scholarly journals Effect of the Freeze-Thaw on the Suspension Stability and Thermal Conductivity of EG/Water-Based Al2O3 Nanofluids

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Tae Jong Choi ◽  
Seok Pil Jang ◽  
Dae Soo Jung ◽  
Hyung Mi Lim ◽  
Young Man Byeon ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Working Fluid ◽  
Suspension Stability ◽  
Particle Size Distributions ◽  
Step Method ◽  
Cooling Systems ◽  
Freeze Thaw ◽  
Particle Size Analyzer ◽  
Water Based

This paper reports the effect of the freeze-thaw on the suspension stability, particle size distribution, and thermal conductivity of EG/water-based nanofluids containing Al2O3 nanoparticles that can be used as improved working fluid for cooling systems. The EG/water-based Al2O3 nanofluids were prepared using a two-step method with a nanodisperser and decanting processes. To investigate the effect of freeze-thaw on the suspension stability and thermal conductivity of nanofluids, the prepared nanofluids were frozen at -32°C for 24 hours using a refrigerating chamber, and then they were completely thawed at room temperature for 24 hours. The suspension stability of the thawed nanofluids was quantitatively analysed for over a day using a Turbiscan. In addition, the particle size distributions and deformation of nanoparticles dispersed in the nanofluids were measured using a particle size analyzer (PSA) and TEM. Also, the thermal conductivity of the nanofluids was measured using a transient hot wire (THW) method in temperature from -10 to 70°C. Based on the results, we show that the suspension stability, thermal conductivity, and particle size of EG/water-based Al2O3 nanofluids were not affected by low temperature.

Thermal Conductivity Behavior of Yttria Nanofluids

2012 ◽  
Author(s):  
Salim J. S. Masharqa ◽  
Waka Tesfai ◽  
Pawan K. Singh ◽  
Matteo Chiesa ◽  
Youssef Shatilla
Keyword(s):  
Thermal Conductivity ◽  
Size Distributions ◽  
Conductivity Measurements ◽  
Nanoparticle Concentration ◽  
Particle Size Distributions ◽  
Step Method ◽  
Cooling Systems ◽  
Conductivity Enhancement ◽  
Acoustic Spectroscopy ◽  
Dependent Viscosity

In this paper the effect of nanoparticle concentration and temperature on the thermal conductivity of Yttria-Ethylene glycol nanofluid has been investigated. In addition, the effect of aging on the viscosity and the thermal conductivity of these nanofluids also have been studied. The nanofluids were prepared by two-step method, and particle size distributions were characterized using acoustic spectroscopy. It was found that the thermal conductivity of Yttria nanofluids increases beyond the classical Hamilton-Crosser model. Moreover, the enhancement in the thermal conductivity of this nanofluid showed high temperature dependence behavior. For instance at 3.0% by volume particles loading, the thermal conductivity enhancement increased from 16.6% at 26 °C to 27.0% at 59 °C, making these nanofluids attractive and effective for cooling systems that operates at high temperatures. Finally, time dependent viscosity and thermal conductivity measurements showed stable behavior for 16 days of study demonstrating the good stability of these nanofluids.

scholarly journals Statistical analysis of thermal conductivity experimentally measured in water-based nanofluids

2021 ◽  
Vol 477 (2250) ◽  
pp. 20210222
Author(s):  
J. Tielke ◽  
M. Maas ◽  
M. Castillo ◽  
K. Rezwan ◽  
M. Avila
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Particle Size ◽  
Particle Concentration ◽  
Statistical Correlation ◽  
Large Scatter ◽  
Water Based ◽  
Homogeneous Media ◽  
Measured Thermal Conductivity ◽  
Specific Particle

