TECHNICAL FIELD

The present invention relates to a refrigerant cycle apparatus.

BACKGROUND ART

In a refrigerant cycle apparatus that cools or heats an object or a target fluid by circulating a refrigerant, such as an air conditioner, the refrigerant may leak. This refrigerant leakage becomes a problem depending on the type of refrigerant, and necessary measures need to be taken. For example, Patent Literature 1 (JP 2014-35171 A) takes measures, in an air conditioner using R32 as a refrigerant, to reduce absolute humidity of target space by performing a dehumidifying operation when a refrigerant leakage is detected and to weaken flammability of the refrigerant in the target space.

SUMMARY OF THE INVENTION

Technical Problem

In this way, various measures against the refrigerant leakage have been proposed, and it is required to further enhance safety when the refrigerant leaks.

Solution to Problem

A refrigerant cycle apparatus according to a first aspect includes a use-side unit, a heat source-side unit, a refrigerant connection pipe, a cutoff unit, a refrigerant leakage detection unit, and a control unit. The refrigerant connection pipe connects the use-side unit to the heat source-side unit. The cutoff unit is provided in the refrigerant connection pipe and configured to cut off inflow of a refrigerant into the use-side unit. The refrigerant leakage detection unit detects leakage of the refrigerant from the use-side unit. The control unit performs pressure reduction control, when the refrigerant leakage detection unit detects the leakage of the refrigerant, to lower pressure of the refrigerant in the use-side unit. The control unit puts the cutoff unit into a cutoff state.

Here, when the refrigerant leakage from the use-side unit is detected, first, the pressure reduction control is performed, and the refrigerant pressure in the use-side unit is lowered. This reduces the pressure difference between the installation space of the use-side unit and the refrigerant of the use-side unit, and a leak speed of the refrigerant decreases. Then, natural ventilation in the installation space of the use-side unit discharges most of the leaked refrigerant to the outside.

Furthermore, here, after the pressure reduction control, the cutoff unit is put into the cutoff state. This eliminates the inflow of the refrigerant from the heat source-side unit, and after a while, the refrigerant leakage from the use-side unit completely stops. Therefore, this refrigerant cycle apparatus is more secure when the refrigerant leaks.

The refrigerant cycle apparatus according to a second aspect is the refrigerant cycle apparatus according to the first aspect with the refrigerant connection pipe including a high pressure-side first refrigerant connection pipe and a low pressure-side second refrigerant connection pipe. The cutoff unit includes a first cutoff valve provided in the first refrigerant connection pipe and a second cutoff valve provided in the second refrigerant connection pipe.

Here, two cutoff valves can separate the use-side unit and the heat source-side unit completely. This can eliminate the inflow of refrigerant from the heat source-side unit into the use-side unit and the inflow of refrigerant, air, or the like from the use-side unit into the heat source-side unit.

The refrigerant cycle apparatus according to a third aspect is the refrigerant cycle apparatus according to the first aspect or the second aspect. When the refrigerant leakage detection unit detects the refrigerant leakage, the control unit performs the pressure reduction control to lower the pressure of the refrigerant in the use-side unit, and thereafter puts the cutoff unit into the cutoff state when a predetermined time elapses.

Here, the control unit performs the pressure reduction control until the predetermined time elapses, and thereafter puts the cutoff unit into the cutoff state. If the cutoff unit is put into the cutoff state in an early stage where the pressure of the refrigerant in the use-side unit has not dropped sufficiently, there is a possibility that a large amount of refrigerant may leak into the installation space of the use-side unit. However, here, since the pressure reduction control is performed until a predetermined time elapses, if the predetermined time is set appropriately based on the volume of the refrigerant flow path of the use-side unit, the pressure of the refrigerant in the use-side unit can be sufficiently lowered before the cutoff unit is put into the cutoff state.

