Influence of Surface Heat Flux Ratio on Heat Transfer Augmentation in Square Channels With Parallel, Crossed and V-Shaped Angled Ribs

1991 ◽  
Author(s):  
J. C. Han ◽  
Y. M. Zhang ◽  
C. P. Lee
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flux Ratio ◽  
Side Wall ◽  
Reynolds Numbers ◽  
Diameter Ratio ◽  
Wall Heat Flux ◽  
Wall Heat Transfer ◽  
Square Channel ◽  
Heat Transfer Augmentation

The effect of wall heat flux ratio on the local heat transfer augmentation in a square channel with two opposite in-line ribbed walls was investigated for Reynolds numbers from 15,000 to 80,000. The square channel composed of ten isolated copper sections has a length-to-hydraulic diameter ratio (L/D) of 20. The rib height-to-hydraulic diameter ratio (e/D) is 0.0625 and the rib pitch-to-height ratio (P/e) equals 10. Six ribbed side to smooth side wall heat flux ratios (Case 1 - q″r1/q″s = q″r2/q″s = 1; Case 2 - q″r1/q″s = q″r2/q″s = 3; Case 3 - q″r1/q″s = q″r2/q″s = 6; Case 4 - q″r1/q″s = 6 and q″r2/q″s = 4; Case 5 - q″r1/q″s = q″r2/q″s = ∞ and Case 6 - q″r1/q″s = ∞ and q″r2/q″s = 0) were studied for four rib orientations (90° rib, 60° parallel rib, 60° crossed rib, and 60° ∨-shaped rib). The results show that the ribbed side wall heat transfer augmentation increases with increasing ribbed side to smooth side wall heat flux ratios, but the reverse is true for the smooth side wall heat transfer augmentation. The average heat transfer augmentation of the ribbed side and smooth side wall decreases slightly with increasing wall heat flux ratios. Two ribbed side wall heating (Case 5 - q″r1/q″s = q″r2/q″s = ∞) provides a higher ribbed-side-wall heat transfer augmentation than the four-wall uniform heating (Case 1 - q″r1/q″s = q″r2/q″s = 1). The effect of wall heat flux ratio reduces with increasing Reynolds numbers. The results also indicate that the 60° ∨-shaped rib and 60° parallel rib perform better than the 60° crossed rib and 90° rib, regardless of wall heat flux ratio and Reynolds number.

Influence of Surface Heat Flux Ratio on Heat Transfer Augmentation in Square Channels With Parallel, Crossed, and V-Shaped Angled Ribs

1992 ◽  
Vol 114 (4) ◽  
pp. 872-880 ◽  
Author(s):  
J. C. Han ◽  
Y. M. Zhang ◽  
C. P. Lee
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flux Ratio ◽  
Side Wall ◽  
Reynolds Numbers ◽  
Diameter Ratio ◽  
Wall Heat Flux ◽  
Wall Heat Transfer ◽  
Square Channel ◽  
Heat Transfer Augmentation

The effect of wall heat flux ratio on the local heat transfer augmentation in a square channel with two opposite in-line ribbed walls was investigated for Reynolds numbers from 15,000 to 80,000. The square channel composed of ten isolated copper sections has a length-to-hydraulic diameter ratio (L/D) of 20. The rib height-to-hydraulic diameter ratio (e/D) is 0.0625 and the rib pitch-to-height ratio (P/e) equals 10. Six ribbed side to smooth side wall heat flux ratios (Case 1—q″r1/q″s = q″r2/q″s = 1; Case 2—q″r1/q″s = q″r2/q″s = 3; Case 3—q″r1/q″s = q″r2/q″s = 6; Case 4—q″r1/q″s = 6 and q″r2/q″s = 4; Case 5—q″r1/q″s = q″r2/q″s = ∞; Case 6—q″r1/q″s = ∞ and q″r2/q″s = 0) were studied for four rib orientations (90 deg rib, 60 deg parallel rib, 60 deg crossed rib, and 60 deg V-shaped rib). The results show that the ribbed side wall heat transfer augmentation increases with increasing ribbed side to smooth side wall heat flux ratios, but the reverse is true for the smooth side wall heat transfer augmentation. The average heat transfer augmentation of the ribbed side and smooth side wall decreases slightly with increasing wall heat flux ratios. Two ribbed side wall heating (Case 5—q″r1/q″s = q″r2/q″s = ∞) provides a higher ribbed side wall heat transfer augmentation than the four-wall uniform heating (Case 1—q″r1/q″s = q″r2/q″s = 1). The effect of wall heat flux ratio reduces with increasing Reynolds numbers. The results also indicate that the 60 deg V-shaped rib and 60 deg parallel rib perform better than the 60 deg crossed rib and 90 deg rib, regardless of wall heat flux ratio and Reynolds number.

