Prediction of Flow and Heat Transfer in Ducts of Square Cross-Section

1973 ◽  
Vol 187 (1) ◽  
pp. 455-461 ◽  
Author(s):  
B. E. Launder ◽  
W. M. Ying
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Cross Section ◽  
Close Agreement ◽  
Heat Transfer Characteristics ◽  
Mean Velocity ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Secondary Motion ◽  
Fully Developed Turbulent Flow

Numerical predictions are presented of the hydrodynamic and heat transfer characteristics of fully developed turbulent flow in square-sectioned ducts. The turbo stresses in the plane of the cross-section, whose gradients cause the well-known secondary motion, are approximated by gradients in the axial mean velocity. Predicted results are in close agreement with available experimental data of primary and secondary velocities as well as the shear stress and heat flux variations around the perimeter.

Prediction of Flow and Heat Transfer in Ducts of Square Cross-Section

1973 ◽  
Vol 187 (1) ◽  
pp. 455-461 ◽  
Author(s):  
B. E. Launder ◽  
W. M. Ying
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Cross Section ◽  
Close Agreement ◽  
Heat Transfer Characteristics ◽  
Mean Velocity ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Secondary Motion ◽  
Fully Developed Turbulent Flow

Numerical predictions are presented of the hydrodynamic and heat transfer characteristics of fully developed turbulent flow in square-sectioned ducts. The turbo stresses in the plane of the cross-section, whose gradients cause the well-known secondary motion, are approximated by gradients in the axial mean velocity. Predicted results are in close agreement with available experimental data of primary and secondary velocities as well as the shear stress and heat flux variations around the perimeter.

Effect of Turbulent Intensity and Axial Gap on Turbine Heat Transfer Using Steady and Harmonic Models

2013 ◽  
Author(s):  
Sridhar Murari ◽  
Sunnam Sathish ◽  
Ramakumar Bommisetty ◽  
Jong S. Liu
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Flow Field ◽  
Turbulence Intensity ◽  
Pressure Coefficient ◽  
Heat Transfer Characteristics ◽  
Complex Flow ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Heat Loads

The knowledge of heat loads on the turbine is of great interest to turbine designers. Turbulence intensity and stator-rotor axial gap plays a key role in affecting the heat loads. Flow field and associated heat transfer characteristics in turbines are complex and unsteady. Computational fluid dynamics (CFD) has emerged as a powerful tool for analyzing these complex flow systems. Honeywell has been exploring the use of CFD tools for analysis of flow and heat transfer characteristics of various gas turbine components. The current study has two objectives. The first objective aims at development of CFD methodology by validation. The commercially available CFD code Fine/Turbo is used to validate the predicted results against the benchmark experimental data. Predicted results of pressure coefficient and Stanton number distributions are compared with available experimental data of Dring et al. [1]. The second objective is to investigate the influence of turbulence (0.5% and 10% Tu) and axial gaps (15% and 65% of axial chord) on flow and heat transfer characteristics. Simulations are carried out using both steady state and harmonic models. Turbulence intensity has shown a strong influence on turbine blade heat transfer near the stagnation region, transition and when the turbulent boundary layer is presented. Results show that a mixing plane is not able to capture the flow unsteady features for a small axial gap. Relatively close agreement is obtained with the harmonic model in these situations. Contours of pressure and temperature on the blade surface are presented to understand the behavior of the flow field across the interface.

Computation of Flow and Heat Transfer in Two-Pass Channels With 60 deg Ribs

2001 ◽  
Vol 123 (3) ◽  
pp. 563-575 ◽  
Author(s):  
Yong-Jun Jang ◽  
Hamn-Ching Chen ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Moment Closure ◽  
Closure Model ◽  
Second Moment ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Sharp Turn ◽  
Second Moment Closure ◽  
Near Wall

Numerical predictions of three-dimensional flow and heat transfer are presented for a two-pass square channel with and without 60 deg angled parallel ribs. Square sectioned ribs were employed along one side surface. The rib height-to-hydraulic diameter ratio e/Dh is 0.125 and the rib pitch-to-height ratio (P/e) is 10. The computation results were compared with the experimental data of Ekkad and Han [1] at a Reynolds number (Re) of 30,000. A multi-block numerical method was used with a chimera domain decomposition technique. The finite analytic method solved the Reynolds-Averaged Navier Stokes equation in conjunction with a near-wall second-order Reynolds stress (second-moment) closure model, and a two-layer k-ε isotropic eddy viscosity model. Comparing the second-moment and two-layer calculations with the experimental data clearly demonstrated that the angled rib turbulators and the 180 deg sharp turn of the channel produced strong non-isotropic turbulence and heat fluxes, which significantly affected the flow fields and heat transfer coefficients. The near-wall second-moment closure model provides an improved heat transfer prediction in comparison with the k-ε model.

