Performance enhancement of a humidification–dehumidification seawater desalination system

Abstract

Performance evaluation of a humidification–dehumidifcation desalination system using three modified cycles (heat recovery, fins, and heat recovery combined with fins) is investigated and discussed. In the heat recovery cycle, a portion of the hot condensing water in the dehumidifier replaces the water evaporated in the humidifier. In the fins cycle, the fins are fixed between the humidifier and dehumidifier to precool the hot air coming out of the humidifier in order to improve the system performance. The impact of various operating parameters such as water temperature, mass flow rate ratio, and cooling water flow rate on the productivity, gain output ratio, recovery ratio and exergetic efficiency is evaluated. The results indicate that increasing the mass flow rate ratio, water temperature, and cooling water flow rate increases significantly the productivity. Compared with the conventional cycle, at a water temperature of 50 °C, the fins cycle increases the productivity, gain output ratio, recovery ratio, and exergetic efficiency by an average of 18%, 12.3%, 13.7% and 15.9%, respectively. Further, the heat recovery cycle increases the gain output ratio and exergetic efficiency at a water temperature of 50 °C by an average of 2.5% and 7.5%, respectively, while it has no effect on the productivity and recovery ratio. The estimated cost of fresh water production for the conventional cycle, heat recovery cycle, fins cycle, and heat recovery combined with fins cycle is about 0.094 $ per L, 0.087 $ per L, 0.072 $ per L, and 0.066 $ per L, respectively.