Turbulent Heat Transfer in Corrugated-Wall Channels With and Without Fins

1987 ◽  
Vol 109 (1) ◽  
pp. 62-67 ◽  
Author(s):  
R. S. Amano ◽  
A. Bagherlee ◽  
R. J. Smith ◽  
T. G. Niess
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Reynolds Stress Model ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Reynolds Stresses ◽  
Flow Recirculation ◽  
Nusselt Numbers ◽  
Visible Effect ◽  
Corrugated Wall

A numerical study is performed examining flow and heat transfer characteristics in a channel with periodically corrugated walls. The complexity of the flow in this type of channel is demonstrated by such phenomena as flow impingement on the walls, separation at the bend corners, flow reattachment, and flow recirculation. Because of the strong nonisotropic nature of the turbulent flow in the channel, the full Reynolds-stress model was employed for the evaluation of turbulence quantities. Computations are made for several different corrugation periods and for different Reynolds numbers. The results computed by using the present model show excellent agreement with experimental data for mean velocities, the Reynolds stresses, and average Nusselt numbers. The study was further extended to a channel flow where fins are inserted at bends in the channel. It was observed that the insertion of fins in the flow passage has a visible effect on flow patterns and skin friction along the channel wall.

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

1985 ◽  
Vol 107 (3) ◽  
pp. 564-569 ◽  
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.

Turbulent Heat Transfer in an Enclosure With a Horizontal Permeable Plate in the Middle

2006 ◽  
Vol 128 (11) ◽  
pp. 1122-1129 ◽  
Author(s):  
Edimilson J. Braga ◽  
Marcelo J. S. de Lemos
Keyword(s):  
Heat Transfer ◽  
Porous Plate ◽  
Porous Matrix ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Turbulent Natural Convection ◽  
Nusselt Numbers ◽  
Model Solutions ◽  
Volume Method ◽  
Rayleigh Numbers

Turbulent natural convection in a vertical two-dimensional square cavity, isothermally heated from below and cooled at the upper surface, is numerically analyzed using the finite volume method. The enclosure has a thin horizontal porous obstruction, made of a highly porous material and extremely permeable, located at the cavity midheight. Governing equations are written in terms of primitive variables and are recast into a general form. For empty cavities, no discrepancies result for the Nusselt number when laminar and turbulent model solutions are compared for Rayleigh numbers up to 107. Also, in general the porous obstruction decreases the heat transfer across the heated walls showing overall lower Nusselt numbers when compared with those without the porous obstruction. However, the presence of a porous plate in the cavity seems to force an earlier separation from laminar to turbulence model solutions due to higher generation rates of turbulent kinetic energy into the porous matrix.

A Stochastic Lagrangian Model for Near-Wall Turbulent Heat Transfer

1997 ◽  
Vol 119 (1) ◽  
pp. 46-52 ◽  
Author(s):  
S. Mazumder ◽  
M. F. Modest
Keyword(s):  
Heat Transfer ◽  
Joint Probability ◽  
Molecular Transport ◽  
Temperature Fluctuations ◽  
Reynolds Stress Model ◽  
Constant Heat Flux ◽  
Lagrangian Model ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Near Wall

The modeling of near-wall turbulent heat transfer necessitates appropriate description of near-wall effects, namely, molecular transport, production of turbulence by inhomogeneities, and dissipation of the temperature fluctuations by viscosity. A stochastic Lagrangian model, based on the velocity-composition joint probability density function (PDF) method, has been proposed. The proposed model, when compared with experimental and direct numerical simulation (DNS) data, overdamps the dissipation of the temperature fluctuations in the inertial sublayer, but reaches the correct limit at the wall. The performance of the model has also been compared to the standard k-ε and the algebraic Reynolds stress model (ARSM) for both constant heat flux and constant temperature boundary conditions at large Reynolds numbers. The Lagrangian nature of the model helps eliminate numerical diffusion completely.

Turbulent Heat Transfer and Fluid Flow in an Unsymmetrically Heated Triangular Duct

1980 ◽  
Vol 102 (4) ◽  
pp. 590-597 ◽  
Author(s):  
C. A. C. Altemani ◽  
E. M. Sparrow
Keyword(s):  
Heat Transfer ◽  
Hydraulic Diameter ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
General Applicability ◽  
Thermal Boundary Conditions ◽  
Nusselt Numbers ◽  
Friction Factors ◽  
Turbulent Airflow ◽  
Thermal Entrance

Experiments were performed to determine entrance-region and fully developed heat transfer characteristics for turbulent airflow in an unsymmetrically heated equilateral triangular duct; friction factors were also measured. Two of the walls were heated while the third was not directly heated. The resulting thermal boundary conditions consisted of uniform heating per unit axial length and circumferentially uniform temperature on the heated walls. Special techniques were employed to minimize extraneous heat losses, and numerical finite-difference solutions played an important role in both the design of the apparatus and in the data reduction. The thermal entrance lengths required to attain thermally developed conditions were found to increase markedly with the Reynolds number and were generally greater than those for conventional pipe flows—a behavior which can be attributed to the unsymmetric heating. The fully developed Nusselt numbers were compared with circular tube correlations from the literature, from which it was shown that the hydraulic diameter is not fully sufficient to rationalize the circular and noncircular duct results. However, excellent Nusselt number predictions were obtained by employing the Petukhov-Popou correlation in conjunction with the measured friction factors for the triangular duct. This approach may have general applicability for predicting noncircular duct heat transfer. The friction factor results also affirmed the inadequacies of the hydraulic diameter but supported a general noncircular duct correlation available in the literature.

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