Effects of Vortex Generators on the Impingement Jet Arrays Heat Transfer

2021 ◽  
Author(s):  
Yue Yang ◽  
Junkui Mao ◽  
Feilong Wang
Keyword(s):  
Heat Transfer ◽  
Thermal Efficiency ◽  
Pressure Loss ◽  
Cooling System ◽  
Jet Impingement ◽  
Vortex Generators ◽  
Maximum Enhancement ◽  
Impingement Jet ◽  
Nusselt Numbers ◽  
Impingement Heat Transfer

Abstract In the jets array cooling system of the gas turbine, the downstream jets will be deflected by the crossflow and the heat transfer in the downstream will be suppressed. In this paper, the rectangular vortex generators are arranged in the jet arrays to enhance the jet impingement heat transfer. Through the numerical simulations, the configuration of rectangular vortex generators (Common-flow-down CFD and Common-flow-up CFU) and the relative position (l2) between the impingements and the rectangular vortex generators are studied. The results show that both of configurations are beneficial to the suppression of the crossflow and enhance the heat transfer in the downstream. The maximum enhancement of the whole regional average Nusselt numbers in CFD-VGs configuration can reach up to 9.09% with lower than 5% increase of the pressure loss and that in CFU-VGs configuration can reach up to 10.8% with lower than 4.8% increase of the pressure loss. From the perspective of the whole regional average Nusselt numbers and the overall thermal efficiency, the CFD-VGs with l2 = 0 has the best performance. However, from the perspective of the whole regional average Nusselt numbers, the CFU-VGs with l2 = 0 has the best performance, while from the perspective of the overall thermal efficiency, the CFU-VGs with l2 = 3 has the best performance.

An Experimental Study of Impingement Heat Transfer on the Surfaces With Micro W-Shaped Ribs

2015 ◽  
Author(s):  
Yu Rao ◽  
Peng Chen ◽  
Jiaqi Zhu
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Flat Plate ◽  
Pressure Loss ◽  
Cooling System ◽  
Cross Flow ◽  
Jet Impingement ◽  
Test Plate ◽  
Plate Spacing ◽  
Impingement Heat Transfer

The paper proposed an idea of using micro-W-shaped ribs on a test plate to improve the impingement heat transfer performance in a multiple-jet impingement cooling system. An experimental study has been conducted on the heat transfer characteristics of multiple-jet impingement onto a flat plate and a roughened plate with micro W-shaped ribs under maximum cross flow scheme. Transient liquid crystal thermography method has been used to obtain the detailed impingement heat transfer distribution for the Reynolds numbers from 15,000 to 30,000.The effects of micro W ribs on the local Nusselt number and the related pressure loss were investigated experimentally. The jet-to-plate spacing H/d=1.5 was used in the experiments for both the flat and the micro-W-rib roughened plate. The experiments showed that the micro W ribs on the plate can enhance the impingement heat transfer globally and locally, and increase the heat transfer uniformity, which are due to the facts that the micro W ribs on the test plate increase the near-wall turbulent mixing by interacting with the wall jets and cross flow. The pressure loss is negligibly increased compared to the impingement onto the flat plate.

scholarly journals Heat Transfer Enhancement of Impingement Cooling by Adopting Circular-Ribs or Vortex Generators in the Wall Jet Region of A Round Impingement Jet

2020 ◽  
Vol 5 (3) ◽  
pp. 17 ◽  
Author(s):  
Ken-Ichiro Takeishi ◽  
Robert Krewinkel ◽  
Yutaka Oda ◽  
Yuichi Ichikawa
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Cooling System ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Vortex Generators ◽  
Wall Jet ◽  
Transfer Enhancement ◽  
Impingement Cooling ◽  
Impingement Jet

In the near future, when designing and using Double Wall Airfoils, which will be manufactured by 3D printers, the positional relationship between the impingement cooling nozzle and the heat transfer enhancement ribs on the target plate naturally becomes more accurate. Taking these circumstances into account, an experimental study was conducted to enhance the heat transfer of the wall jet region of a round impingement jet cooling system. This was done by installing circular ribs or vortex generators (VGs) in the impingement cooling wall jet region. The local heat transfer coefficient was measured using the naphthalene sublimation method, which utilizes the analogy between heat and mass transfer. As a result, it was clarified that, within the ranges of geometries and Reynolds numbers at which the experiments were conducted, it is possible to improve the averaged Nusselt number Nu up to 21% for circular ribs and up to 51% for VGs.

