蒸发式冷凝器传热传质数值模拟研究

Numerical Simulation Investigation on Heat and Mass Transfer in Evaporative Condensers

摘要: 采用VOF法，建立二维水蒸气传热传质顺流和逆流的计算模型，计算所得的平均液膜厚度模拟值比实验测量值大3.03%~6.90%，比Nusselt理论的预测值大8.33%~10.34%，在合理的误差范围，说明该模型切实可行。运用该模型计算并分析水与空气顺流和逆流过程中，液态水的流动分布、空气与水流速度分布以及空气中水蒸气的质量含量分布情况，结果表明：在气–液两相逆流过程的气–液界面的总传热量中，潜热传热量所占比值在90%以上，比气–液两相顺流时高，在气–液相界面处是以水蒸发传质引起的潜热换热为主、温差引起的显热传热为辅的换热形式，逆流比顺流更有利于传热。

Abstract: The VOF (volume of fluid) method is used to establish a two-dimensional water vapor heat and mass transfer parallel flow and counter flow model. The deviation of calculated film thickness, which is changed with Re values, is greater than the experimental measurement’s value by 3.03% - 6.90%, and the predicted value of the Nusselt theory by 8.33% - 10.34%; it indicates that the model is feasible. The model is used to calculate and analyze liquid water flow distribution, air and water quality and velocity distribution, water vapor quality content distribution in the air, in water and air’s parallel flow and counter flow processes. The results show that: in gas-liquid two- phase counter flow process, the ratio of latent heat transfer rate in total heat transfer rate is above 90% at gas-liquid interface, higher than that of gas-liquid two-phase parallel flow; at air-liquid interface, the main heat transfer is latent heat transfer caused by water’s evaporation and mass transfer, and the supplemented heat transfer is sensible heat transfer caused by temperature difference; counter flow is more conducive to heat transfer than parallel flow.