Parametric analysis of a humidification dehumidification desalination system using a direct-contact dehumidifier

Humidification dehumidification (HDH) technology is efficient to evaporate freshwater from seawater or brackish water. In this paper, a water-heated HDH desalination system to recover waste heat through plate heat exchangers (PHEs) is proposed, and heat and mass coupled processes are both applied in the humidifier and dehumidifier. In view of the mathematical models based on energy equilibrium and entropy generation, characteristics of the advised desalination system at different appointed key parameters are calculated and analyzed. Surface areas involved in the PHEs, which contain the low grade heat collector (LGHC) and the hot water recuperator (HWR), are obtained. The simulation results show that the modified heat capacity ratio (HCR) of the humidifier, HCRh, is always at HCRh>1 for the prescribed operation conditions, while the balance condition of the dehumidifier, HCRd = 1, is available, which is significant for the performance of the HDH desalination system. A maximum value of GOR, GOR = 2.01, is attained corresponding to the minimum irreversible loss of the whole desalination system. Furthermore, in consideration both of the heat and mass transfer area as well as the water production, the unit cost is acquired as Cu,c = 26.94￥t-1h and Cu,t = 68.13￥t-1h, which indicates a great superiority of the HDH desalination system using a direct-contact dehumidifier compared with the traditional type.