Experimental investigation of a heat pump-assisted solar humidification–dehumidification desalination system with a free-flow solar humidifier

Abstract

Global water scarcity is one of the biggest human concerns in recent decades. Seawater desalination becomes the dominant way to access the new drinkable waters. The present study developed a heat pump-assisted humidification–dehumidification water desalination system. The designed system is equipped with a novel solar humidifier that works based on the free-flow solar water collectors. The effect of air flow rate and mode of the air circulation system on the performance of the designed system was experimentally investigated. The results reveal that raising the air flow rate improved water evaporation rate and the solar humidifier efficiency, while closing the air circuit led to a reduction in the evaporation rate. The maximum evaporation amount and water productivity were around 1.38 and 1 kg/h/m2 in the average solar irradiance of 877 W/m2. The closed-loop air circulation system resulted in a significantly higher effectiveness of dehumidification and produced higher desalinated water compared with the open-circuit mode. The lowest specific electrical energy consumption and the highest gained output ratio values of, respectively, 0.15 kWh/kg and 2.36 were observed at the air flow rate of 0.019 m3/s/m2 of solar humidifier when closing the air circulation system.