COMBUSTION STUDIES ON TWO INTERACTING PMMA SPHERES IN A CONVECTIVE FLOW FIELD

Abstract

Consider the vaporisation of a motionless, cold, droplet after it is placed in a hot, stagnant, gravity free environment of an infinite extent. The system pressure is much less than the critical pressure of the liquid such that critical phenomena are not important. The lack of forced or natural convection then implies that spherical symmetry prevails. For vaporisation, the presence of oxygen in the environment is irrelevent (Fig. 1.1). Since the droplet temperature, in particular its surface value, is lower than that of the ambience, heat is transferred towards the droplet through conduction. At the surface, part of this heat is transferred to the droplet interior causing the droplet to heat up. The rest of the heat is used to gasify the liquid such that a high concentration of fuel •vapour, generally at its saturation value, exists at the droplet surface. When the fuel vapour concentration in the environment is lower than that at the surface, a concentration gradient exists through which the fuel vapour is transported outward. The depletion of the fuel vapour at the surface renders further gasification possible. Thus through the above mechanism, a liquid mass can be converted continuously into vapour and eventually dispersed to the ambience. The (J\ rate controlling processes are heat and mass