Numerical Simulation on Molten Metal Collision Behavior Using SPH Method Combined with Fractal Analysis on Morphology of Stacking Pattern

2016 ◽  
Vol 715 ◽  
pp. 203-209
Author(s):  
Masatoshi Futakawa ◽  
Kihei Tsutsui ◽  
Hiroyuki Kogawa ◽  
Takashi Naoe
Keyword(s):  
Proton Beam ◽  
Impact Velocity ◽  
Fractal Analysis ◽  
High Heat ◽  
Proton Accelerator ◽  
Beam Power ◽  
High Heat Flux ◽  
Stacking Pattern ◽  
And Behavior ◽  
The Impact

The developments of the high power proton accelerators become a worldwide interest to provide various applications, where the targets are demanded to efficiently produce secondary beams and to survive intensive MW class proton beam power supplied by the accelerators. Solid metal targets might be melted by very high heat flux that is caused by the intensive proton beam bombardment. In fact, the incident occurred at J-PARC (Japan Proton Accelerator Research Complex), in which the gold solid target was locally melted to explosively jet molten gold. The molten gold jet collided with a structural beryllium flange plate that has a function of vacuum boundary. Some parts of molten gold were splashed and the other stuck on the flange plate. The relationship between the impact velocity and the morphology of the sticking pattern on the plate was quantitatively evaluated by introducing fractal analysis. It was found that the fractal dimension is correlated with the impact velocity and might be a useful factor to indicate the localized impact force and behavior.

Two-Phase Cooling Characteristics of Mono-Dispersed Droplets Impacted on a Heated Surface

2011 ◽  
Author(s):  
S. R. Mahmoudi ◽  
K. Adamiak ◽  
G. S. P. Castle
Keyword(s):  
Heat Flux ◽  
Impact Velocity ◽  
Heated Surface ◽  
Experimental Studies ◽  
Volumetric Flow Rate ◽  
High Heat ◽  
High Heat Flux ◽  
Two Phase ◽  
Mass Fluxes ◽  
The Impact

Droplet impact cooling has been shown to be a promising method for high heat flux removal applications. Recent experimental studies have revealed that even higher heat transfer at low mass fluxes and low Weber number can be achieved with only few degrees of superheat. In the present work, mono-dispersed droplet cooling of a horizontal upward facing heated surface was investigated at low Weber numbers. The impact velocity and frequency of free falling stream of droplets were varied dependently through changing the gap between the heated surface and tip of different capillaries and variation of volumetric flow rate (0.5–4.7 cc/min).The range of impact velocity and droplet frequency was ranged between 0.28 to 1.3 m/s and 0.5 Hz to 5 Hz, respectively using different capillaries size between 17g to 22g. The coolant was 25°C deionized water and all the experiments were performed at atmospheric pressure. The time-averaged two-phase characteristic curves were obtained up to Critical Heat Flux (CHF)-regime. Through the extensive set of experiments, two separate correlations are proposed to predict the average CHFs based on the Weber between 3<We<10, 10<We<100 and Strouhal number ranged and 6.35×10−3<St<3.88×10−2 1.81×10−3<St<3.86×10−2, respectively. The correlation predicts the average CHFs with absolute errors less than 20% and 25%, respectively.

Empirical Optimization of High Density Plate-Fin Heat Sink for Constant Pumping Power in Low Profile Cooling Application

2005 ◽  
Author(s):  
Kazuaki Yazawa ◽  
Tatsuro Yoshida ◽  
Shinji Nakagawa ◽  
Masaru Ishizuka
Keyword(s):  
Fluid Dynamic ◽  
Dynamic Performance ◽  
High Heat ◽  
Heat Sinks ◽  
High Heat Flux ◽  
Pumping Power ◽  
Low Profile ◽  
Data Points ◽  
Narrow Space ◽  
The Impact

Since the VLSI processors are increasing power in accordance with exponential law, cooling solutions for such as personal computers have been evolving for over a decade. Recent heat sinks are designed with high dense fins and low profile to adapt to a high heat flux source within a slim enclosure. To achieve such compact cooling solution, thin fin and small gap is desirable. In addition, the pumping power is also limited by the allowable narrow space for fans. Thus it is important to minimize the thermal resistance for given pumping power that we define the optimum. Due to the lack of literatures on topic of low profile and high dense fins experiments, an apparatus was specially built to measure the thermal and fluid dynamic performance at the same time. Since such a high dense fin arrangement requires extra space on the sides by manufacturing reasons, the impact of bypass flow needs to be considered. The experiments are carefully carried out and the results are precisely compared with numerical analysis. The numerical model aiming to find the optimum for given pumping power is discussed with extrapolating the data points. This report is concluded with the best configuration of plate fins of low profile heat sinks for a given fan performance.

