Numerical Analysis of Local Heat Transfer From a Flat Plate to a Pair of Circular Air Impingining Jets

2004 ◽  
Author(s):  
X. Terry Yan ◽  
Yavaraj Saravanan
Keyword(s):  
Heat Transfer ◽  
Numerical Analysis ◽  
Flat Plate ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Impinging Jets ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Local heat transfer from a flat plate to a pair of circular air impinging jets is investigated numerically. A pair of impinging jets from fully-developed pipe flows are used for the numerical simulations. The Reynolds Averaged Navier-Stokes equations(RANS) and energy equation are solved for the three dimensional flow. Eddy-viscocity based turbulence models, RNG k-epsilon and V2F models, are used. Hybrid meshes are used for the three dimensional flows and mesh independent solutions are obtained. The flow Reynolds number, which is based on the jet diameter, is kept at 23,000. In the analysis, local heat transfer coefficients are obtained for the jet-to-plate distance, L/D, ranging from 2 to 10 and the jet-to-jet spacing, S/D, in the range of 1.75 to 7.0. Both local and average heat transfer coefficients are evaluated and compared with available experimental data under same flow conditions. The effect of using different turbulence models in the numerical analysis is evaluated and the selection of proper turbulence models under such a flow condition is suggested.

Experimental Investigation of Local Heat Transfer Distribution on Smooth and Roughened Surfaces Under an Array of Angled Impinging Jets

2001 ◽  
Author(s):  
Lamyaa A. El-Gabry ◽  
Deborah A. Kaminski
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Cross Flow ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Impinging Jets ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Roughened Surface

Abstract Measurements of the local heat transfer distribution on smooth and roughened surfaces under an array of angled impinging jets are presented. The test rig is designed to simulate impingement with cross-flow in one direction which is a common method for cooling gas turbine components such as the combustion liner. Jet angle is varied between 30, 60, and 90 degrees as measured from the impingement surface, which is either smooth or randomly roughened. Liquid crystal video thermography is used to capture surface temperature data at five different jet Reynolds numbers ranging between 15,000 and 35,000. The effect of jet angle, Reynolds number, gap, and surface roughness on heat transfer efficiency and pressure loss is determined along with the various interactions among these parameters. Peak heat transfer coefficients for the range of Reynolds number from 15,000 to 35,000 are highest for orthogonal jets impinging on roughened surface; peak Nu values for this configuration ranged from 88 to 165 depending on Reynolds number. The ratio of peak to average Nu is lowest for 30-degree jets impinging on roughened surfaces. It is often desirable to minimize this ratio in order to decrease thermal gradients, which could lead to thermal fatigue. High thermal stress can significantly reduce the useful life of engineering components and machinery. Peak heat transfer coefficients decay in the cross-flow direction by close to 24% over a dimensionless length of 20. The decrease of spanwise average Nu in the crossflow direction is lowest for the case of 30-degree jets impinging on a roughened surface where the decrease was less than 3%. The decrease is greatest for 30-degree jet impingement on a smooth surface where the stagnation point Nu decreased by more than 23% for some Reynolds numbers.

Heat Transfer Enhancement by Turbulent Impinging Jets

2000 ◽  
Author(s):  
M. Kumagai ◽  
R. S. Amano ◽  
M. K. Jensen
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Stokes Equations ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Impinging Jets ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Abstract A numerical and experimental investigation on cooling of a solid surface was performed by studying the behavior of an impinging jet onto a fixed flat target. The local heat transfer coefficient distributions on a plate with a constant heat flux were computationally investigated with a normally impinging axisymmetric jet for nozzle diameter of 4.6mm at H/d = 4 and 10, with the Reynolds numbers of 10,000 and 40,000. The two-dimensional cylindrical Navier-Stokes equations were solved using a two-equation k-ε turbulence model. The finite-volume differencing scheme was used to solve the thermal and flow fields. The predicted heat transfer coefficients were compared with experimental measurements. A universal function based on the wave equation was developed and applied to the heat transfer model to improve calculated local heat transfer coefficients for short nozzle-to-plate distance (H/d = 4). The differences between H/d = 4 and 10 due to the correlation among heat transfer coefficient, kinetic energy and pressure were investigated for the impingement region. Predictions by the present model show good agreement with the experimental data.

Temperature Distributions in Laminar Flat Plate Shear Flow

1968 ◽  
Vol 90 (1) ◽  
pp. 32-36 ◽  
Author(s):  
A. F. Emery ◽  
K. F. Brettman
Keyword(s):  
Heat Transfer ◽  
Flat Plate ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Shearing Flow ◽  
Heat Transfer Coefficients ◽  
Temperature Distributions ◽  
High Shearing ◽  
The Heat Transfer Coefficient

An approximate solution to the heat transfer coefficient on a flat plate in a linear shearing flow is given. It is shown that high shearing rates may significantly increase the local heat transfer coefficients.

