Abstract
A new multiple-effect concentrator of seawater was proposed and the heat and mass transfer in the concentrator was theoretically analyzed. In the concentrator, ten or more thin plates covered with seawater-soaked wicks are arranged vertically with narrow gaps between them, and the heat of vapor condensation on the uncovered surfaces of plates is recovered and used for further evaporation from the wicks on the plates. The heat of hot concentrated seawater and condensate from the concentrator is recovered and used for preheating the seawater fed to the wicks. Along the wicks, the evaporation rate gradually decreases as the salt concentration and the boiling point elevation become higher at distances closer to the concentrate exits. The evaporation is more rapid from the higher temperature wicks which are closer to the first plate heated with supplied vapors since vapor diffusion through gaps is more rapid at higher emperatures. With the greater number of evaporating wicks, the total evaporation rate from all wicks increases to more then 10 times the amount of the supplied vapor for 13 or more wicks, though the production rate of concentrate decreases with the number of wicks because of an increase in the thermal resistance through the plate array. The simple design of the concentrator may greatly reduce the construction cost, and make up for the decrease in production rate.
