Modeling and optimization of a desalination unit using humidification-dehumidification HDH principle

Abstract

Humidification-Dehumidification desalination ( HDH ) process is an existing, widely-spread and developing technology. This technology has high potential to serve people who suffer lack of water at undeveloped, poor countries as it could be built and operated using locally available natural resources.

HDH cycle is considered man-made rain cycle. It utilizes vaporization of water from saline solution into a carrier gas (usually air). Then this saturated air with water vapor passes over a cold surface, leading to condensation process obtaining fresh potable water suitable for human usage.

This work focuses on the heat and mass transfer processes inside each of the humidifier and the dehumidifier sections. In the humidifier process, counter flow between air and water at atmospheric pressure, where direct contact between air and water occurs. In the dehumidifier section, air flows over a coil containing flowing water in opposite direction. Based on mass balance and governing flow equations, the mathematical modeling equations of both humidifier and dehumidifier sections are established. Outputs were achieved through optimizing a matlab model with imbedded integration capabilities at different inlet conditions at both sub-cycle.

Output results of simulation process depend on liquid-gas ratio, entering temperature of air in addition to water temperature entering both sections as well as the height of both humidifier and dehumidifier. These design parameters can provide great reference significance for the design, optimization and regulation of humidifiers and dehumidifiers sections.