Study of a portable microclimate cooling system based on vapor compression refrigeration cycle

A man-portable microclimate cooling system for personal cooling in high temperature circumstances is developed to solve the heat stress problems for helicopter and armored vehicle crewmen. The system is based on a vapor compression refrigeration cycle and the refrigerant used is R134a. The dimensions of the system are 190 mm×190 mm×100 mm and the weight is only 2.75 kg. It can be powered by a lithium ion battery or with DC power supply. It utilizes a new miniature DC compressor and a miniature electronic expansion valve (EXV) which operates in a pulse width modulation mode. A miniature microchannel plate type evaporator is developed and an aluminum microchannel condenser is applied. By utilizing the above components of small scale and high efficiency, the whole system realize the miniaturization and practicality of vapor compression refrigeration systems. Experiments are carried out in both fixed and variable speed modes to investigate the effects of EXV duty cycle and refrigerant charge amount on the cooling performance. The results show that the system has a cooling capacity of 260 W under the ambient temperature of 45 °C and water temperature of 20 °C, which is sufficient for cooling one person under a high work load. And the cooling coefficient of performance (COP) reaches highest when the EXV operates at 45% of its duty cycle with a refrigerant charge amount of 120 g.