Heat Exchanger Design for Two-Stage HDH Desalination Unit

Based on the thermal water cycle principle, a two-stage humidification-dehumidification (HDH) desalination cycle has been developed for producing the maximum water output. In the two-stage HDH cycle, a heat exchanger (condenser) plays a major role because it transfers maximum heat, as well as condensation, between the working fluids. This work aims to design a heat exchanger for a two-stage HDH cycle with the heating and humidification process. So in this cycle, the heat exchanger is used as a two-stage air preheater and a dehumidifier to improve the desalinated yield with the optimum area and performance index. In a two-stage plant, the humidifier and air preheater use hot water. For more desalination yield, the first-stage dehumidifier uses chilled water, and an air-cooled evaporator in the VCR is used as a second-stage dehumidifier. So airflow rate, transverse pitch and tube diameter are selected as parameters to optimise the objectives. At 100 kg/h of airflow rate, the second-stage dehumidifier yields 7.62 LPH of freshwater, whereas the first-stage dehumidifier yields only 0.22 LPH of freshwater. The obtained trend demonstrates that high desalinated water production is feasible with optimal heat exchanger area and performance.