Measuring Vapor Concentration and Diffusive Flux Distributions of an Evaporating Drop*

Measurements of the distribution of the vapor concentration surrounding an evaporating sessile drop are important for revealing the nature of the vapor phase transport mechanisms, which for many conditions controls the evaporation rate and can affect the liquid phase transport. From the measured concentration distribution, the gradient can be computed to yield the diffusive flux distribution throughout the vapor field. This presentation will explain the experiments to measure the vapor distribution, the computational simulation of the measurements which is used to analyze the effects of the propagation of uncertainties caused by measurement noise, and the digital filtering technique to reduce the uncertainties. The measured vapor concentration and gradient distributions surrounding an evaporating methanol drop are presented and those distributions indicate that vapor phase convection is a significant transport mechanism.