Performance and Integration Implications of Addressing Localized Hotspots Through Two Approaches: Clustering of Micro Pin-Fins and Dedicated Microgap Coolers

2015 ◽  
Author(s):  
Craig E. Green ◽  
Peter A. Kottke ◽  
Thomas E. Sarvey ◽  
Andrei G. Fedorov ◽  
Yogendra Joshi ◽  
...  
Keyword(s):  
Numerical Modeling ◽  
Heat Fluxes ◽  
Thermal Design ◽  
System Level ◽  
Two Phase ◽  
Minimal Impact ◽  
Pressure Drops ◽  
Pin Fins ◽  
Effective Heat Transfer Coefficient ◽  
Fluidic Routing

An evaluation of two approaches to localized hotspot cooling is conducted through both numerical modeling and experimental demonstration, with the advantages and limitations of each approach highlighted. The first approach, locally increasing the density of pins in a micro pin fin heat sink, was shown through numerical modeling to deliver a factor of two enhancement in effective heat transfer coefficient by doubling the pin density near the hotspot. This simpler approach to maintaining temperature uniformity eliminates the need for hotspot specific fluid routing and delivery, and also has minimal impact on the larger flow field. Dedicated hotspot coolers, on the other hand, have the ability to dissipate significantly larger heat fluxes while maintaining manageable pressure drops, because the flow rate to the dedicated cooler can be closely matched to the demands of the hotspot. Dissipation of hotspot heat fluxes in excess of 2 kW/cm2 is demonstrated experimentally using a two phase dedicated hotspot cooler. However, dedicated coolers require additional fluidic routing and manifolding to efficiently deliver the coolant to the hotspot. These integration concerns are considered in concert with the performance of the hotspot cooler itself to enable better informed thermal design for both system level and device level cooling.

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.

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.

Thermal Design of a Hierarchical Radially Expanding Cavity for Two-Phase Cooling of Integrated Circuits

2015 ◽  
Author(s):  
Arvind Sridhar ◽  
Chin Lee Ong ◽  
Stefan Paredes ◽  
Bruno Michel ◽  
Thomas Brunschwiler ◽  
...  
Keyword(s):  
Design Process ◽  
Thermal Model ◽  
Thermal Design ◽  
Design Flow ◽  
Qualitative Description ◽  
System Level ◽  
Two Phase ◽  
Ongoing Research ◽  
Level Pressure ◽  
Phase Liquid

A major challenge in the implementation of evaporative two-phase liquid-cooled ICs with embedded fluid microchannels/cavities is the high pressure drops arising from evaporation-induced expansion and acceleration of the flowing two-phase fluid in small hydraulic diameters. Our ongoing research effort addresses this challenge by utilizing a novel hierarchical radially expanding channel networks with a central embedded inlet manifold and drainage at the periphery of the chip stack. This paper presents a qualitative description of the thermal design process that has been adopted for this radial cavity. The thermal design process first involves construction of a system-level pressure-thermal model for the radial cavity based on both fundamental experiments as well as numerical simulations performed on the building block structures of the final architecture. Finally, this system-level pressure-thermal model can be used to identify the design space and optimize the geometry to maximize thermal performance, while respecting design specifications. This design flow presents a good case study for electrical-thermal co-design of two-phase liquid cooled ICs.

Recent Advances in Thermal Modeling of Micro-Evaporators for Cooling of Microprocessors

2007 ◽  
Author(s):  
John R. Thome ◽  
Re´mi Revellin ◽  
Bruno Agostini ◽  
Jung Eung Park
Keyword(s):  
Flow Pattern ◽  
Hot Spots ◽  
Bubble Dynamics ◽  
Flow Boiling ◽  
Heat Fluxes ◽  
Base Temperature ◽  
Two Phase ◽  
Pressure Drops ◽  
Flow Boiling Heat Transfer ◽  
Recent Experimental Work

Cooling of microprocessors using flow boiling of low pressure refrigerants in multi-microchannel evaporator cooling elements is a promising technique for dissipation of footprint heat fluxes of over 300 W/cm2 while maintaining the chip safely below its maximum working temperature, providing a nearly uniform chip base temperature and minimizing energy consumption. The present invited lecture focuses on our recent experimental work and modeling of two-phase flow and boiling in single and multi-microchannels, covering: bubble dynamics, bubble coalescence, flow pattern recognition, diabatic flow pattern map, critical heat flux, hot spots, flow boiling heat transfer and two-phase pressure drops.

