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.

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.

An Experimental and Numerical Study of Heat Transfer and Pressure Losses of V- and W-Shaped Ribs at High Reynolds Numbers

2007 ◽  
Author(s):  
Michael Maurer ◽  
Jens von Wolfersdorf ◽  
Michael Gritsch
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Pressure Loss ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Transfer Enhancement ◽  
Height Ratio ◽  
Reduced Pressure ◽  
Pressure Losses

An experimental and numerical investigation was conducted to assess the thermal performance of V- and W-shaped ribs in a rectangular channel. The ribs were located on one channel sidewall in order to simulate a typical combustor liner cooling. The cross section of the channel had an aspect ratio of 2:1. Local heat transfer coefficients were measured using the transient thermochromic liquid crystal technique. Pressure taps along the channel sidewall were used to obtain the periodic pressure losses. The rib height-to-hydraulic diameter ratio (e/Dh) was set to 0.02, and the rib pitch-to-height ratios (P/e) were 5 and 10. The Reynolds numbers investigated varied from 80,000 to 500,000. All rib configurations were additionally investigated numerically and the obtained computational results were compared with experimental data. For all computations the commercial software FLUENT™ was used with a two-layer k-ε turbulence model. It could be demonstrated that applying W-shaped ribs instead of V-shaped ribs has the advantage of an increased heat transfer enhancement, but is accompanied by a rise in pressure loss. Reducing the rib pitch-to-height ratio from 10 to 5 decreases the heat transfer enhancement, but results in a significantly reduced pressure loss. Finally, the best thermal performance was found for W-shaped ribs with a pitch-to-height ratio of 10, having a slightly increased pressure loss but with considerable rise in heat transfer enhancement compared to V-shaped ribs.

Numerical Study on the Flow and Heat Transfer Characteristics in Rectangular Channels With Grooves and Different Protrusions

2017 ◽  
Author(s):  
Feng Zhang ◽  
Xinjun Wang ◽  
Jun Li ◽  
Daren Zheng ◽  
Junfei Zhou
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Pressure Loss ◽  
Numerical Study ◽  
Transfer Enhancement ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Rectangular Channels

The present work represents a numerical study on the flow and heat transfer characteristics in rectangular channels with protrusion-grooved turbulators. The Reynolds averaged Navier-Stokes equations, coupled with SST turbulence model, are adopted and solved. In this paper, six geometric protrusion shapes (circular, rectangular, triangular, trapezoidal, circular with leading round concave and circular with trailing round concave) are selected to perform the study. The flow structure, heat transfer enhancement, friction factor as well as thermal performance factor of the rectangular channel fitted with combined groove and different protrusions have been obtained at the Reynolds number ranging from 5000 to 20000. The results indicate that the protrusion shapes affect the velocity distribution near the groove surface. The case of circular protrusion with leading round concave provides the highest overall heat transfer enhancement, while it also causes the highest pressure loss penalty. The case of rectangular protrusion has the lowest overall heat transfer enhancement with high pressure loss penalty. The case of circular protrusion has similar overall heat transfer enhancement with cases of trapezoidal protrusion as well as circular protrusion with trailing round concave, but the pressure loss penalty of the case of circular protrusion is the lowest. In addition, the best overall thermal performance can be observed for circular protrusion-grooved channel.

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.

Heat Transfer and Pressure Loss in Rectangular One-Side-Ribbed Channels With Different Aspect Ratios

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Sébastien Kunstmann ◽  
Jens von Wolfersdorf ◽  
Uwe Ruedel
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Heat Transfer Enhancement ◽  
Gas Turbines ◽  
Pressure Loss ◽  
Rectangular Channel ◽  
Channel Height ◽  
Transfer Enhancement ◽  
Height Ratio ◽  
Aspect Ratios

An investigation was conducted to assess the thermal performance of W-shaped, 2W-shaped and 4W-shaped ribs in a rectangular channel. The aspect ratios (W/H) were 2:1, 4:1, and 8:1. The ribs were located on one channel wall. The rib height (e) was kept constant with a rib height-to-hydraulic diameter ratio (e/Dh) of 0.02, 0.03, and 0.06. The rib pitch-to-height ratio (P/e) was 10. The Reynolds numbers investigated (Re > 90 000) are typical for combustor liner cooling configurations of gas turbines. Local heat transfer coefficients using the transient thermochromic liquid crystal technique and overall pressure losses were measured. The rib configurations were investigated numerically to visualize the flow pattern in the channel and to support the understanding of the experimental data. The results show that the highest heat transfer enhancement is obtained by rib configurations with a rib section-to-channel height ratio (Wr/H) of 1:1. W-shaped ribs achieve the highest heat transfer enhancement levels in channels with an aspect ratio of 2:1, 2W-shaped ribs in channels with an aspect ratio of 4:1 and 4W-shaped ribs in channels with an aspect ratio of 8:1. Furthermore, the pressure loss increases with increasing complexity of the rib geometry and blockage ratio.

