Refrigeration cycle device
A refrigeration cycle apparatus in which working refrigerant is a zeotropic refrigerant mixture containing at least a first refrigerant and a second refrigerant having a higher boiling point than the first refrigerant at the same pressure, the refrigeration cycle apparatus including at least a main passage in which a compressor, a first heat exchanger, a first expansion valve, and a second heat exchanger are sequentially connected, the first refrigerant having a property of disproportionation, the first refrigerant having a smaller composition ratio in the compressor than a composition ratio of the first refrigerant passing through the main passage.
1. A refrigeration cycle apparatus, comprising:
a main passage in which a compressor, a first heat exchanger, a first expansion valve, and a second heat exchanger are sequentially connected operating with a working refrigerant being a zeotropic refrigerant mixture containing at least a first refrigerant and a second refrigerant having a higher boiling point than the first refrigerant at a same pressure, the first refrigerant having a property of disproportionation;
a second expansion valve disposed in series with the first expansion valve between the first heat exchanger and the second heat exchanger on the main passage;
a pressure sensor disposed between the first expansion valve and the second expansion valve configured to detect a pressure of the refrigerant; and
a controller configured to control the refrigeration cycle apparatus, wherein
the main passage includes an oil separator connected between the compressor and the first heat exchanger and configured to separate the zeotropic refrigerant mixture containing the first refrigerant at a composition ratio of the refrigerant mixture, the composition ratio being lower than a composition ratio of the first refrigerant in the zeotropic refrigerant mixture passing through the main passage,
the zeotropic refrigerant mixture having the lower composition ratio of the first refrigerant and separated by the oil separator being supplied into the compressor from the oil separator through a bypass, and
the controller is configured to
control an opening degree of the second expansion valve such that a pressure in a refrigerant pipe between the first expansion valve and the second expansion valve detected by the pressure sensor is a predetermined target pressure value so as to decrease the composition ratio of the first refrigerant in the main passage, and
control an opening degree of the first expansion valve independently from the control of the opening degree of the second expansion valve.
2. The refrigeration cycle apparatus of claim 1 , wherein the bypass has a bypass expansion device having an adjustable opening degree.
3. The refrigeration cycle apparatus of claim 2 , wherein the opening degree of the bypass expansion device is maximized at a start of the compressor.
4. The refrigeration cycle apparatus of claim 2 , wherein the controller is configured to control the opening degree of the bypass expansion device to increase with a discharging temperature or a discharging pressure of the compressor.
5. The refrigeration cycle apparatus of claim 1 , wherein the bypass is connected to a suction pipe of the compressor.
6. The refrigeration cycle apparatus of claim 1 , wherein the first refrigerant is HFO1123 and the second refrigerant contains at least one of R32, HFO1234yf, and HFO1234ze.
7. The refrigeration cycle apparatus of claim 1 , wherein the controller is configured to control the opening degree of the second expansion valve such that the refrigerant between the first expansion valve and the second expansion valve has a predetermined saturation temperature.