Abstract Based on the advancement of computational capability, high-precision analyses of multi-dimensional thermal hydraulic phenomena in nuclear power plants have been carried out. One of the multi-dimensional phenomena is two-phase flow in the upper downcomer. The quantification of momentum transfer between a downward liquid flow and a transverse gas flow in the reflood phase is significant because it determines the bypass flow rate of the emergency core coolant (ECC). Multi-dimensional modules of thermal-hydraulic analysis codes have been used to simulate this multi-dimensional two-phase flow. However, the model and correlations incorporated in the multi-dimensional modules are ones developed from one-dimensional experimental results. Because the characteristics of multi-dimensional phenomena are different from one-dimensional conditions, the implemented models and correlations might produce inaccurate results. Therefore, new models based on multi-dimensional experimental data should be developed. This study involved the twodimensional, two-phase experiments performed using 1/10 and 1/5 scale facilities. These were simplified unfolded downcomers of the Advanced Power Reactor 1400 (APR1400). The local measurement methods, pitot tubes, ultrasonic thickness gauge, and depth-averaged PIV, were applied to measure local variables: air velocity, liquid film velocity, and liquid film thickness. Local experimental data on the two-dimensional film flow were used to produce the wall and to inform interfacial friction factors from two-dimensional, two-phase momentum conservation equations. New wall and interfacial friction models were developed incorporating newly proposed physical concepts.
[1]
Dong-Jin Euh,et al.
Experimental study on two-dimensional film flow with local measurement methods
,
2015
.
[2]
N. D. Sylvester,et al.
A Review of Explicit Friction Factor Equations
,
1985
.
[3]
L. Herranz,et al.
Review of droplet entrainment in annular flow: Interfacial waves and onset of entrainment
,
2014
.
[4]
R. Lockhart.
Proposed Correlation of Data for Isothermal Two-Phase, Two-Component Flow in Pipes
,
1949
.
[5]
C F Colebrook,et al.
TURBULENT FLOW IN PIPES, WITH PARTICULAR REFERENCE TO THE TRANSITION REGION BETWEEN THE SMOOTH AND ROUGH PIPE LAWS.
,
1939
.
[6]
G. Wallis.
One Dimensional Two-Phase Flow
,
1969
.
[7]
Amods.
Korea Atomic Energy Research Institute
,
2000
.
[8]
Dong-Jin Euh,et al.
Scaling for the ECC bypass phenomena during the LBLOCA reflood phase
,
2004
.
[9]
S. M. Ghiaasiaan,et al.
Wall friction in annular-dispersed two-phase flow
,
1996
.
[10]
Dong-Jin Euh,et al.
Assessment of wall friction model in multi-dimensional component of MARS with air–water cross flow experiment
,
2017
.