Performance analysis of a direct contact humidifier of a humidification-dehumidification desalination system: A heat and mass transfer

In humidification-dehumidification water desalination (HDHWD) systems, the direct contact heat exchanger serves as a crucial component that significantly affects the efficiency of converting saline or brackish water into fresh water. This research focuses on the development of a numerical model to simulate heat and mass transfer processes occurring
between hot sprayed seawater and air within a direct-contact humidifier. The model was employed to examine the influence of various operational parameters, including the inlet temperature of seawater, seawater mass flow rate, inlet air temperature, and air mass flow rate, on the humidifier’s effectiveness and the rate of freshwater evaporation. The results
demonstrate that the optimal humidifier effectiveness is attained when the mass flow rate ratio of seawater to air is unity. Additionally, the inlet temperature of seawater and the mass flow rate ratio between seawater and air emerged as the most critical factors governing the humidifier's freshwater production capacity. The maximum value of water evaporation is 341kg/hr that occurs at operating conditions of inlet seawater temperature of 90℃, inlet air temperature of 30℃, inlet air relative humidity of 50%, and seawater to air mass ratio of 5. The findings found that freshwater productivity improves by approximately 25% when the seawater temperature is increased by 10%.