Effect of Orientation and Draining on Linear Spray Array Thermal Management

2007 ◽  
Author(s):  
Benjamin M. Regner ◽  
Timothy A. Shedd
Keyword(s):  
Heat Transfer ◽  
Fluid Management ◽  
High Heat ◽  
Practical Implementation ◽  
High Heat Flux ◽  
Large Area ◽  
Candidate Solution ◽  
The Impact ◽  
Volumetric Flux ◽  
Uniform Droplet

Spray cooling is a candidate solution for high heat flux cooling applications, and previous work has investigated the impact of parameters of conical sprays such as volumetric flux and Sauter mean diameter on heat transfer performance. However, there has been little work on the impact of drainage and spray orientation on spray performances. In addition, conical sprays are not very practical for large area coverage in compact packages, so this study, presents a novel arrangment that uses linear sprays impinging at an angle such that fluid management and uniform droplet coverage of large areas are both improved. Results for the heat transfer coefficient and CHF of a constrained, practical implementation of a spray array (as opposed to a laboratory-only geometry) are presented for FC-72, FC-40 and HFE-7000.

FGMs High-Heat-Flux Environments: Cost/Performance Issues

MRS Bulletin ◽  
1995 ◽  
Vol 20 (1) ◽  
pp. 50-51 ◽  
Author(s):  
John J. Lannutti
Keyword(s):  
Heat Flux ◽  
Short Circuit ◽  
High Heat ◽  
Processing Technique ◽  
Processing Route ◽  
Alumina Powder ◽  
High Heat Flux ◽  
Advanced Composite ◽  
Optimum Material ◽  
And Behavior

This article focuses exclusively on the application of functionally gradient materials (FGMs) as structural components in high-heat-flux environments. Preliminary data suggest that FGMs can equal or surpass the properties of fiber-reinforced composites (FRCs) in these applications at a fraction of the material costs. An optimistic value of $1 per foot for 100-μm-diameter Saphikon alumina fiber yields a per-pound cost of $48,000. In contrast, a costly alumina powder used for FGMs might be in the range of .$20 per pound. While many counter-arguments can be advanced, this price differential cannot be easily overcome.One relative difficulty with FGMs is their inherent compositional flexibility which, ironically, is normally considered an advantage. Determination of the optimum material combination for a given application should precede any effort directed toward determining the “best” processing route. This combination will then specify the processing technique. This would “short circuit” the expensive learning curve historically associated with FRCs.“Processing for processing's sake” is no longer a viable option in today's composite research market. Without necessary advances in the predictive modeling of structure, composition (and, concurrently, cost) and behavior, FGMs may remain an “on-the-horizon” advanced composite.

Quantum-Well Si/SiC Self-Cooling for Thermal Management of High Heat Flux GaN HEMT Semiconductor Devices

2012 ◽  
Author(s):  
Peng Wang ◽  
Michael Manno ◽  
Avram Bar-Cohen
Keyword(s):  
Heat Flux ◽  
Quantum Well ◽  
Thermal Management ◽  
Hot Spot ◽  
Semiconductor Devices ◽  
High Heat ◽  
Wide Bandgap ◽  
High Heat Flux ◽  
High Electron ◽  
The Impact

Wide bandgap semiconductor technology is expected to have a dramatic impact on radar and communications systems. To take full advantage of the power capabilities and small device sizes of wide bandgap semiconductors, new and novel thermal management solutions, especially for high power density, monolithic microwave integrated circuits (MMICs) are in high demand. In this paper, a quantum-well Si/SiC self-cooling concept for hot spot thermal management at the multi-fingered GaN high electron mobility transistor (HEMTs) in the GaN-on-SiC package is proposed and investigated using a three dimensional (3-D) thermal-electric coupling simulation. The impact of electric current, cooler size, Si/SiC substrate thickness, Si/SiC thermal conductivity, and interfacial parasitic effect on the hot spot cooling is examined and discussed. The preliminary modeling results strongly suggest that self-cooling phenomenon inherent in the quantum-well Si/SiC substrate can be used to remove local high heat flux hot spot on the semiconductor devices.

