Modified Model for Effective Thermal Conductivity of Nanofluids Containing Carbon Nanotubes

2007 ◽  
Vol 21 (3) ◽  
pp. 658-660 ◽  
Author(s):  
Yingsong Zheng ◽  
Haiping Hong
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Effective Thermal Conductivity ◽  
Modified Model

scholarly journals Experimental study on density, thermal conductivity, specific heat, and viscosity of water-ethylene glycol mixture dispersed with carbon nanotubes

2017 ◽  
Vol 21 (1 Part A) ◽  
pp. 255-265 ◽  
Author(s):  
Jayabalan Ganeshkumar ◽  
Durai Kathirkaman ◽  
Kandhaswamy Raja ◽  
Vellisamy Kumaresan ◽  
Ramalingam Velraj
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Ethylene Glycol ◽  
Specific Heat ◽  
Fold Increase ◽  
Modified Model ◽  
Multi Wall Carbon Nanotubes ◽  
Conductivity Enhancement ◽  
Mwcnt Concentration ◽  
Nanoparticle Aggregates

This article presents the effect of adding multi wall carbon nanotubes (MWCNT) in water ? ethylene glycol mixture on density and various thermophysical properties such as thermal conductivity, specific heat and viscosity. Density of nanofluids was measured using standard volumetric flask method and the data showed a good agreement with the mixing theory. The maximum thermal conductivity enhancement of 11 % was noticed for the nanofluids with 0.9 wt. %. Due to lower specific heat of the MWCNT, the specific heat of the nanofluids decreased in proportion with the MWCNT concentration. The rheological analysis showed that the transition region from shear thinning to Newtonian extended to the higher shear stress range compared to that of base fluids. Viscosity ratio of the nanofluids augmented anomalously with respect to increase in temperature and about 2.25 fold increase was observed in the temperature range of 30 ? 40 ?C. The modified model of Maron and Pierce predicted the viscosity of the nanofluids with the inclusion of effect of aspect ratio of MWCNT and nanoparticle aggregates.

Prediction of mechanical and thermal properties of polymer nanocomposites reinforced by coiled carbon nanotubes for possible application as impact absorbent

2019 ◽  
Vol 234 (4) ◽  
pp. 882-902
Author(s):  
Armin Kianfar ◽  
Mir Masoud Seyyed Fakhrabadi ◽  
Mahmoud Mosavi Mashhadi
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Finite Element ◽  
Effective Thermal Conductivity ◽  
Representative Volume Element ◽  
Volume Element ◽  
Volume Fractions ◽  
Finite Element Software ◽  
Representative Volume ◽  
Representative Volume Elements

This paper presents three-dimensional finite element modeling of nanocomposite materials made from polyethylene polymer reinforced by coiled carbon nanotubes. A method of Python scripting was used to generate representative volume elements in order to determine the mechanical behavior in elastic and plastic zones as well as effective thermal conductivity using the finite element software. The properties of the nanocomposites are investigated by considering the interphase zone between carbon nanofillers and matrix. The effects of different volume fractions, geometrical parameters, and orientations of the nanofillers on the elastic and thermal characteristics of the nanocomposites are studied considering both cohesive interaction and perfect bonding between the fillers and matrix. Moreover, the effects of applying strain on the effective thermal conductivity of the representative volume elements are analyzed. The results reveal that both stress–strain curves and thermal conductivity coefficients of the nanocomposites are following similar trends vs. the changes of the volume fractions as well as the geometries and orientations of the coiled carbon nanotubes. Analysis of the tensile toughness of all samples reveals that it is affected by both stress and the number of fillers in the representative volume element. In addition, thermal-displacement analysis shows that thermal conductivity coefficient decreases by increasing the applied strain on the representative volume element, while the intensity of decrease of the nanocomposite thermal conductivity depends on the volume fraction and interaction of the nanofillers and interphase zone. Finally, crashworthiness analysis of the nanocomposite material proves that they are appropriate candidates for absorbing energy under impact loadings in comparison to metals.

Measurements of the Intrinsic Thermal Conductivity of Individual Multi-Wall Carbon Nanotubes

2011 ◽  
Author(s):  
Juekuan Yang ◽  
Scott W. Waltermire ◽  
Yang Yang ◽  
Deyu Li ◽  
Yunfei Chen
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Heat Source ◽  
Thermal Resistance ◽  
Effective Thermal Conductivity ◽  
Experimental Studies ◽  
Contact Thermal Resistance ◽  
Multi Wall Carbon Nanotubes ◽  
The Past ◽  
Thermal Conductivities

