Crossflows from jet array impingement cooling: Hole spacing, target plate distance, Reynolds number effects

2015 ◽  
Vol 88 ◽  
pp. 7-18 ◽  
Author(s):  
Junsik Lee ◽  
Zhong Ren ◽  
Phil Ligrani ◽  
Michael D. Fox ◽  
Hee-Koo Moon
Keyword(s):  
Reynolds Number ◽  
Target Plate ◽  
Impingement Cooling ◽  
Reynolds Number Effects ◽  
Cooling Hole ◽  
Plate Distance ◽  
Jet Array

JET ARRAY IMPINGEMENT COOLING LOCAL NUSSELT NUMBER VARIATIONS: EFFECTS OF HOLE ARRAY SPACING, JET-TO-TARGET PLATE DISTANCE, AND REYNOLDS NUMBER

2016 ◽  
Vol 47 (2) ◽  
pp. 119-140 ◽  
Author(s):  
Mary Jennerjohn ◽  
Junsik Lee ◽  
Zhong Ren ◽  
Phillip Ligrani ◽  
Mark McQuilling ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Nusselt Number ◽  
Local Nusselt Number ◽  
Hole Array ◽  
Target Plate ◽  
Impingement Cooling ◽  
Plate Distance ◽  
Jet Array

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.

Thermal Performance of Micro-Jet Impingement Device With Parallel Flow, Jet-Adjacent Fluid Removal

2018 ◽  
Author(s):  
Todd M. Bandhauer ◽  
David R. Hobby ◽  
Chris Jacobsen ◽  
Dave Sherrer
Keyword(s):  
Reynolds Number ◽  
Thermal Resistance ◽  
Thermal Performance ◽  
Heated Surface ◽  
Jet Impingement ◽  
Impinging Jets ◽  
Thermal Interface Material ◽  
Cooling Device ◽  
Impingement Cooling ◽  
Jet Array

In a variety of electronic systems, cooling of various components imposes a significant challenge. A major aspect that inhibits the performance of many cooling solutions is the thermal resistance between the chip package and the cooling structure. Due to its low thermal conductivity, the thermal interface material (TIM) layer imposes a significant thermal resistance on the chip to cooling fluid thermal path. Advanced cooling methods that bypass the TIM have shown great potential in research and some specialty applications, yet have not been adopted widely by industry due to challenges associated with practical implementation and economic constraints. One advanced cooling method that can bypass the TIM is jet impingement. The impingement cooling device investigated in the current study is external to the integrated circuit (IC) package and could be easily retrofitted onto any existing microchip, similar to a standard heatsink. Jet impingement cooling has proven effective in previous studies. However, it has been shown that jet-to-jet interference severely degrades thermal performance of an impinging jet array. The present research addresses this challenge by utilizing a flow path geometry that allows for withdrawal of the impinging fluid immediately adjacent to each jet in the array. In this study, a jet impingement cooling solution for high-performance ICs was developed and tested. The cooling device was fabricated using modern advanced manufacturing techniques and consisted of an array of micro-scale impinging jets. A second array of fluid return paths was overlain across the jet array to allow for direct fluid extraction in the immediate vicinity of each jet, and fluid return passages were oriented in parallel to the impinging jets. The following key geometric parameters were utilized in the device: jet diameter (D = 300μm), distance from jet to impinging surface (H/D = 2.5), spacing between jets (S/D = 8), spacing between fluid returns (Sr/D = 8), diameter of fluid returns (Dr/D = 5). The device was mounted to a 2cm × 2cm uniformly heated surface which produced up to 165W and the resulting fluid-to-surface temperature difference was measured at a variety of flow rates. For this study, the device was tested using single-phase water. Jet Reynolds number ranged from 300–1500 and an average heat transfer coefficient of 13,100 W m−2 K−1 was achieved at a Reynolds number of only Red = 305.

Recent Trends of Impingement Cooling System Enhancement for Gas Turbine

2013 ◽  
Vol 465-466 ◽  
pp. 496-499
Author(s):  
Mohd Firdaus Bin Abas ◽  
Abdullah Aslam ◽  
Hamidon bin Salleh ◽  
Nor Adrian Bin Nor Salim
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Turbine Blades ◽  
Impinging Jets ◽  
Target Plate ◽  
Impingement Cooling ◽  
Impingement Jet ◽  
Rib Turbulators ◽  
Recent Trends ◽  
Plate Distance

Efforts have been given to improve the turbine blades ability to withstand high temperature for a long period of time by implementing effective cooling system. There are many aspects that should be considered when implementing impingement cooling. This paper will only cover two trending aspects in impingement cooling implementation; the jet-to-target plate distance and the application of ribs in promoting better impingement cooling performance. For target plate distance to impingement jet diameter value, H/d > 1, the area-averaged Nusselt number also decreases as the H/d value increases. This may have been due to a reduction of the amount of momentum exerted by the impinging jets onto the target plate. For H/d < 1, the results have been proven otherwise. Heat transfer in impingement/effusion cooling system in crossflow with rib turbulators showed higher heat transfer rate than that of a surface without ribs because the ribs prevent the wall jets from being swept away by the crossflow and increase local turbulence of the flow near the surface. It could be concluded that both H/d ratio and ribs installation play an important role in enhancing impingement cooling systems heat transfer effectiveness.

