Critical heat flux and heat transfer for high heat flux applications

1986 ◽  
Vol 29 (2) ◽  
pp. 337-340 ◽  
Author(s):  
R.D. Boyd ◽  
L.N. Powell ◽  
L.L. Schluter
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
High Heat ◽  
High Heat Flux

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.

Nanofluid Boiling Heat Transfer and Critical Heat Flux Enhancement: Mechanism to Be Revealed

2013 ◽  
Author(s):  
Junmei Wu ◽  
Jiyun Zhao ◽  
Yun Wang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Boiling Heat Transfer ◽  
Heat Transfer Performance ◽  
Bubble Dynamics ◽  
High Heat ◽  
Solid Particles ◽  
High Heat Flux ◽  
Transfer Performance

As a novel strategy to improve heat transfer characteristics of fluids by the addition of solid particles with diameters below 100 nm, nanofluids exhibits unprecedented heat transfer properties and are being considered as potential working fluids to be used in high heat flux systems such as nuclear reactors, electronic cooling systems and solar collectors. The present paper reviews the state-of-the-art studies on nanofluid boiling heat transfer performance and critical heat flux (CHF) enhancement. It is found that some results on nanofluids boiling heat transfer performance are inconsistent or contradictory in data published. The knowledge on the mechanism of nanofluids boiling CHF enhancement is insufficient. Bubble dynamics of nanofluids boiling is suggested to be investigated to identify the exact contributions of solid surface modifications and suspended nanoparticles to CHF enhancement in nanofluids boiling heat transfer.

scholarly journals Prospects for using two-phase micro-size systems for high heat flux removal

2021 ◽  
Vol 2057 (1) ◽  
pp. 012058
Author(s):  
V V Kuznetsov ◽  
A S Shamirzaev ◽  
A S Mordovskoy
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Flow Boiling ◽  
High Heat ◽  
High Heat Flux ◽  
Micro Channel ◽  
Copper Target ◽  
Jet Cooling ◽  
Micro Channels

Abstract Heat transfer in active systems for high heat removal based on the micro-channels and hybrid micro-channel/micro-jet is considered. The application of these systems allows significantly increasing the critical heat flux for a dense arrangement of the heat stressed equipment. The characteristics of heat transfer and critical heat flux during subcooled flow boiling of water in the micro-channel heat sink and during micro-jet impingement in narrow channel are obtained. The experiments are performed for the horizontal segmented microchannels with a cross section of 340×2000 μm2 made on the top of copper target and for impingement micro-jet cooling of the copper target in the gap of 1000 μm. It has been found that, compared with impingement micro-jet cooling in similar condition, the micro-channel cooling is more effective for high heat flux removal although it creates the considerably high wall temperature.

Effect of Decreasing Heat Transfer Surface Size on Boiling Heat Transfer

2013 ◽  
Author(s):  
Yasuo Koizumi ◽  
Yoshiki Morita
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Boiling Heat Transfer ◽  
High Heat ◽  
Heat Transfer Surface ◽  
Single Bubble ◽  
Test Fluid ◽  
High Heat Flux ◽  
Surface Diameter

Pool boiling heat transfer experiments were performed for small heat transfer surfaces at 0.101 MPa by using ethanol as test fluid. The test heat transfer surfaces were made of copper. The diameters of the heat transfer surfaces were 1.0, 2.0, 3.0, 5.0, 7.0 10.0 and 20.0 mm. When the heat flux was low, small isolated bubbles left from the heat transfer surface irrespective of size of the heat transfer surface. As the heat flux was increased, coalescent large bubbles were formed on the heat transfer surface in the case that the surface diameter was larger than 5.0 mm. Large bubbles left from place to place of the coalescent large bubbles on the heat transfer surface. In the case that the surface diameter was smaller than 3.0 mm, a single bubble stayed on the heat transfer surface and a single bubble periodically left form the bubble when the heat flux was increased to the middle and high heat flux region. As the diameter of the boiling surface became smaller, the boiling heat transfer was enhanced and the critical heat flux increased. The dependency of the critical heat flux on the heat transfer surface size was well correlated with the Ded and Lienhard relation developed for spheres.

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.

Development of Advanced High Heat Flux Cooling System for Power Electronics

2009 ◽  
Author(s):  
Yasuhisa Shinmoto ◽  
Shinichi Miura ◽  
Koichi Suzuki ◽  
Yoshiyuki Abe ◽  
Haruhiko Ohta
Keyword(s):  
Heat Flux ◽  
Power Electronics ◽  
Critical Heat Flux ◽  
Heating Surface ◽  
Narrow Channel ◽  
High Heat ◽  
High Heat Flux ◽  
Gap Size ◽  
Narrow Channels ◽  
Very High

Recent development in electronic devices with increased heat dissipation requires severe cooling conditions and an efficient method for heat removal is needed for the cooling under high heat flux conditions. Most researches are concentrated on small semiconductors with high heat flux density, while almost no existing researches concerning the cooling of a large semiconductor, i.e. power electronics, with high heat generation density from a large cooling area. A narrow channel between parallel plates is one of ideal structures for the application of boiling phenomena which uses the cooling for such large semiconductors. To develop high-performance cooling systems for power electronics, experiments on increase in critical heat flux (CHF) for flow boiling in narrow channels by improved liquid supply was conducted. To realize the cooling of large areas at extremely high heat flux under the conditions for a minimum gap size and a minimum flow rate of liquid supplied, the structure with auxiliary liquid supply was devised to prevent the extension of dry-patches underneath flattened bubbles generated in a narrow channel. The heating surface was experimented in two channels with different dimensions. The heating surfaces have the width of 30mm and the lengths of 50mm and 150mm in the flow direction. A large width of actual power electronics is realizable by the parallel installation of the same channel structure in the transverse direction. The cooling liquid is additionally supplied via sintered metal plates from the auxiliary unheated channels located at sides or behind the main heated channel. To supply the liquid to the entire heating surface, fine grooves are machined on the heating surface for enhance the spontaneous liquid supply by the aid of capillary force. The gap size of narrow channels are varied as 0.7mm, 2mm and 5mm. Distribution of liquid flow rate to the main heated channel and the auxiliary unheated channels were varied to investigate its effect on the critical heat flux. Test liquids employed are R113, FC72 and water. The systematic experiments by using water as a test liquid were conducted. Critical heat flux values larger than 2×106W/m2 were obtained at both gap sizes of 2mm and 5mm for a heated length of 150mm. A very high heat transfer coefficient as much as 1×105W/m2K was obtained at very high heat flux near CHF for the gap size of 2mm. This paper is a summary of experimental results obtained in the past by the present authors.

Sign in / Sign up

Export Citation Format

Share Document