Boiling of liquid film on vertical wall with various types of roughness

Studies have been aimed at determining the influence of the type of roughness of the wetted wall, in the anticipated optimal range of the depth of surface irregularities, on the heat transfer rate in nucleate boiling of films of distilled water and aqueous NaCL solutions. Figures show the heat transfer coefficient in boiling of water and CFCL3 freon, relative to boiling heat transfer coefficient in a large volume as a function of heat flux density. In another figure, shown are characteristic dependences of the mean heat transfer coefficient on the heat flux density for transfer to water films with Re /SUB in/ = 5200, for various wetted surfaces. These studies have shown that the type of roughness, within the range of optimal depths of the irregularities, has a substantial influence on the process of nucleate boiling in the film. For pure low-viscosity liquids that do not give any precipitate and are not aggressive with respect to the wall material, a considerable intensification of the process is achieved by boiling the film on a roughened surface, particularly one with irregularities that are transverse or checkerboard relative to the flow of the film