Direct Liquid Cooling of High Flux Micro and Nano Electronic Components
25 Sep 2006-Vol. 94, Iss: 8, pp 1549-1570
TL;DR: This paper begins with a discussion of the thermophysics of phase-change processes and a description of the available dielectric liquid cooling techniques and their history, and describes the phenomenology of pool boiling, spray/jet impingements, gas-assisted evaporation, and synthetic jet impingement with dielectrics liquids.
Abstract: The inexorable rise in chip power dissipation and emergence of on-chip hot spots with heat fluxes approaching 1 =kW/cm2 has turned renewed attention to direct cooling with dielectric liquids. Use of dielectric liquids in intimate contact with the heat dissipating surfaces eliminates the deleterious effects of solid-solid interface resistances and harnesses the highly efficient phase-change processes to the critical thermal management of advanced IC chips. In the interest of defining the state-of-the-art in direct liquid cooling, this paper begins with a discussion of the thermophysics of phase-change processes and a description of the available dielectric liquid cooling techniques and their history. It then describes the phenomenology of pool boiling, spray/jet impingement, gas-assisted evaporation, and synthetic jet impingement with dielectric liquids. Available correlations for predicting the heat transfer coefficients and limiting heat transfer rates, as well as documented empirical results for these promising techniques for on-chip hot spot cooling, are also provided and compared
Citations
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TL;DR: In this article, a review of spray cooling is presented, focusing on the relatively high-flux, low-temperature mechanisms and predictive tools associated with the single-phase liquid cooling and nucleate boiling regimes, as well as critical heat flux (CHF).
346 citations
Cites background from "Direct Liquid Cooling of High Flux ..."
...[25] addressing pool boiling, spray/jet impingement, gas-assisted evaporation, and synthetic jet impingement with dielectric liquids....
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01 Dec 2014
TL;DR: In this paper, the authors make the argument that optimum surfaces need to address the specificities of phase change heat transfer in the way that a key matches its lock, which calls for the design and fabrication of adaptive surfaces with multiscale textures and non-uniform wettability.
Abstract: Owing to advances in micro- and nanofabrication methods over the last two decades, the degree of sophistication with which solid surfaces can be engineered today has caused a resurgence of interest in the topic of engineering surfaces for phase change heat transfer. This review aims at bridging the gap between the material sciences and heat transfer communities. It makes the argument that optimum surfaces need to address the specificities of phase change heat transfer in the way that a key matches its lock. This calls for the design and fabrication of adaptive surfaces with multiscale textures and non-uniform wettability. Among numerous challenges to meet the rising global energy demand in a sustainable manner, improving phase change heat transfer has been at the forefront of engineering research for decades. The high heat transfer rates associated with phase change heat transfer are essential to energy and industry applications; but phase change is also inherently associated with poor thermodynamic efficiency at low heat flux, and violent instabilities at high heat flux. Engineers have tried since the 1930s to fabricate solid surfaces that improve phase change heat transfer. The development of micro and nanotechnologies has made feasible the high-resolution control of surface texture and chemistry over length scales ranging from molecular levels to centimeters. This paper reviews the fabrication techniques available for metallic and silicon-based surfaces, considering sintered and polymeric coatings. The influence of such surfaces in multiphase processes of high practical interest, e.g., boiling, condensation, freezing, and the associated physical phenomena are reviewed. The case is made that while engineers are in principle able to manufacture surfaces with optimum nucleation or thermofluid transport characteristics, more theoretical and experimental efforts are needed to guide the design and cost-effective fabrication of surfaces that not only satisfy the existing technological needs, but also catalyze new discoveries.
287 citations
TL;DR: In this article, the state-of-the-art of multi-level thermal management techniques for both air- and liquid-cooled data centers is reviewed. But the main focus is on the sources of inefficiencies and the improvement methods with their configuration features and performances at each level.
272 citations
235 citations
TL;DR: A review of small heat pipes, including their design, analysis, and fabrication, is presented in this article, where the authors also discuss the potential of nano-wicks, such as carbon nanotubes (CNTs), to represent the future of heat pipes.
205 citations
Cites background from "Direct Liquid Cooling of High Flux ..."
...Proprieties of possible working fluids for HPs to cool electronics [126-128]....
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...most engineering surfaces and relatively low critical pressures, thermal conductivities, and specific heats, but air solubilities approaching 50% by volume, some 25 times higher than in water [124-126]....
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References
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TL;DR: In this paper, a water-cooled integral heat sink for silicon integrated circuits has been designed and tested at a power density of 790 W/cm2, with a maximum substrate temperature rise of 71°C above the input water temperature.
Abstract: The problem of achieving compact, high-performance forced liquid cooling of planar integrated circuits has been investigated. The convective heat-transfer coefficient h between the substrate and the coolant was found to be the primary impediment to achieving low thermal resistance. For laminar flow in confined channels, h scales inversely with channel width, making microscopic channels desirable. The coolant viscosity determines the minimum practical channel width. The use of high-aspect ratio channels to increase surface area will, to an extent, further reduce thermal resistance. Based on these considerations, a new, very compact, water-cooled integral heat sink for silicon integrated circuits has been designed and tested. At a power density of 790 W/cm2, a maximum substrate temperature rise of 71°C above the input water temperature was measured, in good agreement with theory. By allowing such high power densities, the heat sink may greatly enhance the feasibility of ultrahigh-speed VLSI circuits.
