Dynamic modeling on bubble growth, detachment and heat transfer for hybrid-scheme computations of nucleate boiling

Abstract

The increasing industrial applications of boiling heat transfer call for high fidelity and efficient numerical predictions, of which a hybrid scheme simulation combining CFD and boiling model is a promising candidate. To this end, the current research put forth a dynamical boiling model. The model dynamically integrates the sub-processes associated with a boiling cycle, including those of the formation of a thermal boundary layer, the evaporation of a sublayer film, the growth and detachment of a bubble as well as the concomitant heat transfer. In the bubble growth period the growth rate is given by summing the evaporation over the vapor-liquid interface surrounded by a micro sublayer film, a macro film in the thermal boundary layer, and bulk fluid respectively. The computation solves transient governing equations for the instantaneous distribution and heat transfer of the micro sublayer film. It also works out automatically an apparent contact angle. The bubble detachment is processed in a new way that calculates the various forces acting on the bubble to trace the detaching process. Numerical results of the boiling from single nuclei agree with experimental data with reasonable accuracies. Comments are given about the possible improvement of the model and the further development toward practical hybrid simulations of the boiling phenomena.