scholarly journals Freeze-Thaw Characteristics of Water-Based Copper Oxide Nanofluid

2018 ◽  
Vol 2 (1) ◽  
Keyword(s):  
Heat Transfer ◽  
Copper Oxide ◽  
Freezing Point ◽  
Average Particle Size ◽  
Solidification Process ◽  
Heat Transfer Fluid ◽  
Average Particle ◽  
Volumetric Concentration ◽  
Freeze Thaw ◽  
Water Based

This research examined the freeze-thaw characteristics of a water-based copper oxide (CuO) nanofluid for its successful application in cold regions, where freezing of heat transfer fluids can occur. The enhanced thermal conductivity (k) of nanofluid makes it valuable as a heat transfer fluid, but k diminishes as the average particle size (APS) of the dispersed nanoparticles grows. Therefore, experiments were conducted to determine the effect of freezing on the APS of nanofluid suspensions due to agglomeration. Additionally, it was studied, if the freezing point of the nanofluid was elevated or depressed as the volumetric concentration of nanoparticles in the suspension was increased from 1 % to 5%. Another objective of this experimental study was to compare the time required for precooling, freezing and subcooling of different concentrations of nanofluids and the base fluid. The results showed that the APS grew by as much as 51.2% larger due to the phenomenon of freezing, which would reduce the heat transfer performance. The addition of nanoparticles did not affect the freezing point of the nanofluids, tested for two particle volumetric concentrations of 1 and 5 %. It was observed that the precooling time of 5% CuO concentration was the longest. For the complete solidification process, the water and 1% CuO had comparable freezing times, while the 5% nanofluid had the shortest freezing time. The subcooling time was increased with particle volumetric concentration.

Synthesis of Emulsion for Water-Based Pigment Ink Jet

2011 ◽  
Vol 380 ◽  
pp. 81-84
Author(s):  
Li Ming Zhang ◽  
Xiu Lan Xin ◽  
Wei Jiang
Keyword(s):  
Particle Size ◽  
Water Resistance ◽  
Average Particle Size ◽  
Average Particle ◽  
Scanning Calorimetry ◽  
Reactive Surfactant ◽  
Potential Value ◽  
Ink Jet ◽  
Water Based ◽  
Pigment Ink

The water-based pigment ink jet emulsion whose particle size was less than 100nm was synthesized by the polymerization of methyl methacrylate, butyl acrylate and ethylhexyl acrylate, and anionic reactive surfactant and nonionic surfactant were used as the emulsifiers. The effects of particle size and water resistance were studied. The glass transition temperature was tested by differential scanning calorimetry. The average particle size of emulsion was range from 60nm to70nm, zeta potential value was less than -60mv; viscosity was 3.5mps; water absorption was 5.9%.

scholarly journals Bergenia ciliate–Mediated Mixed-Phase Synthesis and Characterization of Silver-Copper Oxide Nanocomposite for Environmental and Biological Applications

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6085
Author(s):  
Fazal Ur Rehman ◽  
Rashid Mahmood ◽  
Manel Ben Ali ◽  
Amor Hedfi ◽  
Mohammed Almalki ◽  
...  
Keyword(s):  
Copper Oxide ◽  
Radical Scavenging Activity ◽  
Average Particle Size ◽  
Radical Scavenging ◽  
Diffusion Method ◽  
Average Particle ◽  
Light Spectrum ◽  
Structural Morphology ◽  
X Ray ◽  
Silver Copper

Bergenia ciliate (B. ciliate) leaf extract was used as a reducing and stabilizing agent for the synthesis of silver-copper oxide nanocomposite (Ag-CuO NC). Scanning and transmission electron microscopies (SEM and TEM) were used to examine the structural morphology, and the average particle size was determined to be 47.65 nm. The phase confirmation and crystalline structure were examined through the X-ray diffraction (XRD) technique, where cubic and monoclinic geometries were assigned to Ag and CuO. The energy dispersive X-ray (EDX), Fourier transform infrared (FTIR) and ultra-violet and visible (UV-Visible) spectroscopies were operated to analyse the elemental composition, functional groups and light absorption phenomena of the Ag-CuO NC. Under the full light spectrum, the photodegradation of Rhodamine 6G was recorded, and 99.42 percent of the dye degraded in 80 min. The Agar well diffusion method was followed to perform antibacterial activity against selected pathogens, and the activity was found to increase with increasing concentration of Ag-CuO NC. The ABTS free radical scavenging activity suggests that the activity of Ag-CuO NC is higher than ascorbic acid.

