Heat Transfer From Rectangular Plates Inclined at Different Angles of Attack and Yaw to an Air Stream

1985 ◽  
Vol 107 (2) ◽  
pp. 307-312 ◽  
Author(s):  
D. G. Motwani ◽  
U. N. Gaitonde ◽  
S. P. Sukhatme
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Rectangular Plates ◽  
Average Heat Transfer Coefficient ◽  
Transfer Coefficients ◽  
Average Heat ◽  
Heat Transfer Coefficients ◽  
Aspect Ratios ◽  
Air Stream ◽  
Angle Of Yaw

Average heat transfer coefficients during forced convection air flow over inclined and yawed rectangular plates have been experimentally determined. Tripping wires at the edges ensured that a turbulent boundary layer prevailed over the plates. The experiments were carried out for a constant surface temperature and covered two plates of different aspect ratios, angles of attack from 0 to 45 deg, angles of yaw from 0 to 30 deg, and Reynolds numbers from 2 times; 104 to 3.5 times; 105. The results show that the average heat transfer coefficient is essentially insensitive to the aspect ratio and angle of yaw. However, it is a function of Reynolds number and the angle of attack. Correlation equations for various angles of attack are suggested.

Rib Heat Transfer Coefficient Measurements in a Rib-Roughened Square Passage

1998 ◽  
Vol 120 (2) ◽  
pp. 376-385 ◽  
Author(s):  
G. J. Korotky ◽  
M. E. Taslim
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Performance ◽  
Blockage Ratio ◽  
Average Heat Transfer Coefficient ◽  
Transfer Coefficients ◽  
Height Ratio ◽  
Average Heat ◽  
Heat Transfer Coefficients

Three staggered 90 deg rib geometries corresponding to blockage ratios of 0.133, 0.167, and 0.25 were tested for pitch-to-height ratios of 5, 8.5, and 10, and for two distinct thermal boundary conditions of heated and unheated channel walls. Comparisons were made between the surface-averaged heat transfer coefficients and friction factors for ribs with rounded corners and those with sharp corners, reported previously. Heat transfer coefficients of the furthest upstream rib and that of a typical rib located in the middle of the rib-roughened region of the passage wall were also compared. It was concluded that: (a) For the geometries tested, the rib average heat transfer coefficient was much higher than that for the area between the ribs. For the sharp-corner ribs, the rib average heat transfer coefficient increased with blockage ratio. However, when the corners were rounded, the trend depended on the level of roundness. (b) High-blockage-ratio (e/Dh = 0.25) ribs were insensitive to the pitch-to-height ratio. For the other two blockage ratios, the pitch-to-height ratio of 5 produced the lowest heat transfer coefficient. Results of the other two pitch-to-height ratios were very close, with the results of S/e = 10 slightly higher than those of S/e = 8.5. (c) Under otherwise identical conditions, ribs in the furthest upstream position produced lower heat transfer coefficients for all cases except that of the smallest blockage ratio with S/e of 5. In that position, for the rib geometries tested, while the sharp-corner rib average heat transfer coefficients increased with the blockage ratio, the trend of the round-corner ribs depended on the level of roundness, r/e. (d) Thermal performance decreased with the blockage ratio. While the smallest rib geometry at a pitch-to-height ratio of 10 had the highest thermal performance, thermal performance of high blockage ribs at a pitch-to-height ratio of 5 was the lowest. (e) The general effects of rounding were a decrease in heat transfer coefficient for the midstream ribs and an increase in heat transfer coefficient for ribs in the furthest upstream position.

Heat Transfer to Mercury Flowing In Line Through an Unbaffled Rod Bundle: Experimental Study of the Effect of Rod Displacement on Rod-Average Heat Transfer Coefficients

1969 ◽  
Vol 91 (4) ◽  
pp. 568-580 ◽  
Author(s):  
P. J. Hlavac ◽  
O. E. Dwyer ◽  
M. A. Helfant
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Uniform Heat Flux ◽  
Average Heat Transfer Coefficient ◽  
Transfer Coefficients ◽  
Average Heat ◽  
Heat Transfer Coefficients ◽  
Rod Bundle

An experimental study of heat transfer to mercury flowing in line through an unbaffled rod bundle was carried out. The “rods” were special electrical heaters whose claddings had different thicknesses and thermal conductivities. The experiments were carried out under a thermal boundary condition approaching that of uniform heat flux in all directions at the inner wall of the rod cladding. It was found that displacement of a rod from its symmetrical position can result in a large reduction in its average heat transfer coefficient. This reduction increases exponentially with the amount of displacement. For a given direction and amount of displacement, the reduction is little affected by variations in cladding thickness and conductivity but is affected considerably by flow rate. Not only does the displaced rod suffer a reduction in its own average heat transfer coefficient, but so do those toward which it is displaced. At the same time, the average coefficients of the rods from which it is displaced remain about the same. Thus the overall average coefficient of the group of affected rods goes down when a single rod is displaced.

