Non-azeotropic refrigerant charge optimization for cold storage unit based on year-round performance evaluation

This investigation aims at estimating a precise range of non-azeotropic refrigerant charge for medium temperature cooling application through performance test. A sample of cold storage unit originally charged R404A is slightly modified without changing the unit structure and components but adding a parallel thermal expansion valve for charging R407A and R407F. Charging tests are operated on the sample under 4 typical work conditions from high to low ambient temperatures to conduct annual performance evaluation with both unit performance and operation safety considered at the same time. Collecting performance parameters including CC, EER and PI, considering the feedback of sub-cooling degree, super-heating degree and DT and calculating the weight of these 4 working conditions in year-round operation contribute to the concluding recommended range of refrigerant charge and refrigerant mass range in liquid reservoir in cold storage unit charged R404A, R407A and R407F respectively.