Design of Plate-Fin Tube Dehumidifiers for Humidification-Dehumidification Desalination Systems

A two-dimensional numerical model of a plate-fin tube heat exchanger for use as a dehumidifier in a humidification-dehumidification (HDH) desalination systems is developed, because typical heating, ventilating, and air conditioning (HVAC) dehumidifier models and plate-fin tube dehumidifier geometries are not intended for the considerably higher temperature and humidity ratio differences which drive heat and mass transfer in HDH desalination applications. The experimentally validated model is used to investigate the influence of various heat exchanger design parameters. Potential improvements on common plate-fin tube dehumidifier designs are identified by examining various methods of optimizing tube diameter, and longitudinal and transverse tube spacing to achieve maximum heat flow for a given quantity of fin material at a typical HDH operating point. Thicker fins are recommended than for HVAC geometries, as the thermal conductive resistance of HVAC fins restricts dehumidifier performance under HDH operating conditions.Elisabeth Meurer FoundationKarl H. Ditze FoundationGerman Academic Exchange ServiceCenter for Clean Water and Clean Energy at MIT and KFUP