Experimental study of heat and mass transfer in convective flows of moist air with droplet condensation as a function of surface roughness and wetting properties

Kurzfassung

Experiments are carried out in order to study the heat transfer in a forced convective air flow with phase transition on glass panes. The measurements are performed in a vertically oriented gap wind tunnel with a rectangular cross section. In addition, one side of the gap is isothermally cooled and a glass pane with a defined surface is mounted on the cooled wall. In the present paper the results of the heat and mass transfer are discussed as a function of the surface roughness and wetting properties for four different surfaces at a Reynolds number of Re = 2300. The heat transmission from the fluid through the glass pane and the corresponding mass transfer is examined in detail for one surface. The result reveals an impact of the droplet radius, vapour density and temperature on the heat transmission coefficient. Further, a linear relation between Sherwood Sh and Nusselt Nu for the present parameter variation is found. In addition, a nondimensional parametrisation and an analysing method are introduced in order to characterise and determine the heat and mass transfer for the present configuration.