First plasma exposure of a pre-damaged ITER-like plasma facing unit in the WEST tokamak: procedure for the PFU preparation and lessons learnt

2021 ◽  
Author(s):  
Marianne Richou ◽  
Yann Corre ◽  
Thorsten Loewenhoff ◽  
Mathilde Diez ◽  
Celine Martin ◽  
...  
Keyword(s):  
Thermal Loading ◽  
High Heat ◽  
High Heat Flux ◽  
Loading Conditions ◽  
Plasma Exposure ◽  
The West ◽  
Crack Network ◽  
Plasma Facing Components ◽  
Major Surface ◽  
The Impact

Abstract The evaluation of the impact of plasma-facing components (PFCs) damage on subsequent plasma operation is an important issue for ITER. During the first phase of operation of WEST, a few ITER like divertor plasma-facing units (PFUs) have been installed on the lower divertor. One PFU was pre-damaged under electron beam gun thermal loading, before its installation in WEST, and the subsequent evolution of the damage was studied after the WEST plasma exposure. This paper presents the procedure followed to get the pre-damaged PFU. It consists in the characterization of the response of tungsten samples representative of WEST PFU under high heat flux (HHF) loading, the selection of damage (namely small cracks, crack network, crack network and W melt droplets). Finally, according to the WEST plasma loading conditions, the blocks with damage within the PFU and the position of the pre-damaged PFU on the WEST lower divertor are attributed. The first results obtained after an initial plasma exposure in WEST lead to assess, as expected with regard to the heat loading conditions, that no major surface aspect modification was found. This result emphasized the possibility to implement as pre-damage some small local droplets of melted tungsten in a high heat loaded zone for a future WEST experimental campaign.

Effects of High Frequency Droplet Train Impingement on Spreading-Splashing Transition, Film Hydrodynamics and Heat Transfer

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Taolue Zhang ◽  
Jorge Alvarado ◽  
J. P. Muthusamy ◽  
Anoop Kanjirakat ◽  
Reza Sadr
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Surface Temperature ◽  
Liquid Film ◽  
High Frequency ◽  
High Heat ◽  
High Heat Flux ◽  
Droplet Impingement ◽  
Dry Out ◽  
The Impact

The objective of this study is to investigate the effects of droplet-induced crown propagation regimes (spreading and splashing) on liquid film hydrodynamics and heat transfer. In this work, the effects of high frequency droplet train impingement on spreading-splashing transition, liquid film hydrodynamics and surface heat transfer were investigated experimentally. HFE-7100 droplet train was generated using a piezo-electric droplet generator at a fixed flow rate of 165 mL/h. Optical and IR images were captured at stable droplet impingement conditions to visualize the thermal physical process. The droplet-induced crown propagation transition phenomena from spreading to splashing were observed by increasing the droplet Weber number. The liquid film hydrodynamics induced by droplet train impingement becomes more complex when the surface was heated. Bubbles and micro-scale fingering phenomena were observed outside the impact crater under low heat flux conditions. Dry-out was observed outside the impact craters under high heat flux conditions. IR images of the heater surface show that heat transfer was most effective within the droplet impact crater zone due to high fluid inertia including high radial momentum caused by high-frequency droplet impingement. Time-averaged heat transfer measurements indicate that the heat flux-surface temperature curves are linear at low surface temperature and before the onset of dry-out. However, a sharp increase in surface temperature can be observed when dry-out appears on the heater surface. Results also show that strong splashing (We = 850) is unfavorable for heat transfer at high heat flux conditions due to instabilities of the liquid film, which lead to the onset of dry-out. In summary, the results show that droplet Weber number is a significant factor in the spreading-splashing transition, liquid film hydrodynamics and heat transfer.

Design and Fabrication of Graded Copper Inverse Opals (g-CIOs) for Capillary-Fed Boiling in High Heat Flux Cooling Applications

2020 ◽  
Author(s):  
Qianying Wu ◽  
Chi Zhang ◽  
Mehdi Asheghi ◽  
Kenneth Goodson
Keyword(s):  
Heat Flux ◽  
Capillary Pressure ◽  
High Heat ◽  
High Heat Flux ◽  
Large Area ◽  
Vapor Extraction ◽  
Inverse Opals ◽  
The Impact ◽  
Capillary Wicking ◽  
Liquid Delivery