Augmented Heat Transfer in Square Channels With Parallel, Crossed, and V-Shaped Angled Ribs

1991 ◽  
Vol 113 (3) ◽  
pp. 590-596 ◽  
Author(s):  
J. C. Han ◽  
Y. M. Zhang ◽  
C. P. Lee
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Diameter Ratio ◽  
Hydraulic Diameter ◽  
Square Channel ◽  
Heat Transfer Augmentation ◽  
Better Than

The effect of the rib angle orientation on the local heat transfer distributions and pressure drop in a square channel with two opposite in-line ribbed walls was investigated for Reynolds numbers from 15,000 to 90,000. The square channel composed of ten isolated copper sections has a length-to-hydraulic diameter ratio of 20; the rib height-to-hydraulic diameter ratio is 0.0625; the rib pitch-to-height ratio equals 10. Nine rib configurations were studied: 90 deg rib, 60 and 45 deg parallel ribs, 60 and 45 deg crossed ribs, 60 and 45 deg ∨-shaped ribs, and 60 and 45 deg ∧-shaped ribs. The results show that the 60 deg (or 45 deg) ∨-shaped rib performs better than the 60 deg (or 45 deg) parallel rib and, subsequently, better than the 60 deg (or 45 deg) crossed rib and the 90 deg rib. The ∨-shaped rib produces the highest heat transfer augmentation, while the ∧-shaped rib generates the greatest pressure drop. The crossed rib has the lowest heat transfer enhancement and the smallest pressure drop penalty.

scholarly journals Velocity Measurements and Local Heat Transfer in a Rotating Ribbed Two-Pass Square Channel With Uneven Wall Heat Flux

1997 ◽  
Author(s):  
Shou-Shing Hsieh ◽  
Ming-Hung Chiang ◽  
Ping-Ju Chen
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Wall Heat Flux ◽  
Velocity Measurements ◽  
Mean Velocity ◽  
Square Channel ◽  
Rotation Numbers

The influence of rotation and uneven wall heat flux effect on the local velocity distribution as well as local heat transfer coefficient in a rotating, two pass rib roughened (rib height e/DH = 0.20; rib pitch p/e = 5) square channel were studied for Reynolds numbers from 5000 to 10000 and rotation numbers from 0 to 0.1602 (≤ 300 rpm). The measured mean velocity under different wall heat flux condition for the specified rib configuration at ReH = 5000 and 10000, ReH = 0, 267, 534 and 801 are presented. Regionally averaged Nusselt number variations with rotation (≤ 800 rpm)along the duct have been determined over the trailing and leading surfaces for a two pass channel. Moreover, LDV measurements with heating were examined. It was found that the Coriolis force as well as centrifugal buoyancy is significant as the rotational speed increases.

scholarly journals Experimental Heat Transfer Investigation of Stationary and Orthogonally Rotating Asymmetric and Symmetric Heated Smooth and Turbulated Channels

1992 ◽  
Author(s):  
H. A. El-Husayni ◽  
M. E. Taslim ◽  
D. M. Kercher
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Rotation Number ◽  
Symmetric Case ◽  
Wall Heat Flux ◽  
Heated Wall ◽  
Wall Heat Transfer ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Smooth Channel

An experimental investigation was conducted to determine the effects of variations in wall thermal boundary conditions on local heat transfer coefficients in stationary and orthogonally rotating smooth wall and two opposite-wall turbulated square channels. Results were obtained for three distributions of uniform wall heat flux: asymmetric, applied to the primary wall only; symmetric, applied to two opposite walls only; and fully-symmetric, applied to all four channel walls. Measured stationary and rotating smooth channel average heat transfer coefficients at channel location L/Dh = 9.53 were not significantly sensitive to wall heat flux distributions. Trailing side heat transfer generally increased with Rotation number whereas the leading wall results showed a decreasing trend at low Rotation numbers to a minimum and then an increasing trend with further increase in Rotation number. The stationary turbulated wall heat transfer coefficients did not vary markedly with the variations in wall heat flux distributions. Rotating leading wall heat transfer decreased with Rotation number and showed little sensitivity to heat flux distributions except for the fully-symmetric heated wall case at the highest Reynolds number tested. Trailing wall heat transfer coefficients were sensitive to the thermal wall distributions generally at all Reynolds numbers tested and particularly with increasing Rotation number. While the asymmetric case showed a slight deficit in trailing wall heat transfer coefficients due to rotation, the symmetric case indicated little change whereas the fully-symmetric case exhibited an enhancement.

