Bubble Growth Dynamics in Boiling

Abstract

<p>This dissertation details a fundamental study of bubble growth dynamics for both spherical vapour bubbles in a uniform temperature field and hemispherical bubbles on a heated plane surface in a non-uniform temperature field in microgravity. The governing equations were solved numerically in order that accurate predictions of bubble growth could be generated for a wide range of system conditions for two fluids, water and R113. One dimensional spherically symmetric bubble growth in an initially uniformly superheated liquid was investigated by first developing grid and time step independent solutions on a computational grid with uniform spacing between adjacent nodes. These solutions were utilized as benchmark solutions for subsequent bubble growth models. A clustered grid arrangement was then implemented to reduce the computational time with insignificant loss of accuracy. The numerical predictions of the uniform and clustered grid arrangements predict the available analytic theories and experimental data with sufficient accuracy. The mechanisms which govern the growth of a spherical vapour bubble in an unbounded liquid were exposed by investigating the complex interaction between the heat transfer and the fluid flow surrounding a bubble as it grows from inception, through the various growth stages, to diffusion controlled growth. The influence of system pressure and liquid superheat were also investigated. Utilizing similar physical arguments, the model developed for spherically symmetric growth was extended to simulate hemispherical growth at a heated plane surface in microgravity. The theory was able to accommodate both spatial and temporal variations in the temperature and velocity fields in the liquid surrounding the bubble as it grows. Utilizing the present theory, the complicated thermal and hydrodynamic interactions between the vapour, liquid and solid have been manifested for a single isolated bubble growing on a heated plane surface from inception.</p>