Experimental and theoretical investigation of the evaporation and stability of a meniscus in a flat micro-channel

Abstract

We present the results of an experimental and theoretical investigation of the evaporation of a liquid meniscus in a high aspect ratio micro-channel electrically heated using transparent resistive coating. Four different liquids are used as working fluids. The external wall of the micro-channel temperature is measured by an infra-red camera and the liquid interface is recorded using a high-speed camera. The results indicate, and consistently, that the evaporation rate increases with the applied power then peaks before declining. The measurements show that there is a maximum in evaporation rate as a function of applied power. Furthermore, a good correlation between the maximum in evaporation rate and the onset of instabilities of the interface is demonstrated. These instabilities, to our mind, are induced by an increasing temperature gradient along the micro-channel wall around the three phase contact line region. A theoretical model was developed to predict evaporation rate near the contact line region. The comparison between the model and experiments highlights the limitations of the microregion models in predicting evaporation rates.