scholarly journals Nonlinear aspects of high heat flux nucleate boiling heat transfer. Part 2, Results

1994 ◽  
Author(s):  
P. Sadasivan ◽  
C. Unal ◽  
R. Nelson
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
High Heat ◽  
High Heat Flux ◽  
Nucleate Boiling Heat Transfer

Enhanced Boiling Heat Transfer From Micro-Porous Cylindrical Surfaces in Saturated FC-87 and R-123

1997 ◽  
Vol 119 (2) ◽  
pp. 319-325 ◽  
Author(s):  
J. Y. Chang ◽  
S. M. You
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Nucleate Boiling ◽  
High Heat ◽  
Bulk Liquid ◽  
High Heat Flux ◽  
High Flux ◽  
Boiling Enhancement ◽  
Nucleate Boiling Heat Transfer ◽  
Enhanced Boiling

The present research is an experimental study of pool boiling heat transfer from cylindrical heater surfaces immersed in saturated FC-87 and R-123. The baseline heater surfaces tested are plain, integral-fin with 709 fins/m, and commercial enhanced (High-Flux and Turbo-B). In addition, a highly effective micro-scale enhancement coating is applied to the plain and integral-fin surfaces to augment nucleate boiling heat transfer. Experiments are performed to understand the effects of surface micro- and macro-geometries on boiling heat transfer. The boiling performance of the micro-porous enhanced plain and integral-fin surfaces are compared with the High-Flux and the Turbo-B surfaces. At high heat flux conditions, the break down of the bulk liquid feed mechanism reduces boiling enhancement from the cylindrical surfaces.

scholarly journals Boiling Heat Transfer Performance of Parallel Porous Microchannels

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2970
Author(s):  
Donghui Zhang ◽  
Haiyang Xu ◽  
Yi Chen ◽  
Leiqing Wang ◽  
Jian Qu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
High Heat ◽  
High Heat Flux ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Boiling Process

Flow boiling in microporous layers has attracted a great deal of attention in the enhanced heat transfer field due to its high heat dissipation potential. In this study, flow boiling experiments were performed on both porous microchannels and a copper-based microchannel, using water as the coolant. As the heat flux was less than 80 W/cm2, the porous microchannels presented significantly higher boiling heat transfer coefficients than the copper-based microchannel. This was closely associated with the promotion of the nucleation site density of the porous coating. With the further increase in heat flux, the heat transfer coefficients of the porous microchannels were close to those of the copper-based sample. The boiling process in the porous microchannel was found to be dominated by the nucleate boiling mechanism from low to moderate heat flux (<80 W/cm2).This switched to the convection boiling mode at high heat flux. The porous samples were able to mitigate flow instability greatly. A visual observation revealed that porous microchannels could suppress the flow fluctuation due to the establishment of a stable nucleate boiling process. Porous microchannels showed no advantage over the copper-based sample in the critical heat flux. The optimal thickness-to-particle-size ratio (δ/d) for the porous microchannel was confirmed to be between 2–5. In this range, the maximum enhanced effect on boiling heat transfer could be achieved.

Boiling Heat Transfer and Critical Heat Flux Enhancement of Upward- and Downward-Facing Heater in Nanofluids

2013 ◽  
Vol 135 (7) ◽  
Author(s):  
Muhamad Zuhairi Sulaiman ◽  
Masahiro Takamura ◽  
Kazuki Nakahashi ◽  
Tomio Okawa
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Flux Enhancement ◽  
Optimum Configuration ◽  
Wall Superheat ◽  
Nucleate Boiling Heat Transfer

Boiling heat transfer (BHT) and critical heat flux (CHF) performance were experimentally studied for saturated pool boiling of water-based nanofluids. In present experimental works, copper heaters of 20 mm diameter with titanium-oxide (TiO2) nanocoated surface were produced in pool boiling of nanofluid. Experiments were performed in both upward and downward facing nanofluid coated heater surface. TiO2 nanoparticle was used with concentration ranging from 0.004 until 0.4 kg/m3 and boiling time of tb = 1, 3, 10, 20, 40, and 60 mins. Distilled water was used to observed BHT and CHF performance of different nanofluids boiling time and concentration configurations. Nucleate boiling heat transfer observed to deteriorate in upward facing heater, however; in contrast effect of enhancement for downward. Maximum enhancements of CHF for upward- and downward-facing heater are 2.1 and 1.9 times, respectively. Reduction of mean contact angle demonstrate enhancement on the critical heat flux for both upward-facing and downward-facing heater configuration. However, nucleate boiling heat transfer shows inconsistency in similar concentration with sequence of boiling time. For both downward- and upward-facing nanocoated heater's BHT and CHF, the optimum configuration denotes by C = 400 kg/m3 with tb = 1 min which shows the best increment of boiling curve trend with lowest wall superheat ΔT = 25 K and critical heat flux enhancement of 2.02 times.

