Performance evaluation of an R134a automotive heat pump system for various heat sources in comparison with baseline heating system

Engine waste heat is commonly used for comfort heating and defogging windows of the passenger compartment of motor vehicles. However, the amount of waste heat to be used for these purposes decreases continuously as a result of increasing engine efficiencies. These requirements can also be met by employing an automotive heat pump (AHP) system. This study presents performance characteristics of an experimental AHP system employing an R134a vapour compression refrigeration circuit and driven by a diesel engine. The AHP system is capable of providing a conditioned air stream by utilizing the heat absorbed from any of the three sources, namely ambient air, engine coolant and exhaust gas. The steady-state and transient performance of the AHP system for each heat source was evaluated by applying energy and exergy analysis to the system based on experimental data. Then, a performance comparison of the AHP system with the three heat sources and baseline heating system was made. It was determined that the AHP system using engine coolant provided the highest indoor coil outlet air temperature during the tests until the steady-state was achieved compared with the AHP system using other heat sources as well as the baseline heating system.