An Updated Force Balance Approach to Investigate Bubble Sliding in Vertical Flow Boiling at Low and High Pressures

Abstract

An analysis of bubble sliding in vertical flow boiling is conducted using a revisited force balance including a recent formulation of the drag coefficient along with a proper derivation of added mass coefficients. The modeling strategy was further performed to avoid the use of too many empirical parameters.This offers the possibility to develop a non-dimensional approach that exhibits physical ranges of dominance for the detaching forces. Applied to experimental measurements, it shows that the main forces triggering departure by sliding at low and high pressures are respectively Added Mass and Drag forces. Predictions of bubble departure diameter using the force balance achieves good agreement over 122 measurements from several experimental data sets.Bubble sliding measurements from the literature at low and high pressures permitted to validate the model which was able to predict bubble velocity provided the use of a correct bubble growth rate.

Keywords: Vertical Flow Boiling, Bubble Departure Diameter, Bubble Sliding, Force Balance, Mechanistic Model, Non-Dimensional Approach