Novel Immersion Cooling Technique for a 3D Chip Stack

2013 ◽  
Author(s):  
Ashish Sinha ◽  
Krishna Kota ◽  
Pablo Hidalgo ◽  
Yogendra Joshi ◽  
Ari Glezer
Keyword(s):  
Heat Transfer ◽  
Heat Dissipation ◽  
Power Input ◽  
Synthetic Jet ◽  
Total Power ◽  
Dielectric Fluid ◽  
Immersion Cooling ◽  
Fluid Convection ◽  
Enhancing Heat Transfer ◽  
Jet Fan

An experimental investigation of a scheme for cooling electronics packaged in a 3D stack arrangement will be presented in this paper. The scheme utilizes immersion cooling of the stacked electronics in an enclosure filled with a dielectric fluid. Convection and conduction within the dielectric fluid drive heat from the 3D stack to the walls of the enclosure from where a ‘synthetic jet /fan air-cooled heat sink’ ultimately dissipates heat to the ambient. Four layers of thick film heaters embedded in FR-4 sheets, each attached to thin copper plates (innovatively stacked in a pyramidal arrangement for conducting heat laterally to the dielectric fluid and simultaneously promoting natural convection in the fluid), were used to simulate a 3D stack of electronics. For a comparative study, several runs were carried out, where the enclosure was filled with dielectric fluid (FC-770), FC-770 in combination with copper wool (with a goal of enhancing heat transfer in FC-770), and water. For a 40 W total power input to the stack, it was observed that the thermal resistance for heat dissipation to ambient from the four heaters varied from 1.67 K/W to 1.96 K/W with FC-770, 1.47 K/W to 1.87 K/W with FC-770 combined with copper wool, and 1.06 K/W to 1.50 K/W with water. The proposed cooling solution is passive and scalable, and is demonstrated to be practicable and effective in cooling 3D stacked electronics.

Development of Synthetic Jet Arrays for Heat Transfer Enhancement in Air-Cooled Heat Sinks for Electronics Cooling

2012 ◽  
Author(s):  
Min Zhang ◽  
Taiho Yeom ◽  
Youmin Yu ◽  
Longzhong Huang ◽  
Terrence W. Simon ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Power Consumption ◽  
Flow Velocity ◽  
Heat Transfer Enhancement ◽  
Channel Flow ◽  
Heat Sink ◽  
Synthetic Jet ◽  
Total Power ◽  
Transfer Enhancement ◽  
Jet Array

Synthetic jet arrays driven by a piston-diaphragm structure with a translational motion were fabricated. A piezo-bow actuator generating large translational displacements at a high working frequency was used to drive the jets. Vibration analysis with a laser vibrometer shows the peak-to-peak displacement of the piston inside the jet cavity of about 0.5 mm at the second resonant vibrational frequency of 1,240 Hz. In this driving condition, the peak velocity of a 20-orifice jet array reaches 45 m/s for each orifice with a total power consumption of 1.6 W. Heat transfer performance of the jet array was tested on a 100-mm-long single channel of a 26-channel heat sink. The synthetic jet flow impinges on the tips of the fins. A cross flow through the channel enters from the two ends of the channel, and exits from the middle. Results show that the activation of jets generates a unit-average heat transfer enhancement of 9.3% when operating with a channel flow velocity of 14.7 m/s, and 23.1% when operating with a channel flow velocity of 8 m/s. The effects of various choices for orifice configuration and different dimensionless distances from the fin tips, z/d, on jet performance were evaluated. By decreasing the length of the fin channel from 100 mm to 89 mm and reducing the orifice number of the jet array from 20 to 18, jet peak velocities of about 54 m/s can be obtained with the same power consumption, and a heat transfer enhancement of 31.0% from the jets can be achieved on the 89-mm-long heat sink channel with a flow velocity of 8 m/s.

Effect of Synthetic Jets Over Natural Convection Heat Sinks

2008 ◽  
Author(s):  
Mehmet Arik ◽  
Yogen Utturkar ◽  
Murat Ozmusul
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Sink ◽  
Heat Dissipation ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Operating Conditions ◽  
Heat Sinks ◽  
Junction Temperature ◽  
Allowable Limit

In moderate power electronics applications, the most preferred way of thermal management is natural convection to air with or without heat sinks. Though the use of heat sinks is fairly adequate for modest heat dissipation needs, it suffers from some serious performance limitations. Firstly, a large volume of the heat sink is required to keep the junction temperature at an allowable limit. This need arises because of the low convective film coefficients due to close spacing. In the present computational and experimental study, we propose a synthetic jet embedded heat sink to enhance the performance levels beyond two times within the same volume of a regular passive heat sink. Synthetic jets are meso-scale devices producing high velocity periodic jet streams at high velocities. As a result, by carefully positioning of these jets in the thermal real estate, the heat transfer over the surfaces can be dramatically augmented. This increase in the heat transfer rate is able to compensate for the loss of fin area happening due to the embedding of the jet within the heat sink volume, thus causing an overall increase in the heat dissipation. Heat transfer enhancements of 2.2 times over baseline natural convection cooled heat sinks are measured. Thermal resistances are compared for a range of jet operating conditions and found to be less than 0.9 K/W. Local temperatures obtained from experimental and computational agreed within ± 5%.

