scholarly journals Numerical Simulation on Forced Convective Condensation of Steam Upward Flow in a Vertical Pipe

2014 ◽  
Vol 6 ◽  
pp. 589250 ◽  
Author(s):  
Guo-Dong Qiu ◽  
Wei-Hua Cai ◽  
Shu-Lei Li ◽  
Zhi-Yong Wu ◽  
Yi-Qiang Jiang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Velocity Field ◽  
Slug Flow ◽  
Annular Flow ◽  
Upward Flow ◽  
Vertical Pipe ◽  
Simulation Results ◽  
Churn Flow ◽  
Good Agreement

A transient three-dimensional volume of fluid (VOF) simulation on condensation of upward flow of wet steam inside a 12 mm i.d. vertical pipe is presented. The effect of gravity and surface tension are taken into account. A uniform wall temperature has been fixed as boundary conditions. The mass flux is 130~6400 kg m−2's−1 and the turbulence inside the vapor phase and liquid phase have been handled by Reynolds stress model (RSM). The vapor quality of fluid is 0~0.4. The numerical simulation results show that, in all the simulation conditions, the bubbly flow, slug flow, churn flow, wispy annular flow, and annular flow are observed; in addition, the results of flow pattern are in good agreement with the regime map from Hewitt and Roberts. The typical velocity field characteristic of each flow pattern and the effect of velocity field on heat transfer of condensation are analyzed, indicating that the slug flow and churn flow have obvious local eddy. However, no obvious eddy is observed in other flow patterns and the streamlines are almost parallel to the flow direction. The simulation results of heat transfer coefficients and frictional pressure drop show good agreement with the correlations from existing literatures.

Numerical Simulation of Condensation of Upward Flow in a Vertical Pipe

2014 ◽  
Author(s):  
Guodong Qiu ◽  
Zhiyong Wu ◽  
Yiqiang Jiang ◽  
Shulei Li ◽  
Weihua Cai
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Velocity Field ◽  
Flow Pattern ◽  
Slug Flow ◽  
Upward Flow ◽  
Vapor Quality ◽  
Vertical Pipe ◽  
Transfer Coefficients ◽  
Good Agreement

A transient three-dimensional volume of fluid (VOF) simulation on condensation of upward flow of wet steam inside a 12 mm i.d. vertical pipe is presented. The effect of gravity and surface tension are taken into account. A uniform wall heat flux have been fixed as boundary conditions. The mass flux is m=130∼6000 kg m−2 s−1 and the turbulence inside the vapor phase and liquid phase have been handled by Reynolds Stress (RS) model. The vapor quality of fluid x=0∼0.4. The numerical simulation results show that in all the simulated conditions only the bubbly flow, slug flow, churn flow and annular flow are observed, in addition the results of flow pattern are in good agreement with the regime map from Hewitt and Roberts. The typical velocity field characteristic of each flow pattern and the effect of velocity field on heat transfer of condensation are analyzed. It can be found that only slug flow has an obvious local eddy around the slug gas in all simulated flow patterns. The trend of heat transfer coefficients rises throughout with the increase of vapor quality for all simulated conditions, which is good agreement with the correlation from Boyko and Kruzhilin.

Numerical Simulation on Thixo-Forging of Magnesium Matrix Composite

2011 ◽  
Vol 189-193 ◽  
pp. 2535-2538 ◽  
Author(s):  
Hong Yan ◽  
Wen Xian Huang
Keyword(s):  
Numerical Simulation ◽  
Matrix Composite ◽  
Metal Flow ◽  
Magnesium Matrix Composite ◽  
Magnesium Matrix ◽  
Simulation Based ◽  
Prior Literature ◽  
Simulation Results ◽  
Computer Numerical Simulation ◽  
Good Agreement

The thixo-forging of magnesium matrix composite was analyzed with computer numerical simulation based on rigid viscoplastic finite element method. The constitutive model of SiCp/AZ61 composite was established in our prior literature. Behavior of metal flow and temperature field were obtained. The differences between traditional forging and thixo-forging processes were analyzed. Results indicated that thixo-forging was better in filling cavity than forging. Simulation results were good agreement with experimental ones.

