scholarly journals Rib Spacing effect on Heat Transfer and pressure loss in a Rectangular channel with semicircular ribs

2021 ◽  
Author(s):  
Mr. Prakash S. Patil ◽  
◽  
Dr. K. K. Dhande ◽  
Keyword(s):  
Heat Transfer ◽  
Rectangular Channel ◽  
Spacing Effect ◽  
Reynolds Numbers ◽  
Flow Conditions ◽  
Transfer Enhancement ◽  
Geometrical Features ◽  
Spacing Ratio ◽  
Result Show ◽  
Better Than

Ribs of various shapes are used for heat transfer enhancement but its performance is significantly depends on geometrical features and flow conditions. This study experimentally find out the influence of rib spacing, semicircular shape ribs with three rib spacing ratio (P/e) = 8, 10 and 12 are studied and located on lower wall of the rectangular channel. Reynolds numbers varied from 10000 to 29,000 and the blockage ratio of the channel (e/Dh) was 0.151.Result show that semicircular rib performed better than plain plate but found more friction. semicircular rib with rib spacing of 50 mm (P/e =10) shows highest thermal performance, enhanced avg. 39 % heat transfer than rib spacing of 40 and 60 mm (P/e=8 & 12). Friction losses observed highest in rib spacing ratio of 8,found average 10 % more friction compared to rib spacing ratio of 10 & 12. Semicircular rib with spacing ratio 8 shows least thermal performances compared to other configurations.

An Experimental and Numerical Study of Heat Transfer and Pressure Loss in a Rectangular Channel With V-Shaped Ribs

2006 ◽  
Author(s):  
Michael Maurer ◽  
Jens von Wolfersdorf ◽  
Michael Gritsch
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Pressure Loss ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Reynolds Numbers ◽  
Transfer Enhancement ◽  
High Reynolds Numbers ◽  
High Reynolds

An experimental and numerical study was conducted to determine the thermal performance of V-shaped ribs in a rectangular channel with an aspect ratio of 2:1. Local heat transfer coefficients were measured using the steady state thermochromic liquid crystal technique. Periodic pressure losses were obtained with pressure taps along the smooth channel sidewall. Reynolds numbers from 95,000 to 500,000 were investigated with V-shaped ribs located on one side or on both sides of the test channel. The rib height-to-hydraulic diameter ratios (e/Dh) were 0.0625 and 0.02, and the rib pitch-to-height ratio (P/e) was 10. In addition, all test cases were investigated numerically. The commercial software FLUENT™ was used with a two-layer k-ε turbulence model. Numerically and experimentally obtained data were compared. It was determined that the heat transfer enhancement based on the heat transfer of a smooth wall levels off for Reynolds numbers over 200,000. The introduction of a second ribbed sidewall slightly increased the heat transfer enhancement whereas the pressure penalty was approximately doubled. Diminishing the rib height at high Reynolds numbers had the disadvantage of a slightly decreased heat transfer enhancement, but benefits in a significantly reduced pressure loss. At high Reynolds numbers small-scale ribs in a one-sided ribbed channel were shown to have the best thermal performance.

Heat Transfer Between Blockages With Holes in a Rectangular Channel

2003 ◽  
Vol 125 (4) ◽  
pp. 587-594 ◽  
Author(s):  
S. W. Moon ◽  
S. C. Lau
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Rectangular Channel ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Hole Array ◽  
Transfer Enhancement ◽  
Large Pressure

Experiments have been conducted to study steady heat transfer between two blockages with holes and pressure drop across the blockages, for turbulent flow in a rectangular channel. Average heat transfer coefficient and local heat transfer distribution on one of the channel walls between two blockages, and overall pressure drop across the blockages were obtained, for nine different staggered arrays of holes in the blockages and Reynolds numbers of 10,000 and 30,000. For the hole configurations studied, the blockages enhanced heat transfer by 4.6 to 8.1 times, but significantly increased the pressure drop. Smaller holes in the blockages caused higher heat transfer enhancement, but larger increase of the pressure drop than larger holes. The heat transfer enhancement was lower in the higher Reynolds number cases. Because of the large pressure drop, the heat transfer per unit pumping power was lower with the blockages than without the blockages. The local heat transfer was lower nearer the upstream blockage, the highest near the downstream blockage, and also relatively high in regions of reattachment of the jets leaving the upstream holes. The local heat transfer distribution was strongly dependent on the configuration of the hole array in the blockages. A third upstream blockage lowered both the heat transfer and the pressure drop, and significantly changed the local heat transfer distribution.

