Mechanism of Critical Heat Flux for Convective Boiling of FC-72 in a Diverging Microchannel Heat Sink

2010 ◽  
Author(s):  
Chun Ting Lu ◽  
Chin Pan
Keyword(s):  
Heat Flux ◽  
Liquid Film ◽  
Critical Heat Flux ◽  
Heat Sink ◽  
Flow Boiling ◽  
High Heat ◽  
High Heat Flux ◽  
Microchannel Heat Sink ◽  
Convective Boiling

The present study explores experimentally the mechanism of critical heat flux (CHF) of FC-72 in a 10 parallel diverging microchannel heat sink with different distributions of artificial nucleation sites (ANS). The effects of mass flux and number of ANS with or without degassing on CHF of FC-72 are investigated. During CHF, flow visualization shows that the dryout of liquid film in annular flow appears near the outlet region with frequent rewetting of liquid film with slug bubble or rewetting of liquid column on the dryout surface. The results demonstrate that diverging microchannels with ANS distributed uniformly along the whole channel (Type-2 system) shows better flow boiling performance and higher CHF and can be recommended as a high-heat-flux microchannel heat sink. Moreover, five CHF correlations in the literature for flow boiling in microchannels are compared, which generally underpredict the CHF data of the present study. This suggests that the present diverging design with ANS enhances the CHF. The comparison also reveals that Bowers and Mudawar correlation predicts the present data best with MAE of 15.8% for the type-2 system.

Flow Boiling of Ammonia in a Diamond-Made Microchannel Heat Sink for High Heat Flux Hotspots

2019 ◽  
Vol 29 (5) ◽  
pp. 1333-1344 ◽  
Author(s):  
Qi Yang ◽  
Jianyin Miao ◽  
Jingquan Zhao ◽  
Yanpei Huang ◽  
Weichun Fu ◽  
...  
Keyword(s):  
Heat Flux ◽  
Heat Sink ◽  
Flow Boiling ◽  
High Heat ◽  
High Heat Flux ◽  
Microchannel Heat Sink

Investigation of On-Chip Hot Spot Cooling Using Microchannel Heat Sink

2013 ◽  
Vol 455 ◽  
pp. 466-469
Author(s):  
Yun Chuan Wu ◽  
Shang Long Xu ◽  
Chao Wang
Keyword(s):  
Heat Flux ◽  
Heat Sink ◽  
Hot Spots ◽  
Hot Spot ◽  
High Heat ◽  
High Heat Flux ◽  
Microchannel Heat Sink ◽  
Three Dimensional Model ◽  
Spot Cooling ◽  
On Chip

With the increase of performance demands, the nonuniformity of on-chip power dissipation becomes greater, causing localized high heat flux hot spots that can degrade the processor performance and reliability. In this paper, a three-dimensional model of the copper microchannel heat sink, with hot spot heating and background heating on the back, was developed and used for numerical simulation to predict the hot spot cooling performance. The hot spot is cooled by localized cross channels. The pressure drop, thermal resistance and effects of hot spot heat flux and fluid flow velocity on the cooling of on-chip hot spots, are investigated in detail.

On the Nature of Critical Heat Flux in Microchannels

2005 ◽  
Vol 127 (1) ◽  
pp. 101-107 ◽  
Author(s):  
A. E. Bergles ◽  
S. G. Kandlikar
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
Flow Distribution ◽  
High Heat ◽  
Operating Conditions ◽  
High Heat Flux ◽  
Clear Understanding ◽  
Wide Range ◽  
Parallel Microchannels

The critical heat flux (CHF) limit is an important consideration in the design of most flow boiling systems. Before the use of microchannels under saturated flow boiling conditions becomes widely accepted in cooling of high-heat-flux devices, such as electronics and laser diodes, it is essential to have a clear understanding of the CHF mechanism. This must be coupled with an extensive database covering a wide range of fluids, channel configurations, and operating conditions. The experiments required to obtain this information pose unique challenges. Among other issues, flow distribution among parallel channels, conjugate effects, and instrumentation need to be considered. An examination of the limited CHF data indicates that CHF in parallel microchannels seems to be the result of either an upstream compressible volume instability or an excursive instability rather than the conventional dryout mechanism. It is expected that the CHF in parallel microchannels would be higher if the flow is stabilized by an orifice at the entrance of each channel. The nature of CHF in microchannels is thus different than anticipated, but recent advances in microelectronic fabrication may make it possible to realize the higher power levels.

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

Conjugated Numerical Study on the Performance of Microchannel Heat Sink Using Al2O3/H2O Nanofluid

2014 ◽  
Author(s):  
J. M. Wu ◽  
J. Y. Zhao
Keyword(s):  
Heat Flux ◽  
Integrated Circuit ◽  
Heat Sink ◽  
Nuclear Reactor ◽  
Numerical Study ◽  
Substrate Surface ◽  
High Heat ◽  
High Heat Flux ◽  
Microchannel Heat Sink ◽  
Size Dependent

High power electronics are widely used in many different areas such as integrated circuit (IC) boards in nuclear reactor control system. Thermal management of electronic devices has been a topic of great interest among many researchers over the last few decades. Microchannel is one of several high-heat-flux removal techniques. Nanofluids with enhanced thermal conductivity and strong temperature- and size-dependent thermal properties are expected to be utilized in microchannels as coolants, which leads to a promising future for such high-heat-flux systems as cooling systems. The performance of the microchannel heat sink (MCHS) using water and Al2O3/water nanofluids, with consideration of different substrate materials, is numerically investigated and compared in the present paper to identify the combined effects of working fluids and substrate materials on the thermal resistance, pumping power and temperature distribution on the substrate surface of a heat sink.

scholarly journals Critical heat flux enhancement of HFE-7100 flow boiling in a minichannel heat sink with saw-tooth structures

2017 ◽  
Vol 9 (2) ◽  
pp. 168781401668902 ◽  
Author(s):  
Ben-Ran Fu ◽  
Shan-Yu Chung ◽  
Wei-Jen Lin ◽  
Lei Wang ◽  
Chin Pan
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Mass Flux ◽  
Heat Sink ◽  
Heat Dissipation ◽  
Flow Boiling ◽  
Convective Boiling ◽  
Tooth Structure ◽  
Flux Enhancement ◽  
System Pressure

A heat sink with convective boiling in micro- or mini-channels is with great potential to meet the requirement of the high heat dissipation of the electronic devices. This study investigates the flow boiling of HFE-7100, having a suitable boiling temperature at atmospheric pressure and dielectric property, in the minichannel heat sink with the modified surface (namely, the saw-tooth structure). The effect of the system pressure on the boiling characteristics was also studied. The results reveal that the critical heat flux can be significantly improved by introducing the saw-tooth structures on the channel surface or boosting the system pressure as well as by increasing the mass flux. Compared to the non-modified channel, the enhancements of the critical heat flux for the parallel and counter saw-tooth channels are 44% and 36%, respectively, at the small mass flux. The boiling visualization further indicates that the minichannels with the saw-tooth structures interrupt the boundary layer and restrain the coalescence of the bubble, which may be the reason for the critical heat flux enhancement. Moreover, the degree of the critical heat flux enhancement, contributed by the saw-tooth modification of the channel, decreases with an increase in the mass flux.

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