scholarly journals Numerical Investigation on Turbulent Flow and Heat Transfer of Helium-Xenon Gas Mixture in a Circular Tube

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Biao Zhou ◽  
Han Zhang ◽  
Yu Ji ◽  
Jun Sun ◽  
Yuliang Sun
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulent Flow ◽  
Circular Tube ◽  
Working Fluid ◽  
Gas Mixture ◽  
Turbulent Heat ◽  
Radial Temperature ◽  
Flow And Heat Transfer ◽  
Xenon Mixture

Gas-cooled space nuclear reactor system usually utilizes the helium-xenon gas mixture as the working fluid. Since the typical helium-xenon mixture has the Prandtl number of about 0.2, which is lower than that of water and air, the turbulent flow and heat transfer features need to be further investigated among the helium-xenon mixture and other fluids. In the current paper, numerical investigations by ANSYS Fluent are performed on helium-xenon mixture flow (HeXe40, M = 40.0 g/mol, Pr = 0.21), airflow (Pr = 0.71), and water flow (Pr = 6.99) in the circular tube. Direct numerical simulation results of liquid metal flow (Pr = 0.01) are also adopted for comparison. Results show that the dimensionless velocity profile and shear stress in the boundary layer of HeXe40 are close to those of other fluids. The empirical correlations from other fluids can also predict well the friction factor of helium-xenon mixtures. Due to the discrepancy in turbulent heat diffusivity ratio, the dimensionless radial temperature profile and turbulent heat conduction of HeXe40 significantly differ from those of other fluids. The molecular conduction region of HeXe40 develops up to y+ ≈ 30 and extends to the logarithmic region of the flow boundary layer. Moreover, the available experimental Nusselt numbers of helium-xenon mixtures are compared with several convective heat transfer correlations, in which Kays correlation is better.

Numerical Modeling of Turbulent Flow and Heat Transfer Within a Bayonet Tube

2007 ◽  
Author(s):  
Feng Sun ◽  
G.-X. Wang
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Experimental Result ◽  
Working Fluid ◽  
Transfer Performance ◽  
Flow And Heat Transfer ◽  
Air Jet ◽  
The Impact

This paper presents a numerical study of turbulent flow and heat transfer in a bayonet tube under steady state. First, various turbulent models and wall treatment methods have been tested and validated against the experimental result from a turbulent air jet. The proper combination of turbulent model and wall treatment is then recommended for the turbulent flow within a bayonet tube. The study focuses on the heat transfer performance at the interface of working fluid and the outer tube wall under different Reynolds numbers. Various geometry parameters are considered in this work and the impact of geometry on the heat transfer performance is investigated. Results indicate that the heat transfer at the bottom of the bayonet tube is enhanced compared with that at the straight part. At low Re (< 8000), the maximum Nu occurs at the stagnation point, while the position of the maximum Nu moves away from the stagnant point as Re exceeds 8000. The results are believed to be helpful for the optimized design of a bayonet tube with fully turbulent flows.

A New Heat Transfer Correlation for Turbulent Flow of Air With Variable Properties in Noncircular Ducts

2014 ◽  
Vol 136 (10) ◽  
Author(s):  
Peng Wang ◽  
Mo Yang ◽  
Zhiyun Wang ◽  
Yuwen Zhang
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Circular Tube ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Hydraulic Diameter ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Variable Properties ◽  
Corner Region

Turbulent flow and heat transfer of air with variable properties in a set of regular polygonal ducts and circular tube have been numerically simulated. All the ducts have the same hydraulic diameter as their characteristic lengths in the Reynolds number. The flow is modeled as three-dimensional (3D) and fully elliptic by using the finite volume method and the standard k-ε turbulence model. The results showed that the relatively strong secondary flow could be observed with variable properties fluid. For the regular polygonal ducts, the local heat transfer coefficient along circumferential direction is not uniform; there is an appreciable reduction in the corner region and the smaller the angle of the corner region, the more appreciable deterioration the corner region causes. The use of hydraulic diameter for regular polygonal ducts leads to unacceptably large errors in turbulent heat transfer determined from the circular tube correlations. Based on the simulation results, a correction factor is proposed to predict turbulent heat transfer in regular polygonal ducts.

Direct numerical simulation of turbulent flow and heat transfer in a spatially developing turbulent boundary layer laden with particles

2018 ◽  
Vol 845 ◽  
pp. 417-461 ◽  
Author(s):  
Dong Li ◽  
Kun Luo ◽  
Jianren Fan
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Turbulent Flow ◽  
Solid Particles ◽  
Heated Wall ◽  
Wall Region ◽  
Flow And Heat Transfer ◽  
Particle Laden Flows ◽  
Near Wall

Direct numerical simulations of particle-laden flows in a spatially developing turbulent thermal boundary layer over an isothermally heated wall have been performed with realistic fully developed turbulent inflow boundary conditions. To the authors’ best knowledge, this is the first time the effects of inertial solid particles on turbulent flow and heat transfer in a flat-plate turbulent boundary layer have been investigated, using a two-way coupled Eulerian–Lagrangian method. Results indicate that the presence of particles increases the mean streamwise velocity and temperature gradients of the fluid in the near-wall region. As a result, the skin-friction drag and heat transfer are significantly enhanced in the particle-laden flows with respect to the single-phase flow. The near-wall sweep and ejection motions are suppressed by the particles and hence the Reynolds shear stress and wall-normal turbulent heat flux are attenuated, which leads to reductions in the production of the turbulent kinetic energy and temperature fluctuations. In addition, the coherence and spacing of the near-wall velocity and temperature streaky structures are distinctly increased, while the turbulent vortical structures appear to be disorganized under the effect of the particles. Moreover, the intensity of the streamwise vortices decreases monotonically with increasing particle inertia.

