Research on Two-Phase Flow Instability in Parallel Narrow Rectangular Channels Under Heaving Condition

2014 ◽  
Author(s):  
Libo Qian ◽  
Yingxian Gao ◽  
Shuhua Ding
Keyword(s):  
Flow Instability ◽  
Numerical Models ◽  
Homogeneous Model ◽  
Static Condition ◽  
Momentum Equation ◽  
Threshold Power ◽  
Two Phase ◽  
Rectangular Channels ◽  
Ocean Conditions ◽  
Static Conditions

A theoretical model for flow instability in parallel rectangular channels under ocean conditions was established using lumped method based on the homogeneous model. The model consists of flow instability under static condition, the model of additional forces generated by ocean conditions, the constitutive and numerical models. The effect of ocean conditions was introduced through additional forces in the momentum equation generated by ocean conditions. The code was validated with the experimental data of flow instability under static conditions. Then the margin of flow instability, the threshold power and the periods of the system under static condition was calculated as a basis condition for comparison. The effect of the heaving condition on flow instability will be analyzed analytically. Besides these, the effect of asymmetric heating and throttling under heaving condition will be shown.

Theoretical Research on Two-Phase Flow Instability in Parallel Rectangular Channels Under Periodic Perturbation

2020 ◽  
Author(s):  
Libo Qian ◽  
Jian Deng ◽  
Tao Huang ◽  
Rong Cai
Keyword(s):  
Pressure Drop ◽  
Channel Model ◽  
Flow Instability ◽  
Rectangular Channel ◽  
Static Condition ◽  
Periodic Perturbation ◽  
Theoretical Research ◽  
Threshold Power ◽  
Additional Pressure ◽  
Rectangular Channels

Abstract A theoretical model for Density Wave Oscillations (DWOs) flow instability in parallel rectangular channels under periodic heaving motion is established with a lumped mathematical model based on homogenous hypothesis. The parallel rectangular channels comprise of the entrance section, the heating section, the riser section and the upper- and lower plenums, which guarantee the isobaric pressure drop condition between channels and the model consists of boiling channel model, pressure drop model, parallel channel model, additional pressure drop model generated by heaving motions, the constitutive and numerical models. The effect of periodic perturbation is introduced through additional pressure drop in the momentum equation. The model is validated with experimental data of a twin-rectangular-channel flow instability experiment under static condition. Then the flow instability in parallel-rectangular-channel system is studied under periodic perturbation and the margin of flow instability and the threshold power of the system under static condition is calculated as basis condition for comparison. The effect of the amplitude and period of perturbation is analyzed analytically and the results show that the amplitude and period of perturbation shows little effect on flow instability. While when the additional pressure difference introduced by heaving motion is comparable with that under static condition, the effect of amplitude becomes stronger. And the period of perturbation strongly effects the threshold power when it is identical to that of natural period of the system, which can be explained by resonance between the perturbation and the system. And this effect is even stronger when the asymmetric heating condition is introduced.

Experimental study on Ledinegg flow instability of two-phase natural circulation in narrow rectangular channels at low pressure

2017 ◽  
Vol 98 ◽  
pp. 321-328 ◽  
Author(s):  
Shi Qi ◽  
Tao Zhou ◽  
Bing Li ◽  
Muhammad Ali Shahzad ◽  
Yaxiong Zou ◽  
...  
Keyword(s):  
Experimental Study ◽  
Flow Instability ◽  
Natural Circulation ◽  
Low Pressure ◽  
Two Phase ◽  
Rectangular Channels

Effect of Rolling Motion on Flow Instability of Parallel Rectangular Channels of Natural Circulation

2018 ◽  
Author(s):  
Xiaoyan Wang ◽  
Siyang Huang ◽  
Wenxi Tian ◽  
Lie Chen ◽  
Suizheng Qiu ◽  
...  
Keyword(s):  
Flow Instability ◽  
Natural Circulation ◽  
Static Condition ◽  
Circulation System ◽  
Rolling Motion ◽  
Boundary Line ◽  
Analysis Model ◽  
Rectangular Channels ◽  
Stable Conditions ◽  
Instability Boundary

In order to study the effect of rolling motion on flow instability of parallel rectangular channels of natural circulation, the natural circulation reactor simulation system is used for physical prototype. And theory analysis model of parallel rectangular channels of natural circulation system under rolling motion is established and coded by Fortran. The results of the program are verified to the experiments, and the results are in good agreement. The flow instability boundaries of different pressure under static and rolling motion are calculated respectively. The results show that: 1) under static condition, with the increase of the pressure, the instability boundary line changes, and the system becomes more stable; 2) under rolling conditions, the heating power of instability boundary decreases comparing to the stable conditions. The instability occurs earlier; 3) the stability of the system decreases with the increasing of rolling amplitude and frequency.

Experimental study of two phase flow instability in parallel narrow rectangular channels

2012 ◽  
Vol 50 ◽  
pp. 103-110 ◽  
Author(s):  
Zhou Yuan ◽  
Yan Xiao ◽  
Wang Yanlin ◽  
Liu Yanjun ◽  
Huang Yanping
Keyword(s):  
Experimental Study ◽  
Two Phase Flow ◽  
Flow Instability ◽  
Phase Flow ◽  
Two Phase ◽  
Rectangular Channels

Thermal-Hydraulic Experiments Under High Pressure Condition

2010 ◽  
Author(s):  
Wei Liu ◽  
Tamai Hidesada ◽  
Kazuyuki Takase ◽  
Hiroki Hayafune ◽  
Satoshi Futagami ◽  
...  
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Pressure Drop ◽  
Flow Instability ◽  
Homogeneous Model ◽  
Pressure Condition ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Transfer Tube ◽  
Churn Flow

For steam generator with straight double-walled heat transfer tube that used in sodium cooled Faster Breeder Reactor, flow instability is one of the most important items need researching. As the first step of the research, thermal hydraulics experiments with water were performed under high pressure condition in JAEA with using a circular tube. Pressure drop, heat transfer coefficients and void fraction data were derived. This paper summarizes the pressure drop characteristics under 15MPa. Several two-phase flow multiplier models were checked and Chisholm model and homogeneous model were found being the best ones for the prediction of present data. A sudden pressure drop decreasing tendency was observed when flow pattern shifts from bubbly/churn flow to annular flow. The reason for this decrease is tried interpreted.

Numerical Modeling of Boiling Heat Transfer in Microchannels

2005 ◽  
Author(s):  
R. K. Sarangi ◽  
A. Bhattacharya ◽  
R. S. Prasher ◽  
S. Narasimhan
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Input ◽  
Annular Flow ◽  
Flow Boiling ◽  
Numerical Models ◽  
Flow Direction ◽  
Homogeneous Model ◽  
Two Phase ◽  
Fluid Medium

In this paper we report the results of our modeling studies on two-phase forced convection in microchannels using water as the fluid medium. The study incorporates the effects of fluid flow rate, power input and channel geometry on the flow resistance and heat transfer from these microchannels. Two separate numerical models have been developed assuming homogeneous and annular flow boiling. Traditional assumptions like negligible single-phase pressure drop or fixed inlet pressure have been relaxed in the models making analysis more complex. The governing equations have been solved from the grass-root level to predict the boiling front, pressure drop and thermal resistance as functions of exit pressure and heat input. The results of both the models are compared to each other and with available experimental data. It is seen that the annular flow model typically predicts higher pressure drop compared to the homogeneous model. Finally, the model has also been extended to study the effects of nonuniform heat input along the flow direction. The results show that the nonuniform power map can have a very strong effect on the overall fluid dynamics and heat transfer.

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