(377t) Simulation and Thermodynamic Performance Evaluation of a Flash Tank Vapor Injection Refrigeration System Using Mixed Refrigerants

Refrigeration systems are used in several applications, such as: providing thermal comfort through air conditioning, supplying cold utilities to industrial applications, preserving food, beverages and pharmaceutical products, among others. However, these systems are large energy consumers and their operation must be optimized in order to reduce costs. Furthermore, an environmental issue must be taken into consideration, regarding the drop-in of ozone depleting refrigerants and fluids with high global warming potential, choosing more eco-friendly ones. This work presents a thermodynamic performance evaluation of a flash tank vapor injection refrigeration system using three different mixed refrigerants: R290/R600a, R290/R600 and R32/R152a. Steady-state simulations were performed in a process simulator to accomplish a parametric analysis considering the influence of the refrigerant composition and the expansion ratio of the upper-stage expansion valve, analyzing the following parameters: coefficient of performance (COP), refrigerant temperature glide at the evaporator and condenser, compression ratio, refrigerant mass flow rate, liquid and vapor composition of the flash tank outlet streams and vapor fraction at evaporator inlet. Considering the operating conditions studied, a maximum COP was obtained for the mixture R290/R600, with 50 wt% R290 and expansion ratio between 50% and 60%. The HFC mixture resulted in the worst values for COP for all conditions studied and was considered unfeasible for some evaluated conditions.