International Journal of Research in Engineering and Innovation Vol-1, Issue-2, (2017), 22-28 ____________________________________________________________________________________________________________________________ International Journal of Research in Engineering and Innovation (IJREI) journal home page: http://www.ijrei.com ISSN (Online): 2456-6934 ___________________________________________________________________________________ Corresponding Author: R.S. Mishra Email Id: rsmishra@dce.ac.in Thermal modelling of three stage vapour compression cascade refrigeration system using entropy generation principle for reducing global warming and ozone depletion using ecofriendly refrigerants for semen preservation R S Mishra Department of Mechanical, Production & Industrial and Automobiles Engineering Delhi Technological University Delhi E mail: rsmishra@dce.ac.in , rsmishra@dtu.ac.in __________________________________________________________________________________ Abstract This paper mainly deals with thermodynamic analysis of three stages cascade vapour compression refrigeration systems using ecofriendly refrigerants used for low temperature applications. The effect of thermal performance parameters (i.e. approaches, condenser temperature, and temperature variations in the evaporators) on the first law thermal performances COPSystem and also in terms of second law efficiency of the cascade system (exergetic efficiency) and System exergy destruction ratio (SEDR) have been optimized thermodynamically using entropy generation principle. The utility of R1234ze and R1234yf and in the high temperature circuits and new ecofriendly refrigerants in the intermediates circuits and R134a or R404a in the low temperature cascade circuit have been optimized. It was observed that in the low temperature (between- 50oC to -100oC) applications. It was observed that the best combination in terms of R1234ze-R134a- R404a gives better thermal performance than using R1234yf-R134a-R404a. Similarly other combination in terms of R1234ze-R134a-R404a gives better thermal performance than using R1234ze-R1234yf-R404a. © 2017 ijrei.com. All rights reserved Keywords: Three stages Cascade VCR, Energy-Exergy Analysis, and Thermodynamic Optimization __________________________________________________________________________________ 1. Introduction Low-temperature refrigeration systems are typically required for low temperature range from –40°C to –100°C for applications chemical, food, pharmaceutical, and other industries. For low temperature applications, single- stage/Double stages systems with reciprocating compressors are not feasible due to higher pressure ratios. High pressure ratio means high discharge and oil temperatures with low volumetric Compressor efficiencies which results low first law efficiency in terms of COP values. Vapor compression cascade refrigeration systems be used to achieve low temperatures applications in such a manner , where series of single-stage units are used that are thermally coupled through evaporator/condenser cascading. Each circuit has a different ecofriendly refrigerant suitable for that temperature. The high- temperature circuit uses high boiling point refrigerants such as R-1234ze, and R1234yf, R 717 and R152a and Intermediate circuit’s ecofriendly refrigerants such as R- 1234yf, R134a, R407c R125, etc. are used. Similarly for the low-temperature cascade circuit low boiling refrigerants are used. In a vapour compression cascade refrigeration system where low pressure vapour in the evaporator stage is compressed and then recycled for condensation in the evaporator of a previous stage, the improvement of passing the low pressure refrigerant’s vapour from an evaporator stage through a heat exchanger to heated vapour to ambient temperature, compressing said heated vapour, removing the compressor work by passing said compressed vapour through a evaporator, then cooling is by compressed