Dynamics Of Bubble Growth Research Articles

The growth of fission gas bubbles in irradiated uranium dioxide

Abstract The growth of fission gas bubbles from supersaturated solution in irradiated uranium dioxide has been studied by electron microscopy under isothermal annealing conditions between 1300° and 1500°C. Measurements of the kinetics of bubble growth have enabled the diffusion coefficients of atomic xenon and krypton in irradiated uranium dioxide to be determined. The diffusion coefficients obtained may be expressed by the equation: The results obtained from the current experiments are believed to be more precise than most of those obtained using the Booth model for gas released from solid samples of irradiated uranium dioxide during a post-irradiation anneal.

Nucleation site instability in nucleate boiling

The pool boiling process is one of the most effective heat transfer modes capable of transferring large amounts of heat with small temperature difference between the heated surface and the fluid. In addition, fundamental knowledge of pool boiling processes is the starting point of flow boiling research and applications. It is therefore no surprise that it has been, and still is, the subject of extensive research globally for quite some time and a critical analysis is now required in order to move forward with enhanced surface designs. The current on-going research focuses on the understanding of boiling fundamentals including bubble generation, growth and bubble dynamics. In this context, fluid-surface interaction is critical. In the first part of this two-part paper we present the factors and parameters affecting the above, starting with the criteria for gas/vapour entrapment, nucleation site stability and the superheat required for heterogeneous nucleation. The models predicting the incipience superheat are critically described, classified into phase instability and superheated boundary-layer based models. This first part includes bubble growth and departure models, elucidating the effect of surface topology and wettability that can inform and facilitate the design of enhanced surfaces that are presented in Part II [10]. Three fluids of industrial interest, i.e. FC-72, HFE7100 and water were used through the discussion, as examples, to represent low and high surface tension fluids and help the understanding of surface-fluid interactions and relation to possible heat transfer enhancements.

On the dynamics of hemispherical phase growth in nonuniform concentration fields

Theoretical calculations on the dynamics of asymptotic bubble growth in an initially nonuniform concentration field are performed. A significant simplification is achieved by noting that the Jakob number for mass transfer is usually small so that the convective transport can be neglected in comparison with the diffusive transport. Numerical solutions are obtained for the growth rate of a hemispherical bubble on a surface with linear and exponential initial concentration fields of the supersaturated gas in the diffusion boundary layers and also for the cases involving concentration fields resulting from the constant interfacial concentration and the constant mass flux experiments.

Dynamics of Hemispherical Phase Growth in Nonuniform Temperature Fields

Theoretical calculations on the dynamics of asymptotic bubble growth in initially nonuniform temperature fields resulting from the constant wall temperature and the constant heat flux experiments are presented.