Optimization and Development for Fin-and-Tube Heat Exchangers With Vortex Generators

2010 ◽  
Author(s):  
Ya-Ling He ◽  
Pan Chu ◽  
Wen-Quan Tao
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Flow Structure ◽  
Heat Exchangers ◽  
Pressure Loss ◽  
Numerical Study ◽  
Moderate Pressure ◽  
Computational Domain ◽  
Transfer Enhancement ◽  
Local Flow

In this paper, heat transfer enhancement and pressure loss penalty for fin-and-tube heat exchangers with rectangular winglet pairs (RWPs) were numerically investigated in a relatively low Reynolds number flow. The purpose of this study was to explore the fundamental mechanism between the local flow structure and the heat transfer augmentation. The RWPs were placed with a special orientation for the purpose of enhancement of heat transfer. The numerical study involved three-dimensional flow and conjugate heat transfer in the computational domain, which was set up to model the entire flow channel in the air flow direction. The effects of attack-angle of RWPs, row-number of RWPs and placement of RWPs on the heat transfer characteristics and flow structure were examined in detail. It was observed that the longitudinal vortices caused by RWPs and the impingement of RWPs-directed flow on the downstream tube were important reasons of heat transfer enhancement for fin-and-tube heat exchangers with RWPs. It was interesting to find that the pressure loss penalty of the fin-and-tube heat exchangers with RWPs could be reduced by altering the placement of the same number of RWPs from inline array to staggered array and simultaneously maintain the heat transfer enhancement level. The results showed that the rectangular winglet pairs (RWPs) can significantly improve the heat transfer performance of the fin-and-tube heat exchangers with a moderate pressure loss penalty.

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.

Heat Transfer Enhancement in a Rectangular Channel With the Combination of Ribs, Dimples and Protrusions

2011 ◽  
Author(s):  
Jibing Lan ◽  
Yonghui Xie ◽  
Di Zhang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Rectangular Channel ◽  
Low Pressure ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Number Range ◽  
Baseline Case ◽  
The One

Rib turbulators can enhance the heat transfer successfully, but in most cases this is associated with large pressure loss penalties. Recently, dimple techniques become an attractive method for gas turbine blade internal cooling because dimples enhance heat transfer with low pressure penalty. In the present paper, a compound heat transfer enhancement technique, heat transfer enhancement in rectangular channel (Aspect ratio = 4) with the combination of ribs, dimples and protrusions, are investigated. The calculations are conducted on five different channel configurations. Case 1 which is the baseline configuration is a rectangular channel with rectangular ribs (e/Dh = 0.078, P/e = 10). In case 2, one row of dimples are placed between two ribs. In case 3, instead of dimples, one row of protrusions are placed between two ribs. In case 4, three rows of dimples are place between two ribs. Case 5 places three rows of protrusions between two ribs instead of dimples. The present paper focuses on Reynolds numbers (based on the channel hydraulic diameter) ranging from 10000 to 60000. In all configurations, the non-dimensional dimple/protrusion depths are 0.2. The results show that the rib+dimple cases provide minor increase in Nu/Nu0, f/f0 and thermal performance. Within the Reynolds number range studied, the Nu/Nu0 values of the three row rib+protrusion case is 17% ∼ 7% higher than that of the baseline case, and the decrease in f/f0 is about 10%. The thermal performance of the three row rib+protrusion case is about 16% higher than that of the baseline case. The Nu/Nu0 values of the one row rib+protrusion case is about 9% higher than that of the baseline case, and the decrease in f/f0 is about 12%. The thermal performance of the one row rib+protrusion case is about 14% higher than that of the baseline case. It can be concluded that rib+protrusion technique in rectangular channel has the potential to provide heat transfer enhancement with low pressure penalty.

Heat Transfer and Pressure Loss in Rectangular One-Side-Ribbed Channels With Different Aspect Ratios

2009 ◽  
Author(s):  
Se´bastien Kunstmann ◽  
Jens von Wolfersdorf ◽  
Uwe Ruedel
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Heat Transfer Enhancement ◽  
Gas Turbines ◽  
Pressure Loss ◽  
Rectangular Channel ◽  
Channel Height ◽  
Transfer Enhancement ◽  
Height Ratio ◽  
Aspect Ratios

An investigation was conducted to assess the thermal performance of W-shaped, 2W-shaped and 4W-shaped ribs in a rectangular channel. The aspect ratios (W/H) were 2:1, 4:1 and 8:1. The ribs were located on one channel wall. The rib height (e) was kept constant with a rib height-to-hydraulic diameter ratio (e/Dh) of 0.02, 0.03 and 0.06. The rib pitch-to-height ratio (P/e) was 10. The Reynolds numbers investigated (Re>90,000) are typical for combustor liner cooling configurations of gas turbines. Local heat transfer coefficients using the transient thermochromic liquid crystal technique and overall pressure losses were measured. The rib configurations were investigated numerically to visualize the flow pattern in the channel and to support the understanding of the experimental data. The results show that the highest heat transfer enhancement is obtained by rib configurations with a rib section-to-channel height ratio (Wr/H) of 1:1. W-shaped ribs achieve the highest heat transfer enhancement levels in channels with an aspect ratio of 2:1, 2W-shaped ribs in channels with an aspect ratio of 4:1 and 4W-shaped ribs in channels with an aspect ratio of 8:1. Furthermore, the pressure loss increases with increasing complexity of the rib geometry and blockage ratio.

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