An experimental study has been performed with a single liquid-vapor meniscus formed in a vertical channel of 600 μm width between two flat parallel plates. A 10 μm thick stainless steel heating foil forms a part of one of the flat plates. HFE7100 was used as test fluid. Liquid is sucked into the gap between the plates due to capillary forces and evaporates inside the gap under steady state conditions. The high evaporation rates in the vicinity of the 3-phase contact line lead to high temperature gradients along the heating foil. The two-dimensional micro-scale temperature field at the back side of the heating foil is observed with an infrared camera. On the basis of these temperature measurements a local temperature drop at the micro region is defined as the difference between the maximum wall temperature underneath the wetted portion of the foil and the minimal wall temperature in the vicinity of the contact line area. The distribution of the local wall heat flux is calculated from the measured wall temperature field using an energy balance for each pixel element. A numerical model of heat transfer in the vicinity of evaporating contact line has been developed. This model takes into account the heat conduction in the heating foil and in the liquid, the heat generation in the foil due to the Joule effect and the local evaporation phenomena in the micro region. A modular modelling strategy has been applied, where the solution of the energy equation on a macroscopic scale is combined with a solution of the set of highly nonlinear ordinary differential equations describing the phenomena in the micro region. The results of the numerical modeling are in agreement with the experimental observations. The measured and computed temperature drop in the micro region increases linearly with the input heat flux. |
