Desalination 245 (2009) 266–283 Effect of design parameters on multi-effect desalination system specifications Mohammad Ameri * , Saeed Seif Mohammadi, Mehdi Hosseini, Maryam Seifi Combined Heat & Power Specialized Unit (CHP), Energy Engineering Department, Power & Water University of Technology, PO Box 16765-1719, Tehran, Islamic Republic of Iran Tel. +98 (21) 7393 2653; Fax: +98 (21) 7731 1446; email: ameri_m@yahoo.com Received 2 March 2008; Accepted 13 July 2008 Abstract Potable water supply has a significant role in today’s developing world. It is very important to determine the specifications of desalination systems in order to achieve cheaper water prices and better operational conditions. Multi-effect desalination (MED) with thermal vapor compressor (TVC) is a progressing, low cost and easy operating system to produce drinking and pure water for both social and industrial applications. In this paper, the effects of different design parameters such as number of evaporation effects, inlet steam pressure, temperature difference of the effects, and feed water temperature on MED system specifications, i.e. performance ratio, required heat transfer area and cooling sea water, are studied. The results show that there is an optimum value for the number of effects for a system with constant production capacity. This optimum value is a function of seawater salinity, effects temperature difference and feed water temperature. The results also show that the increase of inlet steam pressure increases the performance ratio and the required heat transfer surface area of the system and decreases the cooling seawater mass flow rate. Keywords: Multi-effect desalination; Thermo-compressor; Performance ratio; Falling film evaporation 1. Introduction The multi-effect desalination (MED) system has various types and configurations. Horizontal tubes falling-film evaporation (HT–FF–MED) with thermal vapor compression (TVC) is the *Corresponding author. most dominating process in today’s MED sys- tems. Low scale formation, easy operation, high performance ratio (PR), and operating with any available source of heat energy (e.g. waste heat from power plants), have caused the HT–FF– MED with TVC to be used widely in Middle East countries [1]. Whenever low cost fuel or waste energy is available, the MED system can be the doi:10.1016/j.desal.200 .0 0 8 7. 12 0011-9164/09/$– See front matter © 2008 Elsevier B.V. All rights reserved.