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.

Forced Convection Heat Transfer Enhancement by Porous Pin Fins in Rectangular Channels

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Jian Yang ◽  
Min Zeng ◽  
Qiuwang Wang ◽  
Akira Nakayama
Keyword(s):  
Heat Transfer ◽  
Three Dimensional ◽  
Convection Heat Transfer ◽  
Heat Fluxes ◽  
Physical Parameters ◽  
Pore Density ◽  
Pressure Drops ◽  
Pin Fin ◽  
Rectangular Channels ◽  
Pin Fins

The forced convective heat transfer in three-dimensional porous pin fin channels is numerically studied in this paper. The Forchheimer–Brinkman extended Darcy model and two-equation energy model are adopted to describe the flow and heat transfer in porous media. Air and water are employed as the cold fluids and the effects of Reynolds number (Re), pore density (PPI) and pin fin form are studied in detail. The results show that, with proper selection of physical parameters, significant heat transfer enhancements and pressure drop reductions can be achieved simultaneously with porous pin fins and the overall heat transfer performances in porous pin fin channels are much better than those in traditional solid pin fin channels. The effects of pore density are significant. As PPI increases, the pressure drops and heat fluxes in porous pin fin channels increase while the overall heat transfer efficiencies decrease and the maximal overall heat transfer efficiencies are obtained at PPI=20 for both air and water cases. Furthermore, the effects of pin fin form are also remarkable. With the same physical parameters, the overall heat transfer efficiencies in the long elliptic porous pin fin channels are the highest while they are the lowest in the short elliptic porous pin fin channels.

Visualization of Two-Phase Flow in Serpentine Heat Exchanger Passages With Microscale Pin Fins

2016 ◽  
Author(s):  
Dhruv C. Hoysall ◽  
Khoudor Keniar ◽  
Srinivas Garimella
Keyword(s):  
Two Phase Flow ◽  
Flow Regimes ◽  
High Heat ◽  
Phase Flow ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Pressure Drops ◽  
Heat Transfer Coefficients ◽  
High Heat Transfer ◽  
Pin Fins

Multiphase flow phenomena in single micro- and minichannels have been widely studied. Microchannel heat exchangers offer the potential for high heat transfer coefficients; however, implementation challenges must be addressed to realize this potential. Maldistribution of phases among the microchannels in the array and the changing phase velocities associated phase change present design challenges. Flow maldistribution and oscillatory instabilities can severely affect heat and mass transfer rates as well as pressure drops. In components such as condensers, evaporators, absorbers and desorbers, changing phase velocities can change prevailing flow regimes from favorable to unfavorable. Geometries with serpentine passages containing pin fins can be configured to maintain favorable flow regimes throughout the length of the component for diabatic phase-change heat and mass transfer applications. Due to the possibility of continuous redistribution of the flow across the pin fins along the flow direction, maldistribution can also be reduced. These features enable the potential of high heat transfer coefficients in microscale passages to be fully realized, thereby reducing the required transfer area, and achieving considerable compactness. The characteristics of two-phase flow through a serpentine passage with micro-pin fin arrays with diameters 350 μm and height 406 μm are investigated here. An air-water mixture is used to represent two-phase flow through the serpentine test section, and a variety of flow features are visually investigated using high-speed photography. Improved flow distribution is observed in the serpentine geometry. Distinct flow regimes, different from those observed in microchannels are also established. These observations are used to obtain void fraction and interfacial area along the length of the serpentine passages and compared with the corresponding values for straight microchannels. Models for the two-phase frictional pressure drops across this geometry are also developed.

scholarly journals Visualization of Two-Phase Flow in Serpentine Heat Exchanger Passages With Microscale Pin Fins

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Dhruv C. Hoysall ◽  
Khoudor Keniar ◽  
Srinivas Garimella
Keyword(s):  
Two Phase Flow ◽  
Flow Regimes ◽  
High Heat ◽  
Phase Flow ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Pressure Drops ◽  
Pin Fin ◽  
High Heat Transfer ◽  
Pin Fins

