Numerical modelling of air–nanofluid bubbly flows in a vertical tube using the MUltiple-SIze-Group (MUSIG) model

2016 ◽  
Vol 102 ◽  
pp. 856-866 ◽  
Author(s):  
Yang Yuan ◽  
Xiangdong Li ◽  
Jiyuan Tu
Keyword(s):  
Numerical Modelling ◽  
Vertical Tube ◽  
Size Group ◽  
Bubbly Flows

Investigation and Modeling of the In-Tube Heat Transfer of Fluids at Supercritical Pressure During Heating

2017 ◽  
Author(s):  
Chen-Ru Zhao ◽  
Zhen Zhang ◽  
Han-Liang Bo ◽  
Pei-Xue Jiang
Keyword(s):  
Heat Transfer ◽  
Numerical Modelling ◽  
Convection Heat Transfer ◽  
Turbulence Models ◽  
Vertical Tube ◽  
Supercritical Pressure ◽  
Flow And Heat Transfer ◽  
Pressure Water ◽  
Predicted Values ◽  
Semi Empirical

Investigations and numerical modelling are performed on the heat transfer to CO2 at supercritical pressure under buoyancy affected conditions during heating in a vertical tube with inner diameter of 2 mm. Numerical modelling are carried out using several low Reynolds number (LRN) k-ε models, including the model due to Launder and Sharma (LS), Abe, Kondoh and Nagano (AKN), Myong and Kasagi (MK) models. The numerical results are compared with the corresponding experimental data and the predicted values using the semi-empirical correlation for convection heat transfer of supercritical fluids without deterioration. The abilities of various LRN models to predict the heat transfer to fluids at supercritical pressures under normal and buoyancy affected heat transfer conditions are evaluated. Detailed information related to the flow and turbulence is presented to get better understanding of the mechanism of the heat transfer deterioration due to buoyancy, as well as the different behavior of various LRN turbulence models in responding to the buoyancy effect, which gives clues in future model improvement and development to predict the buoyancy affected heat transfer more precisely and in a broader range of conditions as they come to be used to simulate the flow and heat transfer in various applications such as in the supercritical pressure water-cooled reactor (SCWR) and the supercritical pressure steam generator in the high temperature gas cooled reactor (HTR).

Bubble Size and Group Influence for CFD Simulation in Vertical Tube Upward Flow

2010 ◽  
Author(s):  
Songwei Li ◽  
Hong Zhang
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Void Fraction ◽  
Wall Temperature ◽  
Cfd Simulation ◽  
Vertical Tube ◽  
Size Group ◽  
Upward Flow ◽  
Wall Area ◽  
Near Wall

The near-wall bubble congregating in vertical tube upward flow exerts an influence on fluid heat transfer. A 0.5m test section is simulated using CFX10.0 to research the bubble influence on the heat transfer. The vapor-water two-phase CFD calculation is done. The bubbles are added at near wall area, taking no account of the mass transfer between water and vapor. The different bubble max diameter and the different MUSIG model size group get different calculation results, these results are compared, include the distribution of vapor void fraction, the wall temperature distribution and near-wall water temperature distribution, the bubble mean diameter. A guide setting is advised. The calculation result shows that the max bubble diameter and the MUSIG size group on the vapor void fraction distribution is large. The near-wall void fraction gets down to the least (nearly zero, while at the inlet, near wall vapor fraction is 0.95) at 0.1m∼0.14m axis height, then rises. The wall temperature gets highest at the same height, and then appears a flat, keeping this temperature about 0.1m long, after that the temperature gets down, then rises along the axis.

Microstructure in soft magnetic E3 (S1, Al) (Sendust) alloys

1988 ◽  
Vol 46 ◽  
pp. 770-771
Author(s):  
June D. Kim
Keyword(s):  
Electron Microscopy ◽  
Magnetic Properties ◽  
Ternary Phase Diagram ◽  
Vertical Tube ◽  
Vacuum Induction Melting ◽  
Induction Melting ◽  
Soft Magnetic ◽  
Quenching Temperature ◽  
Thin Foils ◽  
Vertical Tube Furnace

Iron-base alloys containing 8-11 wt.% Si, 4-8 wt.% Al, known as “Sendust” alloys, show excellent soft magnetic properties. These magnetic properties are strongly dependent on heat treatment conditions, especially on the quenching temperature following annealing. But little has been known about the microstructure and the Fe-Si-Al ternary phase diagram has not been established. In the present investigation, transmission electron microscopy (TEM) has been used to study the microstructure in a Sendust alloy as a function of temperature.An Fe-9.34 wt.% Si-5.34 wt.% Al (approximately Fe3Si0.6Al0.4) alloy was prepared by vacuum induction melting, and homogenized at 1,200°C for 5 hrs. Specimens were heat-treated in a vertical tube furnace in air, and the temperature was controlled to an accuracy of ±2°C. Thin foils for TEM observation were prepared by jet polishing using a mixture of perchloric acid 15% and acetic acid 85% at 10V and ∼13°C. Electron microscopy was performed using a Philips EM 301 microscope.

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