Experimental evaluation of some proposed R22 alternatives in chillers and unitary A/C equipment

Tests were conducted on two instrumented air-cooled water chillers (15 kW and 30 kW cooling capacity). Refrigerants evaluated included R22 as the baseline fluid, R407C and R410B. When testing with R407C, the retrofit procedure did not involve any major hardware change. The results with the first chiller equipped with a counter-current plate evaporator showed that both capacity and EER are maintained within 5%. The second chiller, which was not equipped with a counter-current evaporator showed poorer results. Capacity and EER were reduced by about 13% and 10%, respectively, as overall heat transfer coefficients were degraded by as much as 30% in the evaporator and about 10% in the condenser. With R410B, two different compressors with reduced displacement were used in the second chiller in order to normalise the cooling capacity to R22 levels and the thermostatic expansion valve was modified. No modification was brought to the heat exchangers. With a properly sized compressor, capacity was maintained at R22 levels, whilst EER was reduced by about 10%. Despite increased compressor isentropic efficiencies, a significant performance degradation was noticed for R410B at higher ambient temperatures, which limits its application when using air as the condensing medium. Cooling and heating tests conducted on a reversible room air conditioner (6 kW cooling capacity) with R22 and R407C and two compressors of equal size and of the same type have shown that capacity and EER with R407C are maintained, with only a marginal degradation in capacity (-4%) and EER (-2%); in the heating mode without frost formation, capacity and efficiency were maintained with R407C ( 1 %, and a maximum 5% degradation in efficiency); under frosting conditions heating duties were improved for R407C (+18%).