NUMERICAL STUDY OF HEAT TRANSFER IN TURBULENT FLOWS, WITH APPLICATION

The horizontal frame members that often protrude from the inner surface of a window can significantly effect the convective heat transfer rate from this inner surface to the room. The purpose of the present numerical study was to determine how the size of a pair of horizontal frame members effect this heat transfer rate. The flow has been assumed to be steady and conditions under which laminar, transitional, and turbulent flows occur are considered. Fluid properties have been assumed constant except for the density change with temperature that gives rise to the buoyancy forces, this being dealt with using the Boussinesq approach. The governing equations have been solved using the FLUENT commercial CFD code. The k-epsilon turbulence model with standard wall functions and with buoyancy force effects fully accounted for has been used. The solution has the following parameters: the Rayleigh number, the Prandtl number, the dimensionless window recess depth, and the dimensionless width and depth of the frame members. Results have been obtained for a Prandtl number of 0.74.

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Numerical Study of Heat Transfer in Turbulent Cross-Flow Over Porous-Coated Cylinder

Volume 1A, Symposia: Keynotes; Advances in Numerical Modeling for Turbomachinery Flow Optimization; Fluid Machinery; Industrial and Environmental Applications of Fluid Mechanics; Pumping Machinery ◽

10.1115/fedsm2017-69582 ◽

2017 ◽

Author(s):

N. Rahmati ◽

Z. Mansoori ◽

M. Saffar-Avval ◽

G. Ahmadi

Keyword(s):

Heat Transfer ◽

Porous Media ◽

Nusselt Number ◽

Turbulent Flows ◽

Metal Foam ◽

Numerical Study ◽

Flow Analysis ◽

Cross Flow ◽

Local Thermal Equilibrium ◽

Turbulent Regime

In the present paper, a numerical study has been conducted to investigate the heat transfer from a constant temperature cylinder covered with metal foam. The cylinder is placed horizontally and is subjected to a constant mean cross-flow in turbulent regime. The Reynolds Averaged Navier-Stokes (RANS) and Darcy-Brinkman-Forchheimer equations are combined and used for flow analysis. The energy equation used assumes local thermal equilibrium between fluid and solid phases in porous media. The k-ω SST turbulence model is used to evaluate the eddy viscosity that is implemented in the momentum and energy equations. The flow in the metal foam (porous media) is in laminar regime. Governing equations are solved using the finite volume SIMPLEC algorithm. The effect of thermophysical properties of metal foam such as porosity and permeability on the Nusselt number is investigated. The results showed that using a metal porous layer with low porosity and high Darcy number in high Reynolds number turbulent flows markedly increases heat transfer rates. The corresponding increase in the Nusselt number is as high as 10 times that of a bare tube without the metal foam.

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Large Eddy Simulation of Heat Transfer Over In-Line Flat-Tube Array in Laminar and Turbulent Flows

Volume 1: Aerospace Heat Transfer; Computational Heat Transfer; Education; Environmental Heat Transfer; Fire and Combustion Systems; Gas Turbine Heat Transfer; Heat Transfer in Electronic Equipment; Heat Transfer in Energy Systems ◽

10.1115/ht2017-5078 ◽

2017 ◽

Cited By ~ 1

Author(s):

Salar Taghizadeh ◽

Sumanta Acharya ◽

Kong Ling ◽

Yousef Kanani ◽

Xuan Ge

Keyword(s):

Heat Transfer ◽

Large Eddy Simulation ◽

Turbulent Flows ◽

Numerical Study ◽

Numerical Models ◽

Leading Edge ◽

Flat Tube ◽

Eddy Simulation ◽

Wide Range ◽

Large Eddy

This study presents a transient three-dimensional numerical study on fluid flow and heat transfer of flat-tube array using large eddy simulation (LES) covering both laminar and turbulent flow regimes. The simulations were performed in a rectangular region containing only one tube with periodic conditions specified on all boundaries. A staggered flat-plate array was first studied, and an existing solution was used for validation purpose. The numerical models were then applied to an in-line array composed of flat tubes with an aspect ratio of 0.25 and fixed tube spacings. By varying the in-flow velocity, the tube array was studied over a wide range of Reynolds number (600–12000). Temperature, velocity, and turbulent kinetic energy distributions as well as the interactions between them are presented and analyzed. Furthermore, the local heat transfer rate was analyzed along the various parts of the tube (leading edge, flat-top and wake or trailing-edge regions). Heat transfer correlation for each region of the tube and the entire tube array is proposed.

