scholarly journals Enhancing heat transport in multiphase Rayleigh–Bénard turbulence by changing the plate–liquid contact angles

2021 ◽  
Vol 933 ◽  
Author(s):  
Hao-Ran Liu ◽  
Kai Leong Chong ◽  
Chong Shen Ng ◽  
Roberto Verzicco ◽  
Detlef Lohse
Keyword(s):  
Heat Transport ◽  
Multiphase Flows ◽  
Volume Fraction ◽  
Pure Water ◽  
Contact Angles ◽  
Water Mixture ◽  
Thermal Plumes ◽  
Oil Water ◽  
Turbulent Wall ◽  
Rayleigh Benard

This numerical study presents a simple but extremely effective way to considerably enhance heat transport in turbulent wall-bounded multiphase flows, namely by using oleophilic walls. As a model system, we pick the Rayleigh–Bénard set-up, filled with an oil–water mixture. For oleophilic walls, using only $10\,\%$ volume fraction of oil in water, we observe a remarkable heat transport enhancement of more than $100\,\%$ as compared to the pure water case. In contrast, for oleophobic walls, the enhancement is only of about $20\,\%$ as compared to pure water. The physical explanation of the heat transport increment for oleophilic walls is that thermal plumes detach from the oil-rich boundary layer and carry the heat with them. In the bulk, the oil–water interface prevents the plumes from mixing with the turbulent water bulk and to diffuse their heat. To confirm this physical picture, we show that the minimum amount of oil necessary to achieve the maximum heat transport is set by the volume fraction of the thermal plumes. Our findings provide guidelines of how to optimize heat transport in wall-bounded thermal turbulence. Moreover, the physical insight of how coherent structures are coupled with one of the phases of a two-phase system has very general applicability for controlling transport properties in other turbulent wall-bounded multiphase flows.

scholarly journals Volume Fraction Measurement in Crude Oil-Water Two-Phase Mixture using a Neutron Beam

2017 ◽  
Vol 2 (2) ◽  
pp. 57-63
Author(s):  
Abdullah A. Kendoush ◽  
Hameed B. Mahood ◽  
Ibrahim G. Fiadh
Keyword(s):  
Crude Oil ◽  
Neutron Source ◽  
Neutron Beam ◽  
Volume Fraction ◽  
Water Mixture ◽  
Two Phase ◽  
Oil In Water ◽  
Oil Water ◽  
Phase Mixture ◽  
Fraction Measurement

A neutron beam has been used to measure the volume fraction of crude oil in water of non- flow two-phase mixture experimentally.241Am-Be neutron source were used with an activity of 3.7x104 MBq. The volume fraction was simulated by using small plastic tubes filled with oil and immersed in non-flow water tube. The results show that it is feasible to measure the volume fraction of crude oil in a crude oil-water mixture.

On the Development of Deadleg Criterion

2005 ◽  
Vol 127 (1) ◽  
pp. 124-135 ◽  
Author(s):  
M. A. Habib ◽  
H. M. Badr ◽  
S. A. M. Said ◽  
I. Hussaini ◽  
J. J. Al-Bagawi
Keyword(s):  
Volume Fraction ◽  
Argon Laser ◽  
Secondary Phase ◽  
Momentum Conservation ◽  
Low Flow ◽  
Water Mixture ◽  
Fluid Mixture ◽  
Water Separation ◽  
Oil Water ◽  
Stagnant Fluid

Corrosion in deadlegs occurs as a result of water separation due to the very low flow velocity. This work aims to investigate the effect of geometry and orientation on flow field and oil/water separation in deadlegs in an attempt for the development of a deadleg criterion. The investigation is based on the solution of the mass and momentum conservation equations of an oil/water mixture together with the volume fraction equation for the secondary phase. Results are obtained for two main deadleg orientations and for different lengths of the deadleg in each orientation. The considered fluid mixture contains 90% oil and 10% water (by volume). The deadleg length to diameter ratio (L/D) ranges from 1 to 9. The results show that the size of the stagnant fluid region increases with the increase of L/D. For the case of a vertical deadleg, it is found that the region of the deadleg close to the header is characterized by circulating vortical motions for a length l≈3 D while the remaining part of the deadleg occupied by a stagnant fluid. In the case of a horizontal deadleg, the region of circulating flow extends to 3–5 D. The results also indicated that the water volumetric concentration increases with the increase of L/D and is influenced by the deadleg orientation. The streamline patterns for a number of cases were obtained from flow visualization experiments (using 200 mW Argon laser) with the objective of validating the computational model.

