Paper 7: Mass Flow Prediction in Natural Circulation Boilers

1969 ◽  
Vol 184 (7) ◽  
pp. 6-15
Author(s):  
A. S. T. Thomson ◽  
A. W. Scott ◽  
D. H. Rooney ◽  
A. M. Bradford
Keyword(s):  
Void Fraction ◽  
Flow Model ◽  
Natural Circulation ◽  
Circulation Rate ◽  
Two Phase ◽  
Flow Prediction ◽  
Friction Pressure ◽  
Type Flow ◽  
Friction Pressure Drop ◽  
Theoretical Results

This paper presents results from a programme of steady-state natural circulation tests carried out on a two-tube experimental boiler. The circuit was constructed using normal commercial tubes and the tests covered the following range of variables: During the tests, measurements were taken of pressure, pressure difference, circulation rate, and density or void fraction at the top of the riser tube. The void fraction data are presented for use. A theoretical analysis was carried out using an annular type flow model in the riser tube with a simple two-phase friction pressure drop expression which required only void fraction data. A comparison was made between the theoretical results and the experimental data and the comparison was extended to include ( a) homogeneous flow, ( b) Martinelli–Nelson correlation, and ( c) Thom correlation. The results indicate that the analysis used, which requires only void fraction data, gave the best correlation over the range of natural circulation conditions covered.

Two-Phase Void Fraction and Pressure Drop in Horizontal Crossflow Across a Tube Bundle

1998 ◽  
Vol 120 (1) ◽  
pp. 140-145 ◽  
Author(s):  
G. P. Xu ◽  
K. W. Tou ◽  
C. P. Tso
Keyword(s):  
Pressure Drop ◽  
Void Fraction ◽  
Mass Velocity ◽  
Flow Model ◽  
Tube Bundle ◽  
Diameter Ratio ◽  
Two Phase ◽  
Friction Pressure ◽  
Oil Flow ◽  
Friction Pressure Drop

Void fraction and friction pressure drop measurements were made for an adiabatic, horizontal two-phase flow of air-water, air-oil across a horizontal in-line, 5 × 20 tube bundle with pitch-to-diameter ratio, P/D, of 1.28. For both air-water and air-oil flow, the experimental results showed that the average void fraction were less than the values predicted by a homogenous flow model, but were well correlated with the Martinelli parameter Xtt and liquid-only Froude number FrLO. The two-phase friction multiplier data exhibited an effect of flow pattern and mass velocity, and they could be well-correlated with the Martinelli parameter.

Hydrodynamics of Two-Phase Flow Across Horizontal In-line and Staggered Rod Bundles

1992 ◽  
Vol 114 (3) ◽  
pp. 450-456 ◽  
Author(s):  
R. Dowlati ◽  
A. M. C. Chan ◽  
M. Kawaji
Keyword(s):  
Pressure Drop ◽  
Void Fraction ◽  
Flow Model ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Gas Velocity ◽  
Rod Bundles ◽  
Two Phase ◽  
Friction Pressure Drop ◽  
Velocity Effect

The void fraction and friction pressure drop measurements have been made for vertical two-phase flow of air-water across staggered and in-line rod bundles with different pitch-to-diameter ratios. All void fraction data showed a strong mass velocity effect and were significantly less than the values predicted by a homogeneous flow model, but were well correlated using the dimensionless gas velocity, jg*. The two-phase friction multiplier data could be well correlated with the Martinelli parameter for G > 200 kg/m2s. The correlations developed for void fraction and two-phase friction multiplier were successfully tested in predicting the total pressure drop in boiling R-113 experiments.

Two-Phase Natural Circulation Cooling Performance Assessment and Safety Analysis for APR1400 Core Catcher System

2014 ◽  
Author(s):  
Ki Won Song ◽  
Shripad T. Revankar ◽  
Hyun Sun Park ◽  
Bo Rhee ◽  
Kwang Soon Ha ◽  
...  
Keyword(s):  
Void Fraction ◽  
Flow Rate ◽  
Natural Circulation ◽  
Scaling Analysis ◽  
Circulation Flow ◽  
Two Phase ◽  
Cooling Performance ◽  
The Core ◽  
Core Catcher ◽  
Circulation Flow Rate

The two-phase natural circulation cooling performance of the APR1400 core catcher system is studied utilizing a drift flux flow model developed via scaling analysis and with an air-water experimental facility. Scaling analysis was carried out to identify key parameters, so that model facility could simulates two-phase natural circulation. In the experimental apparatus, instead of steam, air is injected into the top wall of the test channel to simulate bubble formation and void distribution due to boiling water in the core catcher channel. Measurement of void fraction critical to the heat transfer between the wall and coolant is carried out at certain key position using double-sensor conductivity probes. Results from the model provide expected natural circulation flow rate in the cooling channel of the core catcher system. The observed flow regimes and the data on void fraction are presented. For a given design of the down comer piping entrance condition bubble entrainment was observed that significantly reduced the natural circulation flow rate.

Computational and Experimental Study of the Flow in Evaporative Crystallizers

2005 ◽  
Author(s):  
Luiz F. Echeverri ◽  
Sumanta Acharya ◽  
Peter W. Rein
Keyword(s):  
Complex Geometry ◽  
Natural Circulation ◽  
Frictional Resistance ◽  
Product Yield ◽  
Circulation Rate ◽  
Physical Parameters ◽  
Two Phase ◽  
Convective Boiling ◽  
Void Fractions ◽  
The Individual

Various evaporative-crystallization systems rely on the natural circulation generated by boiling as the only driving force for the fluid flow. The circulation resulting from the balance between the buoyancy forces of the vapor bubbles and the frictional resistance plays an important role in the convective-boiling heat transfer, and it is desired that this circulation be as high as practically possible to maximize the capacity of the equipment and to lead to high-quality product yield. Although the basic mechanisms that govern the individual processes of boiling, buoyancy, and two-phase interactions have been extensively studied in simpler geometries, their combined behavior in the complex geometry of evaporative-crystallizers and the interaction of numerous physical and chemical variables make it difficult to understand and optimize the key parameters leading to improved product yield. In the present study measurements and computations have been reported both in a lab-scale test rig and in a full-scale crystallizer in order to obtain a better understanding of the physical processes. It is observed that one of the key physical parameters that influence the circulation rate is the drag coefficient, and that, existing correlations have to be corrected for flow contamination and high void fractions to obtain reasonable agreement with measurements.

Prediction of friction pressure drop for low pressure two-phase flows on the basis of approximate analytical models

2017 ◽  
Vol 64 (12) ◽  
pp. 898-911 ◽  
Author(s):  
N. O. Zubov ◽  
O. N. Kaban’kov ◽  
V. V. Yagov ◽  
L. A. Sukomel
Keyword(s):  
Pressure Drop ◽  
Low Pressure ◽  
Analytical Models ◽  
Two Phase Flows ◽  
Two Phase ◽  
Friction Pressure ◽  
Friction Pressure Drop
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