Numerical Simulation Of Droplet Entrained By Vapor Across The Wire Mesh Demister

Wire mesh demister is widely used in thermal desalination plants to remove the seawater droplets entrained by vapor. If the demister does not separate the entrained seawater droplets efficiently, it will cause the reduction of distilled water quality and the formation of scale on the inner face of the vapor tube in the condenser and the corrosion of the tube material. The separation efficiency and the pressure drop are two main performance parameters of wire mesh demister. A limited number of studies in literature are found on demister performance parameter. Some researchers focus on the semi-empirical correlation obtained from experiment for the removal efficiency and the pressure drop, and others focus on studies concerning the available models on the demister performance which are solved using CFD. Two mathematical models are used to model the wire mesh demister in this study, which are the porous media model and the staggered array model. And then the critical factors that influence the performance of the wire mesh demister are discussed. Demister performance research has practical significance for engineering applications. The demister performance has strong effect on the total heat transfer area in the plant, which is directly related to the plant capital cost. Also, the demister performance affects the product quality, which is related to the plant operating cost. In addition, this study is novel and contributes to the further study of the demister performance. The work has been carried out can be summarized as follows:1. The wire mesh demister is simulated as porous media. The dry pressure drop is discussed as a function of vapor velocity, wire diameter, packing density.2. Numerical simulations of wire mesh demister with various geometries and operating conditions are performed with staggered array model. The wire efficiency and the pressure gradient are obtained from simulation, and they can be used to compute the separation efficiency and pressure drop. The effect of wire diameter, packing fraction, pad thickness on the separation efficiency and the relation between the Stokes number and the wire efficiency are investigated. In addition, the figure of merit is used to evaluate the performance of different wire mesh demisters comprehensively.3. The prediction models of the separation efficiency, pressure drop and merit of demister are obtained based on response surface methodology by means of the statistical software Design-Expert. And the interaction of the influence factors is estimated from the response surface and contour line. The present prediction model can estimate the effects of different geometries and operation conditions on the demister performance directly and contribute to the optimum design of wire mesh demisters.