The impact of a balanced humidification-dehumidification desalination system driven by a vapor-compression heat-pump system

Abstract

This study adopts a numerical thermo-economic investigation of a novel desalination system. In this system, a vapor compression (VC) heat pump is used to drive a balanced humidification-dehumidification (HDH) desalination unit with multiple extractions. The mathematical model of the proposed VC-HDH system is validated experimentally. The system is examined for water production under a condenser temperature of 45 °C, evaporator temperature of −5°C, feed saline water temperature of 30 °C, feed saline water flow rate of 1 kg/s, and an energy effectiveness value of 0.85 for the HDH unit’s components. The results show that without air extraction, the system can produce 6.62 kg/h of desalinated water for 0.011 $/l with a gained-output-ratio (GOR) value of 9.1. On the other hand, when a single air extraction is applied, about 20 kg/h of desalination water is produced by the system for 0.0042 $/l and 29 GOR. Increasing the number of air extractions to two yields a freshwater production rate of approximately 40 kg/h for 0.0026 $/l and a GOR value of 57. A considerable positive effect of the HDH unit’s performance is found on the system’s performance on both thermodynamic and economic scales. For better desalination performance, it is found that the feed water temperature should be maintained between 25 °C and 30 °C. Finally, the theoretical ceiling of the proposed system’s GOR is estimated.