Numerical and experimental study of heat and mass transfer in the humidifier of the closed air open water humidification–dehumidification desalination systems

This paper presents the findings from a combination of theoretical and experimental investigations into the heat and mass transfer processes within the humidifier of a closed air open water (CAOW) humidification–dehumidification desalination (HDD) system. To develop a theoretical model of the system, heat and mass balance equations were formulated. Subsequently, the effects of input working parameters on output parameters were assessed using a calculation program. Additionally, an experimental model was constructed and tested to evaluate the heat and mass transfer efficiency of the humidifier, which was quantified using the Merkel (Me) number. The investigation into the influence of the input parameters on the output parameters of the humidifier, as facilitated by the theoretical model, was done. The results indicate that the performance of the humidifier is significantly affected by the Me number. Based on the outcomes of the theoretical study, a proposed Me value of approximately 1.6 for the humidifier has been established. Furthermore, it has been demonstrated by the experimental results that the Me number is exclusively dependent on the height of the backing material, the temperature of the spray water, and the mass-flow ratio between water and air. An equation for determining the Me number of the backing material has been formulated based on the experimental and numerical studies on heat and mass transfer inside the humidifier.