Turbulence structure of air-water bubbly flow—III. transport properties

An experimental study of heat and bubble transport in turbulent air-water bubbly flow was carried out by means of tracer techniques. Helium tracer gas concentration data and temperature distributions were used to extract bubble and heat diffusivity information. The results indicated that the turbulent velocity components of the liquid phase play a predominant role in the turbulent transport process. A systematic increase of diffusivity of heat, ?_H, with quality and water velocity was observed. An empirical correlation for the diffusivity ratio ?_H,TP/?_H,SP is presented. The Péclet number, u′_covbar|dφ, for bubble dispersion can be approximated by 2.0, independent of the flow variables. The bubble-to-heat diffusivity ratio, φ/?_H, approaches unity with increasing quality and water velocity. Momentum transport is also discussed, based on a mixing length theory.