Thermal Analysis of Cold Plate for Direct Liquid Cooling of High Performance Servers

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Bharath Ramakrishnan ◽  
Yaser Hadad ◽  
Sami Alkharabsheh ◽  
Paul R. Chiarot ◽  
Bahgat Sammakia
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Thermal Resistance ◽  
High Heat ◽  
High Heat Flux ◽  
Cold Plate ◽  
Liquid Cooling ◽  
Maximum Heat ◽  
Effective Heat ◽  
Cold Plates

Data center energy usage keeps growing every year and will continue to increase with rising demand for ecommerce, scientific research, social networking, and use of streaming video services. The miniaturization of microelectronic devices and an increasing demand for clock speed result in high heat flux systems. By adopting direct liquid cooling, the high heat flux and high power demands can be met, while the reliability of the electronic devices is greatly improved. Cold plates which are mounted directly on to the chips facilitate a lower thermal resistance path originating from the chip to the incoming coolant. An attempt was made in the current study to characterize a commercially available cold plate which uses warm water in carrying the heat away from the chip. A mock package mimicking a processor chip with an effective heat transfer area of 6.45 cm2 was developed for this study using a copper block heater arrangement. The thermo-hydraulic performance of the cold plates was investigated by conducting experiments at varying chip power, coolant flow rates, and coolant temperature. The pressure drop (ΔP) and the temperature rise (ΔT) across the cold plates were measured, and the results were presented as flow resistance and thermal resistance curves. A maximum heat flux of 31 W/cm2 was dissipated at a flow rate of 13 cm3/s. A resistance network model was used to calculate an effective heat transfer coefficient by revealing different elements contributing to the total resistance. The study extended to different coolant temperatures ranging from 25 °C to 45 °C addresses the effect of coolant viscosity on the overall performance of the cold plate, and the results were presented as coefficient of performance (COP) curves. A numerical model developed using 6SigmaET was validated against the experimental findings for the flow and thermal performance with minimal percentage difference.

Heat Transfer Enhancement in Compact Phase Change Microchannel Heat Exchangers for High Flux Laser Diodes

2018 ◽  
Author(s):  
Jensen Hoke ◽  
Todd Bandhauer ◽  
Jack Kotovsky ◽  
Julie Hamilton ◽  
Paul Fontejon
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Phase Change ◽  
Flow Boiling ◽  
Laser Diodes ◽  
High Heat ◽  
Heat Fluxes ◽  
High Heat Flux ◽  
Maximum Heat ◽  
Average Maximum

Liquid-vapor phase change heat transfer in microchannels offers a number of significant advantages for thermal management of high heat flux laser diodes, including reduced flow rates and near constant temperature heat rejection. Modern laser diode bars can produce waste heat loads >1 kW cm−2, and prior studies show that microchannel flow boiling heat transfer at these heat fluxes is possible in very compact heat exchanger geometries. This paper describes further performance improvements through area enhancement of microchannels using a pyramid etching scheme that increases heat transfer area by ∼40% over straight walled channels, which works to promote heat spreading and suppress dry-out phenomenon when exposed to high heat fluxes. The device is constructed from a reactive ion etched silicon wafer bonded to borosilicate to allow flow visualization. The silicon layer is etched to contain an inlet and outlet manifold and a plurality of 40μm wide, 200μm deep, 2mm long channels separated by 40μm wide fins. 15μm wide 150μm long restrictions are placed at the inlet of each channel to promote uniform flow rate in each channel as well as flow stability in each channel. In the area enhanced parts either a 3μm or 6μm sawtooth pattern was etched vertically into the walls, which were also scalloped along the flow path with the a 3μm periodicity. The experimental results showed that the 6μm area-enhanced device increased the average maximum heat flux at the heater to 1.26 kW cm2 using R134a, which compares favorably to a maximum of 0.95 kw cm2 dissipated by the plain walled test section. The 3μm area enhanced test sections, which dissipated a maximum of 1.02 kW cm2 showed only a modest increase in performance over the plain walled test sections. Both area enhancement schemes delayed the onset of critical heat flux to higher heat inputs.

