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    杨永昌, 张涛, 陈思远, 唐盛伟. 降膜微通道内液相成膜特性及气-液传热过程数值模拟[J]. 华东理工大学学报(自然科学版), 2019, 45(2): 189-196. DOI: 10.14135/j.cnki.1006-3080.20180323002
    引用本文: 杨永昌, 张涛, 陈思远, 唐盛伟. 降膜微通道内液相成膜特性及气-液传热过程数值模拟[J]. 华东理工大学学报(自然科学版), 2019, 45(2): 189-196. DOI: 10.14135/j.cnki.1006-3080.20180323002
    YANG Yongchang, ZHANG Tao, CHEN Siyuan, TANG Shengwei. Numerical Simulation of Liquid Hydrodynamics and Gas-Liquid Heat Transfer Behaviors in a Falling Film Microchannel[J]. Journal of East China University of Science and Technology, 2019, 45(2): 189-196. DOI: 10.14135/j.cnki.1006-3080.20180323002
    Citation: YANG Yongchang, ZHANG Tao, CHEN Siyuan, TANG Shengwei. Numerical Simulation of Liquid Hydrodynamics and Gas-Liquid Heat Transfer Behaviors in a Falling Film Microchannel[J]. Journal of East China University of Science and Technology, 2019, 45(2): 189-196. DOI: 10.14135/j.cnki.1006-3080.20180323002

    降膜微通道内液相成膜特性及气-液传热过程数值模拟

    Numerical Simulation of Liquid Hydrodynamics and Gas-Liquid Heat Transfer Behaviors in a Falling Film Microchannel

    • 摘要: 采用流体体积函数(VOF)模型对浓硫酸(w=98%)在降膜微通道内的降膜流动及气-液两相传热行为进行了二维数值模拟。重点分析了液相入口流速对液膜厚度、液膜内速度分布的影响,结果表明液膜厚度与入口流速成正比,液膜内速度呈抛物线型分布。模拟研究了气-液两相入口流速、温度等因素对相间传热系数的作用规律,结果表明传热系数随气、液入口流速的增加而增加,随气相入口温度的增加而降低。与传统设备相比,降膜微通道内模拟所得的液膜努塞尔(Nu)数提高约8.77倍。

       

      Abstract: Falling film micro-reactor (FFMR) has incomparable advantage in highly exothermic and fast reactions when compared with conventional reactors due to its characteristics of high specific surface area, easy separation of products and low scale-up effect. The superior chemical reaction performance exhibited by the FFMR strongly depends on the hydrodynamic behaviors of the liquid film and the heat transfer characteristics of gas-liquid interphase in the falling film microchannel. A transient computational fluid dynamics (CFD) model with the volume of fluid (VOF) method was employed to simulate the hydrodynamic behaviors of concentrated sulfuric acid w=98 % in a home-made falling film microchannel reactor. The gas-liquid heat transfer behaviors of H2SO4-air in the FFMR was also simulated. Surface tension plays a significant role on film-forming process within the Re and Ca range of 0.001 33―0.066 7 and 7.00×10−5―3.50×10−3, respectively. The influences of liquid inlet velocity on the liquid film thickness and velocity distribution of the film were studied systematically. The results show that the liquid film thickness is proportional to the liquid inlet velocity and the velocity profiles across the film are parabolic curves. The simulated results match the Nusselt predicated results well within a deviation of 0.5%. The effects of gas inlet velocity, gas temperature and liquid inlet velocity on heat transfer coefficient were analyzed. Simulation results show that the increase of both gas inlet velocity and liquid inlet velocity exerts a positive effect on heat transfer coefficient, but the influence of gas temperature on heat transfer coefficient is negative for the increasing viscosity of gas with increasing temperature in FFMR, the heat transfer resistance strongly depends on the heat transfer resistance of gas side. The Nusselt number in FFMR is almost 8.77 times of that in the traditional reactors, which indicates that gas-liquid heat transfer can be intensified effectively by the FFMR. The results are scientific significance to discover the falling film behaviors and gas-liquid heat transfer in FFMR, and provide a theoretical basis for exploring and designing of new reactors.

       

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