Optimized Heat Transfer for High Power Electronic Cooling Using Arrays of Microjets

2004 ◽  
Vol 127 (7) ◽  
pp. 760-769 ◽  
Author(s):  
Matteo Fabbri ◽  
Vijay K. Dhir
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
High Heat ◽  
Copper Surface ◽  
Electronic Cooling ◽  
Geometrical Parameters ◽  
Air Cooling ◽  
Jet Cooling ◽  
High Heat Transfer ◽  
Forced Air

Electronic cooling has become a subject of interest in recent years due to the rapidly decreasing size of microchips while increasing the amount of heat flux that they must dissipate. Conventional forced air cooling techniques cannot satisfy the cooling requirements and new methods have to be sought. Jet cooling has been used in other industrial fields and has demonstrated the capability of sustaining high heat transfer rates. In this work the heat transfer under arrays of microjets is investigated. Ten different arrays have been tested using deionized water and FC40 as test fluids. The jet diameters employed ranged between 69 and 250μm and the jet Reynolds number varied from 73 to 3813. A maximum surface heat flux of 310W∕cm2 was achieved using water jets of 173.6μm diameter and 3mm spacing, impinging at 12.5m∕s on a circular 19.3mm diameter copper surface. The impinging water temperature was 23.1°C and the surface temperature was 73.9°C. The heat transfer results, consistent with those reported in the literature, have been correlated using only three independent dimensionless parameters. With the use of the correlation developed, an optimal configuration of the main geometrical parameters can be established once the cooling requirements of the electronic component are specified.

Heat Transfer Behavior of Silica Nanoparticles in Pool Boiling Experiment

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Denitsa Milanova ◽  
Ranganathan Kumar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Chemical Composition ◽  
Particle Deposition ◽  
Ph Value ◽  
Pool Boiling ◽  
High Heat ◽  
Boiling Regime ◽  
High Heat Transfer ◽  
The Wire

The heat transfer characteristics of silica (SiO2) nanofluids at 0.5vol% concentration and particle sizes of 10nm and 20nm in pool boiling with a suspended heating Nichrome wire have been analyzed. The influence of acidity on heat transfer has been studied. The pH value of the nanosuspensions is important from the point of view that it determines the stability of the particles and their mutual interactions toward the suspended heated wire. When there is no particle deposition on the wire, the nanofluid increases critical heat flux (CHF) by about 50% within the uncertainty limits regardless of pH of the base fluid or particle size. The extent of oxidation on the wire impacts CHF, and is influenced by the chemical composition of nanofluids in buffer solutions. The boiling regime is further extended to higher heat flux when there is agglomeration on the wire. This agglomeration allows high heat transfer through interagglomerate pores, resulting in a nearly threefold increase in burnout heat flux. This deposition occurs for the charged 10nm silica particle. The chemical composition, oxidation, and packing of the particles within the deposition on the wire are shown to be the reasons for the extension of the boiling regime and the net enhancement of the burnout heat flux.

Nucleate Boiling of Dielectric Liquids on Hydrophobic Patterned Surfaces

2014 ◽  
Author(s):  
Nihal E. Joshua ◽  
Denesh K. Ajakumar ◽  
Huseyin Bostanci
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nucleate Boiling ◽  
High Heat ◽  
Copper Surface ◽  
Dielectric Liquid ◽  
Working Fluid ◽  
Patterned Surfaces ◽  
High Heat Flux ◽  
Dielectric Liquids

This study experimentally investigated the effect of hydrophobic patterned surfaces in nucleate boiling heat transfer. A dielectric liquid, HFE-7100, was used as the working fluid in the saturated boiling tests. Dielectric liquids are known to have highly-wetting characteristics. They tend to fill surface cavities that would normally trap vapor/gas, and serve as active nucleation sites during boiling. With the lack of these vapor filled cavities, boiling of a dielectric liquid leads to high incipience superheats and accompanying temperature overshoots. Heater samples in this study were prepared by applying a thin Teflon (AF400, Dupont) coating on 1-cm2 smooth copper surfaces following common photolithography techniques. Matching size thick film resistors, attached onto the copper samples, generated heat and simulated high heat flux electronic devices. Tests investigated the heater samples featuring circular pattern sizes between 40–100 μm, and corresponding pitch sizes between 80–200 μm. Additionally, a plain, smooth copper surface was tested to obtain reference data. Based on data, hydrophobic patterned surfaces effectively eliminated the temperature overshoot at boiling incipience, and considerably improved nucleate boiling performance in terms of heat transfer coefficient and critical heat flux over the reference surface. Hydrophobic patterned surfaces therefore demonstrated a practical surface modification method for heat transfer enhancement in immersion cooling applications.

