Two-Phase Convective Cooling for Ultrahigh Power Dissipation in Microprocessors

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Peter A. Kottke ◽  
Thomas M. Yun ◽  
Craig E. Green ◽  
Yogendra K. Joshi ◽  
Andrei G. Fedorov
Keyword(s):  
High Heat ◽  
Heat Fluxes ◽  
High Mass ◽  
Two Phase ◽  
Worst Case ◽  
Pressure Drops ◽  
System Pressure ◽  
Performance Trends ◽  
Wide Range ◽  
Contraction And Expansion

We present results of modeling for the design of microgaps for the removal of high heat fluxes via a strategy of high mass flux, high quality, and two-phase forced convection. Modeling includes (1) thermodynamic analysis to obtain performance trends across a wide range of candidate coolants, (2) evaluation of worst-case pressure drop due to contraction and expansion in inlet/outlet manifolds, and (3) 1D reduced-order simulations to obtain realistic estimates of different contributions to the pressure drops. The main result is the identification of a general trend of improved heat transfer performance at higher system pressure.

Effect of Rapid Steam Off-Take on Natural Circulation in Boilers

1969 ◽  
Vol 184 (3) ◽  
pp. 215-223
Author(s):  
H. C. Simpson ◽  
D. H. Rooney ◽  
T. M. S. Callander
Keyword(s):  
Gamma Ray ◽  
Natural Circulation ◽  
Sudden Change ◽  
Heat Fluxes ◽  
Two Phase ◽  
Flow Area ◽  
Pressure Drops ◽  
Flow Models ◽  
System Pressure ◽  
Type Flow

This paper describes investigations into the effect of a sudden change in system pressure, caused by rapid steam off-take, on a natural circulation loop. The work was carried out on a two-tube experimental boiler with a water drum connecting the bottom of the riser and downcomer tubes, which were respectively 2 in o.d. x 9 s.w.g. and 11/4 in o.d. x 6 s.w.g., giving a riser to downcomer flow area ratio of 3·9. The experimental range covered starting pressures of 1000, 800, 650, and 500 lbf/in2 (gauge), with pressure drops of 100 lbf/in2 at rates ranging from 1 to 34·5 lbf/in2 s. Heat fluxes to the riser tube ranged from 21 000 to 136 000 Btu/h ft2 and initial mass velocities from 0·70 to 1·11 million lb/h ft2 in the downcomer tube. During the transients, continuous recordings were taken of system pressure, circulation, pressure difference, and fluid density at a point in both the riser and the downcomer tube, using the gamma-ray attenuation method. The system behaviour was analysed theoretically by setting up the appropriate two-phase conservation equations and solving them using (1) a finite difference method, (2) a stepwise solution on the basis of quasi-steady flow. The first method was eventually discarded in favour of the second. The theoretical flow models considered in the analysis include a vapour core annular type flow in the riser, and a homogeneous type flow in the downcomer, during the transient. The theoretical results are compared with the experimental data.

scholarly journals Study of Pressure Drops and Heat Transfer of Nonequilibrial Two-Phase Flows

Water ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 2275
Author(s):  
Aleksandr V. Belyaev ◽  
Alexey V. Dedov ◽  
Ilya I. Krapivin ◽  
Aleksander N. Varava ◽  
Peixue Jiang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Flow Regime ◽  
Flow Boiling ◽  
Experimental Studies ◽  
High Mass ◽  
Calculation Methods ◽  
Two Phase Flows ◽  
Two Phase ◽  
Pressure Drops ◽  
Wide Range

Currently, there are no universal methods for calculating the heat transfer and pressure drop for a wide range of two-phase flow parameters in mini-channels due to changes in the void fraction and flow regime. Many experimental studies have been carried out, and narrow-range calculation methods have been developed. With increasing pressure, it becomes possible to expand the range of parameters for applying reliable calculation methods as a result of changes in the flow regime. This paper provides an overview of methods for calculating the pressure drops and heat transfer of two-phase flows in small-diameter channels and presents a comparison of calculation methods. For conditions of high reduced pressures pr = p/pcr ≈ 0.4 ÷ 0.6, the results of own experimental studies of pressure drops and flow boiling heat transfer of freons in the region of low and high mass flow rates (G = 200–2000 kg/m2 s) are presented. A description of the experimental stand is given, and a comparison of own experimental data with those obtained using the most reliable calculated relations is carried out.

