Effective thermal conductivity and rheological characteristics of ethylene glycol-based nanofluids with single-walled carbon nanohorn inclusions

A physical-statistical model for predicting the effective thermal conductivity of nanofluids is proposed. The volumetric unit of nanofluids in the model consists of solid, liquid, and gas particles and is treated as a system made up of regular geometric figures, spheres, filling the volumetric unit by layers. The model assumes that connections between layers of the spheres and between neighbouring spheres in the layer are represented by serial and parallel connections of thermal resistors, respectively. This model is expressed in terms of thermal resistance of nanoparticles and fluids and the multinomial distribution of particles in the nanofluids. The results for predicted and measured effective thermal conductivity of several nanofluids (Al2O3/ethylene glycol-based and Al2O3/water-based; CuO/ethylene glycol-based and CuO/water-based; and TiO2/ethylene glycol-based) are presented. The physical-statistical model shows a reasonably good agreement with the experimental results and gives more accurate predictions for the effective thermal conductivity of nanofluids compared to existing classical models.

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A numerical study on the effective thermal conductivity of biological fluids containing single-walled carbon nanotubes

International Journal of Heat and Mass Transfer ◽

10.1016/j.ijheatmasstransfer.2009.06.016 ◽

2009 ◽

Vol 52 (23-24) ◽

pp. 5591-5597 ◽

Cited By ~ 19

Author(s):

Hai M. Duong ◽

Dimitrios V. Papavassiliou ◽

Kieran J. Mullen ◽

Brian L. Wardle ◽

Shigeo Maruyama

Keyword(s):

Thermal Conductivity ◽

Carbon Nanotubes ◽

Effective Thermal Conductivity ◽

Numerical Study ◽

Biological Fluids ◽

Single Walled Carbon Nanotubes ◽

Single Walled Carbon ◽

Walled Carbon Nanotubes

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Enhanced Thermal Conductivity of Water With Surfactant Encapsulated and Individualized Single-Walled Carbon Nanotube Dispersions

ASME 2012 Third International Conference on Micro/Nanoscale Heat and Mass Transfer ◽

10.1115/mnhmt2012-75021 ◽

2012 ◽

Author(s):

S. Harish ◽

Kei Ishikawa ◽

Erik Einarsson ◽

Taiki Inoue ◽

Shohei Chiashi ◽

...

Keyword(s):

Thermal Conductivity ◽

Carbon Nanotube ◽

Effective Thermal Conductivity ◽

Volume Fraction ◽

Thermal Conductivity Enhancement ◽

Optical Absorption Spectroscopy ◽

Single Walled Carbon Nanotube ◽

Conductivity Enhancement ◽

Single Walled Carbon ◽

Higher Temperature

In the present work, the effective thermal conductivity of single walled carbon nanotube dispersions in water was investigated experimentally. Single-walled carbon nanotubes (SWNTs) were synthesized using the alcohol catalytic chemical vapour deposition method. The diameter distribution of the SWNTs was determined using resonance Raman spectroscopy. Sodium deoxycholate (SDC) was used as the surfactant to prepare the nanofluid dispersions. Photoluminescence excitation spectroscopy (PLE) reveals that majority of the nanotubes were highly individualized when SDC was employed as the surfactant. The nanofluid dispersions were further characterized using transmission electron microscopy, atomic force microscopy (AFM) and optical absorption spectroscopy (OAS). Thermal conductivity measurements were carried out using a transient hot wire technique. Nanotube loading of up to 0.3 vol% was used. Thermal conductivity enhancement was found to be dependent on nanotube volume fraction and temperature. At room temperature the thermal conductivity enhancement was found to be non-linear and a maximum enhancement of 13.8% was measured at 0.3 vol% loading. Effective thermal conductivity was increased to 51% at 333 K when the nanotube loading is 0.3 vol%. Classical macroscopic models fail to predict the measured thermal conductivity enhancement precisely. The possible mechanism for the enhancement observed is attributed to the percolation of nanotubes to form a three-dimensional structure. Indirect effects of Brownian motion may assist the formation of percolating networks at higher temperature thereby leading to further enhancements at higher temperature.

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