Influence of the relative velocity between water and air on their heat transfer at the flow of a film along a profiled surface

Abstract:

The process of cooling of the circulation water in film cooling towers depends on the intensity of the air flow that can be formed in these apparatus by natural draught or by forced ventilation. The air flow velocity affects substantially the heat transfer of contacting phases.
Earlier, we carried out experiments with profiled flumes in still ambient air. The aim of the present work is to investigate the heat transfer under the conditions of forced air flow over a liquid film in the countercurrent mode.
Using the specially developed experimental facility, we have studied the influence of the relative velocity between water and air on the convective heat transfer from a liquid film, which flows down along the surface with spherical dimples of different sizes. We have revealed the influence of different factors on the heat transfer intensity.
We have found the values of heat transfer coefficients for different relative velocities of the contacting phases on Our experiments have shown that the convective heat transfer from a water film to ambient air grows significantly under conditions of forced blow-off as compared with a still medium.