Analytical Model Quantifying the Net Coolant Flow Rate to a Microstructured Copper Surface validated with Two-Phase PIV Measurements

2021 ◽  
Author(s):  
Matt Harrison ◽  
Joshua Gess
Keyword(s):  
Heat Transfer ◽  
Analytical Model ◽  
Flow Rate ◽  
Circular Disk ◽  
Nucleate Boiling ◽  
High Heat ◽  
Heat Fluxes ◽  
Coolant Flow ◽  
Coolant Flow Rate ◽  
Two Phase

Abstract Using Particle Image Velocimetry (PIV), the amount of fluid required to sustain nucleate boiling was quantified to a microstructured copper circular disk. Having prepared the disk with preferential nucleation sites, an analytical model of the net coolant flow rate requirements to a single site has been produced and validated against experimental data. The model assumes that there are three primary phenomena contributing to the coolant flow rate requirements at the boiling surface; radial growth of vapor throughout incipience to departure, bubble rise, and natural convection around the periphery. The total mass flowrate is the sum of these contributing portions. The model accurately predicts the quenching fluid flow rate at low and high heat fluxes with 4% and 30% error of the measured value respectively. For the microstructured surface examined in this study, coolant flow rate requirements ranged from 0.1 to 0.16 kg/sec for a range of heat fluxes from 5.5 to 11.0 W/cm2. Under subcooled conditions, the coolant flow rate requirements plummeted to a nearly negligible value due to domination of transient conduction as the primary heat transfer mechanism at the liquid/vapor/surface interface. PIV and the validated analytical model could be used as a test standard where the amount of coolant the surface needs in relation to its heat transfer coefficient or thermal resistance is a benchmark for the efficacy of a standard surface or boiling enhancement coating/surface structure.

High Heat Flux Subcooled Flow Boiling of Methanol in Microtubes

2015 ◽  
Author(s):  
Farzad Houshmand ◽  
Hyoungsoon Lee ◽  
Mehdi Asheghi ◽  
Kenneth E. Goodson
Keyword(s):  
Heat Flux ◽  
Pressure Drop ◽  
Flow Boiling ◽  
High Heat ◽  
Heat Fluxes ◽  
Two Phase ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow ◽  
Inner Diameter ◽  
Phase Pressure

As the proper cooling of the electronic devices leads to significant increase in the performance, two-phase heat transfer to dielectric liquids can be of an interest especially for thermal management solutions for high power density devices with extremely high heat fluxes. In this paper, the pressure drop and critical heat flux (CHF) for subcooled flow boiling of methanol at high heat fluxes exceeding 1 kW/cm2 is investigated. Methanol was propelled into microtubes (ID = 265 and 150 μm) at flow rates up to 40 ml/min (mass fluxes approaching 10000 kg/m2-s), boiled in a portion of the microtube by passing DC current through the walls, and the two-phase pressure drop and CHF were measured for a range of operating parameters. The two-phase pressure drop for subcooled flow boiling was found to be significantly lower than the saturated flow boiling case, which can lead to lower pumping powers and more stability in the cooling systems. CHF was found to be increasing almost linearly with Re and inverse of inner diameter (1/ID), while for a given inner diameter, it decreases with increasing heated length.

scholarly journals On the transition between turbulence regimes in particle-laden channel flows

2018 ◽  
Vol 845 ◽  
pp. 499-519 ◽  
Author(s):  
Jesse Capecelatro ◽  
Olivier Desjardins ◽  
Rodney O. Fox
Keyword(s):  
Reynolds Number ◽  
Fluid Phase ◽  
Stokes Number ◽  
Channel Flows ◽  
High Mass ◽  
Inertial Particles ◽  
Mass Loading ◽  
Two Phase ◽  
Phase Dynamics ◽  
Wide Range

Turbulent wall-bounded flows exhibit a wide range of regimes with significant interaction between scales. The fluid dynamics associated with single-phase channel flows is predominantly characterized by the Reynolds number. Meanwhile, vastly different behaviour exists in particle-laden channel flows, even at a fixed Reynolds number. Vertical turbulent channel flows seeded with a low concentration of inertial particles are known to exhibit segregation in the particle distribution without significant modification to the underlying turbulent kinetic energy (TKE). At moderate (but still low) concentrations, enhancement or attenuation of fluid-phase TKE results from increased dissipation and wakes past individual particles. Recent studies have shown that denser suspensions significantly alter the two-phase dynamics, where the majority of TKE is generated by interphase coupling (i.e.  drag) between the carrier gas and clusters of particles that fall near the channel wall. In the present study, a series of simulations of vertical particle-laden channel flows with increasing mass loading is conducted to analyse the transition from the dilute limit where classical mean-shear production is primarily responsible for generating fluid-phase TKE to high-mass-loading suspensions dominated by drag production. Eulerian–Lagrangian simulations are performed for a wide range of particle loadings at two values of the Stokes number, and the corresponding two-phase energy balances are reported to identify the mechanisms responsible for the observed transition.

