scholarly journals Bubble dynamics and mechanistic boiling heat transfer prediction on a scored copper surface

2021 ◽  
Vol 2116 (1) ◽  
pp. 012009
Author(s):  
Zhen Cao ◽  
Zan Wu ◽  
Bengt Sundén
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Bubble Dynamics ◽  
Mechanistic Model ◽  
Transient Heat Conduction ◽  
Nucleation Site ◽  
Copper Surface ◽  
Heat Fluxes ◽  
Transfer Model ◽  
Microlayer Evaporation

Abstract In this study, pool boiling heat transfer of de-ionized water was experimentally studied on a scored copper surface at a heat-flux range of 0 - 60 W/cm2. Bubble dynamics in an isolated bubble region were carefully investigated, including bubble departure diameters, bubble departure frequencies, and active nucleation site densities. The bubble dynamics were compared with available models, indicating the suitable models regarding the present experimental results. Then, based on the bubble dynamics, a mechanistic heat transfer model, developed in our previous studies, was employed to predict the present boiling curve. In the mechanistic model, heat fluxes from natural convection, transient heat conduction, and microlayer evaporation were incorporated.

Pool Boiling Heat Transfer Enhancement of Water Using Brazed Copper Microporous Coatings

2015 ◽  
Author(s):  
Seongchul Jun ◽  
Hyoseong Wi ◽  
Ajay Gurung ◽  
Miguel Amaya ◽  
Seung M. You
Keyword(s):  
Heat Transfer ◽  
Coating Thickness ◽  
Boiling Heat Transfer ◽  
Average Particle Size ◽  
Nucleate Boiling ◽  
Copper Surface ◽  
Heat Fluxes ◽  
Porous Coating ◽  
Average Particle ◽  
Nucleate Boiling Heat Transfer

A novel, high-temperature, thermally-conductive, microporous coating (HTCMC) is developed by brazing copper particles onto a copper surface. This coating is more durable than many previous microporous coatings and also effectively creates reentrant cavities by optimizing brazing conditions. A parametric study of coating thicknesses of 49–283 μm with an average particle size of ∼25 μm was conducted using the HTCMC coating to understand nucleate boiling heat transfer (NBHT) enhancement on porous surfaces. It was found that there are three porous coating regimes according to their thicknesses. The first regime is “microporous” in which both NBHT and critical heat flux (CHF) enhancements gradually grow as the coating thickness increases. The second regime is “microporous-to-porous transition” where NBHT is further enhanced at lower heat fluxes but decreases at higher heat fluxes for increasing thickness. CHF in this regime continues to increase as the coating thickness increases. The last regime is named as “porous”, and both NBHT and CHF decrease as the coating thickness increases further than that of the other two regimes. The maximum nucleate boiling heat transfer coefficient observed was ∼350,000 W/m2K at 96 μm thickness (“microporous” regime) and the maximum CHF observed was ∼2.1 MW/m2 at ∼225 μm thickness (“porous” regime).

Pool Boiling Heat Transfer Enhancement of Water Using Brazed Copper Microporous Coatings

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
Seongchul Jun ◽  
Hyoseong Wi ◽  
Ajay Gurung ◽  
Miguel Amaya ◽  
Seung M. You
Keyword(s):  
Heat Transfer ◽  
Coating Thickness ◽  
Boiling Heat Transfer ◽  
Average Particle Size ◽  
Nucleate Boiling ◽  
Copper Surface ◽  
Heat Fluxes ◽  
Porous Coating ◽  
Average Particle ◽  
Thermally Conductive

A novel, high-temperature, thermally conductive, microporous coating (HTCMC) is developed by brazing copper particles onto a copper surface. This coating is more durable than many previous microporous coatings and also effectively creates re-entrant cavities by varying brazing conditions. A parametric study of coating thicknesses of 49–283 μm with an average particle size of ∼25 μm was conducted using the HTCMC coating to understand nucleate boiling heat transfer (NBHT) enhancement on porous surfaces. It was found that there are three porous coating regimes according to their thicknesses. The first regime is “microporous” in which both NBHT and critical heat flux (CHF) enhancements gradually grow as the coating thickness increases. The second regime is “microporous-to-porous transition” where NBHT is further enhanced at lower heat fluxes but decreases at higher heat fluxes for increasing thickness. CHF in this regime continues to increase as the coating thickness increases. The last regime is named “porous,” and both NBHT and CHF decrease as the coating thickness increases beyond that of the other two regimes. The maximum NBHT coefficient observed was ∼350,000 W/m2K at 96 μm thickness (microporous regime) and the maximum CHF observed was ∼2.1 MW/m2 at ∼225 μm thickness (porous regime).

