A Detailed Examination of Gas and Liquid Phase Transient Processes in Convective Droplet Evaporation

A finite volume numerical technique has been used to model the evaporation of an n-heptane droplet with an initial Reynolds number of 100 in air at 800 K, 1 atm. The effects of variable thermophysical properties, liquid phase motion and heating, and transient variations in droplet size and velocity are included in the analysis. With appropriate corrections for the effects of variable properties and liquid phase heating, quasi-steady correlations are shown to predict accurately the transient histories of the drag coefficient and Nusselt and Sherwood numbers. For the case investigated here, the transient effects of importance were the variation in droplet velocity, the decline in the liquid phase velocities, and the rise in the droplet surface and volume average temperatures. In spite of the transient rise in the droplet temperature, the nature of the liquid phase heating, as characterised by the liquid Nusselt number, was found to remain constant during most of the droplet lifetime.