Comparison of refrigerants R410a and R404a for use in low temperature applications: A computer model study

The motivation for this thesis is the need for efficient and environmentally friendly refrigerants in low temperature applications. This study provides a perspective for comparison of refrigerant R410a with R404a. As R410a is now widely used commercially, further knowledge is desired on how different an R410a system is from established refrigerant systems and any possibilities for retrofitting. This thesis uses a computer model simulation to specifically compare the performance of R410a and R404a in a supermarket freezer display case system designed for R404a with a standard capacity of 3.42 kW. The computer model is assembled from existing algorithms and correlations for heat transfer, pressure drop, and thermodynamics and run using Engineering Equation Solver (EES). The results are then compared with separate physical experimental results for this exact in-house laboratory refrigeration system. Complimenting the experimental results, the EES model simulates the refrigeration cycle for each refrigerant at four different settings of ambient air temperature into the condenser. The EES model results are compared in graphs and tables to the laboratory results. The model results also show that in this Hussman R404a display case system, R410a still operates more efficiently with a COP generally 0.16-0.19 greater than that of R404a. As expected, R410a operates at a higher compressor discharge pressure and temperature than R404a. After the EES model is verified by comparison to the experimental study, the model is used to predict refrigeration cycle behavior in the case of the heat exchanger component geometry being slightly altered