Microchannel heat exchangers offer the potential for high heat transfer coefficients; however, implementation challenges must be addressed to realize this potential. Maldistribution of phases among the microchannels and the changing phase velocities associated with phase change present design challenges. Flow maldistribution and oscillatory instabilities can affect transfer rates and pressure drops. In condensers, evaporators, absorbers, and desorbers, changing phase velocities can change prevailing flow regimes from favorable to unfavorable. Geometries with serpentine passages containing pin fins can be configured to maintain favorable flow regimes throughout the component for phase-change heat and mass transfer applications. Due to the possibility of continuous redistribution of the flow across the pin fins along the flow direction, maldistribution can also be reduced. These features enable high heat transfer coefficients, thereby achieving considerable compactness. The characteristics of two-phase flow through a serpentine passage with micro-pin fin arrays with diameter 350 μm and height 406 μm are investigated. An air–water mixture is used to represent two-phase flow through the serpentine test section, and flow features are investigated using high-speed photography. Improved flow distribution is observed in the serpentine geometry. Distinct flow regimes, different from those observed in microchannels, are also established. Void fraction and interfacial area along the length of the serpentine passages are compared with the corresponding values for microchannels. A model developed for the two-phase frictional pressure drops across this serpentine micro-pin fin geometry predicts experimental values with a mean absolute error (MAE) of 7.16%.

A Comparative Study of Flow Boiling in a Microchannel With Piranha Pin Fins

2016 ◽  
Vol 138 (11) ◽  
Author(s):  
X. Yu ◽  
C. Woodcock ◽  
Y. Wang ◽  
J. Plawsky ◽  
Y. Peles
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Flow Boiling ◽  
High Heat ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Flow Conditions ◽  
Pressure Drops ◽  
Flow And Heat Transfer ◽  
Pin Fins

In this paper, we report on the recent development of an advanced microscale heat sink, termed as piranha pin fin (PPF). A 200 μm deep microchannel embedded with PPFs was fabricated and tested. Fluid flow and heat transfer performance were evaluated with HFE7000 as the working fluid. The surface temperature, pressure drop, heat transfer coefficient, and critical heat flux (CHF) conditions were experimentally obtained and discussed. A 676 W/cm2 CHF was achieved based on the heater area and at an inlet mass flux of 2460 kg/m2 s. Microchannels with different PPF configurations were investigated and studied for different flow conditions. It was found that a microchannel with PPFs can dissipate high heat fluxes with reasonable pressure drops. Flow conditions and PPF configuration played important roles for both fluid flow and heat transfer performances. These studies extended knowledge and provided useful reference for further PPF design in microchannel for flow boiling.

Two-Phase Liquid Cooling for Thermal Management of IGBT Power Electronic Module

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
Peng Wang ◽  
Patrick McCluskey ◽  
Avram Bar-Cohen
Keyword(s):  
Power Electronics ◽  
Thermal Management ◽  
Single Phase ◽  
Heat Dissipation ◽  
Heat Fluxes ◽  
System Level ◽  
Cooling Power ◽  
Cold Plate ◽  
Two Phase ◽  
Cold Plates

Recent trends including rapid increases in the power ratings and continued miniaturization of semiconductor devices have pushed the heat dissipation of power electronics well beyond the range of conventional thermal management solutions, making control of device temperature a critical issue in the thermal packaging of power electronics. Although evaporative cooling is capable of removing very high heat fluxes, two-phase cold plates have received little attention for cooling power electronics modules. In this work, device-level analytical modeling and system-level thermal simulation are used to examine and compare single-phase and two-phase cold plates for a specified inverter module, consisting of 12 pairs of silicon insulated gate bipolar transistor (IGBT) devices and diodes. For the conditions studied, an R134a-cooled, two-phase cold plate is found to substantially reduce the maximum IGBT temperature and spatial temperature variation, as well as reduce the pumping power and flow rate, in comparison to a conventional single-phase water-cooled cold plate. These results suggest that two-phase cold plates can be used to substantially improve the performance, reliability, and conversion efficiency of power electronics systems.

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