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Panasonic has developed the world's first CO2 rotary 2-stage compression compressor that uses the CO2 found in the natural world as a refrigerant and is therefore eco-friendly, and it is now offering these compressors on the market.
Two characteristics are yielded 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.
The figure above shows the structure of Panasonic rotary 2-stage compressor and flow of the refrigerant through the compressor.
The low-pressure suction gas is introduced into the first-stage compression mechanism at the bottom where it is compressed to the intermediate pressure, after which it is discharged inside the shell. The gas is then introduced through the pipe outside the shell into the second-stage compression mechanism at the top, where it is further compressed, after which it is discharged to the refrigeration cycle.
When the transcritical CO2 refrigeration cycle is applied in refrigerator and freezer equipment, the theoretical efficiency (COP) is said to be generally lower than that of HFC. An effective way to offset this is to employ: 1) an internal heat exchanger, and 2) an intermediate cooler.
§ Internal heat exchanger
The cooling performance is enhanced by exchanging the heat between the evaporator outlet pipe and gas cooler outlet pipe.
§ Intermediate cooling
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.
Panasonic has developed a multipurpose CO2 Gas Cooling Unit that is applicable for self contained light commercial refrigerators and/or freezers.
|Application||Low (LT) and Medium (MT) Temperature refrigeration unit|
|Rated Output||400 / 650 / 900W|
|Voltage||230V (Frequency: 50Hz)|
|Applicable ambient temperature||15 ∼ 30C|
|Evaporating Temperature of LT use||-35 ∼ -20C|
|Evaporating Temperature of MT use||-25 ∼ -5C|