关键词: 薄膜蒸发器, 温度场, 给热系数, 传递边界层

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