立式蒸发式冷凝器传热传质的CFD模拟

The CFD Simulation on Heat and Mass Transfer of Vertical Evaporative Condenser

基于VOF算法,建立了立式蒸发式冷凝器气-液两相顺流传热传质的计算模型。根据CFD模型,计算了在不同气、液相进口条件下,管壁温度的分布、气-液相界面处潜热和显热换热量的关系,模拟得到的管壁温度分布与实验数据吻合很好。计算结果表明,降低进口空气的相对湿度、增大气相流速或者液相流量,都可增强气-液相间热质交换的剧烈程度;气-液相界面处的换热主要形式是由于水蒸发引起的潜热换热,占80%以上,它远远大于由于温度梯度而引起的显热换热量;气-液相界面处的蒸发潜热主要受空气的相对湿度影响,其次是气相流速和液相流量。

Based on the volume of fluid method （VOD）, a computational fluid dynamics model （CFD） was established for predicting the heat and mass transfer process of the gas-liquid concurrent-flow used as cooling medium flowing in the tube-side of a vertical evaporative condenser. The proposed CFD model was used to analyze the temperature profiles on the tube wall and the relative relationship between the latent heat transfer and sensible heat transfer through the gas-liquid interface under different gas-liquid inlet conditions. The results show that, according to the CFD model, the calculated temperature distributions along the tube wall at different liquid flow rates and gas flow velocities agree well with the experimental data. The simulations also reveal that the main part of the heat transfer on the gas-liquid interface is the latent heat transfer caused by evaporation, which is much greater than the sensible heat transfer caused by the temperature gradient; the amount of latent heat transfer is above 80% of the total heat transfer of the gas-liquid interface. Since the evaporative latent heat transfer depends mainly on the air relative humidity, and secondly on the gas velocity and liquid flow rate, it was found that the heat and mass transfer process through the gas-liquid interface can be enhanced by lowering the relative humidity of the gas flow, or increasing the gas velocity or liquid flow rate.