THERMAL STATE AND HYDRODYNAMICS OF EVAPORATING LIQUID HYDROCARBON DROPLETS. 1. A POSSIBILITY OF NATURAL CIRCULATION OF THE LIQUID IN THE DROPLET

Abstract

The paper presents the simulation results of a high molecular weight hydrocarbon n-decane droplet evaporation in still air. Evaporation of symmetrically heated droplets of different diameters was investigated. Droplets are heated in two ways - only by conduction from high-temperature air or by conduction and by a symmetrical absolutely black air temperature heat radiation source. The internal thermal state and evaporation was modelled together with the external heating of the droplet. Although in the “external” liquid droplet heat and mass transfer task heat flow was seen as independent, the hydrodynamic Stefan flow effects on heating and evaporation intensity were taken into account. While in the „internal" task, the gradient of temperature inside of the droplet was assessed based on the interaction between conduction and radiation. The results of calculation are summarized by the similarity theory methods using Ra and Fo criteria and specific dimensionless coordinates. Universal (independent from conductively heated droplet diameter) evaporation and warming curves are presented. The thermal radiation influence on droplet evaporation intensity, thermal and hydrodynamic state is shown by the deviation from the aforementioned universal curves. The possibility of spontaneous circulation inside of the hydrocarbon droplet in given heat and mass transfer cases was evaluated based on the experimental data of natural circulation in spherical water volume.

DOI: http://dx.doi.org/10.5755/j01.mech.18.2.1573