Bubble Diameter Effects on CFD Simulation for Subcooled Boiling Flow in Rolling Circular Tube

Abstract

Eulerian two-fluid model coupled with wall boiling model was employed to calculate the three dimensional flow field and local parameter distribution with different bubble diameter models in circular tube under static and rolling condition. The wall boiling model utilized in this study was validated by Bartolomei experiment data, and a good agreement can be obtained. The calculation results of local void fraction are compared with experiment data to verify the accuracy of the numerical calculation for subcooled boiling flow under rolling condition. The Zeitoun bubble mean diameter model which the most recommended correlation for bubble diameter under low pressure and several fixed bubble diameters are applied to simulate the same condition in low pressure. These results are compared, include the distribution of void fraction, velocity distribution and radial flow induced by rolling motion. A good agreement with the experimental data has been achieved when Zeition bubble mean diameter and 2 mm fixed bubble diameter are used to describe vapor diameter in static condition. The local void fraction fluctuation has the same period with the rolling motion, and the fluctuation amplitude increases with the increase of rolling amplitude and rolling frequency. The difference shown in rolling condition between calculation results and experimental data demonstrates that better agreement with the experimental data has been achieved in the near-wall region about local void fraction which has bigger fluctuation amplitude. Higher void fraction has gotten using Zeition bubble mean diameter model to describe bubble diameter in subcooled boiling flow, tiny difference has showed in temperature, velocity and radial velocity in different bubble diameter model. Accurate vapor diameter model or method to describe vapor diameter coupled with suitable interphase force model is needed in rolling condition under low pressure to fit the calculation of subcooled boiling better under rolling condition.