Heat and Mass Transfer Model for Droplets with Internal Circulation

In large droplets the internal resistance to heat or mass transfer has to be accounted for. Two respective models for low and high Reynolds numbers are investigated. The models are solved numerically for a range of modified Peclet numbers and the corresponding transfer numbers, representing either the Nusselt or Sherwood numbers, are determined. The results for each model are fitted to produce an expression that can be easily evaluated for use in a CFD code. The fits has mean deviations of 0.63% and 0.035% for the low and high Reynolds number models respectively. A proposed switching Reynolds number is used to combine the models and the combined model is compared to temperature measurements of free falling water droplets. It was found that the model is in good agreement with the data for the smallest droplets whereas it deviates as much as 40% for the larger droplets in the data set