4,214 citations
"Direct Liquid Cooling of High Flux ..." refers background in this paper
...To overcome this limitation, attention was directed to the enormous promise of direct liquid cooling, both in the form of miniaturized, compact heat exchangers, or microchannels, etched into the silicon chips [ 7 ] and immersion of bare chips in dielectric liquids, as well as the impingement of these liquids on the chip surfaces [8], [9]....
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TL;DR: In this article, the authors present a comprehensive survey emphasizing the engineering applications and empirical equations, presented for the prediction of heat and mass transfer coefficients within a large and technologically important range of variables.
Abstract: Publisher Summary Heating or cooling of large surface area products is often carried out in devices consisting of arrays of round or slot nozzles, through which air impinges vertically upon the product surface. This chapter presents a comprehensive survey emphasizing the engineering applications and empirical equations, presented for the prediction of heat and mass transfer coefficients within a large and technologically important range of variables. The local variations of the transfer coefficients are based on the experimental data for single round nozzles (SRN), arrays of round nozzles (ARN), single slot nozzles (SSN), and arrays of slot nozzles (ASN). The variation of local transfer coefficients is graphically represented. It also explores how to apply these equations in heat exchanger and dryer design as well as in optimization. The flow field of impinging flow is diagrammatically represented. External variables influencing heat and mass transfer in impinging flow depends on mass flow rate, kind and state of the gas and on the shape, size, and position of the nozzles relative to each other and to the solid surface. The design of high-performance arrays of nozzles is also discussed.
1,548 citations
"Direct Liquid Cooling of High Flux ..." refers background or methods in this paper
...Convective Single-Jet Impingement: One of the most widely used correlations for the average Nusselt number in a single-jet impingement is due to Martin and takes the following form [ 49 ]:...
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...The range of validity for this correlation, developed from extensive gas jet data, as well as some data for water and other higher Pr number liquids, and including some high Schmidt number mass transfer data, is given by Martin [ 49 ] as: 2 � 103 � Red � 105 ,0 :6 G PrðScÞ G...
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...Consequently, the optimum distance, yielding the highest heat transfer rates, can be expressed as a function of the relative nozzle area � J and is empirically found as [ 49 ]...
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01 Jan 1951
1,114 citations
TL;DR: In this paper, the collision dynamics of a liquid droplet on a solid metallic surface were studied using a flash photographic method, which provided clear images of the droplet structure during the deformation process.
Abstract: The collision dynamics of a liquid droplet on a solid metallic surface were studied using a flash photographic method. The intent was to provide clear images of the droplet structure during the deformation process. The ambient pressure (0.101 MPa), surface material (polished stainless steel), initial droplet diameter (about 1.5 mm), liquid (n-heptane) and impact Weber number (43) were fixed. The primary parameter was the surface temperature, which ranged from 24 degrees C to above the Leidenfrost temperature of the liquid. Experiments were also performed on a droplet impacting a surface on which there existed a liquid film created by deposition of a prior droplet. The evolution of wetted area and spreading rate, both of a droplet on a stainless steel surface and of a droplet spreading over a thin liquid film, were found to be independent of surface temperature during the early period of impact. This result was attributed to negligible surface tension and viscous effects, and in consequence the measurements made during the early period of the impact process were in good agreement with previously published analyses which neglected these effects. A single bubble was observed to form within the droplet during impact at low temperatures. As surface temperature was increased the population of bubbles within the droplet also increased because of progressive activation of nucleation sites on the stainless steel surface. At surface temperatures near to the boiling point of heptane, a spoke-like cellular structure in the liquid was created during the spreading process by coalescence of a ring of bubbles that had formed within the droplet. At higher temperatures, but below the Leidenfrost point, numerous bubbles appeared within the droplet, yet the overall droplet shape, particularly in the early stages of impact (< 0.8 ms), was unaffected by the presence of these bubbles. The maximum value of the diameter of liquid which spreads on the surface is shown to agree with predictions from a simplified model.
1,032 citations
"Direct Liquid Cooling of High Flux ..." refers background in this paper
...The influence of surface temperature on droplet impact dynamics was investigated in a comprehensive photographic study [ 72 ]....
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TL;DR: In this article, the authors derived a correlation for the Nusselt number of the form suggested by this evidence using a selection of the data and showed that this exponent should be a function of nozzle-to-plate spacing and of the radial displacement from the stagnation point.
1,030 citations
"Direct Liquid Cooling of High Flux ..." refers background in this paper
...Many studies have dealt with the heat transfer characteristics and performance limits of impinging jets for both single-phase [ 38 ], [39] and two-phase [40] thermal transport....
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