Abstract
This study presents design specifications for a 20 kW refrigerant cycle for the thermal management system of urban air mobility. The secondary-loop whose operating liquid is water is applied to both the evaporator and condenser. The lightweight compressor by the high-speed operation is also applied. The design condition of the refrigerant cycle is based on the refrigerant cycle for vehicle air conditioners using refrigerant R134a. The coefficient of performance (COP) and the specific speed of the compressor are calculated according to various refrigerants, and U·A (total heat transfer coefficient·area) value of each evaporator and condenser side are calculated by the heat equilibrium equation. After reviewing various refrigerants applicable in the future, it was confirmed that R1233zd had an advantageous COP in cooling and heating conditions, and a high-speed centrifugal compressor of 100,000 rpm class can be applied to the R1233zd refrigerant cycle. In addition, the U·A values that determine the size of the heat exchanger are 0.62 kW/K for the evaporator and 1.43 kW/K for the condenser.
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