An Experimental Study of Mixed, Forced, and Free Convection Heat Transfer From a Horizontal Flat Plate to Air

1982 ◽  
Vol 104 (1) ◽  
pp. 139-144 ◽  
Author(s):  
X. A. Wang
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Flat Plate ◽  
Free Stream ◽  
Convection Heat Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Stream Velocity ◽  
Heated Plate ◽  
Buoyancy Effect

A heated flat plate is tested in a wind tunnel to study mixed convection in both upward and downward positions. It is found that the local heat transfer coefficient is strongly dependent on the free stream velocity and the temperature difference between the surface and the free stream. The buoyancy effect is more pronounced for the heated plate facing upward. This paper correlates the experimental data in terms of Nusselt, Grashof, and Reynolds numbers. The points of onset of instability caused by the buoyancy effect are also examined and correlated in terms of the dimensionless groups. Experimental data are compared with analysis documented in the literature, and the agreement is found satisfactory.

Effects of Embedded Vortices on Film-Cooled Turbulent Boundary Layers

1989 ◽  
Vol 111 (1) ◽  
pp. 71-77 ◽  
Author(s):  
P. M. Ligrani ◽  
A. Ortiz ◽  
S. L. Joseph ◽  
D. L. Evans
Keyword(s):  
Heat Transfer ◽  
Boundary Layers ◽  
Film Cooling ◽  
Free Stream ◽  
Flow Behavior ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Turbulent Boundary Layers ◽  
Stream Velocity ◽  
Longitudinal Vortices

Heat transfer effects of longitudinal vortices embedded within film-cooled turbulent boundary layers on a flat plate were examined for free-stream velocities of 10 m/s and 15 m/s. A single row of film-cooling holes was employed with blowing ratios ranging from 0.47 to 0.98. Moderate-strength vortices were used with circulating-to-free stream velocity ratios of −0.95 to −1.10 cm. Spatially resolved heat transfer measurements from a constant heat flux surface show that film coolant is greatly disturbed and that local Stanton numbers are altered significantly by embedded longitudinal vortices. Near the downwash side of the vortex, heat transfer is augmented, vortex effects dominate flow behavior, and the protection from film cooling is minimized. Near the upwash side of the vortex, coolant is pushed to the side of the vortex, locally increasing the protection provided by film cooling. In addition, local heat transfer distributions change significantly as the spanwise location of the vortex is changed relative to film-cooling hole locations.

An Experimental Investigation of Natural Convection With Vertical Cylinders in Mercury

1974 ◽  
Vol 96 (4) ◽  
pp. 455-458 ◽  
Author(s):  
L. E. Wiles ◽  
J. R. Welty
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Natural Convection ◽  
Flat Plate ◽  
Convection Heat Transfer ◽  
Vertical Cylinder ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Flat Plates

An experimental investigation of laminar natural convection heat transfer from a uniformly heated vertical cylinder immersed in an effectively infinite pool of mercury is described. A correlation was developed for the local Nusselt number as a function of local modified Grashof number for each cylinder. A single equation incorporating the diameter-to-length ratio was formulated that satisfied the data for all three cylinders. An expression derived by extrapolation of the results to zero curvature (the flat plate condition) was found to agree favorably with others’ work, both analytical and experimental. The influence of curvature upon the heat transfer was found to be small but significant. It was established that the effective thermal resistance through the boundary layer is less for a cylinder of finite curvature than for a flat plate. Consequently, local heat transfer coefficients for cylinders are larger than those for flat plates operating under identical conditions.

Impairment of Local Heat Transfer of the Turbulent Mixed Convection in a Vertical Flat Plate

2018 ◽  
Author(s):  
Myeong-Seon Chae ◽  
Bum-Jin Chung
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Mixed Convection ◽  
Flat Plate ◽  
Forced Convection ◽  
Convection Heat Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Convection Heat ◽  
Vertical Flat Plate

The heat transfer of the buoyancy-aided turbulent mixed convective flow in a vertical flat plate was investigated experimentally. Mass transfer experiments were carried out based on the heat and mass transfer analogy. The Rayleigh numbers ranged from 1.69 × 108 to 2.11 × 1013, depending on the height of the vertical flat plate. The Reynolds numbers varied from 4,585 to 17,320 for turbulent regimes. The test results for turbulent forced convections agreed well with the forced convection correlations established by Petukhov et al. The local heat transfer rates of the turbulent mixed flow exhibited the impairment of heat transfer compared to the forced convection and non-monotonous behavior along the axial position due to buoyancy effect. The local minimum heat transfer was 38.6% lower than the forced convection heat transfer. The turbulent mixed convection heat transfer is affected by the height of vertical plate.

Magnetohydrodynamic Effects Upon Heat Transfer for Laminar Flow Across a Flat Plate

1960 ◽  
Vol 82 (2) ◽  
pp. 87-93 ◽  
Author(s):  
R. D. Cess
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Flat Plate ◽  
Free Stream ◽  
Frictional Heating ◽  
Convection Heat Transfer ◽  
Constant Heat Flux ◽  
Stream Velocity ◽  
Electrically Conducting ◽  
Prandtl Numbers

Forced-convection heat transfer for laminar flow of electrically conducting fluids across a flat plate is considered for a magnetic field of constant inductance acting normal to the free stream velocity and fixed relative to the plate. The boundary condition on the surface of the plate is taken to be either a constant temperature or constant heat flux, and solutions are presented for the following cases: (a) Fluids having a Prandtl number of unity for which both Joule heating and frictional heating are accounted for; (b) fluids having moderate and large Prandtl numbers for negligible Joule and frictional heating; and (c) fluids having low Prandtl numbers for negligible frictional heating.

