AUTHOR=Gao Jinchen , Yue Yanwei , Meng Zhaoming , Li Xiaoyu , Shen Geyu 

TITLE=Influence of the Size and the Angle of Branches Connected to the Main Horizontal Pipe on the Onset of Gas Entrainment

JOURNAL=Frontiers in Energy Research

VOLUME=8

YEAR=2020

URL=https://www.frontiersin.org/journals/energy-research/articles/10.3389/fenrg.2020.00008

DOI=10.3389/fenrg.2020.00008

ISSN=2296-598X

ABSTRACT=<p>The influence of the size and the angle of the branch on the onset of gas entrainment is explored in the present study. Since previous studies were performed on small-sized branches and the angles of the branches were specific (0° or −90°), it is difficult to apply them to arbitrary-angled branches. So we conducted a series of experiments in a different direction of −30°, −45°, −60°, and −90° angles with the main pipe of 80-mm diameter and a branch of 31-mm diameter (T-tube). A new correlation is developed and can predict the most experimental data well within the error range of ±20%. And the new correlation can predict the onset of gas entrainment at arbitrary-angled branch and is not constrained by the angle of branches; that is, it has good versatility. We also gained some meaningful conclusions by analyzing experimental data and the entrainment phenomenon: gas is entrained by a vortex flow, and the size of the branch and the angle of the branch have little effect on the form of entrainment at a given <italic>h</italic><sub><italic>b</italic></sub>/<italic>d</italic>. The critical Froude number (<italic>Fr</italic><sub><italic>L</italic></sub>) gradually increases as the angle of the branch changes from −90° to −30°. When this is compared with previous models, it can be found that the correlation of the onset of gas entrainment based on small-sized branches is not suitable for large-scale branches. But we have defined a new critical liquid level (<inline-formula><mml:math id="M1" xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mrow><mml:mi>h</mml:mi></mml:mrow><mml:mrow><mml:mi>b</mml:mi></mml:mrow><mml:mrow><mml:mo>*</mml:mo></mml:mrow></mml:msubsup></mml:math></inline-formula>) to successfully expand the scope of application of the correlation.</p>