关键词: 降膜蒸发, 蒸发式冷凝器, 传质, 传热, 水平圆管, 相变

Abstract:

The thermal process calculation software of the evaporative condenser was compiled on the MATLAB platform. The thermal performance of the horizontal circular tube falling film evaporative condenser was calculated and analyzed. This study thoroughly explored the impact of various factors, such as the wind speed outside the tube bundle and the water spray density, on crucial parameters including heat transfer, external heat transfer coefficient, and mass transfer coefficient. The results of the calculations indicate that an increase in the head-on wind speed significantly enhances the heat transfer efficiency. This improvement is largely attributed to the disturbances that the wind creates on the liquid film outside the tubes, which, in turn, has a profound impact on the mass transfer processes as well. Notably, when the wind speed reaches approximately 4.21 m·s⁻¹, a critical threshold is observed where the trends of the outlet air temperature and humidity reverse, further intensifying the evaporation of the liquid film. Additionally, the study found that increasing the water spray density can lead to a slight improvement in heat transfer, it also results in a rise in the temperature of the water film on the tube surfaces. This temperature increase, coupled with a reduction in the outlet air humidity, can actually impede both heat and mass transfer processes. Consequently, it was determined that there exists an optimal spray density, which is approximately 0.068 kg·m⁻¹·s⁻¹, where the benefits of increased spray do not offset the drawbacks of higher water film temperatures.

Key words: falling film evaporation, evaporative condenser, mass transfer, heat transfer, horizontal circular tube, phase change