Two characteristics are provided by CO2 natural refrigerant:
High working pressure and high differential pressure.
These pressure levels are 4 to 10 times higher than with HFC refrigerants.
For this reason, the following factors must be taken into account in the development of CO2 compressors:
What Panasonic did to translate these factors into reality is to divide the compression of the CO2 refrigerant into two stages so that the inside of the shell is at the intermediate pressure, and the result was the world’s first rotary 2-stage compression CO2 compressor.
Resistant to high working pressure
The internal intermediate pressure structure makes it easy to design the shell.
Resistant to large pressure difference
The 2-stage compression makes it possible to disperse the differential pressure and compression load.
Compact size and light weight
The shell has thinner walls due to the internal intermediate pressure structure, and a compact concentrated winding motor is provided.
Minimized noise and vibration levels
Equalization of a torque on that of twin rotary compressor is achieved thanks to the compression mechanism’s 2-cylinder structure in which the two cylinders face each other at 180 degrees.
Just right for hot water heaters in cold climates
The internal intermediate pressure structure enables discharging at a higher temperature than with regular rotary compressors. Users can select the volume ratio (displacement volume ratio between the first and second stages) that suits the intended application, which makes the compressors just right for use in winter and for water heaters in cold climates.
The cooling performance is enhanced by exchanging the heat between the evaporator outlet pipe and gas cooler outlet pipe.
When the CO2 is compressed in the single stage, the discharge temperature reaches quite a high level. Since intermediate cooling is enabled by the rotary 2-stage compression mechanism, it is possible to reduce the discharge temperature significantly.
In this way, rotary 2-stage compression CO2 compressors can offer useful solutions even in the refrigeration and freezing fields where compressors have had a poor track record to date