Assessment of exergy efficiency and Sustainability Index of an air?water heat pump

This study is undertaken to predict the second law performance of an air/water heat pump. Through energy and exergy analyses, analytical expressions are derived for the Coefficient of Performance (COP) and Exergy Efficiency (ηexe). The system is analysed to predict how the mass flow rate of R-134a, condensation and evaporation temperatures influence the system performance at various operating conditions. The results indicate that a higher COP and ηexe may arise when increasing the mass flow rate of the refrigerant, increasing the evaporation temperature, or lowering the condensation temperature. Additional results are presented for the optimum performance of the system.