WATER HEATED HUMIDIFICATION-DEHUMIDIFICATION DESALINATION ACCOMPANYING AIR HEATING VIA EXIT BRINE

Abstract

The pure water shortage around the globe is worrying for human beings, therefore extraction of pure water from seawater is achieved through desalination technologies. Thermal desalination processes are many, but humidification-dehumidification (HDH) desalination is preferable because of its simplicity and usable for a small scale unit, and easily maintainable. The HDH is based on evaporation and condensation of water vapors in humidifier and dehumidifier, respectively with carrying gas like air. The energy is needed for two purposes: water vapor evaporation (the latent heat of evaporation) while another purpose is to increase the ability of air to carry away those vapors in the humidifier. The water-heated and air-heated system have higher water productivity than the bare water or air heated system alone.  Therefore, in this study, modeling and thermal analysis of a water-heated HDH system along with air pre-heating (before humidifier) was achieved by utilizing the brine heat energy. The model is based on thermodynamics principles, mass, and energy conservation laws. It was found that 3.6% of energy was recovered from brine and was utilized in heating the air before humidifier, which increased the inlet air temperature and hence enhanced the evaporation, and finally, condensation was increased and that was observed with 2.6% increase in the system productivity.