Flow Field and Heat Transfer Characteristics in an Impingement/Effusion Cooling System for Combustor Liner

2005 ◽  
Author(s):  
Quanhong Xu ◽  
Chi Zhang ◽  
Yuzhen Lin ◽  
Gaoen Liu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Flow Field ◽  
Transfer Coefficient ◽  
Cooling System ◽  
Impingement Jet ◽  
Impingement Heat Transfer ◽  
Double Skin ◽  
Combustor Liner ◽  
Effusion Hole

The present study is conducted to investigate the characteristics of the flow field and heat transfer in an impingement/effusion cooling scheme for gas turbine combustor liner. It is designed to provide an insight, through the study of the flow field, into the physical mechanisms responsible for the enhanced impingement heat transfer near the effusion hole entrance. In this impingement/effusion cooling scheme, the angle between the impingement hole and effusion hole and the wall surface are 90 deg and 30 deg respectively. The square arrays of impingement/effusion holes are used with equal numbers of holes offset half a pitch relative to each plate so that an impingement jet is located on the center of each four effusion holes and vice versa. The flow field of the double skin wall space is described by the way of Particle Image Velocimetry (PIV). Two kinds of target plates, with and without effusion holes, are used in the impingement heat transfer study. Through changing the impingement Reynolds and the impingement gap, the change of the impingement heat transfer coefficient on the target plates is investigated. The impingement heat transfer test results show that the impingement heat transfer is enhanced near the entrance of the effusion holes, which could fully explain the feature of the impingement heat transfer coefficient on the target plate.

Heat Transfer Enhancement of Jet Impingement on a Flat Plate Attached by a Porous Medium with a Center Cavity

2010 ◽  
Vol 297-301 ◽  
pp. 427-432 ◽  
Author(s):  
Pey Shey Wu ◽  
Chia Yu Hsieh ◽  
Shen Ta Tsai
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Nusselt Number ◽  
Flat Plate ◽  
Porous Layer ◽  
Jet Impingement ◽  
Stagnation Zone ◽  
Transfer Enhancement ◽  
Maximum Enhancement ◽  
Impingement Heat Transfer

Jet impingement heat transfer on a target plate covered with a thick porous layer with or without a cylindrical center cavity is experimentally investigated using the transient liquid crystal technique. Based on the results of jet impingement on a bare flat plate, heat transfer enhancement due to the attachment of porous medium is assessed. The varying parameters in the experiments include the nozzle-to-plate distance, jet Reynolds number, jet-to-cavity diameter ratio, and the cavity depth. Results of Nusselt number distribution, stagnation-zone Nusselt number, and averaged Nusselt number over a region of 3 times the hole diameter are documented. Experimental results show that the attachment of the porous layer with a center cavity can either hamper, or effectively enhance the jet impingement heat transfer over a flat plate. The maximum enhancement occurs at jet Reynolds number of 12400 when the cavity is a through hole and the cavity has the same diameter as the jet. The stagnation-zone Nusselt number increases 58.3% and the averaged Nusselt number increases 77.5% at the maximum enhancement condition. On the other hand, the addition of the thick porous layer without a center cavity gave rise to severe adverse effect on jet impingement heat transfer.

Combination of Impingement and Trip Strips for Combustor Liner Backside Cooling

Volume 3 ◽  
2004 ◽  
Author(s):  
Ryan Hebert ◽  
Srinath V. Ekkad ◽  
Vivek Khanna
Keyword(s):  
Heat Transfer ◽  
Cross Flow ◽  
Jet Impingement ◽  
Reynolds Numbers ◽  
Combination Technique ◽  
Impingement Jet ◽  
Impingement Heat Transfer ◽  
Flow Effects ◽  
Heat Transfer Degradation ◽  
Cooling Air

Effective cooling of modern low NOx combustor liners is achieved through combinations of impingement and other heat transfer enhancement methods. In the present study, a combination of impingement and trip strips is studied to determine the optimum location of trip strips with respect to impingement jet arrays. Heat transfer with pure impingement has degradation downstream due to increased cross-flow effects. To counter the cross-flow induced heat transfer degradation, a combination technique wherein impingement is combined with ribs placed in between impingement rows or downstream of the impingement array is studied. Three configurations with increased rib placements and reduced impingement holes are studied and compared with pure impingement cases for the same jet Reynolds number. Three jet Reynolds numbers are studied for Rej = 10000, 20000, and 30000. Detailed heat transfer distributions are obtained using the transient liquid crystal technique. Results show that the presence of ribs increases jet impingement heat transfer on the surface with lower mass flows. The effectiveness of the combination ribs and impingement can provide higher heat transfer with reduced cooling air requirements.