Experimental Validation and Design Simulations of a Passive Two-Phase Cooling System for Datacenters

2020 ◽  
Author(s):  
Jackson B. Marcinichen ◽  
John R. Thome ◽  
Raffaele L. Amalfi ◽  
Filippo Cataldo
Keyword(s):  
Thermal Performance ◽  
Experimental Validation ◽  
Cooling System ◽  
Electronics Cooling ◽  
Operating Conditions ◽  
Two Phase ◽  
Data Set ◽  
Pressure Drops ◽  
Wide Range ◽  
Important Challenge

Abstract Thermosyphon cooling systems represent the future of datacenter cooling, and electronics cooling in general, as they provide high thermal performance, reliability and energy efficiency, as well as capture the heat at high temperatures suitable for many heat reuse applications. On the other hand, the design of passive two-phase thermosyphons is extremely challenging because of the complex physics involved in the boiling and condensation processes; in particular, the most important challenge is to accurately predict the flow rate in the thermosyphon and thus the thermal performance. This paper presents an experimental validation to assess the predictive capabilities of JJ Cooling Innovation’s thermosyphon simulator against one independent data set that includes a wide range of operating conditions and system sizes, i.e. thermosyphon data for server-level cooling gathered at Nokia Bell Labs. Comparison between test data and simulated results show good agreement, confirming that the simulator accurately predicts heat transfer performance and pressure drops in each individual component of a thermosyphon cooling system (cold plate, riser, evaporator, downcomer (with no fitting parameters), and eventually a liquid accumulator) coupled with operational characteristics and flow regimes. In addition, the simulator is able to design a single loop thermosyphon (e.g. for cooling a single server’s processor), as shown in this study, but also able to model more complex cooling architectures, where many thermosyphons at server-level and rack-level have to operate in parallel (e.g. for cooling an entire server rack). This task will be performed as future work.

Spatial and Temporal Wall Temperature Fluctuations in Two-Phase Flow in Microgap Coolers

2010 ◽  
Author(s):  
Jessica Sheehan ◽  
Avram Bar-Cohen
Keyword(s):  
Heat Transfer ◽  
High Heat ◽  
Heat Fluxes ◽  
Operating Conditions ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Heat Transfer Coefficients ◽  
High Heat Transfer ◽  
Volumetric Cooling ◽  
Very High

Heat transfer to an evaporating refrigerant and/or dielectric liquid in a microgap channel can provide very high heat transfer coefficients and volumetric cooling rates. Recent studies at Maryland have established the dominance of the annular flow regime in such microgap channels and related the observed high-quality peak of an M-shaped heat transfer coefficient curve to the onset of local dryout. The present study utilizes infrared thermography to locate such nascent dryout regions and operating conditions. Data obtained with a 210 micron microgap channel, operated with a mass flux of 195.2 kg/m2-s and heat fluxes of 10.3 to 26 W/cm2 are presented and discussed.

A Review of Two-Phase Forced Cooling in Three-Dimensional Stacked Electronics: Technology Integration

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Craig Green ◽  
Peter Kottke ◽  
Xuefei Han ◽  
Casey Woodrum ◽  
Thomas Sarvey ◽  
...  
Keyword(s):  
Heat Flux ◽  
Heat Sink ◽  
Three Dimensional ◽  
High Heat ◽  
Heat Fluxes ◽  
Thermal Design ◽  
High Heat Flux ◽  
Two Phase ◽  
Forced Cooling ◽  
Fluidic Routing

Three-dimensional (3D) stacked electronics present significant advantages from an electrical design perspective, ranging from shorter interconnect lengths to enabling heterogeneous integration. However, multitier stacking exacerbates an already difficult thermal problem. Localized hotspots within individual tiers can provide an additional challenge when the high heat flux region is buried within the stack. Numerous investigations have been launched in the previous decade seeking to develop cooling solutions that can be integrated within the 3D stack, allowing the cooling to scale with the number of tiers in the system. Two-phase cooling is of particular interest, because the associated reduced flow rates may allow reduction in pumping power, and the saturated temperature condition of the coolant may offer enhanced device temperature uniformity. This paper presents a review of the advances in two-phase forced cooling in the past decade, with a focus on the challenges of integrating the technology in high heat flux 3D systems. A holistic approach is applied, considering not only the thermal performance of standalone cooling strategies but also coolant selection, fluidic routing, packaging, and system reliability. Finally, a cohesive approach to thermal design of an evaporative cooling based heat sink developed by the authors is presented, taking into account all of the integration considerations discussed previously. The thermal design seeks to achieve the dissipation of very large (in excess of 500 W/cm2) background heat fluxes over a large 1 cm × 1 cm chip area, as well as extreme (in excess of 2 kW/cm2) hotspot heat fluxes over small 200 μm × 200 μm areas, employing a hybrid design strategy that combines a micropin–fin heat sink for background cooling as well as localized, ultrathin microgaps for hotspot cooling.

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.

High heat flux flow boiling in silicon multi-microchannels – Part III: Saturated critical heat flux of R236fa and two-phase pressure drops

2008 ◽  
Vol 51 (21-22) ◽  
pp. 5426-5442 ◽  
Author(s):  
Bruno Agostini ◽  
Rémi Revellin ◽  
John Richard Thome ◽  
Matteo Fabbri ◽  
Bruno Michel ◽  
...  
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
High Heat ◽  
High Heat Flux ◽  
Two Phase ◽  
Flux Flow ◽  
Pressure Drops ◽  
Phase Pressure
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