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Abstract
A parametric study of the fundamental exchange processes for energy, mass and momentum between the liquid and gas phase of vaporizing, multicomponent-liquid droplets is presented. The applicable model, which examines an isolated, vaporizing, multicomponent droplet in a laminar, axisymmetric, convective environment, considers the different volatilities of the liquid components, the alteration of the liquid-phase properties due to the spatial/temporal variations of the species concentrations and also the effects of multicomponent gaseous diffusion. In addition, the model accounts for variable thermophysical properties, surface blowing and droplet surface regression due to vaporization, transient droplet heating with internal liquid circulation, and finally, droplet deceleration with respect to the free flow due to drag. The numerical calculation employs finite-difference techniques and an iterative solution procedure that provides time-varying spatially-resolved data for both phases. The effects of initial droplet composition, ambient temperature, initial Reynolds number, and volatility differential between the two liquid components are investigated for a liquid droplet consisting of two components with very different volatilities. It is found that hydrocarbon mixtures with higher concentration of the less volatile substance actually vaporize faster on account of intrinsically higher liquid heating rates. An evaluation of the potential for droplet microexplosion of some hydrocarbon mixtures shows that the liquid-droplet temperatures remain below the limit of superheat of the mixture, even when the calculated equilibrium vapor pressures exceed the ambient value.