Forced Air Cooling With Synthetic Jet Ejectors

2005 ◽  
Author(s):  
Raghav Mahalingam ◽  
Ari Glezer
Keyword(s):  
Mass Flux ◽  
Heated Surface ◽  
High Heat ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Low Flow ◽  
Air Cooling ◽  
Zero Mass ◽  
High Heat Transfer ◽  
Forced Air

This paper discusses the concept of synthetic jet ejectors for forced air cooling and some practical implementations of the same. Synthetic or “zero-mass-flux” jets, unlike conventional jets, require no mass addition to the system, and thus provide means of efficiently directing airflow across a heated surface. Because these jets are zero net mass flux in nature and are comprised entirely of the ambient fluid, they can be conveniently integrated with the surfaces that require cooling without the need for complex plumbing. A synthetic jet ejector mechanism for obtaining high heat transfer rates at low flow rates is discussed. Synthetic jet ejectors consist of a primary “zero-mass-flux” unsteady jet driving a secondary airflow through a channel. Several practical implementations of synthetic jets are introduced from low form factor, low power spot cooling applications to high heat dissipation applications and flow bypass control where synthetic jets are used to enhance fan performance.

Heat Transfer Analysis of Microgrooved Evaporator and Condenser Surfaces Utilized in a High Heat Flux Two-Phase Flow Loop

2007 ◽  
Author(s):  
Edvin Cetegen ◽  
Thomas Baummer ◽  
Serguei Dessiatoun ◽  
Michael Ohadi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
High Heat ◽  
Phase Flow ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Pressure Drops ◽  
Heat Transfer Coefficients ◽  
High Heat Transfer ◽  
Microgrooved Surface

This paper investigates the heat transfer and pressure drop analysis of micro grooved surfaces utilized in evaporators and condensers of a two-phase flow cooling loop. These devices utilize the vapor-liquid phase change to transfer large amounts of heat, and they offer substantially higher heat flux performance with lower pumping power than most liquid cooling technologies. Microgrooved surfaces, combined with force-fed evaporation and condensation technology discussed in this paper yield high heat transfer coefficients with low pressure drops. Our most recent results, aiming to test the limits of the technology, demonstrated dissipation of almost 1kW/cm2 from silicon electronics using HFE 7100 as the working fluid. In a compact two phase system, the heat generated by the electronic components can be absorbed by microgrooved evaporators and rejected through the microgrooved surface condensers to liquid cooled slots with high heat transfer coefficients and low pressure drops on the refrigerant side. In the case of air-cooling, the same microgrooved surface heat exchanger can reject heat with a heat transfer coefficient of 3847 W/cm2 and a pressure drop of 4156 Pa. These heat transfer processes have the added capability of being combined and used together in a self-contained system cooled either by liquid or air.

Development of Heat Sinks for Air Cooling and Water Cooling Using Lotus-Type Porous Metals

2011 ◽  
Author(s):  
H. Chiba ◽  
T. Ogushi ◽  
H. Nakajima
Keyword(s):  
Heat Transfer ◽  
Porous Materials ◽  
Heat Sink ◽  
High Heat ◽  
Heat Sinks ◽  
Air Cooling ◽  
Water Cooling ◽  
Cooling Performance ◽  
High Heat Transfer ◽  
Micro Channels

In recent years, since heat dissipation rates and high frequency electronic devices have been increasing, a heat sink with high heat transfer performance is required to cool these devices. Heat sink utilizing micro-channels with several ten microns are expected to provide an excellent cooling performance because of their high heat transfer capacities due to small channel. Therefore, various porous materials such as cellular metals have been investigated for heat sink applications. However, heat sink using conventional porous materials has a high pressure drop because the cooling fluid flow through the pores is complex. Among the described porous materials, a lotus-type porous metal with straight pores is preferable for heat sinks due to the small pressured drop. In present work, cooling performance of the lotus copper heat sink for air cooling and water cooling is introduced. The experimental data for air cooling show 13.2 times higher than that for the conventional groove fins. And, the data for the water cooling show 1.7 times higher than that for the micro-channels. It is concluded that lotus copper heat sink is the most prospective candidate for high power electronics devices.

Heat Transfer Investigations in Multiple Impinging Jets at Low Reynolds Number

2010 ◽  
Author(s):  
Arvind G. Rao ◽  
Myra Kitron-Belinkov ◽  
Vladimir Krapp ◽  
Yeshayahou Levy
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Low Reynolds Number ◽  
Turbine Blades ◽  
Jet Impingement ◽  
High Heat ◽  
Geometrical Parameters ◽  
Transitional Region ◽  
High Heat Transfer ◽  
Low Reynolds

Jet impingement is a well established cooling methodology used for cooling turbine blades in gas turbine engines. Jet impingement results in high heat transfer coefficients as compared to other conventional modes of single phase heat transfer. Most of the research in jet impingement has been confined to high Reynolds number regime. In order to increase the applicability of this technique to non conventional applications like in a low pressure micro turbine combustors or turbine blades, the behavior of such systems in the low Reynolds number regime should be understood. The present paper is a continuation of earlier investigations on the heat transfer behavior of a large jet impingement array in the low Reynolds number regime, especially in the laminar and transitional region. More experiments have been conducted with different geometrical parameters of the array to analyze the effect of these parameters on the average heat transfer coefficient. Numerical simulations with existing CFD tools were carried out in order to understand the fluid mechanics inside such a complex system. The CFD model was validated with the experiments. Different turbulence models were used and it was found that the SST-k-ω model was the best for modeling jet impingement phenomena. It is anticipated that the results obtained from the present exercise will give better insights in optimizing the design of multiple jet impingement cooling systems for high heat density applications.

