MVRC系统水平管含盐废水喷淋降膜传热数值研究

The horizontal falling film evaporator is a key component of the mechanical vapor recompression crystallization (MVRC) system, in which it can be used to evaporate wastewater and recover secondary vapor energy from salty wastewater. However, the heat transfer and flow characteristics of the salty wastewater sprayed outside the horizontal falling film evaporator tube are obviously different from ordinary water as the spray medium. In this paper, a three-dimensional numerical model was established for a horizontal falling film evaporator in the mechanical vapor recompression crystallization system, and a mixture of water and sodium sulfate was used to simulate the real salty wastewater. The VOF model was applied to track the liquid-gas interface of salty wastewater spray falling film over a horizontal tube in the evaporator. The effects of different sodium sulfate content, heat flux, spray density and spray temperature on the heat transfer coefficient h_θ were investigated, and a dimensionless correlation equation was established. The results show that: 1) the heat transfer characteristic can be divided into three regions around the tube; 2) the local heat transfer coefficient decreases with increase of sodium sulfate content in the thermal developing region; 3) the local heat transfer coefficient increases with the increase of the spray density and spray temperature, and is little affected by heat flux in the thermal developing region.