This investigation focuses on the renewable geothermal energy source utilized as a reservoir for a water chiller unit in the cooling mode. Two hydrocarbon refrigerants, R290 and R600a were suggested to be implemented in a closed loop system to produce chilled water for air conditioning purposes. The traditional R-22 and its substitute R410A were also investigated in a direct expansion geothermal system. The analysis was carried out at the evaporation and condensation temperature ranges of (-25 to -5) °C and (15 to 35) °C respectively. The data showed that R-290 revealed similar coefficient of performance as that of R-22. R-410A exhibited a lower coefficient of performance than that of the R-22 refrigerant by (1-5) %. On the contrary, R-600a showed a higher coefficient of performance than that of the R-22 by about (3) % for the investigation range of operating conditions. R-410A refrigerant exhibited the highest load in comparison with R-22 among other circulated refrigerants by (1.5) %. R-600a showed a lower condenser load than that of the R-22 system by a negligible margin value. The hydrocarbon refrigerants and the azeotrop mixture were found to be proper candidates to replace R-22 in geothermal system.

geothermal energy source, refrigerant alternatives, hydrocarbon refrigerants, water chillers