Theoretical investigation of using a direct contact dehumidifier in humidification–dehumidification desalination unit based on an open air cycle

In the present work, a kind of direct contact dehumidification process used in humidification–dehumidification system is introduced instead of using the conventional indirect condensers. In the purposed system, air is dehumidified by spraying cold water into the hot and humid air stream. The freshwater production, efficiency and effects of various parameters including air flow rate, conditions of inlet cold and hot water and velocity and diameter of droplets on the performance of the system are investigated. Results showed that increasing initial velocity and diameter of water droplets decreases water production. Furthermore, it has been demonstrated that increasing the flow rate and temperature of hot water and reducing the flow rate and temperature of cold water will increase freshwater production and the efficiency. It is found that increasing air flow rate has negative effect on production and energy consumption of the system. Direct contact dehumidifier has a good potential in desalination of seawater which can resolve many operational problems of indirect condensers like: corrosion, salt water leakage, and hydraulic pressure drop.