Experimental and Numerical Study of Heat Transfer and Turbulent Flow Characteristics in Three-Short-Pass Serpentine Cooling Channels With Miniature W-Ribs

2020 ◽  
Vol 142 (12) ◽  
Author(s):  
Yu Rao ◽  
Zhongqiu Guo ◽  
Deqiang Wang
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Numerical Simulations ◽  
Heat Transfer Enhancement ◽  
Pressure Loss ◽  
Numerical Study ◽  
Total Heat ◽  
Transfer Enhancement ◽  
Total Heat Transfer ◽  
Serpentine Channel

Abstract Detailed experimental and numerical studies have been conducted on the heat transfer, pressure loss, and turbulent flow structure of a three-short-pass serpentine cooling channel with miniature W-shaped ribs on the wall under the Reynolds numbers from 8500 to 60,000. Steady-state heat transfer experiments were done to obtain the globally averaged and total heat transfer performance of each ribbed pass of the serpentine channel, and the streamwise pressure loss characteristics of the serpentine-channel flow were also obtained by multipoint pressure measurements. Additionally, the transient liquid crystal thermography technique was also used to obtain the local heat transfer distributions on the miniature W-ribbed surface of each pass. Furthermore, numerical simulations were done by using the AKN k–ε turbulence model to reveal the detailed turbulent flow and heat transfer characteristics in the serpentine channel. The experiments indicate that the miniature W-ribbed short pass has significantly enhanced total heat transfer by a factor of up to 4.0. The total heat transfer enhancement shows appreciably different values in different passes of the serpentine channel, and the second pass shows about 15% higher heat transfer enhancement than the first pass, and the third pass shows the highest heat transfer enhancement, which is about 15% higher than the second pass. The pressure loss measurements indicate that the two flow turnings contribute more than 90% of the total pressure loss in the serpentine channel with one ribbed pass with the miniature W ribs. The numerical simulations indicate that the flow turnings significantly increase the turbulent mixing in the flow of the downstream pass, and the miniature W-ribs on the wall appreciably improve the near-wall vortex mixing, which contributes the heat transfer enhancement.

Numerical Prediction of Turbulent Flow and Heat Transfer Enhancement in a Square Passage With Various Truncated Ribs on One Wall

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Gongnan Xie ◽  
Jian Liu ◽  
Weihong Zhang ◽  
Giulio Lorenzini ◽  
Cesare Biserni
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulent Flow ◽  
Heat Transfer Enhancement ◽  
Pressure Loss ◽  
Numerical Study ◽  
Skew Angle ◽  
Transfer Enhancement ◽  
Reduced Pressure ◽  
Flow And Heat Transfer

Repeated ribs are often employed in the midsection of internal cooling passages of turbine blades to augment the heat transfer by air flowing through the internal ribbed passages. Though the research of flow structure and augmented heat transfer inside various ribbed passages has been well conducted, previous works mostly paid much attention to the influence of rib topology (height-to-pitch, blockage ratio, skew angle, rib shape). The possible problem involved in the usage of ribs (especially with larger blockage ratios) is pressure loss penalty. Thus, in this case, the design of truncated ribs whose length is less than the passage width might fit the specific cooling requirements when pressure loss is critically considered. A numerical study of truncated ribs on turbulent flow and heat transfer inside a passage of a gas turbine blade is performed when the inlet Reynolds number ranges from 8000 to 24,000. Different truncation ratio (truncated-length to passage-width) rib geometries are designed and then the effect of truncation ratio on the pressure drop and heat transfer enhancement is observed under the condition of constant total length. The overall performance characteristics of various truncated rib passages are also compared. It is found that the heated face with a rib that is truncated 12% in length in the center (case A) has the highest heat transfer coefficient, while the heated face with a rib that is truncated 4% at three locations over its length, in the center and two sides (case D), has a reduced pressure loss compared with passages of other designs and provides the lowest friction factors. Although case A shows larger heat transfer augmentation, case D can be promisingly used to augment side-wall heat transfer when the pressure loss is considered and the Reynolds number is relatively large.

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.

A Numerical Study of Heat Transfer and Flow Structure in Channels With Miniature V Rib-Dimple Hybrid Structure on One Wall

2018 ◽  
Author(s):  
Peng Zhang ◽  
Yu Rao ◽  
Yanlin Li
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Numerical Simulations ◽  
Numerical Study ◽  
Reynolds Numbers ◽  
Hybrid Structure ◽  
Transfer Enhancement ◽  
Nusselt Numbers ◽  
Flow And Heat Transfer ◽  
Flow Mixing

This paper presents a numerical study on turbulent flow and heat transfer in the channels with a novel hybrid cooling structure with miniature V-shaped ribs and dimples on one wall. The heat transfer characteristics, pressure loss and turbulent flow structures in the channels with the rib-dimples with three different rib heights of 0.6 mm, 1.0 mm and 1.5 mm are obtained for the Reynolds numbers ranging from 18,700 to 60,000 by numerical simulations, which are also compared with counterpart of a pure dimpled and pure V ribbed channel. The results show that the overall Nusselt numbers of the V rib-dimple channel with the rib height of 1.5 mm is up to 70% higher than that of the channels with pure dimples. The numerical simulations show that the arrangement of the miniature V rib upstream each dimple induces complex secondary flow near the wall and generates downwashing vortices, which intensifies the flow mixing and turbulent kinetic energy in the dimple, resulting in significant improvement in heat transfer enhancement and uniformness.

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 ENHANCEMENT IN A RECTANGULAR COOLING CHANNEL WITH AIRFOIL SHAPED FINS

2020 ◽  
pp. 1-29
Author(s):  
Lesley Wright ◽  
Andrew F. Chen ◽  
Hao-Wei Wu ◽  
Je-Chin Han ◽  
Ching-pang Lee ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Surface Area ◽  
Total Heat ◽  
Cooling Channel ◽  
Heat Transfer Area ◽  
Transfer Enhancement ◽  
Total Heat Transfer ◽  
Cooling Passage

Abstract This paper experimentally investigates heat transfer in a cooling passage with airfoil shaped fins for channel Reynolds numbers 10,000 to 40,000. This study uses airfoil shaped fins, instead of circular or oblong-shaped pins, for heat transfer augmentation. The airfoil shaped fins have more surface area than traditional pins. Assuming they both provide similar internal surface heat transfer coefficients, airfoil shaped fins will perform better than circular or oblong fins due to increased surface area. There is a need to obtain the heat transfer enhancement and pressure drop penalty in this cooling passage with airfoil shaped fins. Results are compared to the same rectangular cooling channel with smooth surfaces. The heat transfer can be enhanced 6 to 8 times while pressure drop is increased 70 to 90 times, as compared with the same channel with a smooth surface. With the fins significantly increasing the heat transfer area, three different methods are proposed for analyzing the heat transfer enhancement: (a) using the smooth channel area with the endwall temperature, (b) combining the total heat transfer area with the endwall temperature, and (c) coupling the total heat transfer area with the area weighted, average temperature including both the endwall and fin temperatures. Finally, compared directly to round pins, the airfoil shaped fins incur similar pressure penalties while providing slightly less heat transfer. The airfoil shaped fins benefit from a significant increase in the heat transfer area, a characteristic similar to more narrow strip fins.

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.

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.

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