Influence of Electronic Expansion Valve Opening on Performance of Constant-Temperature and -Humidity Cabinets

The regulation of the throttling device has an important impact on the performance of constant-temperature and humidity cabinets. Based on a constant-frequency refrigeration system, the effects of EEV (electronic expansion valve) opening from 10% to 30% on the evaporator superheat, compressor discharge temperature, evaporator fin temperature, and temperature and humidity in the cabinet under different target conditions were experimentally studied. When the opening of the electronic expansion valve is 15%-30%, the superheat (8-15 ℃) and discharge temperature can be guaranteed in safe and reasonable ranges. When the opening of the electronic expansion valve is below 20%, a bypass capillary tube is set for a safe compressor operation with liquid cooling in suction. Under the conditions of low temperature and humidity and high temperature and humidity, the larger opening reduces the temperature and humidity adjustment time by 10-20 min. Under the conditions of a low temperature and high humidity and a high temperature and low humidity, the larger opening causes energy consumption for additional humidity compensation or thermal compensation and prolongs the temperature and humidity adjustment time. Under different target conditions, the relative humidity and dry bulb temperature in the small opening (15%) cabinet are closer to the target temperature and humidity than those for the large opening (25%, 30%), and the temperature and humidity control accuracy is higher.