Effect of Self-Rewetting Fluids on Pulsating Heat Pipe Thermal Performance

2009 ◽  
Author(s):  
Koji Fumoto ◽  
Masahiro Kawaji ◽  
Tsuyoshi Kawanami
Keyword(s):  
Surface Tension ◽  
Heat Pipe ◽  
Heat Transport ◽  
Heated Surface ◽  
Pure Water ◽  
Channel Cross Section ◽  
Working Fluid ◽  
High Heat Flux ◽  
Aqueous Alcohol ◽  
Water Mixture

Pulsating heat pipes (PHPs) have recently emerged as a possible cooling device for high heat flux electronics to replace conventional cooling devices. In this study, new experimental results were obtained for using self-rewetting fluids to enhance the heat transport of PHPs. Unlike other common liquids, the surface tension of self-rewetting fluids increases with temperature. The increase in surface tension at high temperatures causes the liquid to be drawn towards a heated surface if a dry spot appears, which improves boiling heat transfer. PHPs were constructed out of multiport extruded aluminum tubing with a square channel cross section. In experiments, heptanol was added to water at a concentration of less than 1 wt% to form the self-rewetting fluid. Several other parameters were adjusted for optimization, such as the aqueous alcohol solution concentration of the working fluid, the fluid fill ratio, and the heat pipe orientation. Using a self-rewetting fluid in PHPs was found to be highly effective in improving their heat transport capability. The PHPs delivered a better performance when oriented vertically rather than horizontally. As a working fluid, the heptanol water mixture outperformed both the butanol water mixture and pure water within the parameters of this experiment.

Detecting Phase-Inversion Region of Surfactant-Stabilized Oil/Water Emulsions Using Differential Dielectric Sensors

2021 ◽  
pp. 1-21
Author(s):  
Kurniawan S. Suminar ◽  
Ilias Gavrielatos ◽  
Ramin Dabirian ◽  
Ram S. Mohan ◽  
Ovadia Shoham
Keyword(s):  
Continuous Flow ◽  
Phase Inversion ◽  
Volume Fraction ◽  
Gas Production ◽  
Water Mixture ◽  
Water Emulsion ◽  
Phase Volume Fraction ◽  
Inversion Region ◽  
Dielectric Sensor ◽  
Oil Water

Summary An experimental and theoretical investigation of surfactant-stabilized oil/water emulsion characteristics was carried out under water sweep (WS) and oil sweep (OS) conditions. Both hydrophilic and hydrophobic surfactants were used, with concentrations less than and more than the critical micelle concentration (CMC). Experimental data were acquired for detection of the phase-inversion region, which was measured simultaneously by several independent methods. These include a circular differential dielectric sensor (C-DDS), a rectangular differential dielectric sensor (R-DDS) (both sensors accurately detect the phase-inversion region), a pressure transducer, and a mass flowmeter. The addition of an emulsifier surfactant to an oil/water mixture generated a stable emulsion, which resulted in a phase-inversion delay. For water-continuous to oil-continuous flow, a hydrophilic surfactant was a better emulsifier, while for oil-continuous to water-continuous flow, a hydrophobic surfactant was a better emulsifier for creating more stable emulsions. The surfactant/oil/water emulsion resulted in an increase of the dispersed-phase volume fraction required for phase inversion, as compared to the case of oil/water dispersions without surfactant. For emulsions with surfactant concentrations above CMC, the presence of micelles contributed to further delay of the phase inversion, as compared to those with surfactant concentrations below CMC. The phase-inversion region exhibits a hysteresis between the OS and WS runs, below CMC and above CMC, which was due to the difference in droplet sizes caused by different breakup and coalescence processes for oil-continuous and water-continuousflow. This research shows that the DDS is an efficient instrumentation that can be used to detect the region where the emulsion phase inversion is expected to occur. Moreover, the experimental results and the pertinent analysis and discussion provide useful insights for a more informed design of surface facilities (including emulsion separators) in oil and gas production operations.

