Exergy analysis of a heat pump tumble dryer

As the market penetration of household tumble dryers increases, the legislation and the consumers are asking for higher energy efficiency and lower environmental impact. In this context, the heat pump has been recognized as an attractive technology which can lead to significant energy saving as compared to traditional electrically heated tumbler dryers. In this paper, exergy analysis is proposed as a tool to identify the losses in a heat pump tumble dryer, thus showing possibilities for performance improvements. The peculiarities of heat pump tumble dryers require an original approach to apply exergy analysis to the system. In fact, the process air flows through the drum and heat pump evaporator and condenser in a closed loop, and the air temperature lift in the condenser is particularly high. The developed method was applied to a specific appliance, considering also heat exchangers and compressor performances. Several refrigerants suitable for heat pump tumble dryers were analysed. The main exergy losses were identified in the compressor and in the drum for all the considered refrigerants, although the relative weight of each component loss was very much dependent on the specific fluid.