Microstructured Surfaces for Single-Phase Jet Impingement Heat Transfer Enhancement

2013 ◽  
Vol 5 (3) ◽  
Author(s):  
Gilberto Moreno ◽  
Sreekant Narumanchi ◽  
Travis Venson ◽  
Kevin Bennion
Keyword(s):  
Heat Transfer ◽  
Single Phase ◽  
Jet Impingement ◽  
Reynolds Numbers ◽  
Surface Roughening ◽  
Submerged Jet ◽  
Nusselt Numbers ◽  
Impingement Heat Transfer ◽  
Microstructured Surfaces ◽  
Microporous Coating

An experimental investigation was conducted to examine the use of microstructured surfaces to enhance jet impingement heat transfer. Three microstructured surfaces were evaluated: a microfinned surface, a microporous coating, and a spray pyrolysis coating. The performance of these surface coatings/structures was compared to the performance of simple surface roughening techniques and millimeter-scale finned surfaces. Experiments were conducted using water in both the free- and submerged-jet configurations at Reynolds numbers ranging from 3300 to 18,700. At higher Reynolds numbers, the microstructured surfaces were found to increase Nusselt numbers by 130% and 100% in the free- and submerged-jet configurations, respectively. Potential enhancement mechanisms due to the microstructured surfaces are discussed for each configuration. Finally, an analysis was conducted to assess the impacts of cooling a power electronic module via a jet impingement scheme utilizing microfinned surfaces.

Experimental Investigation of Impinging Heat Transfer of the Pulsed Chevron Jet on a Semicylindrical Concave Plate

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Yuan-wei Lyu ◽  
Jing-zhou Zhang ◽  
Xi-cheng Liu ◽  
Yong Shan
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Flat Surface ◽  
Jet Impingement ◽  
Concave Surface ◽  
Wall Jet ◽  
Surface Distance ◽  
Maximum Reduction ◽  
Nusselt Numbers ◽  
Impingement Heat Transfer

Impinging heat transferred by a pulsed jet induced by a six-chevron nozzle on a semicylindrical concave surface is investigated by varying jet Reynolds numbers (5000 ≤ Re ≤ 20,000), operational frequencies (0 Hz ≤ f ≤ 25 Hz), and dimensionless nozzle-to-surface distances (1 ≤ H/d ≤ 8) while fixing the duty cycle as DC = 0.5. The semicylindrical concave surface has a cylinder diameter-to-nozzle diameter ratio (D/d) of 10. The results show that the nozzle-to-surface distance has a significant impact on the impingement heat transfer of the pulsed chevron jet. An optimal nozzle-to-surface distance for achieving the maximum stagnation Nusselt number appears at H/d  =  6. In the wall jet zone, the averaged Nusselt number is the largest at H/d = 2 and the smallest at H/d = 8. In comparison with the chevron steady jet impingement, the effect of nozzle-to-surface distance on the convective heat transfer becomes less notable for the pulsed chevron jet impingement. The stagnation Nusselt number under the pulsed chevron jet impingement is mostly less than that under the chevron steady jet impingement. However, at H/d = 8, the pulsed chevron jet is more effective than the steady jet. This study confirmed that the pulsed chevron jet produced higher azimuthally averaged Nusselt numbers than the steady chevron jet in the wall jet flow zone at large nozzle-to-surface distances. The stagnation Nusselt numbers by the pulsed chevron jet impingement have a maximum reduction of 21.0% (f = 20 Hz, H/d = 4, and Re = 2000) compared with that of the steady chevron jet impingement. Also, the pulsed chevron jet impingement heat transfer on a concave surface is less effective compared to a flat surface. The stagnation Nusselt numbers on the semicylindrical concave surface have a maximum reduction of about 37.7% (f = 20 Hz, H/d = 8, and Re = 5000) compared with that on the flat surface.

Effect of Cross-Shaped Circular Jet Array on Impingement Heat Transfer

2012 ◽  
Author(s):  
Yoshisaburo Yamane ◽  
Makoto Yamamoto ◽  
Shinji Honami
Keyword(s):  
Heat Transfer ◽  
Jet Impingement ◽  
Target Surface ◽  
Impinging Jets ◽  
Thermochromic Liquid Crystal ◽  
Nusselt Numbers ◽  
Impingement Heat Transfer ◽  
Oil Flow ◽  
Square Array ◽  
Jet Array

The purpose of this study is to clarify heat transfer characteristics for the high cooling performance with multiple jet impingement. In the present study, the influence of the interaction among adjacent impinging jets on heat transfer of target surface is experimentally investigated. The study is focused on the effect of jet injection shape on the heat transfer. 3×3 square array of cross-shaped circular jet is tested. Injection distances L are 2 and 4 jet hole diameters, and jet-to-jet spacing S are 4, 6 and 8 jet hole diameters. Experiments are conducted for a constant Reynolds number Re = 4,680 based on the jet hole diameter. Steady state thermochromic liquid crystal technique is employed to measure local and area averaged Nusselt numbers. The flow field is visualized by smoke-wire and oil flow techniques. It is found that the cross-shaped circular jet array improves heat transfer at the intermediate area enclosed by four impinging jets compared to that of circular jet array at the narrow injection distance. In the case of cross-shaped circular jet array, the wall jet produces a stronger turbulence than that of circular jet, which makes the heat transfer push up toward the apex of square detachment line at injection distance L/D = 2 and jet-to-jet spacing S/D = 6 and 8.

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