EXPERIMENTAL STUDY OF SHERWOOD-NUSSELT RELATION IN TURBULENT CONVECTIVE MOIST AIRFLOW WITH DROPLET CONDENSATION AS A FUNCTION OF THE SURFACE PROPERTIES

Abstract

Condensation of droplets on an overflowed cool surface is a phenomenon which occurs in our everyday life, technical applications, and nature. The heat transfer in turbulent convective flows with moist air is determined by the physical mechanisms convection, phase transition and vapour diffusion as well as by the boundary conditions such as surface roughness and the contact angle between the droplets and the surface. Moreover, during the phase change latent heat is released or consumed, which in turn influences the heat transfer. In addition, the agglomeration of the droplets and the local high density gradients further leads to an increase of turbulence in the boundary layer and this in turn results in a higher heat transfer and mass transfer due to phase change. A fundamental understanding of the impact of surface roughness and the wetting properties on the complex mutual interplay between phase transition, fluid flow and heat transfer is of vital interest.