WASTE HEAT RECOVERY FROM TWO-STAGE VAPOUR COMPRESSION REFRIGERATION SYSTEM USING AN AUXILIARY CONDENSER

Abstract

One of the most important and much needed concerns shown by the researchers world over is related to energy. And there are several aspects related to energy on which researches are being focused e.g. optimal use of energy, new or renewable sources of energy and reuse or recovery of waste energy etc. The main motive of this work is to recover and use waste heat from a energy consuming system. The present study focuses on a simple thermodynamic analysis, heat transfer analysis, and exergy analysis of modified two stage vapour compression refrigeration system equipped with auxiliary condenser with various operating variables using R-717, R-134a, R-507a, R-152a, and R-1234yf as the refrigerants both ultra low GWP and zero ODP refrigerants in modified two stage vapour compression system. In the present work emphasis is on waste heat recovery from auxiliary condenser using water as a cooling fluid of a vapour compression refrigeration system utilized in air conditioning system or ice plants. The modified vapour compression system consists of a waste heat recovery device called auxiliary condenser. A mathematical computational model has been developed for calculating coefficient of performance (COP), exergetic efficiency, exergy destruction and efficiency defects to evaluate the performance of integrated vapour compression system. Throughout the process, condenser temperature is kept at 313K and 323K. Evaporator temperature is kept in the range from 233K to 255K. Results obtained for selected condenser temperature are compared and discussed elaborately. Among the system components, evaporator shows highest efficiency defect value and compresser shows the lowest. Thus, the effects of the pressure drop and fouling in the evaporator, condenser, auxiliary condenser is neglected. Results indicate that there is an increase in overall coefficient of performance and cooling capacity using an auxiliary condenser in two stage vapour compression refrigeration system. A comparison of between the properties of refrigerants R-717, R-507a, R-134a, R-152a and R-1234yf is also presented. The computational analysis has allowed the determination of the best energetic performance of the system. The analysis can represent a real system with a reasonable accuracy and is useful for future research work of whole system.