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

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

doi:10.3389/fenrg.2020.00008

Abstract

The influence of the size and the angle of the branch on the onset of gas entrainment is explored in the present study. Since the 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 in diameter and a branch of 31 mm in 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, 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 h_b/d; The critical Froude number ({Fr}_L) gradually increases as the angle of the branch changes from -90° to -30°; By comparing with previous models, it can be found that the correlation of 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 (hb*) to successfully expand the scope of application of correlation.

Highlights

In the AP1000 reactor of the third-generation nuclear power plant, the T-tube structure is widely used in the pipeline of the fourth-stage automatic depressurization system (ADS-4) and the passive residual heat removal system (PRHRS) (Schulz, 2008; Lin, 2010). Zuber (1980) pointed out that for the T-tube structure, when the gas–liquid stratified flow exists in the horizontal main pipe, the relative position of the branch/break and the gas–liquid interface will cause two different entrainment phenomena
This paper aims to investigate the effect of the size of the branch and the angle of the branch on the onset of gas entrainment and develop a more universal correlation for the prediction of onset of gas entrainment
The experiment on onset of gas entrainment was carried out in different directions of −30◦, −45◦, −60◦, and −90◦ through a branch with a diameter of 31 mm

Summary

Introduction

In the AP1000 reactor of the third-generation nuclear power plant, the T-tube structure is widely used in the pipeline of the fourth-stage automatic depressurization system (ADS-4) and the passive residual heat removal system (PRHRS) (Schulz, 2008; Lin, 2010). Zuber (1980) pointed out that for the T-tube structure, when the gas–liquid stratified flow exists in the horizontal main pipe, the relative position of the branch/break and the gas–liquid interface will cause two different entrainment phenomena. Zuber (1980) pointed out that for the T-tube structure, when the gas–liquid stratified flow exists in the horizontal main pipe, the relative position of the branch/break and the gas–liquid interface will cause two different entrainment phenomena. If the branch/break location is below the gas–water interface, the gas may be entrained by the continuous liquid stream through the branch/break, causing gas entrainment. If the branch/break location is above the interface, the liquid may be entrained by the continuous gas stream through the branch/break, causing liquid entrainment. During lossof-coolant accidents (LOCAs), gas entrainment may occur at the location of the break below the Influence of Branches on Onset horizontal interface. In a pressurized water reactor (PWR), gas entrainment may cause failure of residual heat removal pump (Guide, 1989). It is of great engineering value to study the gas entrainment phenomenon

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Conclusion