Chapter 2 - Single Effect Evaporation

Abstract

This chapter presents a discussion on modeling and analysis for a single-effect evaporation desalination system. Although, this system offers very limited use in the desalination industry, it constitutes basic elements found in industrial desalination systems. Modeling and analysis of this simple system is necessary to understand the basics and fundamentals of the desalination process, which are also found in actual desalination systems. Detailed results are presented to show the dependence of the factors controlling the fresh water cost that are the thermal performance ratio, specific heat transfer area, and specific cooling water flow rate, on design and operating variables. These variables are the brine boiling temperature, the intake seawater temperature, and water salinity. Analysis of the single-effect evaporation desalination system shows the need for more efficient management of the system energy. Also, systemoperation is recommended at higher boiling temperatures. Proper energy management will result in higher system performance ratios. This will be found in other single-effect systems, which utilize vapor compression, or in multi-effect configurations. System operation at higher boiling temperature results in reduction of the specific heat transfer area and the specific cooling water flow rate. This reduction lowers the first cost, that is, construction cost of the evaporator, condenser, and seawater pump. In addition, the operating cost is lower as a result of reduction in the energy required to operate the seawater-pumping unit.