Innovative Realizations of High Heat-Flux Boiling and Condensing Flows for Milli-Meter and Micro-Meter Scale Applications

2014 ◽  
Author(s):  
Michael Kivisalu ◽  
Amitabh Narain ◽  
Patcharapol Gorgitrattanagul ◽  
Ranjeeth Naik
Keyword(s):  
Heat Flux ◽  
Heat Load ◽  
High Heat ◽  
Electronic Cooling ◽  
System Level ◽  
High Heat Flux ◽  
Zero Gravity ◽  
Pressure Drops ◽  
Condensing Flows ◽  
High Heat Load

For shear driven mm-scale flows, the traditional boiler and condenser operations pose serious problems of degraded performance (low heat-flux values, high pressure drops, and device-and-system level instabilities). The innovative devices are introduced for functionality and high heat load capabilities needed for shear dominated electronic cooling situations that arise in milli-meter scale operations, certain gravity-insensitive avionics-cooling and zero-gravity applications.

Spot Cooling of Local-High Heat Load by High-Velocity Thin Liquid Flow

2006 ◽  
Author(s):  
Hiroyasu Ohtake ◽  
Yasuo Koizumi ◽  
Ken Nemoto ◽  
Hisashi Sakurai
Keyword(s):  
Heat Flux ◽  
Heat Load ◽  
Liquid Velocity ◽  
High Heat ◽  
Test Channel ◽  
Maximum Heat ◽  
Maximum Heat Flux ◽  
Dry Patch ◽  
High Heat Load ◽  
Spot Cooling

Spot cooling of local-high heat load by high-velocity thin liquid flow was examined experimentally. Steady state experiments were conducted using a copper thin-film and rectangular sub-millimeter-channels. The width of the test channel was 2 mm. The heights of the test channel were 0.5 and 0.2 mm. The width and length of a test heater was 2 mm and 2 mm, respectively. The test liquid was degassed pure water. The liquid velocities were 1.5, 5, 10 and 15 m/s. The liquid subcooling was 20 K. Location of the heater in the test channel also was an experimental parameter: the positions of the heater from the exit of the test channel were 30 mm (middle) and 0 mm (exit). Experimental results showed that the maximum heat flux (CHF or cooling limit) during experiment with the heater at exit of the test channel was similar to that with the heater at middle of the test channel: the maximum heat flux was independent of the position of heater in the test channel. The maximum heat flux occurred when bubbles coalesced together or a dry patch appeared on the heater. The coalescence bubble covered over the heater was observed at CHF in condition of low liquid velocity. For condition of high liquid velocity, a dry patch appeared on the heater, and then the dry region extended over the heater to come around the CHF. The maximum heat flux (critical heat flux) was about 8 MW/m2 in a range of present experiments. The CHF for the present sub-millimeter channel was similar to that for conventional channel. Furthermore, models were proposed using heat transfer around a coalesced bubble and at a dry patch on a heater.

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

Analysis of Vapor Blanket Formation in the Porous Wick of a Loop Heat Pipe With High Heat Load

2013 ◽  
Author(s):  
X. M. Huang ◽  
X. Jin ◽  
B. B. Chen ◽  
W. Liu
Keyword(s):  
Mass Transfer ◽  
Heat Flux ◽  
Heat Pipe ◽  
Heat And Mass Transfer ◽  
Heat Load ◽  
High Heat ◽  
Loop Heat Pipe ◽  
Porous Wick ◽  
High Heat Load ◽  
Theoretical Results

A loop heat pipe has different transport mechanisms depending on heat flux. The interface of liquid and vapor cannot maintain at the surface of the wick when heat flux is high, and a vapor blanket will form in the wick. To investigate when the vapor blanket appears and how it affects heat and mass transfer in the system is very import to minimize the device. A mathematical model of heat and mass transfer in the evaporator, coupled with analysis of fluid flow in the loop, is developed in the paper. The model is applied to calculate the critical heat load that the vapor blanket forms, and to analyze how the blanket delays. A comparison of theoretical results and experimental measurements is further presented. The consistence of the results validates the model and the mechanisms.

Thermal Design of Microchannel Heat Sinks for Low-Orbit Micro-Satellites

2005 ◽  
Author(s):  
Amaury J. H. Heresztyn ◽  
Nicole C. DeJong Okamoto
Keyword(s):  
Heat Flux ◽  
Fluid Model ◽  
High Heat ◽  
Thermal Design ◽  
Heat Sinks ◽  
High Heat Flux ◽  
Propulsion Systems ◽  
Pressure Drops ◽  
Nuclear Propulsion ◽  
Microchannel Heat Sinks

As reduction in the size of electronics creates demand for smaller, less expensive and faster-to-produce spacecraft, the use of high heat flux electronics or advanced nuclear propulsion systems will increase the stress on the thermal subsystem. This work presents a thermal management solution to this problem using liquid-cooled microchannel heat sinks. First, a simple computer model is used to illustrate the need for an atypical cooling method when high-heat flux electronics are used. Second, a thermal/fluid model of microchannel heat sinks is developed and applied to address the satellite thermal need. The total thermal resistances and pressure drops show excellent comparison with published experimental and analytical results. Finally, the model of the microchannel heat sink is optimized to remove 25 W/cm2 over a footprint of 3.7cm2. The mass flow rate needed was significantly lower (almost 5–10 times lower) when compared to other published results, which means that micro-pumps available on the market will be sufficient. The integration of the microchannel system with the satellite is also discussed.