Experimental Analysis for Optimization of Thermal Performance of a Server in Single Phase Immersion Cooling

2019 ◽  
Author(s):  
Pravin A. Shinde ◽  
Pratik V. Bansode ◽  
Satyam Saini ◽  
Rajesh Kasukurthy ◽  
Tushar Chauhan ◽  
...  
Keyword(s):  
Power Consumption ◽  
Thermal Performance ◽  
Heat Dissipation ◽  
Operating Cost ◽  
Heat Removal ◽  
Dielectric Fluid ◽  
Inlet Temperature ◽  
Processing Unit ◽  
Central Processing ◽  
Immersion Cooling

Abstract Liquid immersion cooling of servers in synthetic dielectric fluids is an emerging technology which offers significant cooling energy savings and increased power densities for data centers. A noteworthy advantage of using immersion cooling is high heat dissipation capacity which is roughly 1200 times greater than air. Other advantages of dielectric fluid immersion cooling include high rack density, better server performance, even temperature profile, reduction in noise etc. The enhanced thermal properties of oil lead to the considerable savings in both upfront and operating cost over traditional methods. In this study, a server is completely submerged in a synthetic dielectric fluid. Experiments are conducted to observe the effects of varying the volumetric flow rate and oil inlet temperature on thermal performance and power consumption of the server. Various parameters like total server power consumption, the temperature of all heat generating components like Central Processing Unit (CPU), Dual in Line Memory Module (DIMM), input/output hub (IOH) chip, Platform Controller Hub (PCH), Network Interface Controller (NIC) are measured at steady state. Since this is an air-cooled server, the results obtained from the experiments will help in proposing better heat removal strategies like heat sink optimization, better ducting and server architecture. Assessment has been made on the effect of thermal shadowing caused by the two CPUs on the nearby components like DIMMs and PCH.

The Effects of Agitator Blade Geometry and Configuration for Augmenting Heat Transfer by Agitation in Channel Flows

2014 ◽  
Author(s):  
Smita Agrawal ◽  
Taiho Yeom ◽  
Youmin Yu ◽  
Mark North ◽  
Terrence Simon ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Exchanger ◽  
Kinetic Energy ◽  
Channel Wall ◽  
Power Input ◽  
Channel Inlet ◽  
Heat Transfer Augmentation ◽  
Enhancing Heat Transfer ◽  
Geometric Changes

Translationally oscillating blades, called agitators, can be used to thoroughly mix the flow inside heat exchanger channels such as those in an electronics module heat sink. Generally, throughflow is provided with an induction fan. Agitation is implemented inside the channel by using either multiple agitator blades, agitator blades with notched edges, full-length long-blade agitators or short-blade agitators. The power needed to drive the agitator blades is dependent on the agitation velocity, geometry and mass. The performance features of a 50mm long agitator blade operating at an oscillation frequency of 500Hz, a 15mm short agitator blade operating at a frequency of 1000Hz, and two blades of length 15mm operating at a frequency of 500 Hz have been compared. Also, runs with other geometric changes, like those with added notches at the tip of the agitator, are made to explore their benefits. The intent is that the notches generate additional vorticity at the channel inlet, which is convected downstream enhancing heat transfer as it passes. Thus, this study numerically finds directions toward optimal agitator configurations and geometries that would give heat transfer augmentation without excessive power input. It was found that a multiple agitator blade configuration containing two short blade agitators operating at frequency 500Hz gives the best performance in terms of heat transfer augmentation when power consumption is considered. Heat flux plots on the channel wall and turbulence kinetic energy plots within the channel have been used to explain the mechanisms of heat transfer augmentation for the various cases.

Interaction of Synthetic Jet Cooling Performance With Gravity and Buoyancy Driven Flows

2007 ◽  
Author(s):  
Mehmet Arik ◽  
Yogen Utturkar ◽  
Mustafa Gursoy
Keyword(s):  
Heat Transfer ◽  
Heat Dissipation ◽  
Cross Flow ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Jet Cooling ◽  
Impingement Heat Transfer ◽  
Buoyancy Driven Flows ◽  
Experimental Findings ◽  
Meso Scale

Meso scale cooling devices have been of interest for low form factor, tight space, and high COP thermal management problems. A candidate meso scale device, known as synthetic jets, operates with micro fluidic principles and disturbs the boundary layer causing significant heat transfer over conventional free convective heat transfer in air. Previous papers have dealt with the impingement and cross flow, but did not study mixed convection for synthetic jet with natural convection. In the present study, we discuss the results of an experimental study to investigate the interplay between jet orientations with respect to gravity, elevated temperature conditions, and synthetic jet heat dissipation capacity. Experiments were performed by placing synthetic at different positions around a square, 25.4mm heated flat surface. The flow physics behind the experimental findings is discussed. It is found that impingement heat transfer outperformed more than 30% compared to other orientations. The jet showed about 15% sensitivity to angular orientations.

