Abstract: The heat transfer calculation model of water and viscous fluid in a thin film evaporator was developed using CFD software CFX4.4. The mean temperature distributions along axial and film thickness directions were obtained, and the film heat transfer coefficient a under different conditions was calculated. The results show that feeding rate and rotor speed have great influence on the film temperature distribution and the film heat transfer coefficient. There is one common optimum feeding rate under different operation conditions for different fluids. At this feeding rate, the mean velocity in fillet section reaches the maximum value and so does the film heat transfer coefficient a. For water, both the ratio of flow boundary layer thickness to film thickness and that of temperature boundary layer thickness to film thickness reach the minimum value under high rotor speed or the optimum feeding rate. There exists an inherent relation between the flow boundary layer and temperature boundary layer, and the film temperature distribution and heat transfer coefficient are affected seriously by the thickness of transfer boundary layers. For viscous fluid, no obvious temperature boundary layer forms under the parameter range considered in this work．

Key words: thin film evaporator, temperature field, heat transfer coefficient, transfer boundary layer

摘要： 应用CFD软件CFX4.4建立了薄膜蒸发器内水及粘性料液的传热计算模型，获得了沿轴向及膜厚方向的液膜平均温度分布，计算了各参数下加热段液膜内给热系数a. 结果表明，进料量及搅拌转速对各料液液膜温度分布及膜内给热系数影响显著. 不同粘度料液在不同操作条件下均存在同一最佳进料量，此时圈形波内截面平均速度 达到最大值, 相应的膜内给热系数a也达到最大值. 高转速或最佳进料量下，纯物质水流动边界层与膜厚之比及温度边界层与膜厚之比均最小，流动边界层与温度边界层存在内在联系. 传递边界层厚度严重影响液膜内温度分布及给热系数. 本研究各工况下，粘性料液尚未形成明显的温度边界层.

关键词: 薄膜蒸发器, 温度场, 给热系数, 传递边界层