medium circulation system 100 may be any system as long as it can cool or heat liquid. Therefore, heat medium circulation system 100 is not limited to an air conditioner. However, if a cooling/heating water heater is used as the heat medium circulation system 100, the annual heat demand of the house can be met. Alternatively, a cold/hot water chiller may be used as the heat medium circulation system 100 . If a hot/cold water chiller is used as the heat medium circulation system 100, it is possible to cope with the heat load of heating and cooling used in the factory or the like, so that the energy efficiency of the factory can be improved.

In the present embodiment, the refrigerant concentration sensor has been described as an example of the leak detection sensor. Any leak detection sensor may be used as long as it can determine that the refrigerant has leaked from the refrigerant circuit 110 into the heat medium circuit 120 . Therefore, the leak detection sensor is not limited to the refrigerant concentration sensor. However, if a refrigerant concentration sensor is used as the leakage detection sensor, it can be realized with a simple configuration. Further, as the leakage detection sensor, a pressure sensor that detects the pressure of the refrigerant circuit 110 or a thermistor that detects the refrigerant temperature during operation may be used. If the pressure and temperature of the refrigerant circuit 110 are detected, the sensor for operation control can be shared, so there is an effect that it can be manufactured at low cost.

In the present embodiment, as an example of the installation position of the electric heating device 143, the structure installed on the surface of the bottom plate 141 of the housing 140 has been described. The electric heating device 143 may be installed at a position where the temperature of the bottom plate 141 rises and the drain water does not freeze when the electric heating device 143 is energized. Therefore, the installation position of the electric heating device 143 is not limited to the surface of the bottom plate 141 . However, if the electric heating device 143 is installed on the surface of the bottom plate 141, the bottom plate 141 and the drain water can be directly heated, so that the heat exchange efficiency can be increased. Also, the electric heating device 143 may be installed on the back surface of the bottom plate 141 . If the electric heating device 143 is installed on the back surface of the bottom plate 141, the refrigerant gas will not come into direct contact with the electric heating device 143 when the electric heating device 143 is short-circuited and a spark is generated. Therefore, there is an effect that it is possible to more reliably prevent ignition when a spark occurs.

In the present embodiment, circuits installed between the transfer pump 121 and the user-side heat exchanger 112 and between the user-side heat exchanger 112 and the switching valve have been described as examples of the installation positions of the

shutoff valves

129a and 129b. The

shutoff valves

129a and 129b may be installed at positions where the refrigerant does not flow into the living space when the refrigerant leaks into the heat medium circuit 120. FIG. Therefore, the installation positions of the

shutoff valves

129a and 129b are not limited to between the transfer pump 121 and the user-side heat exchanger 112 or between the user-side heat exchanger 112 and the switching valve. However, by installing the

shutoff valves

129a and 129b on the downstream side of the discharge device, the leaked refrigerant existing in the heat medium circuit 120 between the

shutoff valves

129a and 129b can be discharged into the atmosphere even after shutting off. Therefore, safety is further improved.

The present disclosure is applicable to a heat medium circulation system using a combustible refrigerant in the refrigerant circuit. Specifically, the present disclosure is applicable to hot water heaters, commercial chillers, and the like.

100 heat medium circulation system 110 refrigerant circuit 111 compressor 112 use side heat exchanger 113 expansion device 114 heat source side heat exchanger 115 four-way valve 116 piping 117 air blower 120 heat medium circuit 121 transfer pump 122 use side terminal 123 hot

water storage tank

124a, 124b switching valve 126 heat medium pipe 127 water heating device 128

degassing device

129a, 129b cutoff valve 130 control device 131 controller 132 user interface 133 high pressure side pressure sensor 134 discharge temperature sensor 135 heat source side heat exchanger temperature sensor 136 outside air temperature sensor 137 water inlet Temperature sensor 138 Outflow temperature sensor 139 Gas sensor 140 Housing 141 Bottom plate 142 Drain hole 143 Electric heating device

Claims

a refrigerant circuit in which a compressor, a user-side heat exchanger, an expansion device, and a heat source-side heat exchanger are connected in a ring and using a combustible refrigerant;
a blower that circulates air through the heat source side heat exchanger;
a housing that houses at least the refrigerant circuit and the blower;
an electric heating device provided on the surface of the bottom plate of the housing;
a controller;
The control device simultaneously starts the operation of the blower device and the energization of the electric heating device, and controls the power consumption of the electric heating device to be lower than that in a stable state for a predetermined time after the start of energization of the electric heating device. A heat medium circulation system characterized by:
The electric heating device has a power density of 2 W/cm 2 or less,
2. The heat medium circulation system according to claim 1, wherein the controller controls the power density to be less than 1 W/cm <2> during the predetermined time.
3. The heat medium circulation system according to claim 1 or 2, wherein the predetermined time is the time until the volume of air generated by the blower reaches or exceeds a predetermined volume of air.
A leakage sensor is provided in the housing to detect leakage of the combustible refrigerant,
4. The control device, when the leak sensor detects leakage of the combustible refrigerant, continues the operation of the blower device and stops power supply to the electric heating device. The heat medium circulation system according to any one of .
The heat medium circulation system according to any one of claims 1 to 4, wherein the combustible refrigerant is propane or a mixed refrigerant containing propane.