Rib Spacing Effect on Heat Transfer and Pressure Loss in a Rotating Two-Pass Rectangular Channel (AR=1:2) With 45-Degree Angled Ribs

2006 ◽  
Author(s):  
Yao-Hsien Liu ◽  
Lesley M. Wright ◽  
Wen-Lung Fu ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Rectangular Channel ◽  
Spacing Effect ◽  
Turbine Blades ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Cooling Channels ◽  
Smooth Channel

Rib turbulators are commonly used to enhance the heat transfer within internal cooling passages of advanced gas turbine blades. Many factors affect the thermal performance of a cooling channel with ribs. This study experimentally investigates the effect of rib spacing on the heat transfer enhancement, pressure penalty, and thus the overall thermal performance in both rotating and non-rotating rectangular, cooling channels. In the 1:2 rectangular channels, 45° angled ribs are placed on the leading and trailing surfaces. The pitch of the ribs varies, so rib pitch-to-height (P/e) ratios of 10, 7.5, 5, and 3 are considered. Square ribs with a 1.59 mm × 1.59 mm cross-section are used for all spacings, so the height-to-hydraulic diameter (e/Dh) ratio remains constant at 0.094. With a constant rotational speed of 550 rpm and the Reynolds number ranging from 5000 to 40000, the rotation number in turn varies from 0.2 to 0.02. Because the skewed turbulators induce secondary flow along the length of the rib, the very close rib spacing of P/e = 3, has the best thermal performance in both rotating and non-rotating channels. This close spacing yields the greatest heat transfer enhancement, while the P/e = 5 spacing has the greatest pressure penalty. In addition, the effect of rotation is more pronounced in the channel with the rib spacing of 3. As more ribs are added, the channel is approaching a smooth channel, and the strength of the rotation induced vortices increases.

Effect of Rib Spacing on Heat Transfer in a Two Pass Rectangular Channel (AR = 2:1) at High Rotation Numbers

2012 ◽  
Vol 134 (9) ◽  
Author(s):  
Jiang Lei ◽  
Je-Chin Han ◽  
Michael Huh
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Heat Transfer Enhancement ◽  
Rectangular Channel ◽  
Orientation Angle ◽  
Reynolds Numbers ◽  
Transfer Enhancement ◽  
Flow Angle ◽  
Rotation Numbers ◽  
Channel Aspect Ratio

In this paper, the effect of rib spacing on heat transfer in a rotating two-passage channel (aspect ratio, AR = 2:1) at orientation angle of 135 deg was studied. Parallel ribs were applied’ on leading and trailing walls of the rotating channel at the flow angle of 45 deg. The rib-height-to-hydraulic diameter ratio (e/Dh) was 0.098. The rib-pitch-to-rib-height (P/e) ratios studied were 5, 7.5, and 10. For each rib spacing, tests were taken at five Reynolds numbers from 10,000 to 40,000, and for each Reynolds number, experiments were conducted at four rotational speeds up to 400 rpm. Results show that the heat transfer enhancement increases with decreasing P/e from 10 to 5 under nonrotation conditions. However, the effect of rotation on the heat transfer enhancement remains about the same for varying P/e from 10 to 5. Correlations of Nusselt number ratio (Nu/Nus) to rotation number (Ro) or local buoyancy parameter (Box) are existent on all surfaces (leading, trailing, inner and outer walls, and tip cap region) in the two-passage 2:1 aspect ratio channel.

Heat Transfer and Pressure Loss Measurements in a Turbulated High Aspect Ratio Channel With Large Reynolds Number Flows

2014 ◽  
Vol 6 (4) ◽  
Author(s):  
Shantanu Mhetras ◽  
Je-Chin Han ◽  
Michael Huth
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Steady State ◽  
Aspect Ratio ◽  
Compressible Flow ◽  
Reynolds Numbers ◽  
Flow Conditions ◽  
Transfer Enhancement ◽  
High Reynolds ◽  
Wide Wall

