Thermodynamic Performance Assessment of Ozone Layer Friendly Natural Refrigerants as Potential Substitutes to HCFC’s

Abstract

Abstract-Due to the environmental concerns related to ozone depletion potential (ODP) and global warming potential (GWP) of the existing refrigerants, industry and researchers in this field are investigating long-term solutions. With extensive work on alternatives to chlorofluorocarbons (CFCs) and hydro chlorofluorocarbons (HCFCs), initially hydro fluorocarbons were considered to be long-term solutions. The global warming of HFCs has become a hurdle to accept them as long-term solutions. Now, the focus is on the use of natural refrigerants like hydrocarbons (HCs) such as R290, R600, ammonia, carbon dioxide and water. These natural substances have very low GWP, and a zero ODP. This paper presents thermodynamic performance analysis of R22 and three of its alternatives natural refrigerants (R290, R600a and R717) for A/C and refrigeration purposes, through a simulation model. The investigation enables to confirm the possibility of using these natural refrigerants as a substitute to R22.Index Terms-Refrigerants, performance, ozone layer, friendly. I. INTRODUCTIONAs per the Montreal protocol, the Chloro fluorocarbons (CFC's) have already been phased out in the developed countries, while the hydro chloro fluorocarbons (HCFC''s) should also be phased out by 2017.During the last two decades, the number of refrigerants likely to be used in refrigerating machines has dramatically increased as a consequence of the elimination of these refrigerants.R22 (HCFC 22) is one of the important refrigerant used in air conditioning all over the world. R22 is controlled substance under the Montreal Protocol. It has to be totally phased out by 2017.HCF 22 replacements options for A/C, heat pumps and refrigeration systems can be grouped in three categories, Fluorocarbons that are used in conventional vapor compression cycles such as R134a, R410a, R407C, alternatives fluids which include propane R290 and R717 and are also used in vapor compression cycles, and finally alternatives cycles that include absorption systems, and use Tran critical fluids (CO 2 and R744) and air cycle. In general these alternative technologies do not currently offer the same energy efficiency as the vapor compression cycle.Several investigations have been carried out in order to One of the main important parameters in choosing new refrigerants, concerns the graph which represents a plot of the saturated vapour against the temperature. This is due to the operating conditions which require the knowledge of the maximal and minimal vapour pressures. Thus it is required to avoid refrigerants which exhibit very low vapour pressure (below atmospheric pressure) at low temperatures in order to avoid air infiltration., while low ratio of compression can be considered as a positive parameter, as it enables to increase the efficiency cycle by reducing the energy consumed by the compressor. A plot of the saturated vapour pressures against the temperatures for the R22 and its potential substitutes is shown in Fig. 1. It can be seen that R407c has nearly the same pattern as R22...