Mechanistic Prediction of Dryout Heat Flux in Annular Two-Phase Flow

2002 ◽  
Author(s):  
Tomio Okawa ◽  
Saeyun Kim ◽  
Isao Kataoka ◽  
Masanori Naitoh
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Annular Flow ◽  
Density Ratio ◽  
Droplet Deposition ◽  
Simple Correlation ◽  
Two Phase ◽  
Transition Length ◽  
The Mean ◽  
Liquid Film Dryout

Incorporating the recently developed correlations for the rates of droplet deposition and entrainment with the film flow model, critical heat flux due to liquid film dryout in steam-water annular flow was predicted. In the present calculations, the predicted critical heat flux is affected not only by the deposition and entrainment rates but also by the entrainment fraction at the transition to annular flow (Transition quality was estimated by Wallis’s correlation). For this reason, the entrainment fraction at the transition was correlated in terms of dimensionless transition length to annular flow and density ratio. A simple correlation for the occurrence of dryout was also proposed. It was demonstrated by numerical simulations that the present method is to predict the available 1,340 data of dryout heat flux with the mean square relative error of 0.068.

Experimental Study on Liquid Film Dryout Under Oscillatory Flow Conditions

2009 ◽  
Author(s):  
Yosuke Yamagoe ◽  
Taisuke Goto ◽  
Tomio Okawa
Keyword(s):  
Heat Flux ◽  
Liquid Film ◽  
Power Density ◽  
Critical Heat Flux ◽  
Boiling Water ◽  
Boiling Water Reactors ◽  
Flow Oscillation ◽  
Two Phase ◽  
Water Reactors ◽  
Liquid Film Dryout

The use of high power density core is one of the promising ways to improve economic efficiency of advanced boiling water reactors. It is however known that in boiling two-phase flows, an increase in power density commonly reduces the margin to the onset of unanticipated flow instability. Hence, in the development of a boiling water reactor of high power density core, ability to predict the occurrence of boiling transition is considered indispensable even when the coolant flow rate is not in the steady state. In the present work, sinusoidal oscillation was applied to the inlet mass flux and the experimental measurement of the critical heat flux was carried out under flow oscillation conditions. It was shown that the critical heat flux decreases monotonically with increased values of oscillation amplitude and oscillation period. These results are consistent with experimental data reported by previous investigators. A simple theory was then proposed to estimate the critical heat flux in oscillatory flow condition. Considering the application to the advanced boiling water reactors, the triggering mechanism of the critical heat flux condition is supposed to be the liquid film dryout in annular two-phase flow regime of high vapor quality. Under the flow oscillation condition, it is expected that long waves are formed on a liquid film due to the time variation of inlet mass flux. Assuming that the wave evolution within a boiling channel is influential in the occurrence of the local dryout of a liquid film, an available nonlinear wave theory was applied to the estimation of critical heat flux under the flow oscillation condition. It was demonstrated that the critical heat fluxes measured under the oscillatory conditions agree with the proposed theory fairly well.

Critical heat flux and the dryout of liquid film in vertical two-phase annular flow

2021 ◽  
Vol 177 ◽  
pp. 121487
Author(s):  
R.W. Morse ◽  
T.A. Moreira ◽  
J. Chan ◽  
K.M. Dressler ◽  
G. Ribatski ◽  
...  
Keyword(s):  
Heat Flux ◽  
Liquid Film ◽  
Critical Heat Flux ◽  
Annular Flow ◽  
Two Phase

Liquid film dryout model for predicting critical heat flux in annular two-phase flow

2009 ◽  
Vol 10 (3) ◽  
pp. 398-417 ◽  
Author(s):  
Bo Jiao ◽  
Li-min Qiu ◽  
Jun-liang Lu ◽  
Zhi-hua Gan
Keyword(s):  
Heat Flux ◽  
Liquid Film ◽  
Critical Heat Flux ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Liquid Film Dryout
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