Droplet heat and mass transfer in a turbulent hot airstream

A three-dimensional numerical model is developed to investigate the effect of turbulence on heat and mass transfer rates of a droplet exposed to a hot airstream. The airstream turbulence, temperature and mean Reynolds number are varied to provide a wide range of test conditions. The ambient pressure is kept atmospheric. In addition, variable thermophysical properties, transient gas and liquid phases, and the effect of radiation are all considered in the numerical study. The turbulence terms in the conservation equations of the gas-phase are modelled by using the shear-stress transport (SST) model. A Cartesian grid based blocked-off technique is used in conjunction with the finite-volume method to solve numerically the governing equations of the gas and liquid phases. The numerical results indicate that the effect of freestrearn turbulence is persistent although it weakens as the airstream temperature increases. The effect of radiation becomes significantly important at elevated airstream temperatures. Comprehensive droplet heat and mass transfer correlations are proposed, which take into consideration all the aforementioned variables. (C) 2007 Elsevier Ltd. All rights reserved.