Characteristics of Heat Transfer and Flow on a Surface With Small-Scale Concave Spherical Pits

2008 ◽  
Author(s):  
J. S. Wang ◽  
Y. Qiu ◽  
L. Y. Li
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Small Scale ◽  
Heat Transfer Mechanism ◽  
Transfer Enhancement ◽  
Special Effect ◽  
Turbulent Drag Reduction ◽  
Turbulent Drag ◽  
Simulation Results ◽  
Turbulent Coherent Structure

Small-scale concave spherical pits, which have a special effect on heat transfer enhancement and turbulent drag reduction, are investigated by numerical simulation in detail. Two kinds of small-scale concave pits structures are designed on surface of a plate, which are located in the bottom of a rectangle channel. The characteristics of heat transfer and flow in channel are investigated and compared with a same channel with plate bottom by means of LES. Flow structure and temperature distribution near the pits are analyzed. The numerical simulation results indicate that the concave spherical pits disturb the flow field and vortex is induced by the pits. The turbulent coherent structure is affected by the induced vortex. The numerical simulation indicates that small scale pit can generate the vortex in couple. The range of vortex is accord with the array of small scale pit. The small scale pit can enhance the intensity of vortex. As a result, the temperature field near the pit is changed with generation of the vortex. The heat transfer mechanism on plate with small scale concave spherical pit is summarized.

scholarly journals Numerical Simulations of V-Shaped Plates Subjected to Blast Loadings: A Validation Study

2016 ◽  
Vol 10 (11) ◽  
pp. 203
Author(s):  
Mohd Zaid Othman ◽  
Qasim H. Shah ◽  
Muhammad Akram Muhammad Khan ◽  
Tan Kean Sheng ◽  
M. A. Yahaya ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Variable Mass ◽  
Blast Loading ◽  
Experimental Results ◽  
Average Difference ◽  
Simulation Results ◽  
Blast Loadings ◽  
Carrier Vehicle ◽  
Good Agreement

A series of numerical simulations utilizing LS-DYNA was performed to determine the mid-point deformations of V-shaped plates due to blast loading. The numerical simulation results were then compared with experimental results from published literature. The V-shaped plate is made of DOMEX 700 and is used underneath an armour personal carrier vehicle as an anti-tank mine to mitigate the effects of explosion from landmines in a battlefield. The performed numerical simulations of blast loading of V-shaped plates consisted of various angles i.e. 60°, 90°, 120°, 150° and 180°; variable mass of explosives located at the central mid-point of the V-shaped vertex with various stand-off distances. It could be seen that the numerical simulations produced good agreement with the experimental results where the average difference was about 26.6%.

Heat Transfer Model and Analysis of Oil-Immersed Electrical Transformers with Heat Pipe Radiator

2012 ◽  
Vol 516-517 ◽  
pp. 312-315
Author(s):  
Guang Hua Li ◽  
Hong Lei Liu ◽  
De Jian Wang
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Temperature Field ◽  
Heat Pipe ◽  
Heat Transfer Model ◽  
Transfer Model ◽  
Cooling Device ◽  
Transformer Design ◽  
Electrical Transformers ◽  
Good Agreement

This paper has formulated a heat transfer model for analyzing the cooling properties of a heat pipe cooling device of oil-immersed electrical transformer. Based on the model, the oil temperature field of a 30 KVA oil-immersed transformer has been numerical simulated, and experiments also had been conducted. Results showed that the numerical simulation has good agreement with experiment results. Results also showed that heat pipe radiator is feasible for oil-immersed electrical transformer cooling. The model can be used to analyze the oil temperature distribution properties in an oil-immersed electrical transformer with heat pipe cooling device, and provide theoretical guide for transformer design and improvement.