Controlling porosity and density of nanocellulose aerogels for superhydrophobic light materials

TAPPI Journal ◽  
2018 ◽  
Vol 17 (03) ◽  
pp. 145-153 ◽  
Author(s):  
Chengua Yu ◽  
Feng Wang ◽  
Shiyu Fu ◽  
Lucian Lucia
Keyword(s):  
Contact Angle ◽  
Freeze Drying ◽  
Engine Oil ◽  
High Porosity ◽  
Water Mixture ◽  
Waste Engine Oil ◽  
Hydrophobically Modified ◽  
Static Contact ◽  
Oil Water ◽  
Hydrophobic Material

A very low-density oil-absorbing hydrophobic material was fabricated from cellulose nanofiber aerogels–coated silane substances. Nanocellulose aerogels (NCA) superabsorbents were prepared by freeze drying cellulose nanofibril dispersions at 0.2%, 0.5%, 0.8%, 1.0%, and 1.5% w/w. The NCA were hydrophobically modified with methyltrimethoxysilane. The surface morphology and wettability were characterized by scanning electron microscopy and static contact angle. The aerogels displayed an ultralow density (2.0–16.7 mg·cm-3), high porosity (99.9%–98.9%), and superhydrophobicity as evidenced by the contact angle of ~150° that enabled the aerogels to effectively absorb oil from an oil/water mixture. The absorption capacities of hydrophobic nanocellulose aerogels for waste engine oil and olive oil could be up to 140 g·g-1 and 179.1 g·g-1, respectively.

scholarly journals Fabrication of silica/PVA-co-PE nanofiber membrane for oil/water separation

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Yuanli Chen ◽  
Hui Fan ◽  
Xinlin Zha ◽  
Wenwen Wang ◽  
Yi Wu ◽  
...  
Keyword(s):  
High Efficiency ◽  
Silicone Oil ◽  
Hydroxyl Groups ◽  
Water Mixture ◽  
Silica Nanospheres ◽  
Nanofiber Membrane ◽  
Water Separation ◽  
Oil Water Separation ◽  
Silica Nanostructures ◽  
Oil Water

AbstractHigh efficiency and anti-pollution oil/water separation membrane has been widely explored and researched. There are a large number of hydroxyl groups on the surface of silica, which has good wettability and can be used for oil-water separation membranes. Hydrophilic silica nanostructures with different morphologies were synthesized by changing templates and contents of trimethylbenzene (TMB). Here, silica nanospheres with radical pores, hollow silica nanospheres and worm-like silica nanotubes were separately sprayed on the PVA-co-PE nanofiber membrane (PM). The abundance of hydroxyl groups and porous structures on PM surfaces enabled the absorption of silica nanospheres through hydrogen bonds. Compared with different silica nanostructures, it was found that the silica/PM exhibited excellent super-hydrophilicity in air and underwater “oil-hating” properties. The PM was mass-produced in our lab through melt-extrusion-phase-separation technique. Therefore, the obtained membranes not only have excellent underwater superoleophobicity but also have a low-cost production. The prepared silica/PM composites were used to separate n-hexane/water, silicone oil/water and peanut oil water mixtures via filtration. As a result, they all exhibited efficient separation of oil/water mixture through gravity-driven filtration.

scholarly journals Gravity-Driven Separation of Oil/Water Mixture by Porous Ceramic Membranes with Desired Surface Wettability

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 457
Author(s):  
Chunlei Ren ◽  
Wufeng Chen ◽  
Chusheng Chen ◽  
Louis Winnubst ◽  
Lifeng Yan
Keyword(s):  
Porous Ceramic ◽  
Ceramic Membranes ◽  
Separation Performance ◽  
Water Mixture ◽  
Alumina Membrane ◽  
Water Separation ◽  
Alumina Membranes ◽  
Oil Water Separation ◽  
Gravity Driven ◽  
Oil Water

Porous Al2O3 membranes were prepared through a phase-inversion tape casting/sintering method. The alumina membranes were embedded with finger-like pores perpendicular to the membrane surface. Bare alumina membranes are naturally hydrophilic and underwater oleophobic, while fluoroalkylsilane (FAS)-grafted membranes are hydrophobic and oleophilic. The coupling of FAS molecules on alumina surfaces was confirmed by Thermogravimetric Analysis and X-ray Photoelectron Spectroscopy measurements. The hydrophobic membranes exhibited desired thermal stability and were super durable when exposed to air. Both membranes can be used for gravity-driven oil/water separation, which is highly cost-effective. The as-calculated separation efficiency (R) was above 99% for the FAS-grafted alumina membrane. Due to the excellent oil/water separation performance and good chemical stability, the porous ceramic membranes display potential for practical applications.

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