Journal Press India^®

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In the present study, the effects of variation in evaporator and condenser temperatures on first and second law efficiency of the cascade system using NH3/CO2 (Ammonia-Carbon dioxide) and C3H6 /CO2 (Propylene -Carbon dioxide) pairs have been carried out. The optimum temperature in cascade condenser temperature corresponding to maximum exergetic efficiency is also determined under for these conditions. It is observed that maximum COP and maximum exergetic efficiency occur at the same cascade condenser temperature. It is observed that optimum cascade temperature increases with increase in evaporator temperature, condenser temperature and approach in cascade condenser. The optimum temperature in cascade condenser for C3H6/CO2 pair is higher than that for NH3/CO2 pair. NH3/CO2 pair offers better exergetic efficiencies at optimum cascade condenser temperature than C3H6/CO2 pair. This also means that overall exergy destruction in NH3/CO2 pair is less than C3H6/CO2 pair.

Keywords

Cascade Refrigeration System; Exergy; Optimum Temperature in Cascade Condenser; Natural Refrigerants; NH3/CO2; C3H6 /CO2

1. Gupta V. K. Numerical optimization of multi-stage cascaded refrigeration-heat pump system.Heat Recovery Systems 1985; 5(4): 305-319.


2. Kanoğlu M. Exergy analysis of multistage cascade refrigeration cycle used for natural gas liquefaction. International Journal of Energy Research 2002; 26: 763–774.


3. Ratts E.B. and Brown J. S. A generalized analysis for cascading single fluid vapour compression refrigeration cycles using an entropy generation minimization method. International Journal of Refrigeration 2000; 23: 353-365.


4. Agnew B. and Ameli S.M. A finite time analysis of a cascade refrigeration system using alternative refrigerants. Applied Thermal Engineering 2004; 24: 2557–2565.


5. Nicola G. D., Giuliani, G. , Polonara, F. and Stryjek, R. Blends of carbon dioxide and HFCs as working fluids for the low-temperature circuit in cascade refrigerating systems. International Journal of Refrigeration 2005; 28: 130–140.


6. Bhattacharyya, S., Mukhopadhyay, S., Kumar A., Khurana R.K. and Sarkar J. Optimization of a CO2/C3H8 cascade system for refrigeration and heating. International Journal of Refrigeration 2005; 28: 1284-1292.


7. Lee T. S., Liu C. H. and Chen T.W. Thermodynamic analysis of optimal condensing temperature of cascade-condenser in CO2/NH3 cascade refrigeration systems. International Journal of Refrigeration 2006; 29:1100-1108.


8. Kruse, H. and Rüssmann, H. The natural fluid nitrous oxide-an option as substitute for low temperature synthetic refrigerants. International Journal of Refrigeration 2006; 29: 799-806.


9. Niu, B. and Zhang, Y. Experimental study of the refrigeration cycle performance for theR744/R290 mixtures. International Journal of Refrigeration 2007; 30: 37-42.


10. Getu, H.M., Bansal P.K. Thermodynamic analysis of an R744/R717 cascade refrigeration system. International Journal of Refrigeration 2008; 31(1): 45-54.


11. Bhattacharyya, S., Bose, S. and Sarkar, J. Exergy maximization of cascade refrigeration cycles and its numerical verification for a transcritical CO2/C3H8 system. International Journal of Refrigeration 2007; 30: 624-632.


12. Bansal, P. K. and Jain, S., Cascade systems: past, present, and future. ASHRAE Transactions 2007; 113(1): 245-252.


13. Dopazo J. A, Fernández-Seara J, Sieres J., Uhía F. J. Theoretical analysis of a CO2–NH3 cascade refrigeration system for cooling applications at low temperatures. Applied Thermal Engineering 2009; 29(8-9):1577-1583.


14. Dincer, I. Refrigeration Systems and Applications. 2003.Wiley, UK, 26.


15. Sözen A. Effect of heat exchangers on performance of absorption refrigeration systems. Energy Conversion Management 2001; 42:1699–1716.


16. Bejan, A., Tsatsaronis, G., Moran, M.Thermal Design and Optimization. John Wiley and Sons 1996, USA, pp. 143-156.


17. Said S.A. and Ismail B. Exergetic assessment of the coolants HCFC123, HFC134a, CFC11and CFC12. Energy 1994; 19(11):1181-1186.


18. Kotas, T.J. The Exergy Method of Thermal Plant Analysis. 1985, Butterworths, London.


19. Klein, S.A. and Alvarado, F. (2005) Engineering Equation Solver, Version 7.441, F ChartSoftware, Middleton, WI.