Refrigerant selection for a heat pump tumble dryer

A heat pump system for a tumble dryer can be an energy efficient alternative that also avoids emissions of dump air from the drying equipment. In this system load is dried by closed loop circulating air, treated in the heat pump. The refrigeration capacity of the heat pump is used to dehumidify moistened air while the heating capacity is used to reheat the cooled dry air. The critical decision for such a system is selection of a proper refrigerant that would be environmentally sound, provide optimal operational conditions and make the product more attractive for customers. Selection presented in the paper includes refrigerants that can be used in a standard subcritical cycle as well as carbon dioxide (CO2), with the trans-critical cycle, in which high refrigerant temperature at the gas cooler inlet represents an advantage in a tumble dryer. The paper presents cycle simulations of a heat pump tumble dryer operating with different refrigerants along with heat exchangers characteristics. Preliminary data from laboratory measurements of a heat pump dryer are also presented and discussed.