Analysis of Heat Pump Clothes Dryer

Abstract

Clothes dryers (CD) offer a rapid means to dry laundry in households, but consume a large portion (4%) of residential electricity. Heat pump clothes dryers (HPCD) can be much more energy-efficient than conventional electric CDs, but have not emerged in the U.S. market yet. In this study, experiments were conducted for a state-of-the-art commercial hybrid HPCD from the European market with two different operational modes followed by Department of Energy’s test procedure. The HPCD’s system performances were analyzed through measurements on humidity ratio (HR), temperature and power consumption for both Eco and Speed Modes. About 70% energy consumption reduction potential was observed as compared with a typical electric CD in the United States. The heating and cooling capacities during the Eco Mode were 1.48 kW and 1.18 kW, respectively, and the dehumidification rate was 0.372 g/s. The heat exchangers were modeled with CoilDesigner and their performances were simulated. The UA of the evaporator was mainly affected by the air flow rate (AFR), inlet air HR and refrigerant MFR while that of the condenser was mainly affected by the condensing temperature, AFR, and refrigerant MFR. The air leakage was estimated to be 24% to 45% in which the water vapor leakage was 26% and the energy loss was 5%. The mass transfer process through the drum was discussed and the mass transfer coefficient k between the cloth surface and air was calculated to be 0.237 g/m²·s. This study provides the performances of HPCDs and their design analysis, which can be used for developing improved HPCDs.