Separate Effects of Mach Number and Reynolds Number on Jet Array Impingement Heat Transfer

2006 ◽  
Author(s):  
Jongmyung Park ◽  
Matt Goodro ◽  
Phil Ligrani ◽  
Mike Fox ◽  
Hee-Koo Moon
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Mach Number ◽  
Impinging Jets ◽  
Experimental Conditions ◽  
Substantial Impact ◽  
Impingement Jet ◽  
Mach Numbers ◽  
High Mach ◽  
Jet Array

Limited available data suggest a substantial impact of Mach number on the heat transfer from an array of jets impinging on a surface at fixed Reynolds number. Many jet array heat transfer correlations currently in use are based upon tests in which the jet Reynolds number was varied by varying the jet Mach number. Hence, this data may be inaccurate for high Mach numbers. Results from the present study are new and innovative because they separate the effects of jet Reynolds number and jet Mach number for the purposes of validating and improving correlations which are currently in use. The present study provides new data on the separate effects of Reynolds number and Mach number for an array of impinging jets in the form of discharge coefficients, local and spatially-averaged Nusselt numbers, and local and spatially-averaged recovery factors. The data are unique because data are given for impingement jet Mach numbers as high as 0.60 and impingement jet Reynolds numbers as high as 60,000, and because the effects of Reynolds number and Mach number are separated by providing data at constant Reynolds number as the Mach number is varied, and data at constant Mach number as the Reynolds number is varied. As such, the present data are given for experimental conditions not previously examined, which are outside the range of applicability of current correlations.

Separate Effects of Mach Number and Reynolds Number on Jet Array Impingement Heat Transfer

2006 ◽  
Vol 129 (2) ◽  
pp. 269-280 ◽  
Author(s):  
Jongmyung Park ◽  
Matt Goodro ◽  
Phil Ligrani ◽  
Mike Fox ◽  
Hee-Koo Moon
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Mach Number ◽  
Impinging Jets ◽  
Experimental Conditions ◽  
Substantial Impact ◽  
Impingement Jet ◽  
Mach Numbers ◽  
High Mach ◽  
Jet Array

Limited available data suggest a substantial impact of Mach number on the heat transfer from an array of jets impinging on a surface at fixed Reynolds number. Many jet array heat transfer correlations currently in use are based on tests in which the jet Reynolds number was varied by varying the jet Mach number. Hence, this data may be inaccurate for high Mach numbers. Results from the present study are new and innovative because they separate the effects of jet Reynolds number and jet Mach number for the purposes of validating and improving correlations that are currently in use. The present study provides new data on the separate effects of Reynolds number and Mach number for an array of impinging jets in the form of discharge coefficients, local and spatially averaged Nusselt numbers, and local and spatially averaged recovery factors. The data are unique because data are given for impingement jet Mach numbers as high as 0.60 and impingement jet Reynolds numbers as high as 60,000, and because the effects of Reynolds number and Mach number are separated by providing data at constant Reynolds number because the Mach number is varied, and data at constant Mach number because the Reynolds number is varied. As such, the present data are given for experimental conditions not previously examined, which are outside the range of applicability of current correlations.

Crossflows From Jet Array Impingement Cooling: Effects of Hole Array Spacing, Jet-to-Target Plate Distance, and Reynolds Number

2014 ◽  
Author(s):  
Junsik Lee ◽  
Zhong Ren ◽  
Phil Ligrani ◽  
Michael D. Fox ◽  
Hee-Koo Moon
Keyword(s):  
Reynolds Number ◽  
Reynolds Numbers ◽  
Impinging Jets ◽  
Hole Array ◽  
Target Plate ◽  
Impingement Jet ◽  
Nusselt Numbers ◽  
Cooling Effects ◽  
Plate Distance ◽  
Jet Array

Data which illustrate the combined and separate effects of hole array spacing, jet-to-target plate distance, and Reynolds number on cross-flows, and the resulting heat transfer, for an impingement jet array are presented. The array of impinging jets are directed to one flat surface of a channel which is bounded on three sides. Considered are Reynolds numbers ranging from 8,000 to 50,000, jet-to-target plate distances of 1.5D, 3.0D, 5.0D, and 8.0D, and steamwise and spanwise hole spacing of 5D, 8D, and 12D, where D is the impingement hole diameter. In general, the cumulative accumulations of cross-flows, from sequential rows of jets, reduce the effectiveness of each individual jet (especially for jets at larger streamwise locations). The result is sequentially decreasing periodic Nusselt number variations with streamwise development, which generally become more significant as the Reynolds number increases, and as hole spacing decreases. In other situations, the impingement cross-flow results in locally augmented Nusselt numbers. Such variations most often occur at larger downstream locations, as jet interactions are more vigorous, and local magnitudes of mixing and turbulent transport are augmented. This occurs in channels at lower Reynolds numbers, where impingement jets are confined by smaller hole spacing, and smaller jet-to-target plate distance. The overall result is complex dependence of local, line-averaged, and spatially-averaged Nusselt numbers on hole array spacing, jet-to-target plate distance, and impingement jet Reynolds number. Of particular importance are the effects of these parameters on the coherence of the shear layers which form around the impingement jets, as well as on the Kelvin-Helmholtz instability vortices which develop within the shear interface around each impingement jet.