Experimental Heat Transfer Investigation of Stationary and Orthogonally Rotating Asymmetric and Symmetric Heated Smooth and Turbulated Channels

1994 ◽  
Vol 116 (1) ◽  
pp. 124-132 ◽  
Author(s):  
H. A. El-Husayni ◽  
M. E. Taslim ◽  
D. M. Kercher
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Rotation Number ◽  
Symmetric Case ◽  
Wall Heat Flux ◽  
Heated Wall ◽  
Wall Heat Transfer ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Smooth Channel

An experimental investigation was conducted to determine the effects of variations in wall thermal boundary conditions on local heat transfer coefficients in stationary and orthogonally rotating smooth wall and two opposite-wall turbulated square channels. Results were obtained for three distributions of uniform wall heat flux: asymmetric, applied to the primary wall only; symmetric, applied to two opposite walls only; and fully symmetric, applied to all four channel walls. Measured stationary and rotating smooth channel average heat transfer coefficients at channel location L/Dh = 9.53 were not significantly sensitive to wall heat flux distributions. Trailing side heat transfer generally increased with Rotation number, whereas the leading wall results showed a decreasing trend at low Rotation numbers to a minimum and then an increasing trend with further increase in Rotation number. The stationary turbulated wall heat transfer coefficients did not vary markedly with the varaitions in wall heat flux distributions. Rotating leading wall heat transfer decreased with Rotation number and showed little sensitivity to heat flux distributions except for the fully symmetric heated wall case at the highest Reynolds number tested. Trailing wall heat transfer coefficients were sensitive to the thermal wall distributions generally at all Reynolds numbers tested and particularly with increasing Rotation number. While the asymmetric case showed a slight deficit in trailing wall heat transfer coefficients due to rotation, the symmetric case indicated little change, whereas the fully symmetric case exhibited an enhancement.

Heat Transfer and Friction Factor in a Square Channel With One, Two, or Four Inclined Ribbed Walls

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
Soo Whan Ahn ◽  
Ho Keun Kang ◽  
Sung Taek Bae ◽  
Dae Hee Lee
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Reynolds Numbers ◽  
Diameter Ratio ◽  
Height Ratio ◽  
Square Channel ◽  
Ribbed Channel ◽  
Nusselt Numbers ◽  
Channel Aspect Ratio ◽  
Turbulent Air Flow

An experimental study was carried out to investigate the heat transfer and friction characteristics of a fully developed turbulent air flow in a square channel with 45 deg inclined ribs on one, two, or four walls. Either two opposite walls or all four walls in the channel were heated. Tests were performed for Reynolds numbers (Re) ranging from 7600 to 24,900, the pitch to rib height ratio (P∕e) of 8.0, the rib height to channel hydraulic diameter ratio (e∕Dh) of 0.0667, and the channel aspect ratio of 1.0. The results show that the local Nusselt number and friction factor increase with the number of ribbed walls. With one ribbed wall, the Nusselt numbers on the ribbed side (B) were 50% and 63% greater than those on the adjacent smooth sides (L∕R) and the opposite smooth side (T), respectively. The Nusselt numbers, when the two opposite walls of a four-wall ribbed channel are heated, are found to be 1.49–1.52 times greater than those obtained when all four walls are heated.

EXPERIMENTAL INVESTIGATION OF THE UNSTEADY WALL HEAT FLUX GENERATED BY THE PROPAGATION OF A SELF-SUSTAINED DETONATION

2020 ◽  
Author(s):  
H. QUINTENS ◽  
◽  
Q. MICHALSKI ◽  
F. VIROT ◽  
J. SOTTON ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Experimental Investigation ◽  
Cylindrical Tube ◽  
Wall Heat Flux ◽  
Gaseous Detonation ◽  
Wall Heat Transfer ◽  
Detonation Propagation ◽  
Tube Type

This study experimentally investigates the wall heat transfer due to gaseous detonation propagation in a cylindrical tube. Type-E thermocouples, embedded into the wall, flushed at the surface and aligned along the last part of the tube, measured successively the temperature lift in the wall during detonation propagation.

Variable Property Effects of Fully Developed Laminar Flow in Concentric Annuli

1988 ◽  
Vol 110 (2) ◽  
pp. 314-320 ◽  
Author(s):  
H. Herwig ◽  
K. Klemp
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Heat Capacity ◽  
Flux Ratio ◽  
Outer Wall ◽  
Diameter Ratio ◽  
Linear Perturbation ◽  
Variable Properties ◽  
Linear Perturbation Theory

By means of a linear perturbation theory, the influences of density, viscosity, thermal conductivity, and specific heat capacity, all varying with temperature, are taken into account. The wall heat flux is assumed to be constant at the inner and outer wall, with an arbitrary ratio between these two. Even for variable properties the problem can be reduced to solving a set of ordinary differential equations with three parameters: heat flux ratio, diameter ratio, and Prandtl number. Skin friction and heat transfer results are given for specific numbers of the parameters, including the limiting cases of pipe and channel flows.

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