Evaporation of a Liquid Droplet

Two idealized models for the preheat s tage of liquid droplets are ana lyzed theoretically . These models conta in the effects of transie nt heat conduction and evaporati on. It is assumed that the droplet surface a rea decreases linearly with time. This assumption necessitates the solution of mov ing boundary problems . These models, however, do not consider gas-phase mass transport . In the finit e-gradient model, the tempe ratures of both the droplet a nd surrounding hot gases vary spatia lly and temporall y. In the zero-gradient model the gas temperatu re varies spatia lly and temporall y but the d roplet temperature vari es onl y tempora ll y, i. e., the drop let temperature is spati a lly uniform. Numeri cal examples, whi ch require exte ns ive ca lcu lat ions of connuent hypergeometric fu nctions, are presented for typical va lues of the d ro ple t latent heat and evaporation rate constant. The tem perature profi les given by the fin ite-gradient and zero-grad ient models agree to within 20 percent of each othe r for a ll cases examined .