The peculiarities of hot liquid droplets heating and evaporation

摘要

The change of the thermal state of a sprayed liquid droplet is calculated using the method of combined analytical and numerical research, which requires the balance of energy flows, incoming to the droplet and outgoing from it. The method evaluates unsteadiness of heat and mass transfer processes and interaction, which occurs under the influence of the Stefan's hydrodynamic flow, radiant flow absorbed in semitransparent liquid and the Knudsen layer, which surrounds the droplets. The expedience of the thermal state's evaluation of dispersed liquid is verified using the parameter, expressed by the ratio of liquid's initial temperature on equilibrium evaporation temperature of droplets. As the above-mentioned parameter is less than 1, liquid is offered to be called "cold"; "warm", as the parameter equals 1 and "hot", as it exceeds 1. In each case the peculiarities of the thermal state change of sprayed liquid droplets are individual during an unsteady phase transformation mode. The characteristic curves, representing the change of transfer parameters, are determined for conductively heated droplets and when the Knudsen layer's influence is neglected. These curves join together variation of the parameters of the thermal state change and phase transformation for droplets of infinitesimal set of diameters, but with the same initial liquid temperature, as the droplets evaporate in gas with constant parameters. Deviations from the characteristic curves allow evaluating the influence of more complicated boundary conditions on the interaction of transfer processes.