scholarly journals A New Statistical-Based Correlation for the Rib Fin Effects on the Overall Heat Transfer Coefficient in a Rib-Roughened Cooling Channel

2007 ◽  
Vol 2007 ◽  
pp. 1-11 ◽  
Author(s):  
M. E. Taslim ◽  
V. Nezym
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Weighted Average ◽  
Average Heat Transfer Coefficient ◽  
Transfer Coefficients ◽  
Average Heat ◽  
Fin Efficiency ◽  
Heat Transfer Coefficients ◽  
Rib Roughened

Heat transfer coefficients in the cooling cavities of turbine airfoils are greatly enhanced by the presence of discrete ribs on the cavity walls. These ribs introduce two heat transfer enhancing features: a significant increase in heat transfer coefficient by promoting turbulence and mixing, and an increase in heat transfer area. Considerable amount of data are reported in open literature for the heat transfer coefficients both on the rib surface and on the floor area between the ribs. Many airfoil cooling design software tools, however, require an overall average heat transfer coefficient on a rib-roughened wall. Dealing with a complex flow circuit in conjunction with180∘bends, numerous film holes, trailing-edge slots, tip bleeds, crossover impingement, and a conjugate heat transfer problem; these tools are not often able to handle the geometric details of the rib-roughened surfaces or local variations in heat transfer coefficient on a rib-roughened wall. On the other hand, assigning an overall area-weighted average heat transfer coefficient based on the rib and floor area and their corresponding heat transfer coefficients will have the inherent error of assuming a 100% fin efficiency for the ribs, that is, assuming that rib surface temperature is the same as the rib base temperature. Depending on the rib geometry, this error could produce an overestimation of up to 10% in the evaluated rib-roughened wall heat transfer coefficient. In this paper, a correction factor is developed that can be applied to the overall area-weighted average heat transfer coefficient that, when applied to the projected rib-roughened cooling cavity walls, the net heat removal from the airfoil is the same as that of the rib-roughened wall. To develop this correction factor, the experimental results of heat transfer coefficients on the rib and on the surface area between the ribs are combined with about 400 numerical conduction models to determine an overall equivalent heat transfer coefficient that can be used in airfoil cooling design software. A well-known group method of data handling (GMDH) scheme was then utilized to develop a correlation that encompasses most pertinent parameters including the rib geometry, rib fin efficiency, and the rib and floor heat transfer coefficients.

Heat Transfer From Rotating Discs With Finite Thickness Subjected to Outer Air Streams

2010 ◽  
Author(s):  
Stefan aus der Wiesche
Keyword(s):  
Heat Transfer ◽  
Large Range ◽  
Finite Thickness ◽  
Reynolds Numbers ◽  
Transfer Coefficients ◽  
Rotating Disc ◽  
Heat Transfer Coefficients ◽  
Rotating Discs ◽  
Air Stream ◽  
Air Streams

The heat transfer from rotating discs in an outer air stream is of major importance for many technical applications. Experimentally determined heat transfer coefficients are presented for a large range of rotational and crossflow Reynolds numbers including also the effects of finite disc thickness and incidence to the uniform air stream. The extreme conditions of a rotating disc in still air and a stationary disc in an air crossflow are considered, too.

Heat Transfer Enhancement for Turbulent Flow Through Blockages With Round and Elongated Holes in a Rectangular Channel

2007 ◽  
Vol 129 (11) ◽  
pp. 1611-1615 ◽  
Author(s):  
H. S. Ahn ◽  
S. W. Lee ◽  
S. C. Lau
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Rectangular Channel ◽  
Transfer Enhancement ◽  
Transfer Coefficients ◽  
Pressure Drops ◽  
Average Heat ◽  
Heat Transfer Coefficients ◽  
Aspect Ratios ◽  
Flow Through

Experiments were conducted to determine the average heat transfer coefficients on three wall segments between blockages with holes in a wide rectangular channel. Eight different configurations of the holes in the blockages—two diameters and four aspect ratios of the holes—were examined. The pressure drops across the blockages were also measured. The results showed that the elongated holes in the blockages in this study enhanced more heat transfer than the round holes, but they also caused larger pressure drops across the blockages.