Study on onset of nucleate boiling with screw tube for fusion reactor application

2021 ◽  
Author(s):  
Ji Hwan Lim ◽  
Minkyu Park
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
High Heat ◽  
Transfer Mechanism ◽  
High Heat Flux ◽  
Heat Transfer Mechanism ◽  
System Parameters ◽  
Smooth Tubes

Abstract The onset of nucleate boiling (ONB) is the point at which the heat transfer mechanism in fluids changes and is one of the thermo-hydraulic factors that must be considered when establishing a cooling system operation strategy. Because the high heat flux of several MW/m2, which is loaded within a tokamak, is applied under a one-side heating condition, it is necessary to determine a correlative relation that can predict ONB under special heating conditions. In this study, the ONB of a one-side-heated screw tube was experimentally analyzed via a subcooled flow boiling experiment. The helical nut structure of the screw tube flow path wall allows for improved heat transfer performance relative to smooth tubes, providing a screw tube with a 53.98% higher ONB than a smooth tube. The effects of the system parameters on the ONB heat flux were analyzed based on the changes in the heat transfer mechanism, with the results indicating that the flow rate and degree of subcooling are proportional to the ONB heat flux because increasing these factors improves the forced convection heat transfer and increases the condensation rate, respectively. However, it was observed that the liquid surface tension and latent heat decrease as the pressure increases, leading to a decrease in the ONB heat flux. An evaluation of the predictive performance of existing ONB correlations revealed that most have high error rates because they were developed based on ONB experiments on micro-channels or smooth tubes and not under one-side high heat load conditions. To address this, we used dimensional analysis based on Python code to develop new ONB correlations that reflect the influence of system parameters.

Experimental Investigation of Boiling Heat Transfer in a Liquid Chamber With Partially Soluble Nanofluids

2021 ◽  
Author(s):  
Noriyuki Unno ◽  
Kazuhisa Yuki ◽  
Risako Kibushi ◽  
Rika Nogita ◽  
Atsuyuki Mitani
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
Electronic Devices ◽  
High Heat ◽  
Experimental Result ◽  
High Heat Flux ◽  
Promising Technique ◽  
Cooling Device ◽  
Cooling Devices

Abstract Boiling heat transfer (BHT) is a promising technique to remove a high heat flux emitted from next-generation electronic devices. However, critical heat flux (CHF) is a big problem in BHT because it restricts the maximum performance of the cooling devices using BHT. Nanofluid has been widely used to improve the CHF. In this study, the authors investigated the BHT of a compact cooling device at low pressure using a special nanofluid: that is made with partially soluble particles in water. The experimental result found that the CHF with the special nanofluid is 170 W/cm2 and is higher than that with nanofluid made with an insoluble nanoparticle.

scholarly journals A Study on the Boiling Heat Transfer from Flat Surfaces under High Heat Flux : 1st Report, Burnout Heat Flux

1962 ◽  
Vol 28 (189) ◽  
pp. 587-595
Author(s):  
Seikan ISHIGAI ◽  
Kiyoshi INOUE ◽  
Akiharu KAWABATA ◽  
Yutaka SADAMORI ◽  
Zyumei KIWAKI ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
High Heat ◽  
High Heat Flux ◽  
Flat Surfaces

Flow Boiling Enhancement in Microchannels With Diffusion Bonded Wire Mesh

2007 ◽  
Author(s):  
Hailei Wang ◽  
Richard Peterson
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Flow Boiling ◽  
Nucleate Boiling ◽  
High Heat ◽  
Wire Mesh ◽  
Working Fluid ◽  
High Heat Flux ◽  
Vapor Quality ◽  
Heating Wall

Flow boiling and heat transfer enhancement in four parallel microchannels using a dielectric working fluid, HFE 7000, was investigated. Each channel was 1000 μm wide and 510 μm high. A unique channel surface enhancement technique via diffusion bonding a layer of conductive fine wire mesh onto the heating wall was developed. According to the obtained flow boiling curves for both the bare and mesh channels, the amount of wall superheat was significantly reduced for the mesh channel at all stream-wise locations. This indicated that the nucleate boiling in the mesh channel was enhanced due to the increase of nucleation sites the mesh introduced. Both the nucleate boiling dominated and convective evaporation dominated regimes were identified. In addition, the overall trend for the flow boiling heat transfer coefficient, with respect to vapor quality, was increasing until the vapor quality reached approximately 0.4. The critical heat flux (CHF) for the mesh channel was also significantly higher than that of the bare channel in the low vapor quality region. Due to the fact of how the mesh was incorporated into the channels, no pressure drop penalty was identified for the mesh channels. Potential applications for this kind of mesh channel include high heat-flux electronic cooling systems and various energy conversion systems.

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