Cascade refrigeration system with environment friendly refrigerants as R290 and ammonia

Abstract

Many industrial applications need low-temperature cooling which single-stage refrigeration systems are unable to produce efficiently due to specific limitations of refrigerants used. Therefore, a cascade refrigeration system is one of the paramount substitutes in such applications. This paper presents a simulation of a cascade refrigeration system with hydrocarbon refrigerant, R290 in a low-temperature circuit (LTC) and natural refrigerant, ammonia in a high-temperature circuit (HTC). Both the refrigerants in this refrigeration system have low GWP and zero ODP, hence, eco-friendly with the environment. The main thrust of this study is to determine various performance parameters of the cascade refrigeration system and carry out exergy analysis as well as parametric analysis of the system. In this simulation the cascade refrigeration system achieves low temperature as -30°C in low temperature evaporator and cooling capacity 15 kW with COP of 6.024. It is observed that the work of compressors in LTC and HTC are 2.49 kW and 11.21 kW respectively, whereas total work of the cascade system is 13.7 kW at these operating conditions. It is considered to utilise refrigerant gas discharge superheat for heating of water to enhance overall performance of the system. The parametric analysis of cascade refrigeration system involves parameters like evaporator temperature, condenser temperature, degree of superheat, sub-cooling after condenser and utilisation of degree of gas discharge superheat for heating of water to determine effect on the system performance.