Refrigeration and air-conditioning apparatus, refrigerant leakage detection device, and refrigerant leakage detection method

1. A refrigeration and air-conditioning apparatus including a refrigerant circuit formed by connecting a compressor, a condenser, an expansion valve, an evaporator, and a liquid reserve container to one another by pipes, the apparatus comprising:

a temperature sensor that measures a surface temperature of a surface of the liquid reserve container; and

a controller that varies a pressure or a temperature inside the liquid reserve container,

wherein the controller

varies the pressure or the temperature inside the liquid reserve container by stopping the compressor, controlling an opening degree of the expansion valve, or closing an opening and closing valve provided at the refrigerant circuit so that a temperature difference between a gas-phase portion inside the liquid reserve container and a liquid-phase portion inside the liquid reserve container occurs, and

detects a liquid level position inside the liquid reserve container, based on a measured value of the temperature sensor when the temperature difference occurs.

2. The refrigeration and air-conditioning apparatus of claim 1 , wherein the controller

stops the compressor to vary the pressure or the temperature inside the liquid reserve container.

3. The refrigeration and air-conditioning apparatus of claim 1 ,

wherein the refrigerant circuit includes the opening and closing valve, and

wherein the controller

closes the opening and closing valve to vary the pressure or the temperature inside the liquid reserve container.

4. The refrigeration and air-conditioning apparatus of claim 1 , wherein the controller

varies a frequency of the compressor by a predetermined value or more relative to a frequency set at a time other than a startup time to vary the pressure or the temperature inside the liquid reserve container.

5. The refrigeration and air-conditioning apparatus of claim 1 , wherein the controller

varies the opening degree of the expansion valve by a predetermined value or more relative to an opening degree set at a time other than a startup time to vary the pressure or the temperature inside the liquid reserve container.

6. The refrigeration and air-conditioning apparatus of claim 1 , further comprising:

an outdoor fan that supplies air to an outdoor heat exchanger functioning as the condenser or the evaporator,

wherein the controller

varies a frequency of the outdoor fan by a predetermined value or more relative to a frequency set at a time other than a startup time to vary the pressure or the temperature inside the liquid reserve container.

7. The refrigeration and air-conditioning apparatus of claim 1 , wherein the controller

detects refrigerant leakage by comparing, with an initial amount of refrigerant, a sum of an amount of refrigerant reserved in the liquid reserve container which is calculated based on the liquid level position and an amount of refrigerant in the refrigerant circuit other than the refrigerant reserved in the liquid reserve container.

8. The refrigeration and air-conditioning apparatus of claim 1 , wherein the controller

detects the liquid level position inside the liquid reserve container, based on a comparison between the measured value of the temperature sensor and a saturation temperature of a low-pressure side pressure.

9. The refrigeration and air-conditioning apparatus of claim 1 ,

wherein the temperature sensor, which includes a plurality of the temperature sensors, is installed in a direction vertical to a side face of the liquid reserve container, and

wherein the controller

detects the liquid level position inside the liquid reserve container, based on a comparison among the measured values of the plurality of temperature sensors.

10. A refrigerant leakage detection device for detecting a liquid level position inside a liquid reserve container provided as one of element devices of a refrigerant circuit to detect refrigerant leakage, the device comprising:

a temperature sensor that measures a surface temperature of a surface of the liquid reserve container; and

a controller configured to vary a pressure or a temperature inside the liquid reserve container,

wherein the controller

varies the pressure or the temperature inside the liquid reserve container by stopping the compressor provided at the refrigerant circuit, controlling an opening degree of an expansion valve provided at the refrigerant circuit, or closing an opening and closing valve provided at the refrigerant circuit so that a temperature difference between a gas-phase portion inside the liquid reserve container and a liquid-phase portion inside the liquid reserve container occurs,

detects the liquid level position inside the liquid reserve container, based on a measured value of the temperature sensor when the temperature difference occurs, and

detects refrigerant leakage by comparing, with an initial amount of refrigerant, a sum of an amount of refrigerant reserved in the liquid reserve container which is calculated based on the liquid level position and an amount of refrigerant in the refrigerant circuit other than the refrigerant reserved in the liquid reserve container.