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.

Effects of Jet-to-Target Plate Distance and Reynolds Number on Jet Array Impingement Heat Transfer

2013 ◽  
Author(s):  
Junsik Lee ◽  
Zhong Ren ◽  
Jacob Haegele ◽  
Geoff Potts ◽  
Jae Sik Jin ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Strong Dependence ◽  
Target Surface ◽  
Reynolds Numbers ◽  
Target Plate ◽  
Stagnation Points ◽  
Nusselt Numbers ◽  
Impingement Heat Transfer ◽  
Plate Distance

Data which illustrate the effects of jet-to-target plate distance and Reynolds number on the heat transfer from an array of jets impinging on a flat plate are presented. Considered are Reynolds numbers Rej ranging from 8,200, to 52,000, with isentropic jet Mach numbers of approximately 0.1 to 0.2. Jet-to-target plate distances Z of 1.5D, 3.0D, 5.0D, and 8.0D are employed, where D is the impingement hole diameter. Steamwise and spanwise hole spacings are 8D. Local and spatially-averaged Nusselt numbers show strong dependence on the impingement jet Reynolds number for all situations examined. Experimental results also illustrate the dependence of local Nusselt numbers on normalized jet-to-target plate distance, especially for smaller values of this quantity. The observed variations are partially due to accumulating cross-flows produced as the jets advect downstream, as well as the interactions of the vortex structures which initially form around the jets, and then impact and interact as they advect away from stagnation points along the impingement target surface. The highest spatially-averaged Nusselt numbers are present for Z/D = 3.0 for Rej of 8,200, 20,900, and 30,000. When Rej = 52,000, spatially-averaged Nusselt numbers increase as Z/D decreases, with the highest value present at Z/D = 1.5.

Effect of Reynolds Number, Hole Patterns, and Target Plate Thickness on the Cooling Performance of an Impinging Jet Array—Part II: Conjugate Heat Transfer Results and Optimization

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Weihong Li ◽  
Li Yang ◽  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Boundary Conditions ◽  
Conjugate Heat Transfer ◽  
Plate Thickness ◽  
Impinging Jet ◽  
Measured Temperature ◽  
Temperature Uniformity ◽  
Target Plate ◽  
Jet Array

This study comprehensively illustrates the effect of Reynolds number, hole spacing, nozzle-to-target distance, and target plate thickness on the conjugate heat transfer (CHT) performance of an impinging jet array. Test models are composed of a specific thermal-conductivity material which exerts a matched model Biot number to that of engine condition. High-resolution temperature measurements are conducted on the impinging-target plate utilizing steady liquid crystal (SLC) with Reynolds numbers ranging from 5000 to 27,500. Different streamwise and spanwise jet-to-jet spacing (i.e., X/D and Y/D: 4–8), nozzle-to-target plate distance (Z/D: 0.75–3), and target plate thickness (t/D: 0.75–2.75) are employed to compose a total of 108 different geometries. Experimental measured temperature is utilized as boundary conditions to conduct finite element simulation. Local and averaged nondimensional temperature and averaged temperature uniformity of target plate “hot side” are obtained. Optimum hole spacing arrangements, impingement distance, and target plate thickness are pointed out to minimize hot side temperature, amount of cooling air and to maximize temperature uniformity. Also included are 2D predictions with different convective boundary conditions, i.e., local 2D distribution and row-averaged heat transfer coefficients (HTCs), to estimate the accuracy of temperature prediction in comparison with the conjugate results.

Effect of Reynolds Number, Hole Patterns, Target Plate Thickness on Cooling Performance of an Impinging Jet Array: Part II — Conjugate Heat Transfer Results and Optimization

2016 ◽  
Author(s):  
Weihong Li ◽  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang ◽  
Li Yang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Boundary Conditions ◽  
Conjugate Heat Transfer ◽  
Plate Thickness ◽  
Impinging Jet ◽  
Test Model ◽  
Temperature Uniformity ◽  
Target Plate ◽  
Jet Array

This study comprehensively illustrates the effect of Reynolds number, hole spacing, jet-to-target distance and target plate thickness on the conjugate heat transfer performance of an impinging jet array. Test model is constructed with a relatively high conductivity material so that the Biot number of the models match engine condition. Highly resolved temperature distributions on the target plate are obtained utilizing steady liquid crystal over a range of Reynolds numbers varying between 5,000 and 27,5000. Effect of streamwise and spanwise jet-to-jet spacing (X/D, Y/D: 4–8), jet-to-target plate distance (Z/D: 0.75–3) and target plate thickness (t/D: 0.75–2.75) are employed composing a test matrix of 108 different geometries. Measured data are utilized as boundary conditions to conduct finite element simulation. Local and averaged non-dimensional temperature and averaged temperature uniformity of target plate “hot side” are obtained. Optimum hole spacing arrangements, impingement distance and target plate thickness are pointed out to minimize hot side temperature, the amount of cooling air and maximize the temperature uniformity. Also included are 2D predictions with different convective boundary conditions, i.e. row-averaged and local heat transfer coefficients, to estimate the accuracy of temperature prediction in comparison with the conjugate results.

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.

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