**ABSTRACT**

The aim of this study is to investigate the effect of low global warming potential refrigerants on the optimum intermediate pressure (POPT'int) and performance (COP) values of a refrigeration system with flash intercooling. For realize, the optimum operating parameters of system were determined in low temperature applications (LTAs) through a theoretical analysis according to the different refrigerants (R290, R404A, R407C, R50A and R22). The theoretical modeling of system is done by optimizing the intermediate pressure at given evaporation (TE) and condensation (TC) temperatures for selected refrigerants. After optimization, the maximized values of COP and second law efficiency are computed from the predicted values of POPT'int. The linear regression method is then used to derive three correlations of POPT'int, maximum values of COP and second law efficiency according to TE and TC. Hence, the POPT'int values maximizing the system performance are found from various TE and TC values for each refrigerant. Due to calculations, increasing TE and TC cause the increase in POPT'int in LTAs. R507A system has the highest POPT'int values and R22 system has the lowest POPT'int values. Although R22 system has slightly more efficient than R290 system, it is being phased out worldwide because of the risk of ODP and GWP considerations. Therefore, it is important to evaluate the R22 replacement options. R290 was discovered to have better performance than the R404A, R407C and R507A systems in terms of COPmax (1.81), GWP (11) and ODP (0) when TE and TC are -35ºC and 40ºC.

**KEYWORDS**

PAPER SUBMITTED: 2018-09-21

PAPER REVISED: 2018-12-11

PAPER ACCEPTED: 2018-12-12

PUBLISHED ONLINE: 2019-01-13

- Torrella, E., Llopis, R., Cabello, R., Experimental Evaluation of The Inter-Stage Conditions of a Two-Stage Refrigeration Cycle Using a Compound Compressor, International Journal of Refrigeration, 32 (2009), 2, 307-315.
- Gupta, V., K., Prasad, M., Graphic Estimation of Design Parameters for Two-Stage Ammonia Refrigerating Systems Parametrically Optimized, Mechanical Engineering Bulletin, Vol: 15, No.4, (1984), 100-104.
- Zubair, S., M., Khan, S., H., On Optimum Interstage Pressure for Two-Stage And Mechanical Subcooling Vapour Compression Refrigeration Cycles, ASME Trans., Journal of Solar Energy Engineering, Vol:117, No: 1, (1995), 64-66.
- Tiedeman, J. S., Sherif, S.A., Optimum Coefficient of Performance and Exergetic Efficiency of a Two-Stage Vapour Compression Refrigeration System, Proceedings of the Institution of Mechanical Engineers., Vol: 217, Part C., (2003), 1027-1037.
- Mbarek, W. H. Tahar, K., Ammar, B., B., Energy Efficiencies of Three Configurations of Two-Stage Vapor Compression Refrigeration Systems, Arab J Sci Eng, Vol. 4, (2016), pp. 2465-2477.
- Jiang, S., Wang, S., Jin, X., Yu, Y., The Role of Optimum Intermediate Pressure in the Design of Two-Stage Vapor Compression Systems: a Further Investigation, Int J Refrig, 70 (2016), pp. 57-70.
- Yuan, M., G., Xia, Z., H., Experimental Study of Heat Pump System with Flash Tank Coupled With Scroll Compressor. Energ Buildings, 40 (2008), pp. 697-701.
- Arora, C., P., Dhar, P., L., Optimization of Multi-Stage Refrigerant Compressors. Proceedings, 13th Int. Congress of Refrigeration, Paris, France, 1971, Vol. 2, pp. 693-700.
- Lee T. S., Liu, C., H., Chen, T. W., Thermodynamic Analysis of Optimal Condensing Temperature of Cascade-Condenser in CO2/NH3 Cascade Refrigeration Systems, Int J Refrig, 29 (2006), 7, pp. 1100-1108.
- Dopazo, J.A., Seara, J. F., Sieres, J., Uhia, F.J., Theoretical Analysis of a CO2-NH3 Cascade Refrigeration System for Cooling Applications at Low Temperatures, Appl Therm Eng., 29 (2009), 8-9, pp. 1577-1583.
- Getu, H., Bansal, P., Thermodynamic Analysis of an R744-R717 Cascade Refrigeration System, Int J Refrig, 31 (2008), 1, pp. 45-54.
- Yilmaz, B., Erdönmez N., Sevindir M., Mancuhan E., Thermodynamic Analysis and Optimization of Cascade Condensing Temperature of a CO2 (R744)/404A Cascade Refrigeration System, Proceedings, 15th Int. Refrigeration and Air Conditioning Conference, Purdue, USA, 2014, 2598, pp.1-10.
- Kilicarslan, A., Hosoz, M., Energy and Irreversibility Analysis of a Cascade Refrigeration System for Various Refrigerant Couples, Energ Convers Manage, 51 (2010), 12, pp. 2947-2954.
- Dokandari, D.A., Hagh, A.S., Mahmoudi, S.M.S., Thermodynamic Investigation and Optimization of Novel Ejector-Expansion CO2/NH3 Cascade Refrigeration Cycles (Novel CO2/NH3 Cycle). Int J Refrig, 46 (2014), pp. 26-36.
- Yilmaz, B., Mancuhan, E., Erdonmez, N., A Parametric Study on a Subcritical CO2/NH3 Cascade Refrigeration for Low Temperature Applications, ASME J. Energy Resour. Technol., 140 (2018), 092004- pp. 1-7.
- Spatz, M.W., Motta, Yana, S., An Evaluation of Options for Replacing HCFC-22 in Medium Temperature Refrigeration Systems, Int J Refrig, 27 (2004), pp. 475-483.
- Llopis , R., Torrella, E., Cabello, R., Sanchez, D., Performance Evaluation of R404A and R507A Refrigerant Mixtures in an Experimental Double-Stage Vapour Compression Plant, Appl Energ, 87 (2010), 5, pp. 1546-1553
- Pansulla, A., Allgood, C., Multi-Year Evaluation of R-449A as a Replacement for R-22 in Low Temperature and Medium Temperature Refrigeration Applications, Proceedings, 16th Int. Refrigeration and Air Conditioning Conference, Purdue, USA, 2016, 2450, pp.1-10.
- Cengel, Y., A., Boles, M., A., Thermodynamics: An Engineering Approach, McGraw-Hill, Singapore, 2007
- EES., 2017, Engineering Equation Solver, Academic Commercial, V10.326, fChart Software Inc.
- ANSI/ASHRAE Standard 34, Designation and Safety Classification of Refrigerants, 2016
- IPCC. Climate Change 2013: The Physical Science Basis, Cambridge University Press, Cambridge, United Kingdom and New York, USA, 2013.
- Quadha, A., En-nacer, M., Adjlout, L., Imine, O., Exergy analysis of a two-stage refrigeration cycle using two natural substitutes of HCFC22, Int. J. Exergy, 2,1 (2005), pp. 14-28.