The Effects of Free-Stream Turbulence Intensity and Velocity Distribution on Heat Transfer to Curved Surfaces

1978 ◽  
Vol 100 (1) ◽  
pp. 159-168 ◽  
Author(s):  
A. Brown ◽  
R. C. Burton
Keyword(s):  
Heat Transfer ◽  
Turbulence Intensity ◽  
Free Stream ◽  
Turbine Blades ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Boundary Layer Transition ◽  
Stream Velocity ◽  
Layer Transition ◽  
Free Stream Turbulence

This paper describes a novel method for measuring the local heat-transfer distribution over a curved surface. The effect of free-stream turbulence intensity, ranging in value from 0.016 to 0.092, on local heat transfer is investigated for a range of Reynolds numbers from 2.0 × 105 to 7.7 × 105. The geometry of the rig was modified to consider three free-stream velocity distributions covering distributions currently in use on suction surfaces of turbine blades. The results are compared with other workers’ experimental results and with available prediction techniques for heat transfer in laminar and turbulent boundary layers. Special attention is paid to the region of boundary-layer transition.

An Experimental Study on Heat Transfer Around Two Side-by-Side Closely Arranged Circular Cylinders

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
Takayuki Tsutsui
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Free Stream ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Circular Cylinders ◽  
Stream Velocity ◽  
Heat Transfer Characteristics ◽  
Minimum Drag ◽  
Coefficient Condition

The present paper describes heat transfer around two side-by-side closely arranged circular cylinders. The flows around two circular cylinders in a side-by-side arrangement can be classified into three flow patterns according to the gap between the two cylinders. The heat transfer characteristics of the cylinders in each flow regime were experimentally investigated. The diameter of the circular cylinders was 40 mm and the gap between the two cylinders varied from 4 mm to 40 mm. The free stream velocity ranged from 4 m/s to 24 m/s, resulting in Reynolds nos. ranging from 1.1×104 to 6.2×104. The local heat transfer coefficient of both cylinders was measured. The overall Nusselt no. of the two cylinders was found to be minimum at G/D(=gap/diameter)=0.4, which is the minimum drag coefficient condition of the two cylinders, too.

Jet-to-Plate Distance Effect on Heat Transfer From a Flat Plate to an Impinging Jet at Various Reynolds Numbers

2012 ◽  
Author(s):  
Patricia Streufert ◽  
Terry X. Yan ◽  
Mahdi G. Baygloo
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Reynolds Number ◽  
Flat Plate ◽  
Numerical Solutions ◽  
Stokes Equations ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Air Jet ◽  
Plate Distance

Local turbulent convective heat transfer from a flat plate to a circular impinging air jet is numerically investigated. The jet-to-plate distance (L/D) effect on local heat transfer is the main focus of this study. The eddy viscosity V2F turbulence model is used with a nonuniform structured mesh. Reynolds-Averaged Navier-Stokes equations (RANS) and the energy equation are solved for axisymmetric, three-dimensional flow. The numerical solutions obtained are compared with published experimental data. Four jet-to-plate distances, (L/D = 2, 4, 6 and 10) and seven Reynolds numbers (Re = 7,000, 15,000, 23,000, 50,000, 70,000, 100,000 and 120,000) were parametrically studied. Local and average heat transfer results are analyzed and correlated with Reynolds number and the jet-to-plate distance. Results show that the numerical solutions matched experimental data best at low jet-to-plate distances and lower Reynolds numbers, decreasing in ability to accurately predict the heat transfer as jet-to-plate distance and Reynolds number was increased.

Experimental Investigation of Corona Wind Heat Transfer Enhancement With a Heated Horizontal Flat Plate

1995 ◽  
Vol 117 (2) ◽  
pp. 309-315 ◽  
Author(s):  
B. L. Owsenek ◽  
J. Seyed-Yagoobi ◽  
R. H. Page
Keyword(s):  
Heat Transfer ◽  
Infrared Camera ◽  
Local Heat Transfer ◽  
Threshold Value ◽  
Local Heat ◽  
Heated Plate ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Heat Transfer Efficiency ◽  
Corona Wind

Corona wind enhancement of free convection was investigated with the needle-plate geometry in air. High voltage was applied to a needle suspended above a heated plate, and heat transfer coefficients were computed by measuring the plate surface temperature distribution with an infrared camera. Local heat transfer coefficients greater than 65 W/m2 K were measured, an enhancement of more than 25:1 over natural convection. The enhancement extended over a significant area, often reaching beyond the 30 cm measurement radius. At high power levels, Joule heating significantly reduced the effective impingement point heat transfer coefficient. The corona wind was found to be more efficient with positive potential than with negative. The heat transfer efficiency was optimized with respect to electrode height and applied voltage. The needle-plate heat transfer effectiveness improved rapidly with increasing height, and became relatively insensitive to height above a threshold value of about 5 cm.

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