Flat-plate heat exchangers are examined for use as dehumidifiers in humidification-dehumidification (HDH) desalination systems. The temperature and humidity ratio differences that drive mass transfer are considerably higher than in airconditioning systems, making current air-conditioning dehumidifier designs and design software ill-suited to HDH desalination applications. In this work a numerical dehumidifier model is developed and validated against experimental data. The model uses a logarithmic mass transfer driving force and an accurate Lewis number. The heat exchanger is subdivided into many cells for high accuracy. The Ackermann correction takes into account the effect of non-condensable gases on heat transfer during condensation. The influence of various heat exchanger design parameters is thoroughly investigated and suitable geometries are identified. Amongst others, the relationship between heat flow, pressure drop and heat transfer area is shown. The thermal resistance of the condensate layer is negligible for the investigated geometries and operating point.A particle embedded polymer as a flat-plate heat exchanger material for seawater operation substantially improves the heat flux relative to pure polymers and approaches the performance of titanium alloys. Thus, the use of particle embedded polymers is recommended. The dehumidifier model can be applied in design and optimization of HDH desalination systems.

The effects of material and design modifications on the temperature distribution of Li-ion cells are simulated numerically. A two-dimensional anisotropic cylindrical coordinate model with linear triangular finite elements is used to simulate the steady-state temperature distribution within the cell. The cell's material and geometry are changed. New cell materials are investigated for thermal performance: a negative electrode of variously-oriented carbon nanotubes, as well as separators made of Separion, of Al 2 O 3 containing Cr particles or of BeO containing Be and Si particles. The cell's diameter and length are varied. A new cell design with an internal cooling tube is proposed. The effect of cooling tube diameter upon cell temperature and the energy efficiency of cooling are investigated. This simple design change significantly improves the temperature distribution at marginal cost. Berechnung der Temperaturverteilung in konstruktiv veränderten

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.