Session: K13-02 Pool Boiling Fundamentals

Paper Number: 115015

115015 - Modeling of Bubble Growth in a Fluctuating Pressure Field 

While most models for pool boiling phenomena, such as nucleation and growth of bubbles, assume constant and uniform conditions such as uniform temperature/heat flux, constant pressure etc., it is well-known that experimental measurements of bubble departure quantities display strong intermittency. Such intermittent and nonlinear behavior has long been treated as nuisance phenomena. However,  intermittency of thermal fluctuations has recently been shown as essential to the collapsing boiling curves from different conditions on to a single universal non-dimensional curve. It is therefore of interest to develop models that predict intermittent behavior. In boiling, the departure diameter is an important parameter to predict the Critical Heat Flux (CHF) of a system. It is calculated using isolated bubble models where the effect of surrounding bubbles is not considered. However, it is well known that interactions between neighboring nucleating bubbles are non-linear and significantly affect the growth process and eventual departure diameters. There is a need for a model which considers these non-linear effects of bubble interactions in estimating the bubble departure diameter. Ideally, such a model should also be able to predict the intermittency of bubble departure diameter and departure times, which are well-known phenomena but are not predicted by isolated-bubble models.

In this work, we modeled bubble growth by including the effects of surrounding bubbles using an oscillating pressure field. To predict the departure diameter of a bubble we use two force models in our study Klausner and Zeng, and H.Beer, and these force models along with the above-mentioned bubble growth model are used to predict the departure diameters. It was observed that the bubble departs at almost same diameter but detaches earlier because of the surrounding bubbles. These calculations were performed at different pressure levels for saturated water and over time to capture multiple bubble departure events. The results of the present model were validated with the existing results available results from O.C.Jones and N.Zuber where the bubble is grown in a pool with a linear drop in pressure and also from results of Z.Wang and S.G.Bankoff where the bubble grows on the wall. The inclusion of an oscillating pressure field is observed to lead to a probability distribution in bubble departure diameter and departure time, which may explain similar experimental observations.

Presenting Author: Vinod Srinivasan University of Minnesota