Thermodynamic analysis of thermal desalination system with humidification–dehumidification cycle

Abstract

Problems. Today desalination of seawaterprovides a worldwide fresh water productionof 24.5 million m 3 perday.One of the promising desalination methods is thermal humidification-dehumidification process. In spite of significant benefits this technology, it has a key drawback – high thermal energy consumption.The aim of the study. Determine the optimal thermodynamic parameters of working substances (air and water) in elements of desalination system with humidification–dehumidification cycleto obtain maximum performance with a minimum energy consumption.Methodology of implementation. Mathematical modeling of the humidification-dehumidification cycle at different input parameters.The thermodynamic model was createdusing equations of mass and energy balances of the desalination system.Research results. System Gain output ratio(GOR) increases with increasing salt watertemperature at the outlet of the dehumidifier.Maximum valuesof GORand recovery ratio (RR) are observed at the maximum temperature difference (maximum heating) of salt water in the dehumidifier. It is shown that values of GOR and RR increasewith increasing salt water temperature at the inlet to the humidifier. It is found that GOR value is independent of the temperature and humidity of the air at the inlet to the humidifier.Conclusions.The maximum valuesof GOR and RR for the humidification-dehumidification cycle with additional water heating are 3.75 and 6%, respectively. To obtain such results,the temperature of salt water at the inlet tothe system (dehumidifier) should be equal to 10 °C, and the temperature of salt water at the inlet to the humidifier – 70 °C. At the same time, temperature and humidity of the airсan have any values. The use of renewable energy for heating salt water in the heater will significantly increase system GOR