Thermal transport through carbon nanotubes (CNTs) attracted a lot of attention over the past decade. Several experimental studies have been carried out to determine the thermal conductivities of CNTs [1–3]. However, the measurements are based on an individual CNT sample between two suspended membranes and the results actually include both the intrinsic thermal resistance of the CNT and the contact thermal resistance between the CNT and the two suspended membranes that serve as a heat source and a heat sink. Hence, the effective thermal conductivity extracted from these measurements should be lower than the intrinsic thermal conductivities of the CNTs measured. To minimize the contact thermal resistance, electron beam induce deposition (EBID) of different metals has been used to increase the contact area between the CNT and the heat source and sink [3,4]. However, it is still not clear how effective this treatment is and to what level the effective thermal conductivity obtained after the EBID treatment reflects the intrinsic one.

scholarly journals Enhancement of the effective thermal conductivity in packed beds by direct synthesis of carbon nanotubes

2015 ◽  
Vol 10 (1) ◽  
pp. JTST0013-JTST0013
Author(s):  
Teerameth JANJARASSKUL ◽  
Seung-Gyu LEE ◽  
Shuhei INOUE ◽  
Yukihiko MATSUMURA ◽  
Tawatchai CHARINPANITKUL
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Effective Thermal Conductivity ◽  
Direct Synthesis ◽  
Packed Beds ◽  
Synthesis Of Carbon Nanotubes

Characterization of Thermal Properties and Heat Transfer Behavior of Microencapsulated Phase Change Material Slurry and Multiwall Carbon Nanotubes in Aqueous Suspension

2007 ◽  
Author(s):  
Jorge L. Alvarado ◽  
Charles Marsh ◽  
Curt Thies ◽  
Guillermo Soriano ◽  
Paritosh Garg
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Heat Transfer Coefficient ◽  
Phase Change ◽  
Transfer Coefficient ◽  
Effective Thermal Conductivity ◽  
Phase Change Material ◽  
Microencapsulated Phase Change Material ◽  
Change Material

In the last decade, microencapsulated phase change material (MPCM) slurries have been proposed and studied as novel coolants for heat transfer applications. Such applications include electronics cooling, and secondary coolants in air conditioning systems among others. Experiments have shown that MPCM’s increase the overall thermal capacity of thermal systems by taking advantage of the phase change material’s latent heat of fusion. However, research has also shown that the overall heat transfer coefficient is diminished due to a reduction in the effective thermal conductivity and increased viscosity of the slurry. For this reason, there is an urgent need to modify the content of microcapsules containing phase change material to increase their effective thermal conductivity and the overall heat transport process. Our solution consists of increasing the thermal conductivity of MPCM by adding carbon nanotubes to the shell and core of the microcapsules. Carbon nanotubes have shown to increase the thermal conductivity of liquids by 40% or more in recent experiments. In this paper, MPCM slurry containing octadecane as phase change material and multi-wall carbon nanotubes (MWCNTs) embedded in the capsule material and core are compared with pure water as heat transfer fluid. Thermal and physical properties of MPCM slurry containing carbon nanotubes were determined using a differential scanning calorimeter and concentric viscometer, respectively. Experimental convective heat transfer coefficient data for MWCNT aqueous suspensions under laminar flow and constant heat flux were determined using a bench-top heat transfer loop. Experimental heat transfer results are presented.

Particle Aspect-Ratio and Agglomeration-State Effects on the Effective Thermal Conductivity of Aqueous Suspensions of Multiwalled Carbon Nanotubes

2010 ◽  
Vol 132 (8) ◽  
Author(s):  
Anna S. Cherkasova ◽  
Jerry W. Shan
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Aspect Ratio ◽  
Effective Thermal Conductivity ◽  
Particle Aggregation ◽  
Multiwalled Carbon ◽  
Agglomeration State ◽  
Particle Aspect Ratio ◽  
Absorption Measurements ◽  
Thermal Conductivities

The effective thermal conductivities of aqueous nanofluids containing surfactant-stabilized multiwalled carbon nanotubes were measured and compared with the predictions of effective medium theory (Nan, C.-W., et al., 1997, “Effective Thermal Conductivity of Particulate Composites With Interfacial Thermal Resistance,” J. Appl. Phys., 81(10), pp. 6692–6699). Detailed characterization of nanotube morphology was carried out through electron microscopy, while the nanotube agglomeration state was monitored through optical microscopy and absorption measurements. An optimum surfactant-to-nanotube mass ratio was found for the particular surfactant, sodium dodecylbenzene sulfonate, which resulted in the greatest increase in thermal conductivity. Taking into consideration the volume-weighted aspect ratio of the nanotubes, the measured thermal conductivities of the suspensions were shown to be in good agreement with calculations for a reasonable choice of interfacial resistance on the particle/liquid interface. The effect of particle aspect ratio on the suspension’s thermal conductivity was further demonstrated and compared with theory by reducing the nanotube length through intense ultrasonication. The effect of particle aggregation on the thermal conductivity was also investigated by destabilizing previously stable suspensions with ethanol addition, which causes surfactant desorption and bundling of nanotubes. The measured thermal conductivities were correlated with absorption measurements and microscopic visualizations to show that particle aggregation decreases the thermal conductivity of the nanofluid by reducing the effective particle aspect ratio.

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