Influences of Target Surface Roughness on Impingement Jet Array Heat Transfer: Part 2 — Effects of Roughness Shape, and Reynolds Number

2016 ◽  
Author(s):  
W. Buzzard ◽  
Z. Ren ◽  
P. M. Ligrani ◽  
C. Nakamata ◽  
S. Ueguchi
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Reynolds Number ◽  
Target Surface ◽  
Impingement Cooling ◽  
Impingement Jet ◽  
Heat Transfer Augmentation ◽  
Small Triangle ◽  
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 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.

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

2016 ◽  
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.

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

2017 ◽  
Vol 31 (2) ◽  
pp. 346-357 ◽  
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

Effects of Mach number and Reynolds number on jet array impingement heat transfer

2007 ◽  
Vol 50 (1-2) ◽  
pp. 367-380 ◽  
Author(s):  
Matt Goodro ◽  
Jongmyung Park ◽  
Phil Ligrani ◽  
Mike Fox ◽  
Hee-Koo Moon
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Mach Number ◽  
Impingement Heat Transfer ◽  
Jet Array

Heat Transfer and Pressure Drop Characteristics for a Turbine Casing Impingement Cooling System

2010 ◽  
Author(s):  
F. Ben Ahmed ◽  
B. Weigand ◽  
K. Meier
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Coefficient ◽  
Mach Number ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Cooling System ◽  
Impinging Jets ◽  
Turbine Casing ◽  
The Heat Transfer Coefficient

Flow mechanisms, heat transfer and discharge coefficient characteristics for a representative part of a turbine casing cooling system, consisting of an array of 20 impinging jets, were numerically investigated. The study focused on the influence of the jet Mach number while maintaining the Reynolds number constant at Re = 7,500. Therefore, the orifice bore diameter or the fluid density had to be varied. The objectives of the current CFD simulations have not been adressed before in literature, not only because heat transfer characteristics and pressure drop are given for impingement jet Mach numbers up to 0.72 at a constant relatively low Reynolds number, but also because fundamental understanding of physical phenomena of the flow in the cylindrical plenum and in the small sharp-edged orifices at the bottom side of the tube is provided. Increasing the Mach number by simultaneously reducing the orifice diameters led to slightly decreasing Nusselt numbers, with average deviations of the order of 14%. However, the heat transfer coefficient increased considerably with increasing Mach number. On the contrary, the variation of the Mach number by varying the density showed only a slight influence on the heat transfer coefficient. The predicted discharge coefficients increased significantly by augmenting the Mach number.

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

2016 ◽  
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.

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

2019 ◽  
Vol 26 (1) ◽  
pp. 15-35 ◽  
Author(s):  
Phillip Ligrani ◽  
Patrick McInturff ◽  
Masaaki Suzuki ◽  
Chiyuki Nakamata
Keyword(s):  
Heat Transfer ◽  
Surface Roughness ◽  
Target Surface ◽  
Impingement Jet ◽  
Jet Array

Heat Transfer in Rotating Serpentine Coolant Passage With Ribbed Walls at Low Mach Numbers

2015 ◽  
Vol 7 (1) ◽  
Author(s):  
Shang-Feng Yang ◽  
Je-Chin Han ◽  
Salam Azad ◽  
Ching-Pang Lee
Keyword(s):  
Heat Transfer ◽  
Mach Number ◽  
Reynolds Numbers ◽  
Working Fluid ◽  
Transfer Coefficients ◽  
Low Mach Number ◽  
Heat Transfer Coefficients ◽  
Rotation Numbers ◽  
Wide Range ◽  
Mach Numbers

This paper experimentally investigates the effect of rotation on heat transfer in typical turbine blade serpentine coolant passage with ribbed walls at low Mach numbers. To achieve the low Mach number (around 0.01) condition, pressurized Freon R-134a vapor is utilized as the working fluid. The flow in the first passage is radial outward, after the 180 deg tip turn the flow is radial inward to the second passage, and after the 180 deg hub turn the flow is radial outward to the third passage. The effects of rotation on the heat transfer coefficients were investigated at rotation numbers up to 0.6 and Reynolds numbers from 30,000 to 70,000. Heat transfer coefficients were measured using the thermocouples-copper-plate-heater regional average method. Heat transfer results are obtained over a wide range of Reynolds numbers and rotation numbers. An increase in heat transfer rates due to rotation is observed in radially outward passes; a reduction in heat transfer rate is observed in the radially inward pass. Regional heat transfer coefficients are correlated with Reynolds numbers for nonrotation and with rotation numbers for rotating condition, respectively. The results can be useful for understanding real rotor blade coolant passage heat transfer under low Mach number, medium–high Reynolds number, and high rotation number conditions.

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