The Characteristics of Turbulent Heat Transfer in a Curved Rectangular Duct With Various Aspect Ratios

2010 ◽  
Author(s):  
Hang Seok Choi ◽  
Tae Seon Park
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Turbulent Flow ◽  
Secondary Flow ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Rectangular Duct ◽  
Flow And Heat Transfer ◽  
Aspect Ratios ◽  
Turbulent Characteristics

The turbulent flow fields of a parallel plate or channel with spatially periodic condition have been widely investigated by many researchers. However the rectangular or square curved duct flow has not been fundamentally scrutinized in spite of its engineering significance, especially for cooling device. Hence, in the present study large eddy simulation is applied to the turbulent flow and heat transfer in a rectangular duct with 180° curved angle varying its aspect ratio. The turbulent flow and the thermal fields are calculated and the representative vortical motions generated by the secondary flow are investigated. From the results, the secondary flow has a great effect on the heat and momentum transport in the flow. With changing the aspect ratio, the effect of the geometrical variation to the secondary flow and its influence on the turbulent characteristics of the flow and heat transfer are studied.

Numerical Study of a New Heat Transfer Correlation for Turbulent Air Flow in Noncircular Ducts With Variable Properties

2013 ◽  
Author(s):  
Mo Yang ◽  
Peng Wang ◽  
Yuwen Zhang ◽  
Zhiyun Wang
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Circular Tube ◽  
Numerical Study ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Hydraulic Diameter ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Variable Properties

Turbulent flow of air with variable properties in a set of regular polygonal ducts and circular tube have been numerically simulated. All the ducts have the same hydraulic diameter as their characteristic length dimension in the Reynolds number. The flow is modeled as three-dimensional and fully elliptic by using the finite volume method and the standard k-ε turbulence model is adopted. The performances of the flow and heat transfer have been thoroughly investigated. The results showed that comparatively strong secondary flow can be observed with variable properties fluid. For the regular polygonal duct, the local heat transfer coefficient along circumferential direction is not uniform and there is an appreciable reduction in the corner region. The use of hydraulic diameter for regular polygonal ducts to determine turbulent flow heat transfer from circular tube correlations leads to unacceptably large errors. Based on the simulation results, a correction factor Cϕ is proposed to ameliorate the previous correlations, and the error in the prediction of turbulent heat transfer with the new correlation is within 6%.

Numerical Simulation of Turbulent Heat Transfer to Near-Critical Water in a Curved Pipe

2002 ◽  
Author(s):  
B. Zheng ◽  
C. X. Lin ◽  
M. A. Ebadian
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Critical Point ◽  
Reynolds Stress Model ◽  
Force Convection ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Constant Wall Temperature ◽  
Curved Pipe ◽  
Flow And Heat Transfer

Numerical simulations are performed to investigate the developing turbulent flow and heat transfer characteristics of water near the critical point in a curved pipe. The Reynolds stress model is employed to simulate the turbulent flow and heat transfer in a curved pipe at a constant wall temperature with or without buoyancy force effect. Due to the great variation in physical properties of water near the critical point, the turbulent heat transfer can be significantly altered as compared with the pure force convection in the curved pipe. This study explores the influence of the near-critical pressure on the development of fluid flow and heat transfer along the pipe. Based on the results of this research, the development of velocity, temperature, and heat transfer coefficient along the pipe are presented graphically and analyzed.

The Highly Turbulent Flow and Heat Transfer in Semi-Closed Rotating Disc Cavity

2019 ◽  
Author(s):  
Guohu Luo ◽  
Zhenqiang Yao ◽  
Shengde Wang ◽  
Hong Shen
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Turbulent Flow ◽  
Prediction Models ◽  
Rotating Disk ◽  
Radial Temperature ◽  
Flow And Heat Transfer ◽  
Radial Heat ◽  
Radial Outflow

Abstract The highly turbulent flow and heat-transfer in a semi-closed rotating disk cavity is numerically simulated based on a hybrid RANS/LES turbulence model. The superimposed radial outflow, which enters into the cavity from the inlet and exits the cavity from the discharge holes, results in the three flow region formed in the disk cavity. The effects of rotating Reynolds’ number and cavity aspect ratio on the pumping mass flow, local momentum coefficient as well as radial heat-transfer coefficient are fully examined. And the corresponding correlations are established with respect to rotating Reynolds’ number and aspect ratio. It is revealed that the radial heat-transfer from the periphery of the cavity to discharge hole is highly correlated to the secondary flow pumped by the rotating disk. Based on those prediction models, an equivalent thermal network for the radial heat-transfer is proposed, which can efficiently predict the radial temperature distribution in the semi-closed disk cavity, and estimate the effects of viscous-heating as well as temperature-viscosity correction.

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