Embodiment design of a mechanical vapor compression desalination unit

This paper presents an embodiment design model of single-effect mechanical vapor compression (MVC) system. The main objective of this study is to define the specific power consumption and the specific heat transfer area of the MVC system, as a function of the need for freshwater. Mathematical models are established based on the functional analysis, the energy and mass balance equations as well as correlations of the thermophysical properties. The input parameters of model are the desired product flow rate, the brine/feed salinity and the feed seawater temperature. The design solutions are qualified using a quality index and they are defined by the temperature of brine and distillate streams as design variables. The overall design problem has been formulated as a Mixed Complementarity Problem (MCP) and solved with the PATH solver using the platform GAMS (General Algebraic Modeling System). The results demonstrate the influence of the design variables on the system architecture and its electric power consumption which define the quality index. A large gap between the design variables reduces the heat transfer area, but increases the specific power consumption of the vapor compressor. This study confirms that the MVC desalination concept is suitable for low product capacity of freshwater.