Parametric distribution of the condensation and evaporation processes in horizontal tube falling film evaporator

Abstract

The heat transfer and flow process for a horizontal tube in the falling film evaporator was simulated by the distributed parameter model. The evaporation process of the natural seawater falling film outside the tube and the condensation process of the steam inside the tube were coupled in the model. The model takes into account the wetted angle associated with the accumulated condensate layer at the bottom of the inner tube. The distribution of heat transfer parameters along the tube circumferential direction and tube axial direction were presented. Results show that the stratified flow divides the tube surface into two zones: the film condensation zone and the condensate zone. The distribution characteristics of heat transfer parameters show significant differences between the two regions. The tube wall temperature exhibits higher values in the film condensation zone than that in the condensate zone. The in-tube condensation heat transfer coefficient, the heat flux and the overall heat transfer have obvious larger values in the film condensation zone than that in the condensate zone. For a certain cross section of the tube, the ratio of the heat transfer in the condensate zone to the overall heat transfer shows a decreasing trend followed by an increasing trend along the tube axial direction.