Simulating disturbance frequency effect on heat transfer enhancement in wavy condensate films

Abstract

It is of great significance to investigate microscopic mechanisms of heat transfer enhancement in wavy condensate films which are frequently encountered in nuclear power plants. A numerical model, in which the wavy interface is tracked by a non-orthogonal coordinate transformation, is developed to study the disturbance frequency effect on heat transfer enhancement along a vertical wall. A sinusoidal disturbance is introduced by a fictitious body force to sustain waves. A disturbance frequency of 16 Hz associated with the critical film Reynolds number is numerically determined by analyzing the neutral stability curve. Compared with other disturbance frequencies, the wave effect on local heat transfer coefficients is the most significant at 16 Hz. The minimum time-averaged thickness and the maximum proportion of substrate film length in the wave length at 16 Hz proves that the film thinning effect is determined by the length of the film substrate rather than the substrate film thickness. The more notable variation of the normal velocity close to the wall at the wave front at 16 Hz accounts for the convection effect of heat transfer enhancement.