Library Subscription: Guest
Home Archives Officers Future meetings American Society of Thermal and Fluids Engineering
Second Thermal and Fluids Engineering  Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

TOWARDS A CFD MODEL OF AIR-NANOFLUID MULTI-DISPERSED BUBBLY FLOWS IN A VERTICAL TUBE

Yang Yuan
School of Engineering, RMIT University, Bundoora, VIC 3083, Australia

Xiangdong Li
School of Engineering, RMIT University, Bundoora, VIC 3083, Australia

Jiyuan Tu
School of Engineering, RMIT University, Bundoora, VIC 3083, Australia; Key Laboratory of Ministry of Education for Advanced Reactor Engineering and Safety, Institute of Nuclear and New Energy Technology, Tsinghua University, 30 Shuang Qing Rd. Haidian District, Beijing 100086, China

Abstract

It was experimentally found that the addition of nanoparticles in the liquid could significantly impact the two-phase flow behaviours of nanofluid bubbly flows. Considering the profound inter-coupling of two-phase flow structures and the overall heat transfer performances, a three-dimensional MUtiple-SIze-Group (MUSIG) model was employed in this study to quantify the effect of nanoparticles on the flow dynamics for the purpose of achieving an effective modelling of nanofluid bubbly flows. The radial profiles of flow parameters including the void fraction, bubble velocity, interfacial area concentration and Sauter mean bubble diameter were predicted and compared against the experimental data. It was found that the inclusion of a correction term kd=1.02 into the drainage time calculation led to improved predictions of void fraction, which predicted results were in better agreement with experimental results. Further analyses indicated that under the driving force of minimised Gibbs free energy, nanoparticles suspending in the liquid tend to spontaneously adsorb at the bubble interface, which was believed to hinder the bubble coalescence by forming a physical barrier and consequently prolonging the film drainage process. The underlying mechanisms of the effects of nanoparticle adsorption on bubble coalescence, such as the altered surface properties, the hindered water flow at bubble surface and the modified disjoining pressure, were also discussed in this study. It was recommended that the key job when modelling the bubbly flows of nanofluids using the MUSIG model is to reformulate the bubble coalescence model accounting for the effects of nanoparticle adsorption.

Purchase $20.00 Check subscription Publication Ethics and Malpractice Recommend to my Librarian Bookmark this Page