AIRFLOW MALDISTRIBUTION EFFECTS ON MEMBRANE-TYPE TOTAL HEAT EXCHANGER PERFORMANCE

Membrane-type total heat exchanger (THX) is often used to reduce the building energy consumption associated with forced ventilation by recovering both heat and moisture from the exhaust indoor air to treat the supply outdoor air. It has a core made of a water vapor permeable membrane that transfers both heat and moisture. Because of the possible channel spacing nonuniformity and some external disturbances, airflow maldistribution may occur in the core when a THX operates, which may affect the THX performance. In this research, a theoretical model for simulating the coupled heat and moisture transfer in the core of a THX is presented, and the effects of the airflow distributions on the THX performance are investigated. Calculations are conducted for two supply outdoor air entering velocity distributions including the linear and parabolic distributions and for different supply outdoor air temperatures and humidities. The results show that the supply outdoor air entering velocity distribution affects the effectiveness performance of THX, with the linear distribution yielding a more significant effect than the parabolic distribution; such distribution also affects the contours of the heat and moisture fluxes across membrane, with the heat flux contours associating more with the sensible effectiveness while the mass flux contours associating more with the latent effectiveness.