Numerical Simulation Research On Falling Film Evaporation Heat Transfer Process In Evaporative Plate Heat Exchanger

Evaporative plate heat exchanger makes use of the falling film evaporation to enhancethe heat transfer efficiency. Compared to traditional heat exchangers, It is more efficient,water-saving, energy-saving and smaller floor area. It has good development prospect inindustries. Because of the lack of the in-depth researches on falling film evaporation heattransfer mechanism, there are still lots of potential for the improvement.This topic adopts the computational numerical simulation method to simulate the heattransfer in falling film evaporation on smooth plate and the heat transfer in falling filmevaporation on corrugated plate to study the influences on heat transfer performance ofvarious factors under different operating conditions. Ths task in the research aims atproviding guidance on design of evaporative plate heat exchanger experimental platform,laying the foundations for further researches.The falling film evaporation heat transfer process in evaporative plate heat exchangerinvolves air-water multiphase flow and interactions between air and water like heat transfer,mass transfer and surface tension effect. The research selects the user-define functions todefine the interactions between two phases, combined with control equations to build thenumerical simulation models. The comparison between experimental results validates thevalidity of the models so that it can be put into use for further researches.The results of numerical simulation experiments on falling film evaporation on smoothplate under different operating conditions indicates that:1) The inlet water flow operatingcondition is0.15~0.20kg/s, the excessive inlet water flow will lead to water film thicknessincrease, thus the heat transfer efficiency decreases;2) The inlet water temperatureoperating condition is280~310K. The convection heat transfer between water film and theplate will decrease because of the excessive inlet water temperature;3) The increase of inletair speed can improve the heat transfer efficiency greatly.The results of numerical simulation experiments on falling film evaporation on corrugated plate indicates that:1) The falling film thickness will become thinner in troughof wave due to the surface tension effect caused by the geometric construction ofcorrugated plate;2) The wall temperature on corrugated plate is periodically distributed.The wall temperature between wave crests is obviously lower;3) Compared to the smoothplate, the heat transfer efficiency of corrugated plate is much higher.