Enhanced Pool Boiling With HFE7000 Over Selectively Sintered Microchannels

2017 ◽  
Author(s):  
Travis S. Emery ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Dissipation ◽  
Pool Boiling ◽  
Electronics Cooling ◽  
Fold Increase ◽  
High Heat ◽  
Heat Fluxes ◽  
Dielectric Fluid ◽  
Maximum Heat ◽  
Maximum Heat Transfer

As the need for efficient thermal management grows, pool boiling’s ability to dissipate high heat fluxes has gained significant interest. The objective of this work was to study the performance of pool boiling at atmospheric pressure using a dielectric fluid, HFE7000. Both plain and enhanced copper surfaces were tested, and these results were then compared to similar testing performed with water and FC-87. The enhanced surfaces utilized microchannels with porous coatings selectively located on different regions of the heat transfer surface. A maximum critical heat flux (CHF) of 41.7 W/cm2 was achieved here, which translated to a 29% CHF increase in comparison to a plain chip. A maximum heat transfer coefficient (HTC) of 104.0 kW/m2°C was also achieved, which translated to a 6-fold increase in HTC when compared to a plain copper chip. More notably, this HTC was achieved at a wall temperature of 38.4 °C. This HTC enhancement was greater than that of water and FC-87 when using the same enhanced surface. The effect of sintering location was found to have a similar effect on CHF with HFE7000 in comparison with water. The effect of microchannel size was shown to have similar effects on CHF when compared with FC-87 and water. From the results found here, it is concluded that the employment of selectively sintered open microchannels with HFE7000 has significant potential for enhanced heat dissipation in electronics cooling applications.

scholarly journals Hydrophilic and Hydrophobic Nanostructured Copper Surfaces for Efficient Pool Boiling Heat Transfer with Water, Water/Butanol Mixtures and Novec 649

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3216
Author(s):  
Matic Može ◽  
Viktor Vajc ◽  
Matevž Zupančič ◽  
Iztok Golobič
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Heat Dissipation ◽  
Pool Boiling ◽  
Chemical Oxidation ◽  
Dielectric Fluid ◽  
Surface Stability ◽  
Copper Surfaces ◽  
Functionalized Surfaces ◽  
Fluorinated Silane

Increasing heat dissipation requirements of small and miniature devices demands advanced cooling methods, such as application of immersion cooling via boiling heat transfer. In this study, functionalized copper surfaces for enhanced heat transfer are developed and evaluated. Samples are functionalized using a chemical oxidation treatment with subsequent hydrophobization of selected surfaces with a fluorinated silane. Pool boiling tests with water, water/1-butanol mixture with self-rewetting properties and a novel dielectric fluid with low GWP (Novec™ 649) are conducted to evaluate the boiling performance of individual surfaces. The results show that hydrophobized functionalized surfaces covered by microcavities with diameters between 40 nm and 2 µm exhibit increased heat transfer coefficient (HTC; enhancements up to 120%) and critical heat flux (CHF; enhancements up to 64%) values in comparison with the untreated reference surface, complemented by favorable fabrication repeatability. Positive surface stability is observed in contact with water, while both the self-rewetting fluids and Novec™ 649 gradually degrade the boiling performance and in some cases also the surface itself. The use of water/1-butanol mixtures in particular results in surface chemistry and morphology changes, as observed using SEM imaging and Raman spectroscopy. This seems to be neglected in the available literature and should be focused on in further studies.

Pool Boiling of HFE 7200–C4H4F6O Mixture on Hybrid Micro-Nanostructured Surface

2012 ◽  
Vol 3 (4) ◽  
Author(s):  
Aravind Sathyanarayana ◽  
Pramod Warrier ◽  
Yunhyeok Im ◽  
Yogendra Joshi ◽  
Amyn S. Teja
Keyword(s):  
Heat Transfer ◽  
Heat Dissipation ◽  
Molecular Design ◽  
Pool Boiling ◽  
Dielectric Constants ◽  
Heat Transfer Fluid ◽  
Fluid Mixture ◽  
Immersion Cooling ◽  
Direct Immersion Cooling ◽  
Direct Immersion

