The research group led by Ri Ju Hyok, a section head at the Faculty of Heat Engineering, has succeeded in designing and manufacturing a cascade cryogenic refrigerator for new material development and cryogenic environmental experiment.
Operated by the cascade refrigeration cycle, it is composed of two refrigeration cycles ― hot cycle and cold cycle. In the hot cycle, middle refrigerants are used, and in the cold cycle, low refrigerants are used. Each cycle is an individual refrigeration system using one refrigerant each.
Evaporation of the refrigerant in the hot cycle is used for condensation of the refrigerant in the cold cycle. The two cycles are connected by an evaporator-condenser that functions as a condenser for the cold cycle and as an evaporator for the hot cycle. The heat gained from the cold cycle is transferred to the refrigerant in the hot cycle that transfers the heat to the environment. The hot cycle is composed of a hot cycle compressor, an air cooling condenser, a throttle valve and an evaporator-condenser, etc. while the cold cycle is made up of a cold cycle compressor, a capillary tube, an evaporator, an expansion vessel, an evaporator-condenser, etc.
An evaporator-condenser can be designed and manufactured as a high efficiency plate or a dual tube heat exchanger.
This cascade cryogenic refrigerator, which provides a temperature range of -40℃~-160℃, has wide applicability to several fields including machine, chemical and electronic industries, biological and metallic material engineering, public health, national defence and sports.
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