The Influence of Free Stream Turbulence on the Local Heat Transfer From Cylinders

1960 ◽  
Vol 82 (2) ◽  
pp. 101-107 ◽  
Author(s):  
R. A. Seban
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Free Stream ◽  
Separated Flow ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Turbulent Intensity ◽  
Transfer Coefficients ◽  
Free Stream Turbulence ◽  
Heat Transfer Coefficients

Local heat-transfer coefficients and recovery factors are presented for three different cylinders in a two-dimensional subsonic air flow, with emphasis on the effect of screen-produced turbulence on these quantities. The increase in turbulent intensity so realized produced larger local heat-transfer coefficients, in a way dependent upon the location on the cylinders, through a direct increase in the heat transfer to the laminar boundary layer, through an earlier transition to turbulence, or through an alteration in the character of the separated flow. Alternatively, recovery factors were affected less, being invariant with respect to the turbulent intensity for attached boundary layer flow, but demonstrating large changes in those separated flow regions for which increased free stream turbulence produced substantial changes in the nature of the separated flow.

scholarly journals Turbulent Natural Convection from a Vertical Plane Surface

1968 ◽  
Vol 90 (1) ◽  
pp. 1-6 ◽  
Author(s):  
R. Cheesewright
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Natural Convection ◽  
Vertical Plane ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Convection Boundary Layer ◽  
Transfer Coefficients ◽  
Turbulent Natural Convection ◽  
Heat Transfer Coefficients

The paper reports the results of an experimental investigation which was intended to clarify the present uncertain position with regard to the distributions of mean temperature and mean velocity in a turbulent natural-convection boundary layer. Data reported for the turbulent boundary layer for Grashof numbers between 1010 and 1011 include local heat transfer coefficients as well as temperatures and velocities. Local heat transfer coefficients and temperature distributions are also reported for the laminar and transitional boundary-layer regions. Results are compared with other experimental data and with theoretical predictions.

Heat Transfer in the Oscillating Turbulent Boundary Layer

1969 ◽  
Vol 91 (4) ◽  
pp. 239-244 ◽  
Author(s):  
James A. Miller
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Mean Velocity ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Local Coefficients

Measurements of local heat-transfer coefficients in the fully established oscillating turbulent boundary layer over a flat plate are reported. In the range of frequencies from 0.1 to 200 cps and amplitudes from 8 to 92 percent of the freestream mean velocity, increases in local Nusselt numbers of 3 to 5 percent were found. It is concluded that substantial increases in local coefficients, sometimes reported in oscillating flows of low standing wave ratio, may be traced to reduced transition Reynolds numbers.

scholarly journals Heat Transfer to Turbine Blades, With Special Reference to the Effects of Mainstream Turbulence

1979 ◽  
Author(s):  
A. Brown ◽  
B. W. Martin
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbine Blades ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Layer Behavior

The mainly empirical criteria used to predict boundary-layer behavior under the combined influence of velocity gradient factor and significant mainstream turbulence are reviewed and assessed by application to recently published blade heat-transfer measurements. Indications are that under the conditions experienced in gas turbine engines, the scale and frequency of mainstream turbulence may be as important as its intensity in determining local heat transfer coefficients round the blades.

scholarly journals Heat Transfer in the Oscillating Turbulent Boundary Layer

1969 ◽  
Author(s):  
J. A. Miller
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Turbulent Boundary Layer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Mean Velocity ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Local Coefficients

Measurements of local heat transfer coefficients in the fully established oscillating turbulent boundary layer over a flat plate are reported. In the range of frequencies from 0.1 to 200 cps and amplitudes from 8 to 92 percent of the freestream mean velocity increases in local Nusselt numbers of 3 to 5 percent were found. It is concluded that substantial increases in local coefficients sometimes reported in oscillating flows of low standing wave ratio may be traced to reduced transition Reynolds numbers.

Heat Transfer With Very High Free-Stream Turbulence: Part I—Experimental Data

1992 ◽  
Vol 114 (4) ◽  
pp. 827-833 ◽  
Author(s):  
P. K. Maciejewski ◽  
R. J. Moffat
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Free Stream ◽  
Turbine Blades ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Mean Velocity ◽  
Free Stream Turbulence ◽  
Free Jet ◽  
Very High

The present research investigates boundary layer heat transfer with very high freestream turbulence, a problem of primary interest in the gas turbine industry where existing boundary layer correlations and codes underpredict local heat transfer rates on first-stage turbine blades and vanes by as much as a factor of three for some engine designs. The problem was studied experimentally by placing a constant-temperature heat transfer surface at various locations in the margin of a turbulent free jet and measuring both the surface heat transfer rate and the turbulence in the free stream. In this experiment, free-stream turbulent fluctuations 20 to 60 percent relative to the mean velocity augment heat transfer 1.8 to 4 times that which would be predicted locally using accepted correlations for turbulent boundary layers at the same Reynolds number.

