WINGLET-PAIR TARGET SURFACE ROUGHNESS INFLUENCES ON IMPINGEMENT JET ARRAY HEAT TRANSFER

The present investigation considers the effects of special roughness patterns on impingement target surfaces to improve the effectiveness and surface heat transfer augmentation levels of impingement jet array cooling. This investigation utilizes various sizes, distributions, shapes, and patterns of surface roughness elements for impingement cooling augmentation. The surface roughness shapes considered here are rectangle and triangle, in combination with larger rectangular pins. Configurations considered include: (i) arrays of small rectangular roughness, (ii) arrays of small triangle roughness, (iii) combinations of small rectangle roughness and large pins together, and (iv) combinations of small triangle roughness and large pins together. Tests are performed at impingement jet Reynolds numbers of 900, 1500, 5000, and 11000. Local and overall impingement cooling performance depends upon the shape of the roughness elements, as well as upon the jet Reynolds number. Depending upon the magnitude of jet Reynolds number, different behavior and trends are observed for the arrays of small rectangle roughness, compared with arrays of small triangle roughness. These differences are related to the abilities of the two different roughness shapes to generate different distributions of local mixing and vorticity at different length and time scales. Overall, results demonstrate the remarkable ability of target surface roughness to produce increased surface heat transfer augmentation levels of impingement jet array cooling, relative to target surfaces which are smooth.

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Influences of Target Surface Roughness on Impingement Jet Array Heat Transfer: Part 1 — Effects of Roughness Pattern, Roughness Height, and Reynolds Number

Volume 5A: Heat Transfer ◽

10.1115/gt2016-56354 ◽

2016 ◽

Cited By ~ 3

Author(s):

W. Buzzard ◽

Z. Ren ◽

P. Ligrani ◽

C. Nakamata ◽

S. Ueguchi

Keyword(s):

Heat Transfer ◽

Surface Roughness ◽

Reynolds Number ◽

Target Surface ◽

Impingement Cooling ◽

Impingement Jet ◽

Heat Transfer Augmentation ◽

Small Rectangle ◽

Roughness Elements ◽

Jet Array

The present investigation considers the effects of special roughness patterns on impingement target surfaces to improve the effectiveness and surface heat transfer augmentation levels of impingement jet array cooling. This investigation utilizes various sizes, distributions, shapes, and patterns of surface roughness elements for impingement cooling augmentation. The surface roughness shape considered here is rectangle, in combination with larger rectangular pins. Combinations of small rectangle roughness and large pins are considered together, along with arrays of small rectangular roughness alone. Tests are performed at impingement jet Reynolds numbers of 900, 1500, 5000, and 11000. Local and overall impingement cooling performance depends upon the pattern, distribution, arrangement, and height of the roughness elements, as well as upon the jet Reynolds number. Depending upon the magnitude of jet Reynolds number, different behavior and trends are observed for the small rectangle roughness and large pins together, compared with arrays of small rectangular roughness alone. Overall, results demonstrate the remarkable ability of target surface roughness to produce increased surface heat transfer augmentation levels of impingement jet array cooling, relative to target surfaces which are smooth.

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Impingement Jet Array Heat Transfer: Target Surface Roughness Shape, Reynolds Number Effects

Journal of Thermophysics and Heat Transfer ◽

10.2514/1.t4951 ◽

2017 ◽

Vol 31 (2) ◽

pp. 346-357 ◽

Cited By ~ 6

Author(s):

Zhong Ren ◽

Warren C. Buzzard ◽

Phillip M. Ligrani ◽

Chiyuki Nakamata ◽

Satoshi Ueguchi

Keyword(s):

Heat Transfer ◽

Surface Roughness ◽

Reynolds Number ◽

Target Surface ◽

Impingement Jet ◽

Reynolds Number Effects ◽

Jet Array

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Effects of hole shape on impingement jet array heat transfer with small-scale, target surface triangle roughness

International Journal of Heat and Mass Transfer ◽

10.1016/j.ijheatmasstransfer.2018.06.025 ◽

2018 ◽

Vol 127 ◽

pp. 585-597 ◽

Cited By ~ 6

Author(s):

Patrick McInturff ◽

Masaaki Suzuki ◽

Phil Ligrani ◽

Chiyuki Nakamata ◽

Dae Hee Lee

Keyword(s):

Heat Transfer ◽

Target Surface ◽

Small Scale ◽

Hole Shape ◽

Impingement Jet ◽

Jet Array

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Influences of target surface small-scale rectangle roughness on impingement jet array heat transfer

International Journal of Heat and Mass Transfer ◽

10.1016/j.ijheatmasstransfer.2017.03.061 ◽

2017 ◽

Vol 110 ◽

pp. 805-816 ◽

Cited By ~ 6

Author(s):

Warren C. Buzzard ◽

Zhong Ren ◽

Phillip M. Ligrani ◽

Chiyuki Nakamata ◽

Satoshi Ueguchi

Keyword(s):

Heat Transfer ◽

Target Surface ◽

Small Scale ◽

Impingement Jet ◽

Jet Array

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Influences of Target Surface Cylindrical Roughness on Impingement Jet Array Heat Transfer: Effects of Roughness Height, Roughness Shape, and Reynolds Number

Volume 8: Heat Transfer and Thermal Engineering ◽

10.1115/imece2016-67655 ◽

2016 ◽

Cited By ~ 1

Author(s):

