Thermo-economic analysis of a water-heated humidification-dehumidification desalination system with waste heat recovery

Abstract

Humidification dehumidification (HDH) processes have been proved to be efficient for producing freshwater from seawater or brackish water. In this paper, an HDH desalination system, in which the seawater is appointed to recover the waste heat, is suggested. Based on the principles of mass and energy conservation, mathematical models for all the contained components as well as the entire desalination system, are built, and then the relevant thermo-economic analysis is also accomplished. The simulation results show that peak values of water production with mw = 99.05 kg h−1 and gained-output-ratio (GOR) with GOR = 1.51 are obtained when the balance condition of the dehumidifier appears at the design conditions, while a bottom value of unit cost of water production (UCWP) is found as UCWP = 37.68$ kg−1 h at the case of mda = 0.14 kg s−1. Hence, the great advantages at the aspect of cost for unit water production compared to the solar drive type is validated. It is also found that reducing the seawater spraying temperature and elevating the humidification effectiveness are beneficial to raise the relevant thermodynamic and economic performance of the desalination system. With respect to the variation for dehumidification effectiveness, the peak value of GOR rises from GOR = 1.28 at εd = 0.8 to GOR = 1.85 at εd = 0.9, while a peak value of UCWP is obtained as UCWP = 50.12$ kg−1 h due to the substantial increase of the heat transfer area for the dehumidifier.