High Heat Flux Dissipation Using Symmetric Dual-Taper Manifold in Pool Boiling

2019 ◽  
Author(s):  
Aranya Chauhan ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pool Boiling ◽  
Heat Removal ◽  
Heating Surface ◽  
High Heat ◽  
Copper Surface ◽  
High Heat Flux ◽  
Maximum Heat ◽  
Continuous Increase

Abstract The trend of miniaturization in electronics presents a great challenge in the thermal management of devices. The continuous increase in the number of transistors in the processor leads to high heat flux generation, limiting the performance of the device. Boiling heat transfer offers a great heat removal competency while maintaining the low chip temperatures. The critical heat flux (CHF) dictates the maximum heat removal ability, and heat transfer coefficient (HTC) defines the efficiency of the boiling process. This pool boiling study is focused on using a manifold containing a symmetric dual taper over the heating surface. The heat transfer performance of this configuration is evaluated for different taper angles in the manifold. The macro-convection assisted by vapor columns during boiling enhance the CHF and HTC limit significantly. A CHF of 287 W/cm2 with an HTC of 116 kW/cm2°C was achieved with a plain copper surface, representing greater than a 2-fold increases in each over a plain surface.

Two-Phase Spray Cooling With Water/2-Propanol Binary Mixture: Investigation of Mass Diffusion Resistance

2016 ◽  
Author(s):  
Sai Sujith Obuladinne ◽  
Huseyin Bostanci
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Performance ◽  
Pure Water ◽  
Spray Cooling ◽  
High Heat ◽  
Working Fluid ◽  
High Heat Flux ◽  
Two Phase ◽  
High Heat Transfer

Two-phase spray cooling has been an emerging thermal management technique offering high heat transfer coefficients (HTCs) and critical heat flux (CHF) levels, near-uniform surface temperatures, and efficient coolant usage that enables to design of compact and lightweight systems. Due to these capabilities, spray cooling is a promising approach for high heat flux applications in computing, power electronics, and optics. The two-phase spray cooling inherently depends on saturation temperature-pressure relationships of the working fluid to take advantage of high heat transfer rates associated with liquid-vapor phase change. When a certain application requires strict temperature and/or pressure conditions, thermophysical properties of the working fluid play a critical role in attaining proper efficiency, reliability, or packaging structure. However, some of the commonly used working fluids today, including refrigerants and dielectric liquids, have relatively poor properties and heat transfer performance. In such cases, utilizing binary mixtures to tune working fluid properties becomes an alternative approach. This study aimed to conduct an initial investigation on the spray cooling characteristics of practically important binary mixtures and demonstrate their capability for challenging high heat flux applications. The working fluid, water/2-propanol binary mixture at various concentration levels, specifically at x1 (liquid mass fraction of 2-proponal in water) of 0.0 (pure water), 0.25, 0.50, 0.879 (azeotropic mixture) and 1.0, represented both non-azeotropic and azeotropic cases. Tests were performed on a closed loop spray cooling system using a pressure atomized spray nozzle with a constant liquid flow rate at corresponding 20°C subcooling conditions and 1 Atm pressure. A copper test section measuring 10 mm × 10 mm × 2 mm with a plain, smooth surface simulated high heat flux source. Experimental procedure involved controlling the heat flux in increasing steps, and recording the steady-state temperatures to obtain cooling curves in the form of surface superheat vs heat flux. The obtained results showed that pure water (x1 = 0.0) and 2-propanol (x1 = 1.0) provide the highest and lowest heat transfer performance, respectively. At a given heat flux level, the HTC values indicated strong dependence on x1, where the HTCs depress proportional to the concentration difference between the liquid and vapor phases. The CHF values sharply decreased at x1≥ 0.25.

Effect of Geometrical Parameters on Flow Mal-Distribution in a Wavy Microchannel

2015 ◽  
Vol 813-814 ◽  
pp. 674-678
Author(s):  
M. Satheeshkumar ◽  
M.R. Thansekhar ◽  
C. Anbumeenakshi ◽  
S. Suresh
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Flow Distribution ◽  
High Heat ◽  
Geometrical Parameters ◽  
Transfer Coefficients ◽  
Geometrical Properties ◽  
Heat Transfer Coefficients ◽  
High Heat Transfer ◽  
Very High

Microchannels are of current interest for use in heat exchangers, where very high heat transfer performance is desired. Microchannels provide very high heat transfer coefficients because of their small hydraulic diameters. In this study, a numerical investigation of fluid flow in microchannels with varying hydraulic diameters is presented. Six channels with wavy shape are considered. Header is the major part in the microchannel, which supplies fluid into different channels. A CFD model was created to simulate the fluid flow in the header and microchannels. In this work, five different shapes of the header were considered namely circular, frustum conical, rectangular, triangular and trapezoidal. The results from these simulations are presented, and it is observed that the flow distribution is significantly affected by geometrical properties of the channel and the header.

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