Rib Heat Transfer Coefficient Measurements in a Rib-Roughened Square Passage

1996 ◽  
Author(s):  
G. J. Korotky ◽  
M. E. Taslim
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Performance ◽  
Blockage Ratio ◽  
Average Heat Transfer Coefficient ◽  
Transfer Coefficients ◽  
Height Ratio ◽  
Average Heat ◽  
Heat Transfer Coefficients

Three staggered 90° rib geometries corresponding to blockage ratios of 0.133, 0.167 and 0.25 were tested for pitch-to-height ratios of 5, 8.5 and 10, and for two distinct thermal boundary conditions of heated and unheated channel walls. Comparisons were made between the surface averaged heat transfer coefficients and friction factors for ribs with rounded corners and those with sharp comers, reported previously. Heat transfer coefficients of the furthest upstream rib and that of a typical rib located in the middle of the rib-roughened region of the passage wall were also compared. It was concluded that: a) For the geometries tested, the rib average heat transfer coefficient was much higher than that for the area between the ribs. For the sharp-corner ribs, the rib average heat transfer coefficient increased with blockage ratio. However, when the corners were rounded, the trend depended on the level of roundness. b) High blockage ratio (e/Dh=0.25) ribs were insensitive to the pitch-to-height ratio. For the other two blockage ratios, the pitch-to-height ratio of 5 produced the lowest heat transfer coefficient. Results of the other two pitch-to-height ratios were very close, with the results of S/e = 10 slightly higher than those of S/e=8.5. c) Under otherwise identical conditions, ribs in the furthest upstream position produced lower heat transfer coefficients for all cases except that of the smallest blockage ratio with S/e of 5. In that position, for the rib geometries tested, while the sharp-comer rib average heat transfer coefficients increased with the blockage ratio, the trend of the round-corner ribs depended on the level of roundness, r/e. d) Thermal performance decreased with the blockage ratio. While the smallest rib geometry at a pitch-to-height ratio of 10 had the highest thermal performance, thermal performance of high blockage ribs at a pitch-to-height ratio of 5 was the lowest. e) The general effects of rounding were a decrease in heat transfer coefficient for the midstream ribs and an increase in heat transfer coefficient for ribs in the furthest upstream position.

An Experimental Investigation of Ice Formation around an Isothermally Cooled Cylinder in Crossflow

1981 ◽  
Vol 103 (4) ◽  
pp. 733-738 ◽  
Author(s):  
K. C. Cheng ◽  
Hideo Inaba ◽  
R. R. Gilpin
Keyword(s):  
Heat Transfer ◽  
Series Solution ◽  
Reynolds Numbers ◽  
Cooling Capacity ◽  
Ice Formation ◽  
Correlation Equations ◽  
Transfer Coefficients ◽  
Average Heat ◽  
Heat Transfer Coefficients ◽  
Ice Water

The problem of steady-state, two-dimensional ice formation around an isothermally cooled circular cylinder in a crossflow is studied experimentally for the ranges of Reynolds numbers, Red, 2.3 × 102 to 8.6 × 104 and cooling temperature ratios, θc, 6.3 to 75.8. The local and average heat transfer coefficients at the ice-water interface are obtained from measured ice profiles by using a series solution of the Laplace equation in the ice. Correlation equations for the average heat transfer are obtained for three regimes of Reynolds numbers. A correlation is also obtained for the cooling capacity that can be stored in the ice layer around a cylinder.

A Prediction Method for Heat Transfer During Film Condensation on Horizontal Low Integral-Fin Tubes

1987 ◽  
Vol 109 (1) ◽  
pp. 218-225 ◽  
Author(s):  
H. Honda ◽  
S. Nozu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Prediction Method ◽  
Film Condensation ◽  
Average Heat Transfer Coefficient ◽  
Transfer Coefficients ◽  
Average Heat ◽  
Heat Transfer Coefficients ◽  
Fin Tubes

A method for predicting the average heat transfer coefficient is presented for film condensation on horizontal low integral-fin tubes. Approximate equations based on the numerical analysis of surface tension drained condensate flow on the fin surface are developed for the heat transfer coefficients in the upper and lower portions of the flooding point below which the interfin space is flooded with condensate. For the unflooded region, the equation is modified to take account of the effect of gravity. These equations are used, along with the previously derived equation for the flooding point, to determine the wall temperature distribution, and in turn the average heat transfer coefficient. It is shown that the present model can predict the average heat transfer coefficient within ±20 percent for most of the available experimental data including 11 fluids and 22 tubes.

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