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 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.

Flow and Heat Transfer in a Rotating Square Channel With 45° Angled Ribs by Reynolds Stress Turbulence Model

2000 ◽  
Author(s):  
Yong-Jun Jang ◽  
Hamn -Ching Chen ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Convective Transport ◽  
Moment Closure ◽  
Closure Model ◽  
Time Step ◽  
Second Moment ◽  
Square Channel ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Near Wall

Numerical predictions of three -dimensional flow and heat transfer are presented for a rotating square channel with 45° angled ribs as tested by Johnson et al. (1994). The rib height-to-hydraulic diameter ratio (e/Dh) is 0.1 and the rib pitch-to-height ratio (P/e) is 10. The cross-section of the ribs has rounded edges and corners. The computation results are compared with Johnson’s et al. (1994) experimental data at a Reynolds number (Re) of 25,000, inlet coolant-to-wall density ratio (Δρ/ρ) of 0.13, and three rotation numbers (Ro) of 0.0, 0.12, 0.24. A multi-block numerical method has been employed with a near-wall second-moment turbulence closure model. In the present method, the convective transport equations for momentum, energy, and turbulence quantities are solved in curvilinear, body-fitted coordinates using the finite-analytic method. Pressure is computed using a hybrid SIMPLER/PISO approach, which satisfies the continuity of mass and momentum simultaneously at every time step. The second-moment solutions show that the secondary flows induced by the angled ribs, rotating buoyancy, and Coriolis forces produced strong non-isotropic turbulent stresses and heat fluxes that significantly affected flow fields and surface heat transfer coefficients. The present near-wall second-moment closure model provided an improved flow and heat transfer prediction.

Flow and Heat Transfer in a Rotating Square Channel With 45 deg Angled Ribs by Reynolds Stress Turbulence Model

2000 ◽  
Vol 123 (1) ◽  
pp. 124-132 ◽  
Author(s):  
Yong-Jun Jang ◽  
Hamn-Ching Chen ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Convective Transport ◽  
Moment Closure ◽  
Closure Model ◽  
Time Step ◽  
Second Moment ◽  
Square Channel ◽  
Flow And Heat Transfer ◽  
Numerical Predictions ◽  
Near Wall

Numerical predictions of three-dimensional flow and heat transfer are presented for a rotating square channel with 45 deg angled ribs as tested by Johnson et al. (1994). The rib height-to-hydraulic diameter ratio e/Dh is 0.1 and the rib pitch-to-height ratio (P/e) is 10. The cross section of the ribs has rounded edges and corners. The computation results are compared with the experimental data of Johnson et al. (1994) at a Reynolds number (Re) of 25,000, inlet coolant-to-wall density ratio Δρ/ρ of 0.13, and three rotation numbers (Ro) of 0.0, 0.12, and 0.24. A multiblock numerical method has been employed with a near-wall second-moment turbulence closure model. In the present method, the convective transport equations for momentum, energy, and turbulence quantities are solved in curvilinear, body-fitted coordinates using the finite-analytic method. Pressure is computed using a hybrid SIMPLER/PISO approach, which satisfies the continuity of mass and momentum simultaneously at every time step. The second-moment solutions show that the secondary flows induced by the angled ribs, rotating buoyancy, and Coriolis forces produced strong nonisotropic turbulent stresses and heat fluxes that significantly affected flow fields and surface heat transfer coefficients. The present near-wall second-moment closure model provided an improved flow and heat transfer prediction.

scholarly journals Computation of Flow and Heat Transfer in Rotating Two-Pass Square Channels by a Reynolds Stress Model

1999 ◽  
Author(s):  
Hamn-Ching Chen ◽  
Yong-Jun Jang ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Reynolds Stress ◽  
Stokes Equations ◽  
Secondary Flows ◽  
Moment Closure ◽  
Closure Model ◽  
Second Moment ◽  
Flow And Heat Transfer ◽  
Second Moment Closure ◽  
Near Wall