Steadily increasing heat dissipation in electronic devices has generated renewed interest in direct immersion cooling. The ideal heat transfer fluid for direct immersion cooling applications should be chemically and thermally stable, and compatible with the electronic components. These constraints have led to the use of Novec fluids and fluroinerts as coolants. Although these fluids are chemically stable and have low dielectric constants, they are plagued by poor thermal properties like low thermal conductivity (about twice that of air) and low specific heat (same as that of air). These factors necessitate the development of new heat transfer fluids with improved heat transfer properties and applicability. C4H4F6O is a new heat transfer fluid which has been identified using computer-aided molecular design (CAMD) and knowledge-based approaches. A mixture of Novec fluid (HFE 7200) with C4H4F6O is evaluated in this study. Pool boiling experiments are performed at saturated condition on a 10 mm × 10 mm silicon test chip with CuO nanostructures on a microgrooved surface, to investigate the thermal performance of this new fluid mixture. The mixture increased the critical heat flux moderately by 8.4% over pure HFE 7200. Additional investigation is necessary before C4H4F6O can be considered for immersion cooling applications.

scholarly journals Enhancement of heat transfer in a synthetic jet actuated by piston cylinder

2021 ◽  
Vol 13 (9) ◽  
pp. 168781402110491
Author(s):  
Arun Jacob ◽  
KA Shafi ◽  
KE Reby Roy
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Heat Dissipation ◽  
Flow Direction ◽  
Experimental Studies ◽  
Jet Impingement ◽  
Stokes Number ◽  
Synthetic Jet ◽  
Stroke Length

Modern electronics demand more powerful cooling systems due to an increase in heat dissipation. The traditional cooling techniques reached their limit and the synthetic jet impingement arises as a promising method for cooling of modern electronic systems. This paper presents the experimental studies on the heat transfer characteristics of a synthetic jet. The synthetic jet is driven by a piston actuator. The effects of dimensionless parameters like the distance between the orifice and heater plate (Z/D), the ratio of stroke length to diameter of orifice ( L/D), Stokes number, and Reynolds number are discussed. The effect of orifice geometry, number of orifices are also presented. The results indicate that the Z/D and Stokes number have a significant influence on the heat transfer rate. As the Stokes number increases the heat transfer increases due to an increase in axial momentum and turbulence in the flow direction. For circular orifice and at high Z/D, the L/D ratio should be higher for better heat transfer. Rectangular orifice performs better than square and circular geometries. When compared to single jet multiple jets have a higher heat transfer rate. Maximum and minimum values of normalized pressure ( Pnr) are achieved for high Stokes number and smaller areas of the orifice.

Piezoelectric Synthetic Jet Integrated With Heat Sink for Heat Transfer Enhancement

2013 ◽  
Author(s):  
Qiao Li ◽  
Longzhong Huang ◽  
Min Zhang ◽  
Mark T. North ◽  
Terrence Simon ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Carbon Fiber ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Ansys Fluent ◽  
Moving Wall ◽  
Enhancing Heat Transfer ◽  
Flow Through ◽  
Zero Net Mass Flux ◽  
Piezoelectric Stack Actuator

Synthetic jets, known as zero-net mass-flux (ZNMF) devices, have been widely used for cooling electronics. A synthetic jet is generally composed of a cavity with an orifice on one side and an oscillating diagram on the other side. The vibration of the diaphragm will generate a periodically impinging flow through the orifice which is found to be effective in enhancing heat transfer. The thermal performance of the synthetic jet is highly dependent on the peak velocity of the synthetic jet is able to generate. The orifice shape, orifice thickness, and the number of the orifices are the factors which affect the vibration condition of the diaphragm and thus to affect the performance of the synthetic jet. This study will use both experimental and computational methods to find out the optimal design of synthetic jet and how these factors affect synthetic jet performance. The synthetic jet arrays are driven by a piezoelectric stack actuator which is vibrating at around 720 Hz and the mean-to-peak amplitude is around 0.2 mm. The jet diaphragm (120 mm × 15 mm) is designed using a composite structure composed of a carbon fiber beam, a carbon fiber frame, and a jet frame fabricated by polymethyl methacrylate (PMMA). Four different orifice shapes (square, single slot, double slot, and triangle) with the same area have been designed and the square orifice has the highest velocity. The effect of the orifice thickness is also studied by testing four kinds of PMMA films with different thicknesses (1.5 mm, 2 mm, 3 mm, and 4.5 mm) and the case with 4.5 mm thick orifice has the best performance. The numerical simulation is conducted using the CFD software ANSYS Fluent to support the experimental results. The vibrating of the diaphragm is defined as a moving wall using a user defined function. The fluid power consumed by the diaphragm is used to determine the performances of different designs. The same trend with orifice thickness has been found and the reason has been demonstrated.

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