The Effect of a Spherical Protuberance on the Local Heat Transfer to a Turbulent Boundary Layer

1968 ◽  
Vol 90 (4) ◽  
pp. 408-412 ◽  
Author(s):  
R. A. Seban ◽  
G. L. Caldwell
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Heat Transfer Coefficient ◽  
Boundary Layer Thickness ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Sphere Diameter ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
The Heat Transfer Coefficient

Local heat transfer coefficients are presented for a single spherical protuberance on a plate, along which the boundary layer was turbulent, for air speeds from 50 to 150 fps. Two spheres were used to produce ratios of sphere diameter to boundary-layer thickness of the order of 2 and 0.7. The heat transfer coefficient behind the sphere depends approximately on the eight-tenths power of the velocity, its maximum is located about 2 dia downstream of the sphere, and the downstream effect is limited spanwise to a region about 4 dia in width.

The Effect of Regulating Elements on Convective Heat Transfer along Shaped Heat Exchange Surfaces

2013 ◽  
Vol 34 (1) ◽  
pp. 5-16 ◽  
Author(s):  
Jozef Cernecky ◽  
Jan Koniar ◽  
Zuzana Brodnianska
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Cfd Simulation ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Temperature Fields ◽  
Transfer Coefficients ◽  
Heat Transfer Intensification ◽  
Heat Transfer Coefficients ◽  
Forced Air

Abstract The paper deals with a study of the effect of regulating elements on local values of heat transfer coefficients along shaped heat exchange surfaces with forced air convection. The use of combined methods of heat transfer intensification, i.e. a combination of regulating elements with appropriately shaped heat exchange areas seems to be highly effective. The study focused on the analysis of local values of heat transfer coefficients in indicated cuts, in distances expressed as a ratio x/s for 0; 0.33; 0.66 and 1. As can be seen from our findings, in given conditions the regulating elements can increase the values of local heat transfer coefficients along shaped heat exchange surfaces. An optical method of holographic interferometry was used for the experimental research into temperature fields in the vicinity of heat exchange surfaces. The obtained values correspond very well with those of local heat transfer coefficients αx, recorded in a CFD simulation.

scholarly journals Heat Transfer Coefficient Determination in a Gravity Die Casting Process with Local Air Gap Formation and Contact Pressure Using Experimental Evaluation and Numerical Simulation

2021 ◽  
Author(s):  
T. Vossel ◽  
N. Wolff ◽  
B. Pustal ◽  
A. Bührig-Polaczek ◽  
M. Ahmadein
Keyword(s):  
Heat Transfer ◽  
Contact Pressure ◽  
Local Heat Transfer ◽  
Casting Process ◽  
Local Heat ◽  
Air Gap ◽  
Gap Formation ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Die Casting Process

AbstractAnticipating the processes and parameters involved for accomplishing a sound metal casting requires an in-depth understanding of the underlying behaviors characterizing a liquid melt solidifying inside its mold. Heat balance represents a major factor in describing the thermal conditions in a casting process and one of its main influences is the heat transfer between the casting and its surroundings. Local heat transfer coefficients describe how well heat can be transferred from one body or material to another. This paper will discuss the estimation of these coefficients in a gravity die casting process with local air gap formation and heat shrinkage induced contact pressure. Both an experimental evaluation and a numerical modeling for a solidification simulation will be performed as two means of investigating the local heat transfer coefficients and their local differences for regions with air gap formation or contact pressure when casting A356 (AlSi7Mg0.3).

scholarly journals Condensation inside smooth horizontal tubes: Part 1. Survey of the methods of heat-exchange prediction

2015 ◽  
Vol 19 (5) ◽  
pp. 1769-1789 ◽  
Author(s):  
Volodymyr Rifert ◽  
Volodymyr Sereda
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Film Condensation ◽  
Experimental Investigations ◽  
Phase Flow ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Horizontal Tubes

Survey of the works on condensation inside smooth horizontal tubes published from 1955 to 2013 has been performed. Theoretical and experimental investigations, as well as more than 25 methods and correlations for heat transfer prediction are considered. It is shown that accuracy of this prediction depends on the accuracy of volumetric vapor content and pressure drop at the interphase. The necessity of new studies concerning both local heat transfer coefficients and film condensation along tube perimeter and length under annular, stratified and intermediate regimes of phase flow was substantiated. These characteristics being defined will allow determining more precisely the boundaries of the flow regimes and the methods of heat transfer prediction.

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