<p style="text-align: justify">A numerical model is developed to analyze heat transfer and condensation of a spherical rising bubble.&nbsp; The model includes bubble shrinkage during condensation, and can be used to analyze the total energy loss of the bubble, raising velocity and bubble condensation rate of a single bubble compared to multiple bubbles with the same total thermal energy. The developed model consists of motion, heat, and mass transfer equations. For the validation, the model results were compared with a bubble condensation experiment data in the literature, which showed a good agreement with the experimental results. The dynamic term of the model is developed using the force balance on a gravity-driven bubble, including hydrodynamic drag force and gravity/buoyancy force, which acting with and against the bubble’s motion direction. For the thermal part of the model, a condensation correlation has been adapted to represent the Nusselt number as a function of Reynolds number , Jakob number&nbsp;and Prandtl number . A MATLAB code is developed in order to calculate the instantaneous velocity, the radius, and the mass loss of the vapor bubble in each time step. &nbsp;Moreover, the fundamental behavior for a single bubble and multiple bubbles was investigated in various initial conditions under the same total thermal energy. The effects of the initial bubble radius and the temperature difference between the liquid and vapor phases were analyzed for both scenarios in order to examine the condensation rate. It was found that the thermal behavior of the condensing bubble can be improved by forcing the bubble to collapse into sub bubbles, which will increase the total interfacial area and the raising velocity. Farther, due to generated sub bubbles, the resultant velocity increased the flow's turbulency and the heat transfer rate accordingly. This study can lead to improved heat transfer and more intensive research area to enhance the condensation rate.</p>

Condensation Heat Transfer Model: A Comparison Study of Condensation Rate Between a Single Bubble and Multiple Rising Bubbles

Paper Proceedings: https://asmedigitalcollection.asme.org/HT/HT2021/volume/84874

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