Prediction of transpiration effects on heat and mass transfer by different turbulence models

The paper reports the results of a study related to transpirating flows, stimulated by the interest that these phenomena, occurring in the presence of simultaneous heat and masstransfer, have for nuclear reactor applications. The work includes a summary and the follow-up of previous experimental and numerical investigations on filmwise condensation and falling film evaporation and of a recent review of different forms of the heat and masstransfer analogy. The particular objective here pursued is to compare transpirationeffects as predicted by differentturbulencemodels with classical suction and blowing multipliers based on stagnant layer theories, in the attempt to clarify their quantitative implications on the predicted mass transfer rates. A commercial and an in-house CFD code have been adopted for evaluating the heat and masstransfer rates occurring over a flat plate exposed to an air-vapour stream, with uniform bulk steam mass fraction and temperature boundary conditions at the wall. This simple configuration was purposely selected since it is a simplified representation of the test section of an experimental facility presently in operation at the University of Pisa. This allows a direct comparison between the heat and masstransfer coefficients predicted by CFD models and classical correlations for Nusselt and Sherwood numbers.