Performance Analysis of Refrigerants R22 and R290 in Vapour Compression Refrigeration Systems Under Different Operating Conditions

A systematic thermodynamic performance analysis of natural refrigerant R290 (propane) and synthetic refrigerant R22 was performed in a standard vapour compression refrigeration cycle at evaporating temperatures ranging from −20◦C to +20◦C and condensing temperatures ranging from 30 to 45◦C. The following conclusions were drawn: 1.     The refrigerating effect of R290 is consistently 63– 82% larger than R22 throughout the entire operating range. This makes propane’s higher latent heat of vaporisation the defining characteristic of R290 and the reason for its lower mass flow rate and charge requirements. 2.     R290 requires approximately twice as much compressor work compared to R22 for the same temperature and sensitivity to the condensing temperature than those of R22. This highlights the crucial need for proper condenser sizing and ambient management when designing R290 systems. 3.     R290 has zero ozone depletion potential (ODP = 0) and a global warming potential (GWP) of 20, providing it with a clear environmental superiority over R22 (GWP = 1700, ODP = 0.055), and is fully in accordance with the international agreements set forth by the Montreal and Kyoto Protocols. 4.     The lower discharge temperature (≈ 11 K), lower pressure ratio, and lower refrigerant mass flow rate (43% less per TR) for R290 all contribute to reduced maintenance requirements and reduced refrigerant emission due to leakage. 5.     Although R290 requires multiple engineered safety features due to its A3 flammability classification, the existence of established standards, charge minimisation, and leak detection methods makes the commercial and residential refrigeration industry able to design safe R290 systems for the majority of applications.   In summary, R290 is strongly recommended as a drop-in and redesigned substitute for R22, especially in moderate-lift and air-conditioning applications. Where high-lift performance is paramount, targeted system design modifications for R290 will be necessary to fully realise its environmental and practical benefits.

[1]    United Nations Environment Programme, Montreal Protocol on Substances that Deplete the Ozone Layer, UNEP, Nairobi, 1987. [2]    United Nations Framework Convention on Climate Change, Kyoto Protocol to the United Nations Framework Convention on Climate Change, UNFCCC, Bonn, 1997. [3]    E. Granryd, “Hydrocarbons as refrigerants — an overview,” International Journal of Refrigeration, vol. 24, pp. 15–24, 2001. [4]    B. Palm, “Hydrocarbons as refrigerants in small heat pump and refrigeration systems — a review,” International Journal of Refrigeration, vol. 31, pp. 552–563, 2008. [5]    S. Devotta et al., “Performance assessment of HC-290 as a drop-in substitute to HCFC-22 in a window air conditioner,” International Journal of Refrigeration, vol. 28, pp. 594–604, 2005. [6]    B. Purkayastha and P.K. Bansal, “Experimental study on HC290 and a commercial liquified petroleum gas mix as suitable replacement for HCFC-22,” International Journal of Refrigeration, vol. 21, pp. 213–217, 1998. [7]    Y.S. Chang et al., “Performance and heat transfer characteristics of hydrocarbon refrigerants in a heat pump system,” International Journal of Refrigeration, vol. 23, pp. 232–242, 2000. [8]    G. Zhou et al., “Performance of a split type air conditioner matched with coiled adiabatic capillary tubes using HCFC-22 and HC-290,” Applied Energy, vol. 24, no. 4, pp. 870–885, 2010. [9]    E.W. Lemmon, M.L. Huber, and M.O. McLinden, NIST Standard Reference Database 23: REFPROP, Version 9.0, National Institute of Standards and Technology, Gaithersburg, 2010. [10] J.M. Calm, “Emissions and environmental impacts from air conditioning and refrigeration systems,” International Journal of Refrigeration, vol. 25, pp. 293–305, 2002.