Analysis on Evaporation of Extended Thin Film Meniscus in Capillary Microstructure

The surface evaporation of the extended meniscus liquid film in the micro channel driven by the capillary force is of the key process in a lot of heat sink and thermal management equipments. The physio-mathematical model was established considering the variation of the apparent contact angle to describe the configuration of the total extended thin film region, including that of equilibrium, interline and intrinsic meniscus regions. In additions, the minimum energy principle was employed to determine the range of thin film interline region. The results indicate that the range of thin film interline region is quite small in the total extended film region, nevertheless the variation of its surface temperature is much obvious, implying that the resulted Maragoni effect can cause great “pump” force to drive the film flow, which may be the main contribution of the interline region to the total extended thin film evaporation. The variations of evaporating rate, and also the resulted mean velocity of liquid film in the thin film interline region under different wall temperature and apparent contact angle were revealed, which showed that there existed the local maximum value of evaporating rate in this region by the coupled influences of the decreased film thickness and variation of the interface temperature.© 2009 ASME