Performance analysis of an evacuated multi-stage solar water desalination system

In this paper, a novel multi-stage evacuated solar desalination system is developed by utilizing latent heat recovery. A transient model is proposed for the solar desalination system. The effect of various design and operating parameters on the system performance is studied to optimize the configuration. The distillate yield increases initially due to enhanced evaporation caused by the presence of a thin layer of water in the stages. The distillate yield decreases with increase in salinity of water due to an increase in ion activity and the reduction of thermodynamically spontaneous change from liquid to vapor. The optimum number of stages, gap between the stages and the supplied mass flow rate for the system were found to be 4, 100 mm and 55 kg/m(2)/day respectively throughout the year. The overall thermal efficiency of the system is found to be 53.9% and 29.6% for the months March and December respectively in India. The maximum yield of 53.2 kg/m(2)/day is found in March at an operating pressure of 0.03 bar. The multi-stage evacuated solar desalination system is a viable option to meet the needs of rural and urban communities. (C) 2011 Elsevier B.V. All rights reserved.