AN EFFECTIVE MASS TRANSFER APPROACH ON WASHER DRYER MACHINE

Drying technology for laundry has developed remarkably in the last twenty years. In line with customer demands, machines having both washing and drying functions, namely, washer-dryers have been developed due to drying space limitations in residences. The high energy consumption of heaters on washer-dryers is a major drawback that needs further development considering global trends towards improved energy ratings. Utilization of heat pumps could lower the energy consumption to some extent, while restricting the already limited space in the washer-dryers which makes drying and lint filtration even more challenging. It is for this reason that most washer-dryers in the market are produced with a resistance heater and condenser combination. In such machines, the heater is turned on and off based on the moisture content of the laundry estimated by an algorithm. The duration in which the resistance heater is on has a significant share on energy consumption. The existing air-water condensers in dryers usually have void inner structures where hot, moist air from the drum and cool tap water are in direct contact enabling condensation. Ineffective air-water contact leads to reduced condensation rate and increases the drying time, hence energy consumption. In this study, in an attempt to enhance heat and mass transfer which directly affect the energy consumption, extended surfaces are considered on the inner surface of the condenser. The effect of added structures on drying performance is numerically investigated. Convective heat and mass transfer coefficients with and without the extended surfaces are evaluated. The corresponding pressure drop is analyzed. The main objective of the study is to obtain an optimum condenser design that maximizes the heat and mass transfer coefficients while maintaining the water flow rate and air pressure drop at feasible levels in terms of fan power and lint blockage. In order to reach an optimum design without ruining air and water flow rates, the design parameters are determined iteratively.