Effects of Surface Topography of Condensation Surface on Initial Dropwise Condensation

Since the magnesium can react with hot water(condensate) and change its chemical compositions,via the magnetic-controlled sputter coating method the magnesium-coating surface was used as the condensation surface in this study,thus making the formation of initial condensation nucleuses detectable.The magnesium-coating surfaces with different topographies were prepared via varying the operating parameters of the sputter coating process,and then the differential box-counting method was used to calculate the fractal dimension of these prepared magnesium-coating surfaces.After that,initial dropwise condensation experiments on these magnesium-coating surfaces were carried out under almost the same experimental parameters,and the relationships between the surface topography and dropwise condensation were analyzed.The results show that when the surface fractal dimensions are different,the numbers of nucleation sites for dropwise condensation on the surface are different too,and the surface topography effects the initial dropwise condensation significantly.Based on the experimental results,a new formula was proposed to evaluate quantitatively the relation between the fractal dimension of the condensation surface and the nucleation site density of the dropwise condensation.