Thermodynamic investigation of a semi-open air, humidification dehumidification desalination system using air and water heaters

In this paper, a semi-open air, open water humidification dehumidification (HDH) desalination system is proposed and studied. It is shown that for both water- and air-heated systems, when the top temperature of the system is fixed, this presented method for air circulation can enhance the performance of the system. Analyzing other parameters reveals that the impact of ambient temperature is more important than that of the ambient relative humidity on system performance; therefore, HDH is efficient for both dry and humid climates. Also, when the ambient temperature is high, closed air loop has a higher performance. Moreover, the proposed system is studied with a dual heating method, in which both water and air were heated using a wide range of heat rate ratio. The results show that the system will have the maximum performance when the heat rate ratio approximately equals one. In case only one of the streams is heated, if the energy intake is low, water heating is a better solution for an efficient system, but when the heat input is high, air heating is more effective. Finally, an entropy generation analysis of the proposed configuration and heating method is conducted. It is suggested that the exergy efficiency can be used for optimization.