Abstract
A new method for simultaneous measurement of weight, temperature and surface area of an evaporating pendant drop in dry air has been proposed by using a precise analytical balance, a microcomputer with A-D converter, and a microscope with image acquisition system. Unsteady simultaneous measurements of weight, temperature and surface area of an alumina slurry drop and one containing dissolved poly(vinyl alcohol) (PVA) have been made for a wide range of free stream temperatures T∞ = 323–393 K and initial concentrations of PVA CPA0 = 0–10 wt% at free stream velocity U∞ = 0.72 m/s and initial concentration of fine alumina particles CA0 = 50 wt%.
The dimensionless diffusion fluxes and Nusselt numbers of an alumina slurry drop are compared with those for a pure water drop and show a fairly good agreement with those for a water drop during the constant rate period of evaporation. The dimensionless diffusion fluxes of an alumina slurry drop containing dissolved PVA are affected by the initial concentrations of PVA and free stream temperatures and show a large deviation from those for a water drop, while Nusselt numbers show a fairly good agreement with those for a water drop.
