PERFORMANCE ANALYSIS OF A TWO STAGE VAPOUR COMPRESSION REFRIGERATION SYSTEM UTILIZING THE WASTE HEAT OF THE INTERCOOLER FOR WATER HEATING

Abstract

There is a growing concern on the availability and utilization of energy. Researchers and scientists are focusing on alternative sources of energy and maximum consumption of available energy which also incorporates recovery and use of waste energy. This work focuses on the aspect of use of waste energy in a multi-stage vapour compression system. There is a limitation to the evaporation temperatures in case of a single stage vapour compression refrigeration system. To overcome this limitation along with decreased throttle losses and higher system performance the need of multi-stage vapour compression system arises. In the present work a thermodynamic model for the multi-stage system having an intercooler with waste heat recovery and a flash chamber is developed. A computer program has been made in Engineering Equation Solver to evaluate the performance of a modified multi-stage vapour compression system (MMVCS) .The first and second law analysis is performed with R-717(Ammonia) as a refrigerant with the input parameters of evaporator temperature as -400 C and condenser temperature as 400 C . The first law efficiency (COP) that can be achieved is approx. 3.24 at a condenser temperature 303 K and evaporator temperature 233 K with effectiveness of intercooler as 0.95. It is also observed that evaporator is the most efficient component in the system as efficiency defect comes out to be least in evaporator whereas throttling valve (corresponding to the higher pressure compressor side) is the worst component followed by the throttling vale of LP side, condenser, compressor, water intercooler and flash chamber. Incorporation of heat recovery through the intercooler proved to be beneficial as the COP of the system is improved by 4-5 % with heat recovery of upto 20 kJ/s with very high tons of refrigeration chosen. The analysis can represent a real system where water can be heated through the heat extracted from the intercooler and it can be used for household purposes and other applications with a reasonable accuracy and is useful for future research work of the whole system.