Al2O3-Water Nanofluids for Heat Transfer Application

MRS Advances ◽  
2019 ◽  
Vol 4 (28-29) ◽  
pp. 1611-1619 ◽  
Author(s):  
Lakshita Phor ◽  
Tanuj Kumar ◽  
Monika Saini ◽  
Vinod Kumar
Keyword(s):  
Heat Transfer ◽  
Heat Load ◽  
Volume Fraction ◽  
Average Particle Size ◽  
Power Input ◽  
Experimental Investigations ◽  
Average Particle ◽  
X Ray Diffraction ◽  
Absorption Bands ◽  
External Power

AbstractThis manuscript aims at synthesizing Al2O3-de-ionized water nanofluid and constructing a practical design of self-cooling device that does not require any external power input. Crystalline phase of powder was confirmed by X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) showed the various functional groups and absorption bands and average particle size was calculated to be 58.608 nm by Field Emission Scanning Electron Microscopy (FESEM) annealed at 900K. Experimental investigations were carried out to determine the effect of volume fraction of Al2O3 nanoparticles in the nanofluid on the rate of heat transfer from heat load to heat sink. Temperature of heat load was taken as 80° C. According to our results, cooling by 15°C, 13°C and 12°C was attained when volume fraction of nanoparticles was 1.5%, 1% and 0.5% respectively. The thermal conductivity was also measured and found to be increasing with the concentration of nanoparticles in nanofluid. Hence, indicating the use of nanofluids with suitable concentration in various cooling applications.

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).

scholarly journals Thermal Conductivity of Metastable Ionic Liquid [C2mim][CH3SO3]

Molecules ◽  
2020 ◽  
Vol 25 (18) ◽  
pp. 4290 ◽  
Author(s):  
Daniel Lozano-Martín ◽  
Salomé Inês Cardoso Vieira ◽  
Xavier Paredes ◽  
Maria José Vitoriano Lourenço ◽  
Carlos A. Nieto de Castro ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Ionic Liquid ◽  
Melting Point ◽  
Solid Phase ◽  
Freezing Point ◽  
Phase Region ◽  
Heat Transfer Fluid ◽  
Diphenyl Oxide ◽  
Conductivity Models

Ionic liquids have been suggested as new engineering fluids, namely in the area of heat transfer, as alternatives to current biphenyl and diphenyl oxide, alkylated aromatics and dimethyl polysiloxane oils, which degrade above 200 °C and pose some environmental problems. Recently, we have proposed 1-ethyl-3-methylimidazolium methanesulfonate, [C2mim][CH3SO3], as a new heat transfer fluid, because of its thermophysical and toxicological properties. However, there are some interesting points raised in this work, namely the possibility of the existence of liquid metastability below the melting point (303 K) or second order-disorder transitions (λ-type) before reaching the calorimetric freezing point. This paper analyses in more detail this zone of the phase diagram of the pure fluid, by reporting accurate thermal-conductivity measurements between 278 and 355 K with an estimated uncertainty of 2% at a 95% confidence level. A new value of the melting temperature is also reported, Tmelt = 307.8 ± 1 K. Results obtained support liquid metastability behaviour in the solid-phase region and permit the use of this ionic liquid at a heat transfer fluid at temperatures below its melting point. Thermal conductivity models based on Bridgman theory and estimation formulas were also used in this work, failing to predict the experimental data within its uncertainty.

scholarly journals A New Collector for Effectively Increasing Recovery in Copper Oxide Ore-Staged Flotation

Minerals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 595
Author(s):  
Renfeng Zhu ◽  
Guohua Gu ◽  
Zhixiang Chen ◽  
Yanhong Wang ◽  
Siyu Song
Keyword(s):  
Particle Size ◽  
Copper Oxide ◽  
High Efficiency ◽  
Average Particle Size ◽  
Economic Feasibility ◽  
Processing Plant ◽  
Average Particle ◽  
Entrainment Rate ◽  
Flotation Process ◽  
New Type

