A Theoretical Thermodynamic Analysis of R1234yf/CO2 Cascade Refrigeration System

Abstract

The cascade refrigeration cycle is a multi-phase thermodynamic cycle that uses multiple refrigeration cycles combined with a heat exchanger to enhance the refrigeration effect. It uses one refrigerant to condense the other main refrigerant operating at the desired evaporator temperature. This method is usually used at a temperature of 243 to 193 K when small hydrocarbon gasses or other low-boiling gasses and vapor are cooled. This paper is devoted to examine energy and exergy characteristics of the CO2—R1234yf cascade refrigeration system to obtain a good thermodynamic and environment friendly alternative via creating a virtual refrigeration system in the EES software to substitute existing refrigerants having a higher GWP value. With GWP value approximately equal to 4, R1234yf take a promising place against refrigerants in use such as R134a, R404A, R410A etc. This paper reflects that for evaporator temperature of 253 K, condenser temperature of 303 K and cascade intermediate temperature of 268 K optimum results for COP, exergetic efficiency and total exergy losses are obtained. This study provides us with results of COP maximization and exergetic efficiency as well as total exergy losses minimization that help us to identify the optimum working conditions for the above stated cascade refrigeration system as well as providing us with a system that is much more environment friendly than the existing combination of refrigerants being used in cascade refrigeration systems.