scholarly journals Investigation of correlation diagram between heat transfer coefficient and void fraction under sodium–water reaction

2012 ◽  
Vol 49 (6) ◽  
pp. 610-617
Author(s):  
Toshinori Matsumoto ◽  
Takashi Takata ◽  
Akira Yamaguchi ◽  
Akikazu Kurihara ◽  
Hiroyuki Ohshima
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Void Fraction ◽  
Correlation Diagram

Numerical Analysis of Heat Transfer Characteristics of External Cooling Channel of the Lower Head

2018 ◽  
Author(s):  
Dan Li ◽  
Changhong Peng ◽  
Yun Guo
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Void Fraction ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
External Cooling ◽  
Lower Head ◽  
Laminar And Turbulent Flow ◽  
The Heat Transfer Coefficient

The heat transfer coefficient of the curved surface reflects the external cooling capacity of the reactor pressure vessel under serious accident. This topic used Ansys fluent software 14.5 as simulation tool, mesh generation of the flow area is carried out after the geometric model of the lower head, and then the heat transfer coefficient of the curved surface is numerically simulated. In this paper, the heat transfer coefficient formulas are fitted according to the laminar and turbulent flow, and the influence of the cavity on the heat transfer coefficient is discussed. Calculation results show that, for single-phase flow both laminar and turbulent flow, the heat transfer coefficients increase with the increase of Re, and increase with the increase of Pr, decrease with the increase of theta; According to the comparison of the heat transfer coefficients under different radii of curved surfaces, reducing the radius is beneficial to increase the heat transfer capability; In subcooled boiling flow, the void fraction is less than 21%, the heat transfer coefficient increases with the increases of the void fraction, the void fraction is conducive to heat transfer; but when the void fraction is higher than 21%, it is opposite.

scholarly journals Numerical study on CTF code to predict void fraction in PWR sub channel conditions

2015 ◽  
Vol 5 (4) ◽  
pp. 30-38
Author(s):  
Minh Giang Hoang ◽  
Tan Hung Hoang ◽  
Phu Khanh Nguyen
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Forced Convection ◽  
Void Fraction ◽  
Single Channel ◽  
Numerical Study ◽  
High Quality ◽  
Operation Conditions ◽  
Channel Conditions

CTF is a version of the widely used COBRA-TF code with capability of 3D simulation for core sub channel thermal hydraulics behavior. Recently, CTF is reviewed and the consideration of CTF to predict void fraction in PWR sub channel conditions such as subcooled region still  need more investigation. Due to the fact that the Chen’s correlation of heat transfer coefficient  is developed for relatively low pressure and high quality conditions associated with forced convection vaporization, and is not strictly valid for  PWR operation conditions, so that, in this study,  some runs of single channel in the benchmark based on NUPEC PWR Sub channel and Bundle Tests (PSBT) are used to investigate  void fraction prediction by CTF  in subcooled region and also to verify  some remarkable notice of CTF from other authors. The goal of the study is to evaluate deviation for CTF void fraction prediction in PWR sub channel conditions.

Two-Phase Crossflow and Boiling Heat Transfer in Horizontal Tube Bundles

1996 ◽  
Vol 118 (1) ◽  
pp. 124-131 ◽  
Author(s):  
R. Dowlati ◽  
M. Kawaji ◽  
A. M. C. Chan
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Void Fraction ◽  
Mass Velocity ◽  
Flow Boiling ◽  
Horizontal Tube ◽  
Two Phase ◽  
Tube Bundles

An experimental study has been conducted to determine the void fraction, frictional pressure drop, and heat transfer coefficient for vertical two-phase crossflow of refrigerant R-113 in horizontal tube bundles under saturated flow boiling conditions. The tube bundle contained 5 × 20 tubes in a square in-line array with pitch-to-diameter ratio of 1.3. R-113 mass velocity ranged from 50 to 970 kg/m2s and test pressure from 103 to 155 kPa. The void fraction data exhibited strong mass velocity effects and were significantly less than the homogeneous and in-tube flow model predictions. They were found to be well correlated in terms of the dimensionless gas velocity, jg*. The two-phase friction multiplier data could be correlated well in terms of the Lockhart–Martinelli parameter. The validity of these correlations was successfully tested by predicting the total pressure drop from independent R-113 boiling experiments. The two-phase heat transfer coefficient data were found to agree well with existing pool boiling correlations, implying that nucleate boiling was the dominant heat transfer mode in the heat flux range tested.

The Characteristics of Steam Bubbles in Subcooled Boiling Flow

2002 ◽  
Author(s):  
Takatoshi Takemoto ◽  
Mitsuo Matsuzaki ◽  
Hroshige Kikura ◽  
Masanori Aritomi ◽  
Asi Bunyajitradulya
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Void Fraction ◽  
Liquid Flow ◽  
Interfacial Area ◽  
Bubble Collapse ◽  
Interfacial Heat Transfer Coefficient ◽  
Interfacial Heat Transfer ◽  
Interfacial Area Concentration

In two-fluid modeling and three-fluid modeling, the accurate prediction of the interfacial area concentration, interfacial heat transfer and interfacial shear stress, were required. In this works, the axial profiles of void fraction, interfacial area concentration and interfacial heat transfer coefficient along the flow direction could be measured. For the steam bubbles whose diameter were less than 8mm, the interfacial area concentration and the mean bubble diameter had a correlation with void fraction despite the variation of liquid flow rate and subcooling. In case the steam bubble collapse occurred due to an irregular bubble condensation and a turbulence of liquid flow, interfacial heat transfer coefficient with the bubble collapse was about twice of that without a bubble collapse. And the interfacial heat transfer coefficient without bubble collapse showed a good agreement with the correlation proposed by Akiyama. In addition, the supposed image processing method could be applied to the present experimental condition.

Two-Phase Flow Behavior and Heat Transfer Characteristics in Kettle Reboiler

2017 ◽  
Author(s):  
Takeru Miyazaki ◽  
Misaki Baba ◽  
Hideki Murakawa ◽  
Hitoshi Asano ◽  
Katsumi Sugimoto ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Void Fraction ◽  
Flow Condition ◽  
Tube Bundle ◽  
Tube Bundles ◽  
Void Fraction Distribution ◽  
Fraction Distribution ◽  
Time Average

Effects of the tube array, such as in-line and staggered, on void-fraction distribution and heat transfer coefficient around a tube were experimentally investigated. The test section was vertical duct with inner size of 90 × 90 mm2. Diameter of the tubes was 15 mm, and the pitch-to-diameter ratio was 1.5 for both tube bundles. Working fluids were air and water. Experiments were carried out at superficial gas velocity defined at minimum area section, Jg, of 0.10 to 0.89 m/s, superficial liquid velocity, Jl, of 0.1 to 0.3 m/s, under the atmospheric condition. Measurements of void-fraction distribution were carried out using X-ray radiography. In addition, heat transfer coefficient around a tube was measured and the heat transfer coefficients in association with the flow regime and the void-fraction distribution were evaluated. Time-average void-fraction was higher around upstream of a tube than that of downstream at bubbly flow condition for both bundles. Under intermittent flow condition, time-average void fraction at the maximum gap were higher than that around the other points in both tube bundles. For in-line tube bundle, enhancement of the heat transfer clearly appeared between ±90 to 180°. For staggered tube bundle, the heat transfer increased all over the pipe.

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