Abstract
A numerical study of the effects of transients and variable properties on single droplet evaporation into an infinite stagnant gas is presented. Sample calculations are reported for octane droplets, initially at 300°K with R o = 0·1, 0·5, 2·5 × 10 −4 m, evaporating into air at temperatures and pressures in the ranges 600–2000°K and 1–10 atm, respectively. It is found that initial size R o is eliminated from the problem on scaling time with respect to R 2 0 and that the evaporative process becomes quasi-steady with ( R R 0 ) 2 = ( R∗ 0 R 0 ) 2− βt R 2 0 , as suggested by experiment. Comparisons of solutions using various reference property schemes with those for variable properties show that best agreement obtains using a simple 1 3 rule wherein properties are evaluated at T r = T s + (T e−T s) 3 and m 1,r = m 1,s + (m 1,e− m 1,s) 3 . The effects of temporal storage of mass species, energy, etc. and radial pressure variations in the vapor phase prove to be negligible, the early transient behavior being solely due to sensible heat effects within the droplet and related variations in vapor-side driving forces.
Published Version
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