Numerical Simulation of High-Temperature Air Direct-Ignition of Pulverized Coal

2005 ◽  
Author(s):  
Z. Z. Kang ◽  
B. M. Sun ◽  
Y. H. Guo ◽  
W. Zhang ◽  
H. Q. Wei
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
High Temperature ◽  
Simulation Method ◽  
Pulverized Coal ◽  
Inlet Velocity ◽  
Operation Optimization ◽  
Structure Improvement ◽  
Simulation Results ◽  
Direct Ignition

Numerical simulation method is employed in this article to investigate various high-temperature air direct-ignition processes of pulverized coal (PC). Several important factors are analyzed, which are the inlet velocity of primary air flow, PC concentration and the velocity and temperature of high temperature air. The flow, combustion and heat transfer in high temperature air oil-free ignition burner can also be obtained from the simulation results, which are in accordance with the experimental data. The research provides guidance for structure improvement and operation optimization of burner.

Numerical Simulation of Synthetic Heat Transfer in Laminar Nanofluid in a Horizontal Pipe

2014 ◽  
Vol 936 ◽  
pp. 409-414
Author(s):  
Mohsen Mirzaei ◽  
Mostafa Jafari Gishin ◽  
Mohammad Abbaspour
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Convective Heat Transfer Coefficient ◽  
Three Dimensional ◽  
Oxide Nanoparticles ◽  
Aluminum Oxide Nanoparticles ◽  
Horizontal Pipe ◽  
Water Based ◽  
Solid Liquid ◽  
Good Agreement

In this study, the effect of solid-liquid volumetric ratio in laminar flow of nanofluid has been investigated numerically. The conservation equations are utilized in three dimensional elliptical forms for laminar and steady flow, and the effects of adding aluminum oxide nanoparticles to water based-fluid are studied. First, the influence of solid-liquid volumetric ratio on the secondary flow vortices, non-dimensional temperature is investigated for a flow with a fixed low Reynolds number and different Grashof numbers in a horizontal pipe. Then, the effect of variation in solid-liquid volumetric ratio on Nusselt number and convective heat transfer coefficient along the pipe is studied. The results of this study are in good agreement with the current literatures.

Numerical Simulation and Stereo PIV Test of Inner Flow in a Double Blades Pump

2011 ◽  
Author(s):  
Kai Wang ◽  
Houlin Liu ◽  
Shouqi Yuan ◽  
Minggao Tan ◽  
Yong Wang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Velocity Field ◽  
Cfd Simulation ◽  
Research Work ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Absolute Velocity ◽  
Operation Condition ◽  
Test Technique ◽  
Simulation Results

A double blades pump is widely used in sewage treatment industry, while at present the research on the internal flow characteristics of the double blades pump is very few. So, the CFD technology and the stereo PIV test technique are applied to study the inner flow in a double blades pump whose specific speed is 110.9. The commercial code FLUENT is used to simulate the inner flow in the double blades pump at 0.6Qd, 0.8Qd, 1.0Qd, 1.2Qd and 1.4Qd. The RNG k-ε turbulence model and SIMPLEC algorithm are used in FLUENT. According to the results of the three-dimensional steady numerical simulation, the distributions of velocity field in the impeller are obtained at the five different operating conditions. The analysis of the numerical simulation results shows that there is an obvious vortex in the impeller passage at off-design conditions. But the number, location and area of the vortex are different from each operation condition. In order to validate CFD simulation results, the stereo PIV is used to test the absolute velocity distribution in the double blades pump at Jiangsu University. The distributions of three-dimensional absolute velocity field at the above five different operating conditions are obtained by the PIV test, and the measured results are compared with the CFD simulation results. The comparison indicates that there are vortexes in impeller passages of the double blades pump under the five operating conditions. But as to the area of the vortex and the relative velocity values of the vortex core, there are some differences between the experiment results and the numerical simulation results. The research work can be applied to instruct the hydraulic design of double blades pumps.

Numerical simulation of churn flow in a vertical pipe

2009 ◽  
Vol 64 (17) ◽  
pp. 3753-3765 ◽  
Author(s):  
Enrico Da Riva ◽  
Davide Del Col
Keyword(s):  
Numerical Simulation ◽  
Vertical Pipe ◽  
Churn Flow
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