Application of Al2O3 Nanofluid on Sintered Copper-Powder Vapor Chamber for Electronic Cooling

2013 ◽  
Vol 789 ◽  
pp. 423-428 ◽  
Author(s):  
Nandy Putra ◽  
Wayan Nata Septiadi ◽  
Ranggi Sahmura ◽  
Cahya Tri Anggara
Keyword(s):  
Heat Flux ◽  
Thermal Performance ◽  
Base Fluid ◽  
Cooling System ◽  
High Heat ◽  
Electronic Cooling ◽  
Working Fluid ◽  
High Heat Flux ◽  
Processing Unit ◽  
Vapor Chamber

The development of electronic devices pushes manufacturers to create smaller microchips with higher performance than ever before. Microchip with higher working load produces more heat. This leads to the need of cooling system that able to dissipate high heat flux. Vapor chamber is one of highly effective heat spreading device. Its ability to dissipate high heat flux density in limited space made it potential for electronic cooling application, like Central Processing Unit (CPU) cooling system. The purpose of this paper is to study the application of Al2O3Nanofluid as working fluid for vapor chamber. Vapor chamber performance was measured in real CPU working condition. Al2O3Nanofluid with concentration of 0.1%, 0.3%, 0.5%, 1%, 2% and 3% as working fluid of the vapor chamber were tested and compared with its base fluid, water. Al2O3nanofluid shows better thermal performance than its base fluid due to the interaction of particle enhancing the thermal conductivity. The result showed that the effect of working fluid is significant to the performance of vapor chamber at high heat load, and the application of Al2O3nanofluid as working fluid would enhance thermal performance of vapor chamber, compared to other conventional working fluid being used before.

Pool Boiling Heat Transfer and Bubble Dynamics Over Plain and Enhanced Microchannels

2010 ◽  
Author(s):  
Dwight Cooke ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Bubble Dynamics ◽  
Pool Boiling ◽  
High Heat ◽  
Heat Fluxes ◽  
Electronic Cooling ◽  
High Heat Flux ◽  
Heat Of Evaporation ◽  
Cooling Ability

Pool boiling is of interest in high heat flux applications because of its potential for removing large amount of heat resulting from the latent heat of evaporation and little pressure drop penalty for circulating coolant through the system. However, the heat transfer performance of pool boiling systems is not adequate to match the cooling ability provided by enhanced microchannels operating under single-phase conditions. The objective of this work is to evaluate the pool boiling performance of structured surface features etched on a silicon chip. The performance is normalized with respect to a plain chip. This investigation also focuses on the bubble dynamics on plain and structured microchannel surfaces under various heat fluxes in an effort to understand the underlying heat transfer mechanism. This work is expected to lead to improved enhancement features for extending the pool boiling option to meet the high heat flux removal demands in electronic cooling applications.

Critical Heat Flux of Multi-Nozzle Spray Cooling

2004 ◽  
Vol 126 (3) ◽  
pp. 482-485 ◽  
Author(s):  
Lanchao Lin ◽  
Rengasamy Ponnappan
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Flat Surface ◽  
Swirling Flow ◽  
Spray Cooling ◽  
High Heat ◽  
High Heat Flux ◽  
Pressure Drops ◽  
Nozzle Pressure ◽  
Nozzle Plate

Tiny nozzles are developed that are capable of creating the swirling flow necessary to generate a full cone spray. Eight miniature nozzles are embedded in a multi-nozzle plate used to generate a spray array for the cooling of high heat flux laser diodes. The target spray cooling area is a 1×2 cm2 flat surface of a copper heater plate. A closed loop spray cooling test setup is established. FC-87, FC-72 and methanol are used as the working fluids. Critical heat flux (CHF) is experimentally investigated at various spray saturation temperatures and nozzle pressure drops (from 0.690 bar to 3.10 bar). It is demonstrated that the spray cooler can reach the CHF levels up to 91.5 W/cm2 with FC-87 and 490 W/cm2 with methanol.

ADVANCED COOLING TECHNOLOGIES FOR MICROPROCESSORS

2006 ◽  
Vol 16 (01) ◽  
pp. 301-313 ◽  
Author(s):  
THOMAS W. KENNY ◽  
KENNETH E. GOODSON ◽  
JUAN G. SANTIAGO ◽  
EVELYN WANG ◽  
JAE-MO KOO ◽  
...  
Keyword(s):  
Heat Flux ◽  
High Power ◽  
High Heat ◽  
Computer Applications ◽  
System Level ◽  
Alternative Methods ◽  
High Heat Flux ◽  
Air Cooling ◽  
Desktop Computer ◽  
Power Sources

Recent trends in processor power for the next generation devices point clearly to significant increase in processor heat dissipation over the coming years. In the desktop system design space, the tendency has been to minimize system enclosure size while maximizing performance, which in turn leads to high power densities in future generation systems. The current thermal solutions used today consist of advanced heat sink designs and heat pipe designs with forced air cooling to cool high power processors. However, these techniques are already reaching their limits to handle high heat flux, and there is a strong need for development of more efficient cooling systems which are scalable to handle the high heat flux generated by the future products. To meet this challenge, there has been research in academia and in industry to explore alternative methods for extracting heat from high-density power sources in electronic systems. This talk will discuss the issues surrounding device cooling, from the transistor level to the system level, and describe system-level solutions being developed for desktop computer applications developed in our group at Stanford University.

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