A Flow Visualization Study of the Jet Dynamics in a Round Jet Impinging on a Foamed Aluminum Porous Media

2009 ◽  
Author(s):  
Elizabeth DiBella ◽  
Ian Azeredo ◽  
Ravi Yakkatelli ◽  
Amy Fleischer
Keyword(s):  
Reynolds Number ◽  
Porous Media ◽  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Flow Dynamics ◽  
Enhancement Effect ◽  
Aluminum Foams ◽  
Impact Surface ◽  
The Impact

The high surface area of foamed metals makes them an attractive choice for impingement heat sinks. If the jet can effectively penetrate the foam, the high surface area will lead to enhanced thermal performance. However, if the jet fails to effectively penetrate the foam, the surface enhancement effect will be reduced. Previous studies have suggested that for high density foams, the jet does not effectively penetrate the foam and under certain flow conditions may in fact deflect off the foam. In this study, the flow dynamics of round jets impinging on both aluminum foams and solid cubes are studied using smoke wire visualization to identify the effects of Reynolds number and jet exit to surface spacing. The differences in the impinging jet dynamics between the foams and the solid cubes are identified. It is found that the penetration of the impinging flow into the porous media is significantly affected by permeability. As permeability decreases, flow deflection off the impact surface of the foam increases, approaching the fluid dynamics behavior of impact on a solid cube. The jet-exit-to-surface spacing and Reynolds number are also found to significantly affect the flow dynamics.

scholarly journals In-Situ Synthesis of Nb2O5/g-C3N4 Heterostructures as Highly Efficient Photocatalysts for Molecular H2 Evolution under Solar Illumination

Catalysts ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 169 ◽  
Author(s):  
Faryal Idrees ◽  
Ralf Dillert ◽  
Detlef Bahnemann ◽  
Faheem Butt ◽  
Muhammad Tahir
Keyword(s):  
Photocatalytic Activity ◽  
Charge Carrier ◽  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Photogenerated Electron ◽  
Band Alignment ◽  
Solar Irradiation ◽  
Electron Hole ◽  
The Impact

This work focuses on the synthesis of heterostructures with compatible band positions and a favourable surface area for the efficient photocatalytic production of molecular hydrogen (H2). In particular, 3-dimensional Nb2O5/g-C3N4 heterostructures with suitable band positions and high surface area have been synthesized employing a hydrothermal method. The combination of a Nb2O5 with a low charge carrier recombination rate and a g-C3N4 exhibiting high visible light absorption resulted in remarkable photocatalytic activity under simulated solar irradiation in the presence of various hole scavengers (triethanolamine (TEOA) and methanol). The following aspects of the novel material have been studied systematically: the influence of different molar ratios of Nb2O5 to g-C3N4 on the heterostructure properties, the role of the employed hole scavengers, and the impact of the co-catalyst and the charge carrier densities affecting the band alignment. The separation/transfer efficiency of the photogenerated electron-hole pairs is found to increase significantly as compared to that of pure Nb2O5 and g-C3N4, respectively, with the highest molecular H2 production of 110 mmol/g·h being obtained for 10 wt % of g-C3N4 over Nb2O5 as compared with that of g-C3N4 (33.46 mmol/g·h) and Nb2O5 (41.20 mmol/g·h). This enhanced photocatalytic activity is attributed to a sufficient interfacial interaction thus favouring the fast photogeneration of electron-hole pairs at the Nb2O5/g-C3N4 interface through a direct Z-scheme.

Determination of PBP by Using a Nano SiO2/GC Modified Electrode

2011 ◽  
Vol 312-315 ◽  
pp. 138-142
Author(s):  
A. Shokuhi Rad
Keyword(s):  
Electrochemical Sensor ◽  
Surface Area ◽  
Modified Electrode ◽  
Electrochemical Sensors ◽  
High Surface ◽  
High Surface Area ◽  
Sio2 Film ◽  
Enhancement Effect ◽  
Nano Sio2

Recently, several metal oxide nanomaterials have been deposited on the surface of electrodes and investigated for the reduction/ oxidation and detection of some biological materials. Electrochemical Sensors with high surface area and porosity are important components in an irresistible wealth of systems for various applications. An electrochemical sensor for the sensitive determination of parabromophenol (PBP) was synthesized based on the nano-SiO2 film-modified electrode. Owing to the exceptional properties of nano-SiO2 such as successfully minimized transport limitations, huge surface area, strong adsorptive ability, subtle electronic properties and catalytic ability, the electrochemical oxidation signal of PBP significantly increases at the nano- SiO2/GC electrochemical sensor, suggesting that nano-SiO2 film exhibits obvious enhancement effect to the determination of PBP. Based on this, a sensitive electrochemical method was developed for the determination of PBP.

Scrutinizing ligand exchange reactions in the formation of the precious group metal–organic framework RuII,II-HKUST-1: the impact of diruthenium tetracarboxylate precursor and modulator choice

2021 ◽  
Vol 50 (15) ◽  
pp. 5226-5235
Author(s):  
Werner R. Heinz ◽  
Dominik Staude ◽  
David Mayer ◽  
Hana Bunzen ◽  
Roland A. Fischer
Keyword(s):  
Surface Area ◽  
Ligand Exchange ◽  
Metal Organic Framework ◽  
High Surface ◽  
High Surface Area ◽  
Exchange Reactions ◽  
Secondary Building Unit ◽  
Building Unit ◽  
Metal Organic ◽  
The Impact

The high surface area univalent Ru(ii) analogue of HKUST-1 (Ru3BTC2; BTC = 1,3,5 benzendicarboxylate) is synthesized by the coordination modulated controlled secondary building unit approach.

Tenacious Mass Transfer Limitations Drive Catalytic Selectivity during Electrochemical Carbon Dioxide Reduction

2019 ◽  
Author(s):  
Kailun Yang ◽  
Recep Kas ◽  
Wilson A. Smith
Keyword(s):  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Catalyst Layer ◽  
Active Surface ◽  
Active Surface Area ◽  
High Concentration ◽  
Copper Electrodes ◽  
Surface Enhanced ◽  
Local Current

<p>This study evaluated the performance of the commonly used strong buffer electrolytes, i.e. phosphate buffers, during CO<sub>2</sub> electroreduction in neutral pH conditions by using in-situ surface enhanced infrared absorption spectroscopy (SEIRAS). Unfortunately, the buffers break down a lot faster than anticipated which has serious implications on many studies in the literature such as selectivity and kinetic analysis of the electrocatalysts. Increasing electrolyte concentration, surprisingly, did not extend the potential window of the phosphate buffers due to dramatic increase in hydrogen evolution reaction. Even high concentration phosphate buffers (1 M) break down within the potentials (-1 V vs RHE) where hydrocarbons are formed on copper electrodes. We have extended the discussion to high surface area electrodes by evaluating electrodes composed of copper nanowires. We would like highlight that it is not possible to cope with high local current densities on these high surface area electrodes by using high buffer capacity solutions and the CO<sub>2</sub> electrocatalysts are needed to be evaluated by casting thin nanoparticle films onto inert substrates as commonly employed in fuel cell reactions and up to now scarcely employed in CO<sub>2</sub> electroreduction. In addition, we underscore that normalization of the electrocatalytic activity to the electrochemical active surface area is not the ultimate solution due to concentration gradient along the catalyst layer.This will “underestimate” the activity of high surface electrocatalyst and the degree of underestimation will depend on the thickness, porosity and morphology of the catalyst layer. </p> <p> </p>

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