A multiblock numerical method has been employed for the calculation of three-dimensional flow and heat transfer in rotating two-pass square channels with smooth walls. The finite-analytic method solves Reynolds-Averaged Navier-Stokes equations in conjunction with a near-wall second-order Reynolds stress (second-moment) closure model and a two-layer k–ε isotropic eddy viscosity model. Comparison of second-moment and two-layer calculations with experimental data clearly demonstrate that the secondary flows in rotating two-pass channels have been strongly influenced by the Reynolds stress anisotropy resulting from the Coriolis and centrifugal buoyancy forces as well as the 180° wall curvatures. The near-wall second-moment closure model provides the most reliable heat transfer predictions which agree well with measured data.

Computation of Discrete-Hole Film Cooling by a Near-Wall Second-Moment Turbulence Closure

1999 ◽  
Author(s):  
Hamn-Ching Chen ◽  
Gengsheng Wei ◽  
Je-Chin Han
Keyword(s):  
Film Cooling ◽  
Moment Closure ◽  
Navier Stokes ◽  
Closure Model ◽  
Complex Flow ◽  
Second Moment ◽  
Finite Analytic Method ◽  
Second Moment Closure ◽  
Effectiveness Prediction ◽  
Near Wall

Abstract A multiblock Favre-Averaged Navier-Stokes (FANS) method has been developed in conjunction with a chimera domain decomposition technique for investigation of flat surface, discrete-hole film cooling performance. The finite-analytic method solves the FANS equations in conjunction with a near-wall second-order Reynolds stress (second-moment) closure model and a two-layer k-ε model. Comparisons of flow fields and turbulence quantities with experimental data clearly demonstrate the capability of the near-wall second-moment closure model for accurate resolution of the complex flow interaction bewteen the coolant jet and the mainstream. The near-wall second-moment anisotropic model provides better agreement in adiabatic film effectiveness prediction than the two-layer k-ε model.

Leading-Edge Film-Cooling Physics: Part II — Heat Transfer Coefficient

2002 ◽  
Author(s):  
William D. York ◽  
James H. Leylek
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Leading Edge ◽  
Numerical Predictions ◽  
Validation Experiment ◽  
Computational Methodology ◽  
Near Wall

A comprehensive study of film cooling on a turbine airfoil leading edge was performed with a documented, well-tested computational methodology. In this paper, numerically predicted heat transfer coefficients on the film-cooled leading edge are compared with experimental data from the open literature. The results are presented as the ratio of heat transfer coefficient with film cooling to that without film cooling, and the physics behind the surface results are discussed. The leading edge model was a half-cylinder in shape with a bluff afterbody to match the validation experiment, and other geometric parameters matched those of Part I of this study. Coolant at a density equal to that of the mainstream flow was injected through three rows of cylindrical film-cooling holes. One row of holes was centered on the stagnation line of the cylinder, and the other two rows were located ±3.5 hole diameters off stagnation. The downstream rows were staggered such that they were centered laterally between holes in the stagnation row. The holes were inclined at 20° with the surface, and made a 90° angle with the streamwise direction (radial injection). Four average blowing ratios were simulated in the range of 0.75 to 1.9, corresponding to the same momentum flux ratios as in Part I of this work. The multi-block, unstructured numerical grid was characterized by high quality and density, especially in the near wall region, in order to minimize error in predictions of the heat transfer. A fully-implicit scheme was used to solve the steady Reynolds-averaged Navier-Stokes equations, and a realizable k-ε model provided turbulence closure. A two-layer near-wall treatment allowed the resolution of the viscous sublayer for maximum accuracy in the prediction of the wall heat transfer coefficient. The numerical predictions exhibited generally good agreement with experimental data. The heat transfer coefficient was observed to increase sharply aft of the holes in the downstream rows. When coupled with the adiabatic effectiveness results of the first paper in this series, it is evident that a systematic computational methodology may be effectively applied to investigate and understand the complicated leading edge film-cooling problem.

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.

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.

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