High Heat Flux Phase Change on Silicon Wick Structures

2012 ◽  
Author(s):  
Qingjun Cai ◽  
Avijit Bhunia ◽  
Yuan Zhao
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Phase Change ◽  
Test Chamber ◽  
Nucleate Boiling ◽  
High Heat ◽  
High Heat Flux ◽  
Maximum Heat ◽  
Wick Structure ◽  
Silicon Pillars

Silicon is the major material in IC manufacture. It has high thermal conductivity and is compatible with precision micro-fabrication. It also has decent thermal expansion coefficient to most semiconductor materials. These characteristics make it an ideally underlying material for fabricating micro/mini heat pipes and their wick structures. In this paper, we focus our research investigations on high heat flux phase change capacity of the silicon wick structures. The experimental wick sample is composed of silicon pillars 320μm in height and 30 ∼ 100μm in diameter. In a stainless steel test chamber, synchronized visualizations and measurements are performed to crosscheck experimental phenomena and data. Using the mono-wick structure with large silicon pillar of 100μm in diameter, the phase change on the silicon wick structure reaches its maximum heat flux at 1,130W/cm2 over a 2mm×2mm heating area. The wick structure can fully utilize the wick pump capability to supply liquid from all 360° directions to the center heating area. In contrast, the large heating area and fine silicon pillars 10μm in diameter significantly reduces liquid transport capability and suppresses generation of nucleate boiling. As a result, phase change completely relies on evaporation, and the CHF of the wick structure is reduced to 180W/cm2. An analytical model based on high heat flux phase change of mono-porous wick structures indicates that heat transfer capability is subjected to the ratio between the wick particle radius and the heater dimensions, as well as vapor occupation ratio of the porous volume. In contrast, phase change heat transfer coefficients of the wick structures essentially reflect material properties of wick structure and mechanism of two-phase interactions within wick structures.

Enhanced Pool Boiling Performance on Micro-, Nano-, and Hybrid-Structured Surfaces

2011 ◽  
Author(s):  
Qian Li ◽  
Wei Wang ◽  
Chris Oshman ◽  
Benoit Latour ◽  
Chen Li ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Thermal Management ◽  
Pool Boiling ◽  
High Heat ◽  
High Heat Flux ◽  
Maximum Heat ◽  
Structured Surfaces ◽  
Maximum Heat Transfer ◽  
Functional Components

Thermal management plays an important role in both high power electronics and energy conversion systems. A key issue in thermal management is the dissipation of the high heat flux generated by functional components. In this paper, various microstructures, nanostructures and hybrid micro/nano-structures were successfully fabricated on copper (Cu) surfaces, and the corresponding pool boiling heat transfer performance was systematically studied. It is found that the critical heat flux (CHF) of hybrid structured surfaces is about 15% higher than that of the surfaces with nanowires only and micro-pillars only. More importantly, the superheat at CHF for the hybrid structured surface is much smaller than that of the micro-pillared surface (about 35%), and a maximum heat transfer coefficient (HTC) of about 90,000W/m2K is obtained. Compared with the known best pool boiling performance on biporous media, a much larger HTC and much lower superheat at a heat flux of 250W/cm2 have been obtained on the novel hybrid-structured surfaces.

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.

Experimental Study on Heat Transfer Augmentation for High Heat Flux Removal in Rib-Roughened Narrow Channels

1998 ◽  
Vol 35 (9) ◽  
pp. 671-678 ◽  
Author(s):  
Md. Shafiqul ISLAM ◽  
Ryutaro HINO ◽  
Katsuhiro HAGA ◽  
Masanori MONDE ◽  
Yukio SUDO
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Flux ◽  
High Heat ◽  
High Heat Flux ◽  
Narrow Channels ◽  
Heat Transfer Augmentation ◽  
Rib Roughened

Development of Cooling System for a Large Area at High Heat Flux by Using Flow Boiling in Narrow Channels