Nanofluids are suspensions of nanoparticles in a base heat-transfer liquid. They have been widely investigated to boost heat transfer since they were proposed in the 1990s. We present a statistical correlation analysis of experimentally measured thermal conductivity of water-based nanofluids available in the literature. The influences of particle concentration, particle size, temperature and surfactants are investigated. For specific particle materials (alumina, titania, copper oxide, copper, silica and silicon carbide), separate analyses are performed. The conductivity increases with the concentration in qualitative agreement with Maxwell’s theory of homogeneous media. The conductivity also increases with the temperature (in addition to the improvement due to the increased conductivity of water). Surprisingly, only silica nanofluids exhibit a statistically significant effect of the particle size, whereby smaller particles lead to faster heat transfer. Overall, the large scatter in the experimental data prevents a compelling, unambiguous assessment of these effects. Taken together, the results of our analysis suggest that more comprehensive experimental characterizations of nanofluids are necessary to estimate their practical potential.

Preparation and Stability Characterization of Copper Oxide Nanofluid by Two Step Method

2015 ◽  
Vol 832 ◽  
pp. 139-143 ◽  
Author(s):  
A.L. Subramaniyan ◽  
Arun Kumar ◽  
Sethupathi ◽  
T. Sorna Kumar ◽  
R. Ilangovan
Keyword(s):  
Particle Size ◽  
Copper Oxide ◽  
Copper Chloride ◽  
Sol Gel ◽  
Cuo Nanoparticles ◽  
Step Method ◽  
Sem Image ◽  
Particle Size Analyzer ◽  
Negative Zeta Potential

Copper oxide (CuO) nanofluids are prepared by two step method. CuO nanoparticles are prepared by sol gel method with Copper chloride as precursor and NaOH as a reducing agent. The prepared CuO nanoparticles are characterized by XRD, SEM and Particle size analyzer. XRD measurements reveal a grain size of 72nm .SEM image reveals an inhomogenous mixture of particles from 500 nm to 3500 nm with irregular morphology and few traces of CuO cones.. The particle size distribution of CuO particles is in the range of 1000-1600nm which is in accordance with the SEM results.CuO –Ethylene Glycol nanofluids are prepared by two step method by ultrasonication of obtained CuO particles.The stability of CuO nanofluid is given with a negative zeta potential of-22.5 mv.

Suspension Stability and Thermal Conductivity of Oxide Based Nanofluids with Low Volume Concentration

2010 ◽  
Vol 160-162 ◽  
pp. 802-808 ◽  
Author(s):  
Wei Lin Zhao ◽  
Bao Jie Zhu ◽  
Jin Kai Li ◽  
Yan Xiang Guan ◽  
Dong Dong Li
Keyword(s):  
Thermal Conductivity ◽  
Volume Concentration ◽  
Average Particle Size ◽  
Sio2 Nanoparticles ◽  
Heat Transfer Fluid ◽  
Suspension Stability ◽  
Average Particle ◽  
Step Method ◽  
Low Volume ◽  
Thermal Conductivities

Nanofluid is a new class of heat transfer fluid which contains suspended metallic or nonmetallic nanoparticles in traditional fluid. In this paper, nanofluids containing low volume concentrations (0.1-0.5vol.%) of Al2O3 and SiO2 nanoparticles were produced using a two-step method with ultrasonication and without any surfactant. Suspension stability of nanofluid was characterized and analyzed using zeta potential, average particle size and absorbancy method. The KD2-pro thermal property meter was used to measure the thermal conductivities of Al2O3(40nm)-water and SiO2(30nm)-water nanofluids at different volume concentrations (0.1-0.5vol.%) and temperature(25-50°C). The results show that adding nanoparticles into base fluid can enhance the thermal conductivity greatly. Furthermore, it is also show that the thermal conductivities increase nearly linearly with the nanoparticle volume concentration increasing, and increase significantly with the temperature increasing. A model of thermal conductivity of nanofluid, which has a much better precision, was proposed. But the values of the model are lower than the measured thermal conductivities.

scholarly journals The Effect of Suspension Stability on the Thermal Conductivity Enhancement of Water-based Au Nanofluids

