Research On Liquid Injection Device Application To R32Refrigeration System

Currently in China,60%of the refrigeration equipment use R22as the refrigerant.Since R22is forbidden in other countries, a majority of China-made equipmentcannot be exported. Although R404a, R410a and R407c can serve as substitutes forR22, all of them are expensive international patented product. Besides, new units needto be designed to match the substitute refrigerant in order to achieve the best results.These severely limit the development of China’s air-conditioning industry.R32is a potential substitute for R22. It is an environmentally friendly and highlysafe refrigerant that are not yet registered as patent. The refrigeration capacity of R32is better than that of R410a, and the amount needed is lower as well, about70%ofR410a. Therefore, R32may probably be the best choice for the future refrigerant.Despite the above mentioned advantages, R32does not perform well in the test ofthermo properties. Given the same working condition, the discharge temperature ofthe system using R32as refrigerant is20℃higher than that of the system usingR410a. Due to its high discharge temperature, the compressor with R32will probablybe damaged if used in a heat pump. This fact means that R32cannot be applied to theheat pump with the existing compressor. In order to expand the applied range of R32,the structure of compressor needs to be improved to reduce the discharge temperature.This paper analyses several methods frequently used to reduce the dischargetemperature of the compressor, including liquid injection, vapor injection, and wetsuction. Comprehensive analysis shows that liquid injection can maintain therefrigerating capacity and expand the range of temperature at which the compressoroperates. In addition, liquid injection device is of high material efficiency, low cost,and high reliability. Based on these advantages, liquid injection is chosen for thecompressor improvement.Extensive experiments have been done with the compressor calorimeter. The dataare presented in an operating envelope. It reflects that the range of temerpature forcompressor’s normal operation is greatly expanded when liquid injection device isapplied, about20%to30%higher. Therefore, liquid injection can be applied in heatpump system as an effective method to reduce the discharge temperature of thecompressor using R32as refrigerant.