A numerical investigation of simulating moisture in motive steam in a thermal-vapor compressor with DPM method

摘要

One of the prevalent phenomena that significantly affects thermal-vapor compressors is the moisture in the motive steam. It has a dominant effect on the thermodynamic and design parameters of a thermal-vapor compressor (TVC), such as entrainment ratio, compression ratio, and flow density. This study investigates a numerical simulation of a thermal-vapor compressor operated with a two-phase flow motive steam that is composed of saturated water vapor and dispersed water droplets. The droplets injected into the computational domain are represented as the second phase and are simulated by the discrete phase model. In this method, transport equations are solved for the continuous phase, whereas droplets regarded in the Lagrangian frame are involved through interaction in source terms. Three critical factors for understanding the effect of moisture on TVC are studied: the mass flow rate, the diameter, and the number of droplets. It will be shown that the presence of moisture in motive steam, which is inevitable to be ignored in the desalination industry and vapor lines, has a negative impact on the efficiency of the thermal-vapor compressors. Eventually, the numerical results are compared with the experimental data, which are accepted with less than 5 error from the actual TVC.