2016 ◽  
Vol 21 (2) ◽  
pp. 111-115
Author(s):  
Tae Jong Choi ◽  
Hyun Jin Kim ◽  
Seung-Hyun Lee ◽  
Yong Jun Park ◽  
Seok Pil Jang
Keyword(s):  
Thermal Conductivity ◽  
Thermal Conductivity Enhancement ◽  
Suspension Stability ◽  
Conductivity Enhancement ◽  
Water Based

scholarly journals Experimental Analysis PVP Coated Silver Nanofluid Properties for Application in Photovoltaic/Thermal (PVT) Collectors

2020 ◽  
Vol 1 (3) ◽  
pp. 28-40
Author(s):  
A. Naderi ◽  
Gazori H. ◽  
M. Bozegi
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Base Fluid ◽  
Fossil Fuels ◽  
Working Fluid ◽  
Solar Collectors ◽  
Step Method ◽  
Energy Technologies ◽  
Pv Module ◽  
Utility Systems

Nowadays, supplying energy for the global population has turned into a prominent issue for countries engendering the consumption of huge amounts of fossil fuels which leads to some serious environmental problems. Among the renewable energy technologies, solar collectors can play major role to improve the efficiency, in air conditioning utility systems by minimum pollution. In photovoltaic/thermal (PVT) solar collectors, which are currently considered as the most advanced type to produce electricity and heat simultaneously, working fluid absorbs Energy from photovoltaic (PV) module engendering to decrease temperature of PV module and increase the electricity efficiency and also provide permissible amount of heat for other residential applications. Meanwhile, utilizing nanofluid as the working fluid in collector, regarding that the nanofluid has enhanced thermal properties relative to the base fluid, leads to a higher collector efficiency. In this research, PVP coated silver nanofluid was prepared in three volume concentration being 250, 500 and 1000 ppm by two-step method. To assess the stability of nanofluid the zeta potential is calculated which is obtained -41.6 V. Also, the prominent thermal properties of the nanofluid were analyzed regarding PVT solar collector applications. According to the results, thermal conductivity of the PVP coated silver nanofluid, improves the properties of base fluid, to the extent that thermal conductivity coefficient grows up 50% in some temperatures and increased from 0.594 for base fluid to 1.098 W/mK by escalation of concentration to 1000 ppm. Thus, PVP coated silver nanofluid can be deemed as the vital working fluid to improve the performance of PVT solar collectors.

scholarly journals Formulasi dan Karakterisasi Sediaan Nanoemulgel Serbuk Lidah Buaya (Aloe Vera L.)

2019 ◽  
Vol 16 (1) ◽  
pp. 28-37
Author(s):  
Teguh Imanto ◽  
Roseh Prasetiawan ◽  
Erindyah Retno Wikantyasning
Keyword(s):  
Particle Size ◽  
Zeta Potential ◽  
Physical Properties ◽  
Physical Stability ◽  
Aloe Vera ◽  
Tween 80 ◽  
Gelling Agent ◽  
Freeze Thaw ◽  
Particle Size Analyzer ◽  
Oil In Water

Aloe vera L. contains antiseptic saponins and anthraquinone complexes as antibacterial. This research was conducted to formulate aloe vera powder into nanoemulgel, characterize and test its physical properties, and to know the effect of gelling agent concentration (carbopol and chitosan) on nanoemulgel. Emulsion type used is oil in water (O / W) with surfactant tween 80 and co-surfactant propylene glycol. Nanoemulsion is characterized by percent of transmittance with UV-Vis spectrophotometer, also potential droplet and zeta size distribution with Particle Size Analyzer. Hydrogels consist of 4 combination formulas of carbopol 0.5%; 1%; 1.5%; 2% and 0.3% chitosan. The formula is tested for physical properties including organoleptic, pH, spreadability, adhesion, viscosity and stability with freeze thaw method. The results showed that the nanoemulsion droplet size was 65.05nm ± 13.49 with zeta potential of -0.1mV and the percent of transmittance above 98%. The result of physical properties of the four formulas shows that the different gelling agent concentration gives different physical properties of viscosity and spreadability. Overall, formula 3 has the best physical properties and physical stability compared to formula 1, 2 and 4.

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