Experimental Study of Heat Transfer Enhancement in Pool Boiling by Using 2-Ethyl 1-Hexanol an Additive

2014 ◽  
Vol 592-594 ◽  
pp. 1601-1606 ◽  
Author(s):  
Sameer Sheshrao Gajghate ◽  
Anil R. Aacharya ◽  
Anil T. Pise ◽  
Ganesh S. Jadhav
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
Bubble Dynamics ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Heat Fluxes ◽  
Optimum Level ◽  
Transfer Coefficients ◽  
Nichrome Wire

The addition of additives to the water is known to enhance boiling heat transfer. In the present investigation, boiling heat transfer coefficients are measured for Nichrome wire, immersed in saturated water with & without additive. An additive used is 2-Ethyl 1-Hexanol with varying concentrations in the range of 10-10000 ppm. Extensive experimentation of pool boiling is carried out above the critical heat flux. Boiling behavior i.e. bubble dynamics are observed at higher heat flux for nucleate boiling of water over wide ranges of concentration of additive in water. Results are encouraging and show that a small amount of surface active additive makes the nucleate boiling heat transfer coefficient considerably higher, and that there is an optimum additive (500-1000ppm) concentration for higher heat fluxes. An optimum level of enhancement is observed up to a certain amount of additive 500-1000ppm in the tested range. Thereafter significant enhancement is not observed. This enhancement may be due to change in thermo-physical properties i.e. mainly due to a reduction in surface tension of water in the presence of additive.

Experimental Study of Effect of Nucleation Site Size on Bubble Dynamics during Nucleate Pool Boiling Heat Transfer

2014 ◽  
Vol 592-594 ◽  
pp. 1596-1600 ◽  
Author(s):  
Abdul Najim ◽  
Anil R. Aacharya
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Bubble Dynamics ◽  
Bubble Diameter ◽  
Pool Boiling ◽  
Growth Period ◽  
Nucleation Site ◽  
Hypodermic Needle ◽  
Nucleate Pool Boiling ◽  
Pool Boiling Heat Transfer

In this paper, effect of nucleation site size on bubble dynamics during nucleate pool boiling heat transfer in saturated water is studied experimentally. Single bubble was generated using right angle tip of a hypodermic needle as a nucleation site. The hypodermic needles were used of inner diameters 0.413mm, 0.514mm, and 0.603 mm with a constant depth of 25mm. The bubble dynamics was studied using SONY Cyber-shot DSC-H100 camera operating at 30 frames per second at atmospheric pressure and at a wall superheat of 5K. The results show that, bubble diameter, bubble height and bubble volume increases with increase in diameter of nucleation site. The bubble growth period is found to be dependent on nucleation site size, and it decreases with increase in diameter of nucleation site. This happens because as volume of vapor bubble increases, buoyancy force starts dominates the capillary force and bubble detaches earlier. Effect of nucleation site size on bubble departure diameter and bubble release frequency is also discussed.

Pool Boiling Heat Transfer Enhancement Through Nanostructures on Silicon Microchannels

2012 ◽  
Vol 3 (3) ◽  
Author(s):  
Z. Yao ◽  
Y.-W. Lu ◽  
S. G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Silicon Nanowires ◽  
Boiling Heat Transfer ◽  
Bubble Dynamics ◽  
Pool Boiling ◽  
Hierarchical Structures ◽  
Heat Fluxes ◽  
Average Height ◽  
Maximum Heat ◽  
Maximum Heat Flux