Analysis of Heat Transfer and Fluid Flow Through a Spirally Fluted Tube Using a Porous Substrate Approach

1994 ◽  
Vol 116 (3) ◽  
pp. 543-551 ◽  
Author(s):  
Vijayaragham Srinivasan ◽  
Kambiz Vafai ◽  
Richard N. Christensen
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Porous Substrate ◽  
The Finite Element Method ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Friction Factors ◽  
Flow Through ◽  
Good Agreement

An innovative approach was opted for modeling the flow and heat transfer through spirally fluted tubes. The model divided the flow domain into two regions. The flutes were modeled as a porous substrate with direction-dependent permeabilities. This enabled modeling the swirl component in the fluted tube. The properties of the porous substrate such as its thickness, porosity, and ratio of the direction-dependent permeabilities were obtained from the geometry of the fluted tube. Experimental data on laminar Nusselt numbers and friction factors for different types of fluted tubes representing a broad range of flute geometry were available. Experimental data from a few of the tubes tested were used to propose a relationship between the permeability of the porous substrate and the flute parameters, particularly the flute spacing. The governing equations were discretized using the Finite Element Method. The model was verified and applied to the other tubes in the test matrix. Very good agreement was found between the numerical predictions and the experimental data.

Fluid Flow and Heat Transfer Characteristics in the Entrance Regions of Circular Pipes

1985 ◽  
Author(s):  
S. Lloyd ◽  
A. Brown
Keyword(s):  
Heat Transfer ◽  
Cross Section ◽  
Circular Cross Section ◽  
Flow Visualisation ◽  
Pressure Measurements ◽  
Hot Wire ◽  
Heat Transfer Characteristics ◽  
Number Range ◽  
Flow And Heat Transfer ◽  
Circular Pipes

This paper describes the results of an experimental investigation into the velocity and turbulence fields and to a lesser extent the heat transfer in the entrance regions of short, circular cross-section pipes with length to diameter ratios up to 20 over the Reynolds number range from 35,000 to 170,000. The velocity and turbulence fields were measured by hot-wire anemometers backed up with pressure measurements and flow visualisation and the heat transfer by heat flux meters.

scholarly journals Numerical Prediction of Flow and Heat Transfer in a Two-pass Square Channel with 90°Ribs

2001 ◽  
Vol 7 (3) ◽  
pp. 195-208 ◽  
Author(s):  
Yong-Jun Jang ◽  
Hamn-Ching Chen ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Moment Closure ◽  
Closure Model ◽  
Second Moment ◽  
Square Channel ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Sharp Turn ◽  
Near Wall

Numerical predictions of three-dimensional flow and heat transfer are presented for a two-pass square channel with°parallel ribs. Square sectioned ribs were employed along the one side surface. The rib height-to-hydraulic diameter ratio (e/Dh) is 0.125 and the rib pitch-to-height ratio(P/e)is 10. The computation results were compared with the experimental data of Ekkad and Han (1997) at a Reynolds number (Re) of 30,000.A multi-block numerical method was used with a chimera domain decomposition technique. The finite analytic method solved the Reynolds-Averaged Navier-Stokes equation in conjunction with a near-wall second-order Reynolds stress (secondmoment) closure model, and a two-layerk − εisotropic eddy viscosity model. Comparing the second-moment and two-layer calculations with the experimental data clearly demonstrated that the rib turbulators and the 180°sharp turn of the channel produced strong non-isotropic turbulence and heat fluxes, which significantly affected the flow fields and heat transfer coefficients. The near-wall second-moment closure model provides an improved heat transfer prediction in comparison with thek − εmodel.

Computation of Flow and Heat Transfer in Two-Pass Rotating Rectangular Channels (AR=1:1, AR=1:2, AR=1:4) With 45-deg. Angled Ribs by Reynolds Stress Turbulence Model

2004 ◽  
Author(s):  
Guoguang Su ◽  
Hamn-Ching Chen ◽  
Je-Chin Han ◽  
James D. Heidmann
Keyword(s):  
Heat Transfer ◽  
Rectangular Channel ◽  
Density Ratio ◽  
Heat Fluxes ◽  
Turbulent Heat ◽  
Mean Velocity ◽  
Flow And Heat Transfer ◽  
Aspect Ratios ◽  
Numerical Predictions ◽  
Rib Turbulators

Numerical predictions of three-dimensional flow and heat transfer are presented for rotating two-pass rectangular channel with 45-deg rib turbulators. Three channels with different aspect ratios (AR=1:1; AR=1:2; AR=1:4) were investigated. Detailed predictions of mean velocity, mean temperature, and Nusselt number for two Reynolds numbers (Re = 10,000 and Re = 100,000) were carried out. The rib height is fixed as constant and the rib-pitch-to-height ratio (P/e) is 10, but the rib height-to-hydraulic diameter ratios (e/Dh) are 0.125, 0.094, and 0.078, for AR=1:1, AR=1:2, and AR=1:4 channel, respectively. The channel orientations are set at 90 deg, corresponding to the cooling passages between mid-portion and the leading edge of a turbine blade. The rotation number varies from 0.0 to 0.28 and the inlet coolant-to-wall density ratio varies from 0.13 to 0.40, respectively. The primary focus of this study is the effect of the channel aspect ratio on the nature of the flow and heat transfer enhancement in a rectangular ribbed channel under rotating conditions. A multi-block Reynolds-averaged Navier-Stokes (RANS) method was employed in conjunction with a near-wall second-moment turbulence closure to provide detailed resolution of the Reynolds stresses and turbulent heat fluxes induced by the rib turbulators under both the stationary and rotating conditions.

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