Performance Evaluation and Characterization of a Direct Absorption Solar Humidifier for Humidification–Dehumidification Desalination

In the present work, a solar humidifier suitable for solar thermal energy-driven humidification–dehumidification desalination has been proposed and experimentally investigated. The proposed solar humidifier compacts the solar heater and humidifier into a single component while reducing energy costs by utilizing solar thermal energy. Several local flow storage and distributor elements are created in the absorber surface that produces a “dam effect” in combination with stainless steel mesh and airflow baffles. The effect of varying flowrates of air and water, inlet water temperature as well as inlet relative humidity on the performance of the solar humidifier is investigated. Humidity based normalized gain (NGhumidity) versus solar humidifier efficiency curve, which depicts a heat and mass performance of the solar humidifier, is reported. This curve is analogous to the normalized gain versus collector efficiency curve of the solar water/air heater. The productivity of the present system is compared with the published results of similar studies. Best mean productivity of 838.5 g/m2/h and best instantaneous productivity of 955.2 g/m2/h were achieved using a present solar humidifier, showcasing the effectiveness of the proposed approach. The comparison of the performance of the solar humidifier with the performance of conventional configuration having separate heating and humidification is also carried out. It was found that the investigated solar humidifier (internal heating configuration) does perform the same in terms of utilization of solar energy for evaporation, if not better, than the conventional separate humidifier and heater (external heating configuration).