Study on the Heat Transfer Mechanism in Nucleate Boiling of Water by Measuring Local Heat Flux and Temperature

Abstract

In this experimental work, the local heat flux and temperature on the boiling surface are measured to determine the heat transfer mechanism taking place during nucleate boiling. Several representative types of heat transfer mechanism have already been proposed by many researchers. These are evaporation on a microlayer, evaporation of a thin liquid meniscus at the three-phase contact line, convection in a liquid area and quenching heat transfer on a quenching area. An important aspect to note is that the heat flux during each of these mechanisms occurs at a different place (e.g., the microlayer, contact line, liquid area. and advancing area) and has a different value with each other. So if the heat flux is measured, the specific dynamic surface areas can be classified and this results in the identification of the specific surface heat transfer mechanisms involved. The heat flux is measured by solving the heat equation with the temperature information which is gotten from the IR camera as the boundary condition. In conclusion, the convection heat transfer on the liquid area is the predominant heat transfer mechanisms during the nucleate boiling of water. Its contribution to overall heat transfer is about 80% in the low input heat flux region, but gradually decreased as the input heat flux increases. It appears that the increased quenching and evaporation on the contact line is the main cause of these trend.