Numerical Analysis of Local Heat Transfer From a Flat Plate to a Swirling Air Impingining Jet

2006 ◽  
Author(s):  
X. Terry Yan ◽  
Rahul S. Kalvakota
Keyword(s):  
Heat Transfer ◽  
Flat Plate ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Local Heat Transfer ◽  
Impinging Jet ◽  
Local Heat ◽  
Flow Profile ◽  
Transfer Coefficients ◽  
Stagnation Region

Local heat transfer from a flat plate to a swirling circular air impinging jet is investigated numerically. Reynolds Averaged Navier-Stokes equations (RANS) and energy equation are solved for the axisymmetric, three dimensional flow. Eddy-viscosity based turbulence models, RNG and V2F, are used. Non-uniform meshes are used for the three dimensional flows and mesh independent solutions are obtained. The flow Reynolds number, which is based on the jet diameter, is kept at 23,000. In the analysis, local heat transfer coefficients are obtained for different swirl numbers, S = 0.21, 0.35 and 0.47 and jet-to-plate distance, L/D, ranging from 2 to 9. Investigation of the effect of swirl flow profile at the exiting plane of the jet on heat transfer is also presented. It is found that different swirl profiles with the same swirl number lead to very different heat transfer behaviors in the stagnation region of the impinging jet.

Heat Transfer From Arrays of Impinging Jets with Large Jet-to-Jet Spacing

1978 ◽  
Vol 100 (2) ◽  
pp. 352-357 ◽  
Author(s):  
B. R. Hollworth ◽  
R. D. Berry
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Target Surface ◽  
Turbulent Jets ◽  
Local Heat ◽  
Impinging Jets ◽  
Transfer Coefficients ◽  
Average Heat ◽  
Turbine Cooling ◽  
Heat Transfer Coefficients

Local and average convective heat transfer coefficients were measured for arrays of widely spaced impinging air jets and correlated in terms of system geometry, air flow, and fluid properties. The configurations were square arrays of circular turbulent jets (spaced from 10–25 diameters apart) incident upon a flat isothermal target surface. Independent parameters were varied over ranges generally corresponding to gas turbine cooling applications. Local heat transfer coefficients were influenced by interference from neighboring jets only when the target plate and the jet orifice plate were less than five jet diameters apart. Average heat transfer coefficients were nearly equal for all the arrays tested as long as the coolant flow per unit area of target surface was held constant. In fact, there was a tendency for the more widely spaced configurations to produce slightly higher average heat transfer under such conditions.

Heat Transfer and Skin Friction for Turbulent Boundary-Layer Flow Longitudinal to a Circular Cylinder

1963 ◽  
Vol 30 (1) ◽  
pp. 37-43 ◽  
Author(s):  
E. M. Sparrow ◽  
E. R. G. Eckert ◽  
W. J. Minkowycz
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flat Plate ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Friction Factors ◽  
Prandtl Numbers ◽  
Layer Flow

An analysis has been carried out for the turbulent velocity and thermal boundary layers which develop along a cylinder whose axis is parallel to the free-stream flow. Local and average friction factors are calculated as functions of the length Reynolds number Rex for various cylinder sizes (characterized, by the radius Reynolds number Rer0). For corresponding flow conditions, the friction factor for a cylinder always exceeds that for the flat plate. Local heat-transfer coefficients corresponding to the case of uniform wall heat flux have been obtained for Prandtl numbers of 0.7 and 5. As with the friction factors, the cylinder heat-transfer coefficients exceed those for the flat plate. This effect of the cylindrical geometry on heat transfer diminishes with increasing Prandtl number.

Local Heat Transfer to Staggered Arrays of Impinging Circular Air Jets

1983 ◽  
Vol 105 (2) ◽  
pp. 354-360 ◽  
Author(s):  
A. I. Behbahani ◽  
R. J. Goldstein
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flat Plate ◽  
Flow Direction ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Air Jets ◽  
Impingement Surface

Measurements are made of the local heat transfer from a flat plate to arrays of impinging circular air jets. Fluid from the spent jets is constrained to flow out of the system in one direction. Two different jet-to-jet spacings, 4 and 8 jet diameters, are employed. The parameters that are varied include jet-orifice-plate to impingement-surface spacing and jet Reynolds number. Local heat transfer coefficients vary periodically both in the flow direction and across the span with high values occurring in stagnation regions. Stagnation regions of individual jets as determined by local heat transfer coefficients move further in the downstream direction as the amount of crossflow due to upstream jet air increases. Local heat transfer coefficients are averaged numerically to obtain spanwise and streamwise-spanwise averaged heat transfer coefficients.

scholarly journals Local Heat Transfer to Staggered Arrays of Impinging Circular Air Jets

1982 ◽  
Author(s):  
A. I. Behbahani ◽  
R. J. Goldstein
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flat Plate ◽  
Flow Direction ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Air Jets ◽  
Impingement Surface

Measurements are made of the local heat transfer from a flat plate to impinging arrays of staggered circular air jets. Fluid from the spent jets is constrained to flow out in one direction. Two different jet-to-jet spacings, 4 and 8 jet diameters, are employed. The parameters that are varied include jet-orifice-plate to impingement-surface spacing and jet Reynolds number. Local heat transfer coefficients vary periodically both in the flow direction and across the span with high values occurring at stagnation regions. Stagnation regions of individual jets as determined by local heat transfer coefficients move further in the downstream direction as the amount of crossflow due to upstream jet air increases. Local heat transfer coefficients are averaged numerically to obtain spanwise and streamwise-spanwise averaged heat transfer coefficients.

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