11. A refrigerant leakage detection method for detecting a liquid level position inside a liquid reserve container provided as one of element devices of a refrigerant circuit, based on a temperature of the liquid reserve container, to detect refrigerant leakage, the method comprising:

controlling at least one of the compressor and the expansion valve, which are actuators, to vary a pressure or a temperature inside the liquid reserve container;

detecting the liquid level position inside the liquid reserve container, based on the temperature of the liquid reserve container; and

determining whether a refrigerant leaks from the refrigerant circuit by comparing, with a reference amount of refrigerant, a sum of an amount of refrigerant calculated from the temperature of the liquid reserve container and an amount of refrigerant reserved in the liquid reserve container.

12. The refrigeration and air-conditioning apparatus of claim 1 , wherein

the controller controls at least one of the compressor and the expansion valve, which are actuators, to vary the pressure or the temperature inside the liquid reserve container.

13. The refrigeration and air-conditioning apparatus of claim 1 , wherein

the controller controls driving of the actuators so as to generate the temperature difference between the gas-phase portion and the liquid-phase portion of the refrigerant within the liquid reserve container, to vary the pressure or the temperature inside the liquid reserve container.

14. The refrigeration and air-conditioning apparatus of claim 1 , wherein

an azeotropic refrigerant or a near-azeotropic refrigerant is filled in the refrigerant circuit.

15. A refrigeration and air-conditioning apparatus comprising:

a refrigerant circuit formed by connecting a compressor, a condenser, an expansion valve, an evaporator, and a liquid reserve container to one another by pipes;

a liquid level detection sensor that detects an amount of liquid refrigerant within the liquid reserve container; and

a refrigerant leakage detection device that determines whether there occurred refrigerant leakage from the refrigerant circuit by detecting an amount of liquid refrigerant within the liquid reserve container at a predetermined time after stop of the compressor by the liquid level detection sensor, and comparing a value obtained by the detection with a predetermined reference value.

16. The refrigeration and air-conditioning apparatus of claim 15 , varying an opening degree of the expansion valve after the stop of the compressor from an opening degree upon the stop of the compressor.

17. The refrigeration and air-conditioning apparatus of claim 15 , wherein the predetermined time is set to five minutes.

18. The refrigeration and air-conditioning apparatus of claim 15 , varying an internal pressure of the liquid reserve container after the stop of the compressor.

19. The refrigeration and air-conditioning apparatus of claim 15 , wherein

the liquid level detection sensor is constituted of a temperature sensor, and detects an amount of liquid refrigerant by measuring a surface temperature of the liquid reserve container.

20. A refrigerant leakage detection device configured to detect refrigerant leakage from a refrigerant circuit formed by connecting a compressor, a condenser, an expansion valve, an evaporator, and a liquid reserve container to one another by pipes, the refrigerant leakage detection device detecting an amount of liquid refrigerant within the liquid reserve container, and comprising a determining section configured to determine whether there occurred refrigerant leakage from the refrigerant circuit based on an amount of excessive liquid refrigerant at a predetermined time after stop of the compressor.

21. The refrigerant leakage detection device of claim 20 , further comprising an output unit configured to output the result of determination by the determining section.

22. A method for detecting refrigerant leakage from a refrigerant circuit formed by connecting a compressor, a condenser, an expansion valve, an evaporator, and a liquid reserve container to one another by pipes, the method comprising:

detecting an amount of liquid refrigerant within the liquid reserve container,

comparing the amount of excessive liquid refrigerant at a predetermined time after stop of the compressor with a predetermined reference value, and

determining that there occurred refrigerant leakage from the refrigerant circuit when the excessive amount of liquid refrigerant is smaller than the reference value.