2009 ◽  
Author(s):  
Shinichi Miura ◽  
Yukihiro Inada ◽  
Yasuhisa Shinmoto ◽  
Haruhiko Ohta
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Rate ◽  
Mass Velocity ◽  
Cooling System ◽  
Volumetric Flow Rate ◽  
High Heat ◽  
High Heat Flux ◽  
Gap Size ◽  
Heated Channel

Advance of an electronic technology has caused the increase of heat generation density for semiconductors densely integrated. Thermal management becomes more important, and a cooling system for high heat flux is required. It is extremely effective to such a demand using flow boiling heat transfer because of its high heat removal ability. To develop the cooling system for a large area at high heat flux, the cold plate structure of narrow channels with auxiliary unheated channel for additional liquid supply was devised and confirmed its validity by experiments. A large surface of 150mm in heated length and 30mm in width with grooves of an apex angle of 90 deg, 0.5mm depth and 1mm in pitch was employed. A structure of narrow rectangular heated channel between parallel plates with an unheated auxiliary channel was employed and the heat transfer characteristics were examined by using water for different combinations of gap sizes and volumetric flow rates. Five different liquid distribution modes were tested and their data were compared. The values of CHF larger than 1.9×106W/m2 for gap size of 2mm under mass velocity based on total volumetric flow rate and on the cross section area of main heated channel 720kg/m2s or 1.7×106W/m2 for gap size of 5mm under 290kg/m2s were obtained under total volumetric flow rate 4.5×10−5m3/s regardless of the liquid distribution modes. Under several conditions, the extensions of dry-patches were observed at the upstream location of the main heated channel resulting burnout not at the downstream but at the upstream. High values of CHF larger than 2×106W/m2 were obtained only for gap size of 2mm. The result indicates that higher mass velocity in the main heated channel is more effective for the increase in CHF. It was clarified that there is optimum flow rate distribution to obtain the highest values of CHF. For gap size of 2mm, high heat transfer coefficient as much as 7.4×104W/m2K were obtained at heat flux 1.5×106W/m2 under mass velocity 720kg/m2s based on total volumetric flow rate and on the cross section area of main heated channel. Also to obtain high heat transfer coefficient, it is more useful to supply the cooling liquid from the auxiliary unheated channel for additional liquid supply in the transverse direction perpendicular to the flow in the main heated channel.

Study on Copper Cold Plate Designs for Electronics Liquid Cooling System

2006 ◽  
Author(s):  
Yi. Feng ◽  
Y. Wang ◽  
C. Y. Huang
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Cooling System ◽  
Pure Copper ◽  
Cold Plate ◽  
Performance Limits ◽  
Liquid Cooling ◽  
Cold Plates ◽  
Management Approaches ◽  
Liquid Cooling System

The increasing power consumption of microelectronic systems and the dense layout of semiconductor components leave very limited design spaces with tight constraints for the thermal solution. Conventional thermal management approaches, such as extrusion, fold-fin, and heat pipe heat sinks, are somehow reaching their performance limits, due to the geometry constraints. Currently, more studies have been carried out on the liquid cooling technologies, as the flexible tubing connection of liquid cooling system makes both the accommodation in constrained design space and the simultaneous cooling of multi heating sources feasible. To significantly improve the thermal performance of a liquid cooling system, heat exchangers with more liquid-side heat transfer area with acceptable flow pressure drop are expected. This paper focuses on the performance of seven designs of source heat exchanger (cold plate). The presented cold plates are all made in pure copper material using wire cutting, soldering, brazing, or sintering process. Enhanced heat transfer surfaces such as micro channel and cooper mesh are investigated. Detailed experiments have been conducted to understand the performance of these seven cooper cold plates. The same radiators, fan, and water pump were connected with each cooper cold plate to investigate the overall thermal performance of liquid cooling system. Water temperature readings at the inlets and outlets of radiators, pump, and colder plate have been taken to interpret the thermal resistance distribution along the cooling loop.

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