Characteristics Of Heat Transfer And Hydrodynamics Of Falling Film Evaporation In A Vertical Wavy Wall Tube

We studied the evaporative heat transfer characteristics of a wavy wall tube that was applied to a falling film evaporator as the heating tube for glucose concentration. We designed and built a set of experiment equipment of two wavy tube evaporators. Experimental study and theoretical analysis on the heat transfer and hydrodynamics characteristics of the new evaporator were carried out. The relationships between the heat transfer coefficients and the operational parameters were analyzed and the heat transfer characteristics of two wavy tubes of different dimension parameters were compared in this paper.The effects of interfacial shear stress and surface curvature on the flow and heat transfer were taken into account in the evaporative falling film inside a vertical wavy wall tube heated by condensing steam outside the tube. Different mathematical model is theorized according to the different flow regimes. In the laminar flow regime, a analytical mathematical model is obtained by analyzing the film flowing in the new evaporator. With a view to interfacial shear stress, we set up a eddy-viscosity function based on experimentally measured profiles for e m published by Ueda et al. in turbulent flow regime. This eddy-viscosity function was continuous through the entire falling film and convenient to calculate, and theoretical model and mathematical correlation of heat transfer coefficient was founded based on momentum equation and energy equation in this field. At the same time, the heat transfer correlations of wavy wall tube evaporator are obtained in both fields. The study indicates that the theoretical models and correlations of heat transfer coefficient of the new evaporator are in good agreement with the experimental results and can facilitate the engineering design.