Nusselt Numbers and drag coefficients of single-component liquid droplets and solid spheres in high temperature, intermediate Reynolds Number flows have been investigate both experimentally and theoretically. A detailed survey of the literature is presented which reveals that the energetic and dynamic behaviour of solid and liquid spheres is well established only in situations where the temperature and concentration differences between the particle surface and the free-stream flow are small. On the other hand, in high temperature flows, the effects of strongly variable thermophysical properties and mass transfer on momentum and heat transfer are poorly understood particularly at intermediate Reynolds Numbers.

In the experimental phase of this investigation, the evaporation of suspended water, Methanol and n-Heptane droplets were followed in laminar air streams up to 1059 K in temperature using a steady-state measurement technique. The droplets were of the order of a millimeter in diameter and the experiments covered the Reynolds Number range between 20 and 2000. In all measurements, the intensity of free-stream turbulence was less than one percent and free convection effects were negligible. A total of 288 data points are analysed and a heat transfer correlation is presented which also accurately predicts solid sphere Nusselt Numbers. It is found that the dynamic blowing effect of evaporation causes large reductions in heat transfer rates, and that the film conditions constitute an appropriate reference state for the evaluation of thermophysical properties. A comparison of this correlation with other experimental data shows very satisfactory agreement.

In the theoretical phase of this investigation, numerical solutions of the coupled equations of motion, energy and species continuity were obtained for variable-property, axisymmetric flows past evaporating droplets and solid spheres in the Reynolds Number range between 10 and 150 using finite-differences. Computations were carried out for water and Methanol droplets vaporizing in air, for water droplets in super-heated steam and, for solid spheres in air at free-stream temperatures up to 1000 K with impressed temperature differences up to 627 K.

The numerical results when compared with the standard drag curves for solid spheres in isothermal flows indicate that the blowing effect of evaporation on momentun transfer is to reduce friction drag very significantly but at the same time increase pressure drag by almost an equal amount;​ the net effect on the total drag force being only a marginal reduction. In all cases, it is found that thermo-physical property variations play a very dominant role in reducing the drag forces acting on cold particles. Correlations are presented for the drag coefficients which show good agreement with experimental data. The numerical heat transfer results confirmed the accuracy of the experimental prediction that Nusselt Numbers are reduced very significantly due to vaporization. The results are analysed in detail and a correlation for stagnation-point heat transfer is also presented.