The refrigerant cycle apparatus according to a fourth aspect is the refrigerant cycle apparatus according to any one of the first to third aspects. When the refrigerant leakage detection unit detects the leakage of the refrigerant, the control unit performs the pressure reduction control to lower the pressure of the refrigerant in the use-side unit, and thereafter puts the cutoff unit into the cutoff state when the pressure of the refrigerant or a temperature of the refrigerant in the use-side unit satisfies a predetermined condition.

Here, the pressure reduction control is performed until the predetermined condition is satisfied, and thereafter the cutoff unit is put into the cutoff state. If the cutoff unit is put into the cutoff state in an early stage where the pressure of the refrigerant in the use-side unit has not dropped sufficiently, there is a possibility that a large amount of refrigerant may leak into the installation space of the use-side unit. However, here, since the pressure reduction control is performed until the pressure of the refrigerant or the temperature of the refrigerant satisfies the predetermined condition, if the predetermined condition is set appropriately, the pressure of the refrigerant of the use-side unit can be sufficiently lowered before the cutoff unit is put into the cutoff state.

The refrigerant cycle apparatus according to a fifth aspect is the refrigerant cycle apparatus according to any one of the first to fourth aspects. In the pressure reduction control to lower the pressure of the refrigerant in the use-side unit, the control unit performs control to prevent the pressure of the refrigerant in the use-side unit from becoming lower than atmospheric pressure.

Here, control is performed such that the pressure of the refrigerant in the use-side unit is maintained equal to or higher than the atmospheric pressure. This inhibits the defect that air enters from a refrigerant leakage location of the use-side unit, for example, a crack location of the refrigerant pipe, and that the air flows into the refrigerant connection pipe or the heat source-side unit.

The refrigerant cycle apparatus according to a sixth aspect is the refrigerant cycle apparatus according to any one of the first to fifth aspects. The heat source-side unit includes a compressor, a heat source-side heat exchanger, and a heat source-side expansion mechanism. The heat source-side heat exchanger radiates heat from the refrigerant discharged from the compressor. The heat source-side expansion mechanism lowers the pressure of the refrigerant from which heat is radiated by the heat source-side heat exchanger. In the pressure reduction control to lower the pressure of the refrigerant in the use-side unit, the control unit increases the degree of decompression of the refrigerant by the heat source-side expansion mechanism to lower the pressure of the refrigerant flowing from the heat source-side unit to the use-side unit.

Here, in the pressure reduction control, the degree of decompression of the refrigerant by the heat source-side expansion mechanism is increased more than before starting the pressure reduction control. For example, to send the refrigerant coming out of the heat source-side heat exchanger functioning as a radiator to the use-side unit without lowering the pressure as much as possible, the heat source-side expansion mechanism, which is in a fully open state before the pressure reduction control is started, reduces the opening degree in the pressure reduction control to lower the pressure of the refrigerant. By sending the refrigerant whose pressure is lowered in this way from the heat source-side unit to the use-side unit, the pressure of the refrigerant in the use-side unit drops quickly.

The refrigerant cycle apparatus according to a seventh aspect is the refrigerant cycle apparatus according to the sixth aspect. The heat source-side unit further includes a bypass route. The bypass route returns a part of the refrigerant discharged from the compressor and from which heat is radiated by the heat source-side heat exchanger to the compressor without going through the use-side unit. When the refrigerant leakage detection unit detects the leakage of the refrigerant, the control unit performs the pressure reduction control to lower the pressure of the refrigerant in the use-side unit and returns the refrigerant to the compressor by using the bypass route.

Here, in the pressure reduction control, by causing the refrigerant to flow through the bypass route of the heat source-side unit, the amount of refrigerant flowing from the heat source-side unit to the use-side unit is reduced. This quickly lowers the pressure of the refrigerant in the use-side unit.

The refrigerant cycle apparatus according to an eighth aspect is the refrigerant cycle apparatus according to any one of the first to seventh aspects. As the refrigerant, a single refrigerant of R32, R1234yf, R1234ze, or R744, or a mixed refrigerant including the refrigerant is used.