Z. Ren ◽

W. Buzzard ◽

P. M. Ligrani

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Roughness Element ◽

Target Surface ◽

Roughness Height ◽

Impingement Jet ◽

Turbulent Reynolds Number ◽

Roughness Elements ◽

Small Cylinder ◽

Jet Array

The present investigation considers the effects of special roughness patterns on impingement target surfaces to improve the effectiveness and surface heat transfer augmentation levels of impingement jet array cooling. This investigation utilizes various sizes, distributions, shapes, and patterns of surface roughness elements for impingement cooling augmentation. In total, fifteen different test surfaces are considered, either with cylinder small roughness, triangle small roughness, or rectangle small roughness element shapes. Six of these test surfaces also employ large roughness elements with rectangular shapes (along with either triangle or rectangle small roughness elements). Tests are performed at impingement jet Reynolds numbers of 900 and 11000. Nusselt number variations for the small cylinder roughness show different trends with streamwise development and changing roughness height, compared to target plates with small rectangle roughness and small triangle roughness. In general, this is because roughness elements which contain surface shapes with sharp edges generate increased magnitudes of vorticity with length scales of the order of the roughness element diameter. Such generation is not always present in an abundant fashion with the small cylinder roughness because of the smooth contours around each roughness element periphery. Such effects are illustrated by several data sets, including Nusselt numbers associated with the small cylinder roughness with a height of 0.250D at a turbulent Reynolds number of 11000.

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Impingement Heat Transfer From a Jet-Array With In-Between Return Holes for the Crossflow

Volume 7A: Heat Transfer ◽

10.1115/gt2020-15742 ◽

2020 ◽

Author(s):

Chen Tang ◽

Sumanta Acharya

Keyword(s):

Heat Transfer ◽

Liquid Crystal ◽

Thin Sheet ◽

Jet Impingement ◽

Target Surface ◽

Transfer Rates ◽

Impingement Heat Transfer ◽

Acrylic Plate ◽

High Heat Transfer ◽

Jet Array

Abstract Jet-impingement heat transfer is commonly used for vane leading edges and end-walls of turbine components for cooling the surfaces. One of the factors that limit high heat transfer rates is the effect of the crossflow which builds up downstream and adversely impacts the jet penetration and the impingement heat transfer rates. The present paper investigates the concept of introducing return holes (RH) for the crossflow to prevent its build-up and therefore reduce its deleterious effects. In the present experimental study, a 3 by 9 jet-array impinging on a target surface is considered with and without return holes. The return holes are located in an in-line pattern between the impingement holes. Experiments are conducted in an impingement channel with closed side walls and for jet-to-target distances (H/D) of 1D to 9D and a jet-Reynolds number of 20,000. Two different crossflow schemes combined with three return hole (RH) configurations are studied. The two crossflow arrangements are: (1) one radial exit and RH’s open for the spent air to exit and (2) all radial exits blocked with the spent air exiting through the RH’s only. Three different area-openings for the RH’s are considered and correspond to 33.3%, 66.7%, and 100% of the total return hole area open. In addition, a baseline case with no RH’s and one radial exit is studied. A transient liquid-crystal based study is conducted using a thin sheet of narrowband Thermochromic Liquid Crystal glued on an acrylic plate serving as the target surface. Local heat transfer coefficients are obtained based on the measured surface temperature and the solution of 1D transient heat conduction in the target acrylic plate. Return holes have significant influence on the crossflow-induced degradation effects at small jet-to-target spacing. The all-blocked crossflow scheme demonstrates good uniformity and axisymmetric Nusselt number distributions.

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Influences of Micro Pin-Fin on Jet Array Impingement Heat Transfer: Effects of Jet to Target Distance, Micro Pin-Fin Shapes, Height, and Reynolds Number

Volume 5A: Heat Transfer ◽

10.1115/gt2018-76942 ◽

2018 ◽

Author(s):

Xunfeng Lu ◽

Weihong Li ◽

Xueying Li ◽

Jing Ren ◽

Hongde Jiang

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Target Surface ◽

Reynolds Numbers ◽

Target Distance ◽

Experimental Methodology ◽

Pin Fin ◽

Impingement Heat Transfer ◽

Surface Heat Transfer Coefficient ◽

Jet Array

In the current research of impingement on pin-fin wall, researchers mainly pay attention to macro pin-fin due to the limitation of manufacture. With the development of additive manufacturing, it is possible to manufacture the micro pin-fin. Hence, impingement on micro pin-fin wall becomes a new cooling technique that has attracted the researchers’ attention. With experimental methodology, the investigation utilizes different jet to target distance, micro pin-fin shapes, height and Reynolds number for impingement cooling augmentation to illustrate the effects on jet array impingement heat transfer. The area-averaged target surface heat transfer coefficient distributions are measured with lumped capacitance method. The impingement hole diameter (D) is 4 millimeter, with streamwise and spanwise jet-to-jet spacing 4D. Considered are effects of jet to target plate distance (Z/D:0.75,3), micro pin-fin shapes (rectangle, pentahedron), and pin-fin height (h/D:0.05,0.2,0.4). In total, ten different test surfaces are considered (smooth surface included). Tests are performed at impingement jet Reynolds numbers from 2000 to 10000 for configuration of Z/D = 0.75, from 5000–20000 for configuration of Z/D = 3. The experimental results illustrate that there are significant heat transfer augmentation (30%–120% more than baseline flow condition) with micro pin-fin on impingement target surface, and discharge coefficient is almost the same.

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