Process simulation and analysis of a closed-loop heat pump clothes dryer

Clothes dryers play an important role in modern daily life which consumes a lot of residential electricity. The closed-loop heat pump clothes dryer is a typical energy-saving application in heat pump drying. To predict and analyze both electricity consumption and drying time, a quasi-steady-state model of the closed-loop heat pump dryer was developed, which consists of a dynamic fabric drying model and a steady-state heat pump system model. Simulation results reached a good agreement with test data of a household heat pump clothes dryer. The error of drying time is within 3 min and that of electricity consumption is -2.3%. Based on the model, the effects of compressor size, area ratio of the evaporator to total, circulating air flow rate, condensing temperature upper bound, and refrigerant charge on specific moisture extraction rate (SMER) and drying time were analyzed. Moreover, comprehensive optimization was performed using response surface method with the Box-Behnken design. The SMER of the redesigned clothes dryer is 2.92 kg/kWh, showing an increase of 5.8%, and the drying time is 129 min, showing a decrease of 14.6% compared with the original design.