A new method, staged flotation for effectively increasing the recovery of ultra-fine copper oxide ore with a new type of collector (ZH-1, C3-5 carbon chain xanthate) is proposed for the first time. The flotation process and mechanism were examined by flotation tests, entrainment rate analysis, laser particle size experiments and microscopic imagery as well as economic feasibility analysis. It was demonstrated that the collector isoamyl sodium xanthate (ISX) shows a good collection ability (recovery exceeded 95%) for azurite, but the recovery was relatively much lower for malachite (only near 80%) due to the different particle size distribution. The new type of xanthate ZH-1 has shown a high-efficiency collection performance for fine-grained malachite. The recovery achieved for −10 μm malachite was more than 95% when the ZH-1 dosage was 150 mg/L, while the average particle size of −10 μm malachite sharply increased from 4.641 μm to 9.631 μm. The batch flotation results indicated that the copper oxide flotation recovery increased from 79.67% to 83.38%, and the grade also raised from 18.08% to 18.14% after using the staged flotation technology with ZH-1 as collector during the flotation of −25 μm ore. It was confirmed that this technology was quite effective for the recovery of copper oxide at the Dishui Copper Processing Plant, which successfully increased its gross profit by 1.6 million US$ per year.

Mesoscale Multi-Physics Simulation of Solidification in Selective Laser Melting Process Using a Phase Field and Thermal Lattice Boltzmann Model

2017 ◽  
Author(s):  
Dehao Liu ◽  
Yan Wang
Keyword(s):  
Heat Transfer ◽  
Selective Laser Melting ◽  
Phase Field ◽  
Lattice Boltzmann ◽  
Solidification Process ◽  
Heat Transfer Fluid ◽  
Melt Flow ◽  
Laser Melting ◽  
Physics Simulation ◽  
Thermal Lattice Boltzmann

Selective laser melting (SLM) is a powder bed based additive manufacturing process by melting fine-grained metallic powders with a laser heating source. Understanding the solidification of alloys during SLM process is of importance for accurate prediction of microstructures and properties for process design and optimization. In this study, a multi-physics model is developed to simulate evolution of alloy microstructure during solidification, which incorporates heat transfer, fluid dynamics, kinetics of phase transformations, and grain growth. In this integrated simulation framework, the phase field method for the dendritic growth of a dilute binary alloy is coupled with the thermal lattice Boltzmann method for the melt flow and heat transfer. The effects of latent heat, melt flow and cooling rate on solidification process are also investigated. The multi-physics simulation results provide new insight to predict the complex solidification process more accurately than single-physics approaches.

scholarly journals Effect of Subcooling on Pool Boiling of Water from Sintered Copper Microporous Coating at Different Orientations

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Seongchul Jun ◽  
Jinsub Kim ◽  
Seung M. You ◽  
Hwan Yeol Kim
Keyword(s):  
Heat Transfer ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Average Particle Size ◽  
Nucleate Boiling ◽  
Copper Surface ◽  
Average Particle ◽  
Pool Boiling Heat Transfer ◽  
Microporous Coating ◽  
Plain Surface

The subcooling effect on pool boiling heat transfer using a copper microporous coating was experimentally studied in water for subcoolings of 10 K, 20 K, and 30 K at atmospheric pressure and compared to that of a plain copper surface. A high-temperature thermally conductive microporous coating (HTCMC) was made by sintering copper powder with an average particle size of 67 μm onto a 1 cm × 1 cm plain copper surface with a coating thickness of ~300 μm. The HTCMC surface showed a two times higher critical heat flux (CHF), ~2,000 kW/m2, and up to seven times higher nucleate boiling heat transfer (NBHT) coefficient, ~350 kW/m2K, when compared with a plain copper surface at saturation. The results of the subcooling effect on pool boiling showed that the NBHT of both the HTCMC and the plain copper surface did not change much with subcooling. On the other hand, the CHF increased linearly with the degree of subcooling for both the HTCMC and the plain copper surface. The increase in the CHF was measured to be ~60 kW/m2for every degree of subcooling for both the HTCMC and the plain surface, so that the difference of the CHF between the HTCMC and the plain copper surface was maintained at ~1,000 kW/m2throughout the tested subcooling range. The CHFs for the HTCMC and the plain copper surface at 30 K subcooling were 3,820 kW/m2and 2,820 kW/m2, respectively. The experimental results were compared with existing CHF correlations and appeared to match well with Zuber’s formula for the plain surface. The combined effect of subcooling and orientation of the HTCMC on pool boiling heat transfer was studied as well.

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).

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