Experiments to investigate heat transfer and pressure loss are performed in a rectangular channel with an aspect ratio of 6 at very high Reynolds numbers under compressible flow conditions. Reynolds numbers up to 1.3 × 106 are tested. The presence of a turbulated wall and the resultant heat transfer enhancement against a smooth surface is investigated. Three dimpled configurations including spherical and cylindrical dimples are studied on one wide wall of the channel. The presence of discrete ribs on the same wide wall is also investigated. A steady state heat transfer measurement method is used to obtain the heat transfer coefficients while pressure taps located at several streamwise locations in the channel walls are used to record the static pressures on the surface. Experiments are performed for a wide range of Reynolds numbers from the incompressible (Re = 100,000–500,000; Mach = 0.04–0.19) to compressible flow regimes (Re = 900,000–1,300,000, Mach = 0.35–0.5). Results for low Reynolds numbers are compared to existing heat transfer data available in open literature for similar configurations. Heat transfer enhancement is found to decrease at high Re with the discrete rib configurations providing the best enhancement but highest pressure losses. However, the small spherical dimples show the best thermal performance. Results can be used for the combustor liner back side cooling at high Reynolds number flow conditions. Local measurements using the steady state, hue-detection based liquid crystal technique are also performed in the fully developed region for case 1 with large spherical dimples. Good comparison is obtained between averaged local heat transfer coefficient measurements and from thermocouple measurements.

Thermal Performance of Double-Sided, Partial Height Strip Fin Arrays in a High Aspect Ratio, Rectangular Channel

2021 ◽  
Author(s):  
Nathaniel J. Tracy ◽  
Lesley M. Wright ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Rectangular Channel ◽  
Reynolds Numbers ◽  
Channel Height ◽  
Gap Size ◽  
Transfer Enhancement ◽  
Fin Thickness ◽  
Full Height

Abstract Friction loss and heat transfer enhancement measurements were obtained for double-sided, partial height, strip fin arrays within a high aspect ratio (AR = 8), rectangular channel. Fins were arranged in a staggered array configuration with channel height to fin thickness ratio H/W = 9.6, spanwise spacing distance to fin thickness ratio S/W = 8.0, and streamwise spacing distance to fin length ratio X/L = 1.0. Shortened strip fins of equal length are positioned directly opposite of each other on the upper and lower channel surfaces with three gap size to channel height ratios considered G/H = 0.2, 0.3, and 0.4. The thermal performance of each fin configuration is determined from the measured pressure drop across the array and regionally averaged heat transfer coefficients at flow Reynolds numbers ranging from Re = 20,000–80,000. The partial height strip fin results are compared to baseline cases of strip fins spanning the full height of the channel and the smooth channel without roughness elements. Linear correlations of friction loss and power correlations of the heat transfer enhancement and thermal performance are provided as functions of flow Reynolds numbers for all cases. Strip fins spanning the full height of the channel provide the greatest heat transfer enhancement of all cases but introducing a gap size can significantly reduce friction losses. Full height strip fins provide the greatest thermal performance for Reynolds numbers ranging from Re = 20,000–30,000, and partial height strip fins with the gap size of G/H = 0.3 provide the greatest thermal performance for flow Reynolds numbers ranging from Re = 40,000–80,000.

Thermal Analysis of Air-Cooled Electronic Equipment

1992 ◽  
Author(s):  
Y. I. Sharaf-Eldeen ◽  
Kannan Rengarajan
Keyword(s):  
Heat Transfer ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Rectangular Channel ◽  
Radiant Heat ◽  
Reynolds Numbers ◽  
Bottom Plate ◽  
Block Type ◽  
Electronic Packages ◽  
Spacing Ratio

Abstract Owing to the increasing miniaturization and number of high-power-dissipating components in electronic packages, proper thermal management has become of vital importance. Numerical simulations were carried for three block-type elements representing electronic components located on the bottom plate of a rectangular channel. The top plate of the channel was parametrically examined in order to assess the radiative heat-transfer component. The effects of the air flow rate in the channel and the spacing, geometry, and emissivity of the blocks were investigated. Two types of heat sources were considered: A uniform heat-generation rate in each block and a point heat-source at the center of each block. Reynolds numbers varying from 10 to 1000 and block length-to-spacing ratio varying from 1 to 3.7 were considered in this work. The results clearly indicate that, when the radiative heat-transfer component is neglected, 33% of the heat generated is conducted through the bottom substrate while the remaining 67% is convected to the cooling medium. However, when the radiative heat transfer is considered in the analysis, the radiant heat loss is estimated to range from 4 to 8%, at a Reynolds number of 500.