Abstract Capillary-fed boiling in microporous copper inverse opals (CIOs) is capable of removing an excess of 1 kW/cm2 at 10–15 °C superheat over small wicking distances ∼ 200 μm. In order to remove heat from large area chips (&gt; 1 cm2), longer capillary wicking distance is desired to reduce the manufacturing complexity of the 3D manifold for liquid delivery and vapor extraction. In this study, we propose graded copper inverse opals (g-CIOs) where smaller pores at the bottom provide high capillary pressure for liquid delivery, while larger pores at the top reduce viscous pressure drop for vapor extraction. This nonhomogeneous wicking material decouples the permeability and capillary pressure in the vertical and lateral directions, resulting in greater CHFs and capillary wicking distances. In this study, we demonstrate the feasibility of fabricating g-CIOs material with up to three different pore diameters (2 μm, 5 μm, and 10 μm) using a multi-step template sintering and copper electrodeposition process. We then leverage and expand upon a well-calibrated experimental model for the prediction of CHF in monoporous CIOs to map the performance metrics for g-CIOs. The model combines a hydraulic resistance network with Darcy’s law and accounts for the nonhomogeneous permeabilities in lateral and vertical directions. Using this model, we study the impact of total wick thickness and graded pore-size combinations on the critical heat fluxes and wicking distances. Our modeling results conclude that a two-layer g-CIOs can potentially reach ∼70% enhancement in the critical heat flux or ∼30% enhancement in the wicking length compared to monoporous CIOs of the same thickness. Our fabrication capability and preliminary modeling results offer the opportunity to design boiling tests with optimized g-CIOs and exploring the potential of dissipating high heat flux for large area cooling applications.

Lid-Integral Cold-Plate Topology: Integration, Performance, and Reliability

2016 ◽  
Vol 138 (1) ◽  
Author(s):  
Gerd Schlottig ◽  
Marco de Fazio ◽  
Werner Escher ◽  
Paola Granatieri ◽  
Vijayeshwar D. Khanna ◽  
...  
Keyword(s):  
Integrated Circuit ◽  
High Heat ◽  
Thermal Interface Material ◽  
High Heat Flux ◽  
Cold Plate ◽  
Wafer Level ◽  
Mechanical Coupling ◽  
Cold Plates ◽  
Compliant Layer ◽  
The Impact

We demonstrate the lid-integral silicon cold-plate topology as a way to bring liquid cooling closer to the heat source integrated circuit (IC). It allows us to eliminate one thermal interface material (TIM2), to establish and improve TIM1 during packaging, to use wafer-level processes, and to ease integration in first-level packaging. We describe the integration and analyze the reliability aspects of this package using modeling and test vehicles. To compare the impact of geometry, materials, and mechanical coupling on warpage, strains, and stresses, we simulate finite element models of five different topologies on an organic land-grid array (LGA) carrier. We measure the thermal performance in terms of thermal resistance from cold-plate base to inlet liquid and obtain 15 mm2 K/W at 30 kPa pressure drop across the package. We build two different topologies using silicon cold-plates and injection-molded lids. Gasket-attached cold-plates pass an 800 kPa pressure test, and direct-attached cold-plates fracture in the cold-plate. The results advise to use a compliant layer between cold-plate and manifold lid and promise a uniformly thick TIM1 layer in the Si–Si matched topology. The work shows the feasibility of composite lids with integrated silicon cold-plates in high heat flux applications.

Lid-Integral Cold Plate Topology Integration, Performance, and Reliability

2015 ◽  
Author(s):  
Gerd Schlottig ◽  
Marco de Fazio ◽  
Werner Escher ◽  
Paola Granatieri ◽  
Vijayeshwar D. Khanna ◽  
...  
Keyword(s):  
High Heat ◽  
Thermal Interface Material ◽  
High Heat Flux ◽  
Wafer Level ◽  
Liquid Cooling ◽  
Test Vehicle ◽  
Mechanical Coupling ◽  
Injection Molded ◽  
Compliant Layer ◽  
The Impact

We demonstrate the Lid-Integral Silicon Coldplate topology as a way to bring liquid cooling closer to the heat source IC. It allows to eliminate one thermal interface material (TIM2), to establish and improve TIM1 during packaging, to use wafer-level processes, and to ease integration in 1st level packaging. We describe the integration, and analyze reliability aspects of this package using modeling and test vehicle builts. To compare the impact of geometry, materials and mechanical coupling on warpage, strains and stresses, we simulate finite element models of five different topologies on an organic LGA carrier. We measure the thermal performance in terms of thermal resistance from coldplate base to inlet liquid and obtain 15mm2K/W at 30 kPa pressure drop across the package. We build two different topologies using silicon coldplates and injection molded lids. Gasket-attached coldplates pass an 800 kPa pressure test, direct-attached coldplates fracture in the coldplate. The results advise to use a compliant layer between coldplate and the manifold lid and promise a uniformly thick TIM1 layer in the Si-Si matched topology. The work shows the feasibility of composite lids with integrated silicon coldplates in high heat flux applications.

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