Observations of the Critical Heat Flux Process During Pool Boiling of FC-72

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
J. Jung ◽  
S. J. Kim ◽  
J. Kim
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Pool Boiling ◽  
High Heat ◽  
Line Length ◽  
Boiling Curve ◽  
High Heat Flux ◽  
Transfer Coefficients ◽  
Ir Camera

Experimental work was undertaken to investigate the process by which pool-boiling critical heat flux (CHF) occurs using an IR camera to measure the local temperature and heat transfer coefficients on a heated silicon surface. The wetted area fraction (WF), the contact line length density (CLD), the frequency between dryout events, the lifetime of the dry patches, the speed of the advancing and receding contact lines, the dry patch size distribution on the surface, and the heat transfer from the liquid-covered areas were measured throughout the boiling curve. Quantitative analysis of this data at high heat flux and transition through CHF revealed that the boiling curve can simply be obtained by weighting the heat flux from the liquid-covered areas by WF. CHF mechanisms proposed in the literature were evaluated against the observations.

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.

Enhanced Flow Boiling Over Open Microchannels With Uniform and Tapered Gap Manifolds

2013 ◽  
Vol 135 (6) ◽  
Author(s):  
Satish G. Kandlikar ◽  
Theodore Widger ◽  
Ankit Kalani ◽  
Valentina Mejia
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Performance ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
High Heat ◽  
High Heat Flux ◽  
Transfer Performance ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Flow boiling in microchannels has been extensively studied in the past decade. Instabilities, low critical heat flux (CHF) values, and low heat transfer coefficients have been identified as the major shortcomings preventing its implementation in practical high heat flux removal systems. A novel open microchannel design with uniform and tapered manifolds (OMM) is presented to provide stable and highly enhanced heat transfer performance. The effects of the gap height and flow rate on the heat transfer performance have been experimentally studied with water. The critical heat fluxes (CHFs) and heat transfer coefficients obtained with the OMM are significantly higher than the values reported by previous researchers for flow boiling with water in microchannels. A record heat flux of 506 W/cm2 with a wall superheat of 26.2 °C was obtained for a gap size of 0.127 mm. The CHF was not reached due to heater power limitation in the current design. A maximum effective heat transfer coefficient of 290,000 W/m2 °C was obtained at an intermediate heat flux of 319 W/cm2 with a gap of 0.254 mm at 225 mL/min. The flow boiling heat transfer was found to be insensitive to flow rates between 40–333 mL/min and gap sizes between 0.127–1.016 mm, indicating the dominance of nucleate boiling. The OMM geometry is promising to provide exceptional performance that is particularly attractive in meeting the challenges of high heat flux removal in electronics cooling applications.

Enhanced Pool Boiling Using Carbon Nanotube Arrays on a Silicon Surface

2005 ◽  
Author(s):  
Sebastine O. Ujereh ◽  
Issam Mudawar ◽  
Placidius B. Amama ◽  
Timothy S. Fisher ◽  
Weilin Qu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Carbon Nanotube ◽  
Integrated Circuit ◽  
Silicon Surface ◽  
Pool Boiling ◽  
Limiting Factor ◽  
High Heat Flux ◽  
Transfer Coefficients ◽  
Chip Surface

Progress in integrated circuit technology has caused device density and power dissipation to increase, resulting in significant cooling challenges. Pool boiling is an attractive cooling option because of its unique combination of passive fluid circulation and high heat flux capability. Having no mechanical pumps, pool boiling hardware is less complex, easier to seal, and free of pump-induced fluid pulsations that are present with many alternative approaches. One of the main obstacles for improvements in pool boiling technology is the limiting factor of critical heat flux (CHF), which limits cooling capacity. The present experimental work considers the introduction of carbon nanotube (CNT) arrays on the chip surface to delay CHF and to enhance boiling heat transfer. Pool boiling curves for a smooth silicon surface and a silicon surface coated with CNTs were obtained. Tests were conducted in which power was input in 1 W increments to the respective silicon surfaces immersed in FC-72 fluid. These experiments reveal significant boiling enhancement. Testing reveals a measured CHF of approximately 15 W/cm2 for a CNT-coated silicon wafer and a CHF of approximately 10 W/cm2 for bare silicon wafers. Further, superheat at fully developed boiling is reduced on CNT-coated surfaces by up to 60%, and effective heat transfer coefficients are enhanced by approximately 400% by the presence of CNTs.

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.

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