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Numerical Study of Turbulent Flows and Convective Heat Transfer of Al2O3-Water Nanofluids In A Circular Tube

Journal of Advanced Research in Fluid Mechanics and Thermal Sciences ◽

10.37934/arfmts.77.2.112 ◽

2020 ◽

Vol 77 (2) ◽

pp. 1-12

Author(s):

Abdelkader Mahammedi ◽

Houari Ameur ◽

Younes Menni ◽

Driss Meddah Medjahed

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Convective Heat Transfer ◽

Turbulent Flows ◽

Convective Heat ◽

Circular Tube ◽

Numerical Study ◽

Constant Heat Flux ◽

Flux Boundary Condition ◽

Pressure Losses

The convective heat transfer of Al2O3-water nanofluids through a circular tube with a constant heat flux boundary condition is studied numerically. Turbulent flow conditions are considered with a Reynolds number ranging from 3500 to 20000. The numerical method used is based on the single-phase model. Four volume concentrations of Al2O3-water nanoparticles (0.1, 0.5, 1, and 2%) are used with a diameter of nanoparticle of 40 nm. A considerable increase in Nusselt number, axial velocity, and turbulent kinetic energy was found with increasing Reynolds number and volume fractions. However, the pressure losses were also increased with the raise of Re and nanoparticles concentration.

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A Numerical Study of Laminar and Turbulent Heat Transfer in a Periodically Corrugated Wall Channel

Journal of Heat Transfer ◽

10.1115/1.3247461 ◽

1985 ◽

Vol 107 (3) ◽

pp. 564-569 ◽

Cited By ~ 41

Author(s):

R. S. Amano

Keyword(s):

Heat Transfer ◽

Turbulent Flows ◽

Solution Method ◽

Numerical Study ◽

Turbulent Heat Transfer ◽

Turbulent Heat ◽

Complex Flow ◽

Flow Phenomena ◽

Corrugated Wall ◽

Laminar And Turbulent Flows

A numerical study is reported on hydrodynamic and heat transfer characteristics in a periodically corrugated wall channel for both laminar and turbulent flows. For turbulent flows the k-ε turbulence model with a refined near-wall model is adopted for the computation of the flow field for step ratios H/W ranging from two to four. The Reynolds number considered in this study varies from 10 to 25,000. The solution method of the governing transport equations is based on the modified hybrid scheme. As a result of extensive computations, the complex flow patterns in the perpendicularly corrugated wall channel are clarified and the mechanisms of heat transfer are explained relating to the flow phenomena of separation, deflection, recirculation, and reattachment. Finally it was observed that the effect of the step ratio on the local Nusselt number is minor. Moreover, it was found that both skin friction and heat transfer patterns change drastically from laminar to turbulent flows.

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A Numerical Study of the Convective Heat Transfer in Low-Reynolds Number Turbulent Flows in Corrugated Pipes

Volume 7: Fluids and Heat Transfer, Parts A, B, C, and D ◽

10.1115/imece2012-87516 ◽

2012 ◽

Author(s):

Ramin K. Rahmani ◽

J. Eric Arnold ◽

George W. Kraus

Keyword(s):

Heat Transfer ◽

Pressure Drop ◽

Convective Heat Transfer ◽

Turbulent Flows ◽

Convective Heat ◽

Numerical Study ◽

Internal Flow ◽

Eddy Simulation ◽

Corrugated Surfaces ◽

The Impact

Enhancement of convective heat transfer in internal turbulent flows with low-to-moderate Re number has been the subject of numerous studies, due to its vast applications. Corrugated surfaces can be used as enhancement devices in the heat convection systems. An ideal corrugation, for heat transfer in internal flow applications, provides a higher heat transfer rate with minimized pressure drop. The ratio of heat flux to the pressure drop can be used to determine the efficiency of a design. Using Large-Eddy Simulation, the heat transfer in low-Re turbulent flow in a pipe is studied to investigate the impact of different corrugated profiles with similar hydraulic diameter.

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