Nucleate pool boiling simulations using the interface tracking method: Boiling regime from discrete bubble to vapor mushroom region

A numerical simulation method to model nucleate pool boiling from multiple nucleation sites has been developed and applied to different boiling-water regimes, ranging from discrete bubbles to the vapor mushroom region. The method is based on an interface tracking method in which the liquid-vapor interface is resolved by a color function within the framework of Computational Fluid Dynamics (CFD). Conjugate heat transfer between the wall and the fluid is included in order to capture the temperature field appropriately, since this has a significant influence on the bubble growing process. The micro layer, which is the thin liquid film existing beneath a growing bubble, is taken into account using a specialized model specifically developed by the authors. A validation case is chosen to test the model, based on an experiment by Gaertner, featuring the boiling of water from a heated, horizontal plate under atmospheric pressure. Estimation of the nucleation site density and the local activation temperatures are taken from experimental measurement, and introduced into the simulation through an in-built, nucleation-site model. The applied heat flux ranges from 50 to 300 kW/m(2), the heat-transfer surface being of dimensions 20 mm x 20 mm. The computed heat transfer coefficient agrees well with the measured value, demonstrating the capability of the described CFD model to predict boiling heat transfer in a mechanistic sense for the flow regimes examined. Comparison of bubble shapes between experiment and computation also shows good agreement. In addition, a variety of statistical data, such as the heat flux partitioning and the ratio of vapor-to-liquid area over the heat transfer surface, which cannot be measured in the experiments, but can be derived from the results of the simulations. (C) 2016 Elsevier Ltd. All rights reserved.