Discussion: “Free-Stream Turbulence Effects on Local Heat Transfer from a Sphere” (Newman, L. B., Sparrow, E. M., and Eckert, E. R. G., 1972, ASME J. Heat Transfer, 94, pp. 7–14)

1972 ◽  
Vol 94 (1) ◽  
pp. 15-15
Author(s):  
Frederick A. Costello
Keyword(s):  
Heat Transfer ◽  
Free Stream ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Free Stream Turbulence ◽  
Turbulence Effects

Free-Stream Turbulence Effects on Local Heat Transfer from a Sphere

1972 ◽  
Vol 94 (1) ◽  
pp. 7-14 ◽  
Author(s):  
L. B. Newman ◽  
E. M. Sparrow ◽  
E. R. G. Eckert
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Number ◽  
Free Stream ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Heat Flux Sensor ◽  
Forward Region ◽  
Number Range ◽  
Free Stream Turbulence

Experiments involving both heat-transfer and turbulence-field measurements were performed to determine the influence of free-stream turbulence on the local heat transfer from a sphere situated in a forced-convection airflow. The research was facilitated by a miniature heat-flux sensor which could be positioned at any circumferential location on the equator of the sphere. Turbulence grids were employed to generate free-stream turbulence with intensities of up to 9.4 percent. The Reynolds-number range of the experiments was from 20,000 to 62,000. The results indicate that the local heat flux in the forward region of the sphere is uninfluenced by free-stream turbulence levels of up to about 5 percent. For higher turbulence levels, the heat-flux increases with the turbulence intensity, the greatest heat-flux augmentation found here being about 15 percent. Furthermore, at the higher turbulence intensities, there appears to be a departure from the half-power Reynolds-number dependence of the stagnation-point Nusselt number. Turbulent separation occurred at Reynolds numbers of 42,000 and 62,000 for a turbulence level of 9.4 percent, these values being well below the transition Reynolds number of 2 × 105 for a sphere situated in a low-turbulence flow.

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.

Heat Transfer Measurements on a Turbine Airfoil With Pressure Side Separation

2009 ◽  
Author(s):  
Helge Ladisch ◽  
Achmed Schulz ◽  
Hans-Jo¨rg Bauer
Keyword(s):  
Heat Transfer ◽  
Free Stream ◽  
Separation Bubble ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Boundary Layer Separation ◽  
Local Heat ◽  
Free Stream Turbulence ◽  
Pressure Surface ◽  
Low Pressure Turbine

Heat transfer measurements on a highly loaded low-pressure turbine airfoil with a separation bubble on the pressure surface are presented. The experiments were conducted in a linear cascade at various free-stream turbulence intensities (Tu1 = 1.6% to 10%) and Reynolds numbers of the inflow. The effect of both quantities on heat transfer, separation and laminar-turbulent transition is quantified. Particle-Image-Velocimetry has been performed to study the characteristics of the separation bubble. The results reveal a considerable influence of the boundary layer separation on the local heat transfer. The size of the separation region is strongly influenced by free-stream turbulence level and Reynolds number.

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.

Sign in / Sign up

Export Citation Format

Share Document