An Experimental and Numerical Study of Heat Transfer and Pressure Loss in a Rectangular Channel With V-Shaped Ribs

2006 ◽  
Vol 129 (4) ◽  
pp. 800-808 ◽  
Author(s):  
Michael Maurer ◽  
Jens von Wolfersdorf ◽  
Michael Gritsch
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Pressure Loss ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Reynolds Numbers ◽  
Transfer Enhancement ◽  
High Reynolds Numbers ◽  
High Reynolds

An experimental and numerical study was conducted to determine the thermal performance of V-shaped ribs in a rectangular channel with an aspect ratio of 2:1. Local heat transfer coefficients were measured using the steady state thermochromic liquid crystal technique. Periodic pressure losses were obtained with pressure taps along the smooth channel sidewall. Reynolds numbers from 95,000 to 500,000 were investigated with V-shaped ribs located on one side or on both sides of the test channel. The rib height-to-hydraulic diameter ratios (e∕Dh) were 0.0625 and 0.02, and the rib pitch-to-height ratio (P∕e) was 10. In addition, all test cases were investigated numerically. The commercial software FLUENT™ was used with a two-layer k-ε turbulence model. Numerically and experimentally obtained data were compared. It was determined that the heat transfer enhancement based on the heat transfer of a smooth wall levels off for Reynolds numbers over 200,000. The introduction of a second ribbed sidewall slightly increased the heat transfer enhancement whereas the pressure penalty was approximately doubled. Diminishing the rib height at high Reynolds numbers had the disadvantage of a slightly decreased heat transfer enhancement, but benefits in a significantly reduced pressure loss. At high Reynolds numbers small-scale ribs in a one-sided ribbed channel were shown to have the best thermal performance.

Numerical Prediction of Heat Transfer Enhancement in a Semiconductor Device With a Swiveled Module Board

2008 ◽  
Author(s):  
S. G. Bhatta ◽  
T. R. Seetharam
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Semiconductor Device ◽  
Rectangular Channel ◽  
Vertical Plane ◽  
Reynolds Numbers ◽  
Circuit Board ◽  
Bottom Plate ◽  
Transfer Enhancement

A three dimensional study of heat transfer from an array of heated blocks is presented. Heated blocks represent electronic modules mounted on horizontal circuit board in a rectangular channel. Numerically obtained average heat transfer coefficients for the top surface of the heated blocks are compared with experimentally obtained values, and it is found that there is a good agreement between the two at lower Reynolds numbers, 7600 to 22000. Further, the horizontal module board affixed with heated modules is swiveled upwards longitudinally in the vertical plane about the front end of the plate for the same Reynolds numbers. The influence of angle of orientation of the heated bottom plate on the heat transfer enhancement from the heated modules is studied, and it is observed that there is a remarkable improvement in heat transfer even for low angle of swivel. It is observed that heat transfer enhancement is accompanied with a penalty in terms of increase in pressure drop; and for low angle of swivel, the pressure drop increase is noted to be moderate.

Effect of Rib Spacing on Heat Transfer in a Two Pass Rectangular Channel (AR=2:1) at High Rotation Numbers

2011 ◽  
Author(s):  
Jiang Lei ◽  
Je-Chin Han ◽  
Michael Huh
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Rectangular Channel ◽  
Orientation Angle ◽  
Reynolds Numbers ◽  
Diameter Ratio ◽  
Transfer Enhancement ◽  
Flow Angle ◽  
Rotation Numbers ◽  
Rotating Channel

In this paper the effect of rib spacing on heat transfer in a rotating two-passage channel (AR=2:1) at orientation angle of 135° was studied. Parallel ribs were applied on leading and trailing walls of the rotating channel at the flow angle of 45°. The rib-height-to-hydraulic diameter ratio (e/Dh) was 0.098. The rib-pitch-to-rib-height (P/e) ratios studied were 5, 7.5, and 10. For each rib-spacing, tests were taken at five Reynolds numbers from 10,000 to 40,000 and for each Reynolds number, experiments were conducted at four rotational speeds up to 400 rpm. Results show that the heat transfer enhancement increases with decreasing P/e from 10 to 5 under non-rotation condition. However, the effect of rotation on the heat transfer enhancement remains about the same for varying P/e from 10 to 5. Heat transfer enhancement due to rotation can be correlated on all surfaces (leading, trailing, inner and outer walls and tip cap region) in the two-passage 2:1 aspect ratio channel.

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