Uniform silicon nanowires (SiNW) were successfully fabricated on the top, bottom, and sidewall surfaces of silicon microchannels by using a two-step electroless etching process. Different microchannel patterns with the channel width from 100 to 300 μm were first fabricated in a 10 mm × 10 mm silicon chip and then covered by SiNW with an average height of 10–20 μm. The effects of the microchannel geometry, micro/nano-hierarchical structures on pool boiling were studied and the bubble dynamics on different sample surfaces were compared. It was found that the combination of the micro/nanostructures promoted microbubble emission boiling under moderate heat fluxes, and yielded superior boiling heat transfer performance. At given wall superheats, the maximum heat flux of the microchannel with SiNW was improved by 120% over the microchannel-only surface, and more than 400% over a plain silicon surface. These results provide a new insight into the boiling mechanism for micro/nano-hierarchical structures and demonstrate their potential in improving pool boiling performance for microchannels.

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

2011 ◽  
Vol 133 (5) ◽  
Author(s):  
Dwight Cooke ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Boiling Heat Transfer ◽  
Bubble Dynamics ◽  
Pool Boiling ◽  
High Heat ◽  
Heat Fluxes ◽  
High Heat Flux ◽  
Silicon Chips ◽  
Heat Of Evaporation

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. It was determined that surface modifications to silicon chips can improve the heat transfer coefficient by a factor up to 3.4 times the performance of a plain chip. Surfaces with microchannels have shown to be efficient for boiling heat transfer by allowing liquid to flow through the open channels and wet the heat transfer surface while vapor is generated. 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.

Boiling Heat Transfer Properties of Copper Surface with Different Microstructures

2021 ◽  
pp. 124589
Author(s):  
Liying Wang ◽  
Yonghua Wang ◽  
Wen Cheng ◽  
Huadong Yu ◽  
Jinkai Xu
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Copper Surface ◽  
Transfer Properties

The Infrared Characteristics of the Wall Temperature of Boiling Heat Transfer in Microchannel

2011 ◽  
Vol 383-390 ◽  
pp. 811-815
Author(s):  
Hu Gen Ma ◽  
Jian Mei Bai ◽  
Rong Jian Xie ◽  
Wen Jing Tu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Wall Temperature ◽  
Boiling Heat Transfer ◽  
Transfer Test ◽  
Axial Direction ◽  
Transfer Model ◽  
Micro Channel ◽  
Vapor Quality ◽  
Test Rig

In this paper, the boiling heat transfer test rig was designed and built, while the characteristics of boiling Heat Transfer of refrigerants in micro-channel was researched. The wall temperature of micro-channel was measured by TH5104 Infrared thermography. The results showed that there were obvious variations for wall temperature of micro-channel along the axial direction when boiling heat transfer occurred in the micro-channel. The temperature distribution affected obviously by the heat flux, mass flow rate; vapor quality and heat transfer model.

Pool Boiling Characteristics of Metallic Nanofluids

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
K. Hari Krishna ◽  
Harish Ganapathy ◽  
G. Sateesh ◽  
Sarit K. Das
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Boiling Heat Transfer ◽  
Volume Fraction ◽  
Pool Boiling ◽  
Heat Fluxes ◽  
Solid Particles ◽  
Heater Surface ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

Nanofluids, solid-liquid suspensions with solid particles of size of the order of few nanometers, have created interest in many researchers because of their enhancement in thermal conductivity and convective heat transfer characteristics. Many studies have been done on the pool boiling characteristics of nanofluids, most of which have been with nanofluids containing oxide nanoparticles owing to the ease in their preparation. Deterioration in boiling heat transfer was observed in some studies. Metallic nanofluids having metal nanoparticles, which are known for their good heat transfer characteristics in bulk regime, reported drastic enhancement in thermal conductivity. The present paper investigates into the pool boiling characteristics of metallic nanofluids, in particular of Cu-H2O nanofluids, on flat copper heater surface. The results indicate that at comparatively low heat fluxes, there is deterioration in boiling heat transfer with very low particle volume fraction of 0.01%, and it increases with volume fraction and shows enhancement with 0.1%. However, the behavior is the other way around at high heat fluxes. The enhancement at low heat fluxes is due to the fact that the effect of formation of thin sorption layer of nanoparticles on heater surface, which causes deterioration by trapping the nucleation sites, is overshadowed by the increase in microlayer evaporation, which is due to enhancement in thermal conductivity. Same trend has been observed with variation in the surface roughness of the heater as well.

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