The Effective Thermal Conductivity of Water Based Nanofluids at Different Temperatures

2015 ◽  
Vol 44 (1) ◽  
pp. 20140537 ◽  
Author(s):  
T. Srinivas ◽  
A. Venu Vinod
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Water Based ◽  
Different Temperatures

Convective Heat Transfer for Water-Based Alumina Nanofluids in a Single 1.02-mm Tube

2009 ◽  
Vol 131 (11) ◽  
Author(s):  
W. Y. Lai ◽  
S. Vinod ◽  
P. E. Phelan ◽  
Ravi Prasher
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Convective Heat Transfer ◽  
Effective Thermal Conductivity ◽  
Convective Heat ◽  
Volume Fraction ◽  
Pure Water ◽  
Submicron Particles ◽  
Strong Temperature Dependence ◽  
Water Based

Nanofluids are colloidal solutions, which contain a small volume fraction of suspended submicron particles or fibers in heat transfer liquids such as water or glycol mixtures. Compared with the base fluid, numerous experiments have generally indicated an increase in effective thermal conductivity and a strong temperature dependence of the static effective thermal conductivity. However, in practical applications, a heat conduction mechanism may not be sufficient for cooling high heat dissipation devices such as microelectronics or powerful optical equipment. Thus, thermal performance under convective heat transfer conditions becomes of primary interest. We report here the heat transfer coefficient h in both developing and fully developed regions by using water-based alumina nanofluids. Our experimental test section consists of a single 1.02-mm diameter stainless steel tube, which is electrically heated to provide a constant wall heat flux. Both pressure drop and temperature differences are measured, but mostly here we report our h measurements under laminar flow conditions. An extensive characterization of the nanofluid samples, including pH, electrical conductivity, particle sizing, and zeta potential, is also documented. The measured h values for nanofluids are generally higher than those for pure water. In the developing region, this can be at least partially explained by Pr number effects.

scholarly journals Physical-Statistical Model of Thermal Conductivity of Nanofluids

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
B. Usowicz ◽  
J. B. Usowicz ◽  
L. B. Usowicz
Keyword(s):  
Thermal Conductivity ◽  
Ethylene Glycol ◽  
Statistical Model ◽  
Effective Thermal Conductivity ◽  
Multinomial Distribution ◽  
Water Based ◽  
Classical Models ◽  
Parallel Connections ◽  
Solid Liquid ◽  
Thermal Resistors

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.

A MODEL FOR PREDICTING THE EFFECTIVE THERMAL CONDUCTIVITY OF NANOPARTICLE-FLUID SUSPENSIONS

2006 ◽  
Vol 05 (01) ◽  
pp. 23-33 ◽  
Author(s):  
S. M. S. MURSHED ◽  
K. C. LEONG ◽  
C. YANG
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Body Centered Cubic ◽  
Geometrical Structures ◽  
New Model ◽  
Water Based ◽  
Classical Models ◽  
Theoretical Results ◽  
Enhanced Thermal Conductivity ◽  
Good Agreement

The uniformity and homogeneously dispersed nanoparticles in base fluids contribute to enhanced thermal conductivity of the mixture. By considering the uniformity and geometrical structures (e.g., body-centered cubic) of homogeneously dispersed nanoparticles in base fluids, a model for determining the effective thermal conductivity (ETC) of such nanoparticle-fluid suspensions, commonly known as nanofluids is proposed in this study. The theoretical results of the effective thermal conductivities of TiO 2/Deionized (DI) water and Al 2 O 3/DI water-based nanofluids are presented, and they are found to be in good agreement with our experimental results and also with those reported in the literature. The new model presented in this study shows a better prediction of the effective thermal conductivity of nanofluids compared to other classical models attributed to Maxwell, Hamilton–Crosser, and Bruggeman.

The Effective Thermal Conductivity of Porous Polymethacrylimide Foams

2014 ◽  
Vol 609-610 ◽  
pp. 196-200 ◽  
Author(s):  
Peng Yue ◽  
Lin Qiu ◽  
Xing Hua Zheng ◽  
Da Wei Tang
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Formation Mechanism ◽  
3Ω Method ◽  
Temperature Range ◽  
Different Temperatures ◽  
The Relationship

A freestanding sensor-based 3ω method was employed to measure the effective thermal conductivity of porous polymethacrylimide (PMI) foams with different densities at different temperatures. Experimental data showed that within the measuring temperature range, the effective thermal conductivity increased with temperature. Moreover, the formation mechanism of the relationship between the effective thermal conductivity and temperature was analyzed in this paper.

scholarly journals The influence of gold nanoparticles on the thermal conductivity of water solutions of graphen

2019 ◽  
pp. 14-20
Author(s):  
V.V. Korskanov ◽  
O.M. Fesenko ◽  
T.V. Tsebrienko ◽  
O.P. Budnik ◽  
V.B. Dolgoshey
Keyword(s):  
Thermal Conductivity ◽  
Gold Nanoparticles ◽  
Effective Thermal Conductivity ◽  
Au Nanoparticles ◽  
Water Solution ◽  
Significant Difference ◽  
Temperature Dependences ◽  
Different Temperatures ◽  
Graphene Nanoparticles ◽  
Degree Of Purification

The objects of study were water dispersions of raw graphene (hereinafter referred to as graphene-n), higher degree of purification of graphene samples (hereinafter graphene), and nanoparticles of graphene-Au nanoparticles based on them. The thermal conductivity of water graphene dispersions and water dispersions of gold graphene nanoparticles nanostructures at different temperatures and component ratios was investigated. The values ​​of effective thermal conductivity of dry nanofillers are calculated. The temperature dependences of the thermal conductivity of the nanofillers were obtained. It is found that the in-thermal conductivity of water dispersions of purified graphene is higher than the thermal conductivity of raw graphene as a result of better packing of nanoparticles in pure graphene nanofillers compared to raw. The effect of enhancement of thermal conductivity of gold nanoparticles, which is accompanied by higher absolute values of thermal conductivity of nanoparticles of graphene-nanoparticles of gold than the corresponding graphene, was revealed. At the same time, there is a significant difference in thermal conductivity between nanoparticles of graphene nanoparticles of gold. It is established that higher values of thermal conductivity of graphene-nanoparticles nanostructures of gold are the result of the reinforcing action of a gold nanoparticle substrate, which is formed as a result of joint sedimentation with graphene during the formation of nano-flakes from water solution during evaporation of water.

Study of the Effective Thermal Conductivity of Nanofluids

2005 ◽  
Author(s):  
Ratnesh K. Shukla ◽  
Vijay K. Dhir
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Brownian Motion ◽  
Effective Thermal Conductivity ◽  
Volume Fraction ◽  
Experimental Results ◽  
Homogeneous Liquid ◽  
Size Dependent ◽  
Water Based ◽  
Base Liquid

Nanofluids, that is liquids containing nanometer sized metallic or non-metallic solid nanoparticles, show an increase in thermal conductivity compared to that of the base liquid. In this paper a model for thermal conductivity of nanofluids based on the theory of Brownian motion of particles in a homogeneous liquid combined with the macroscopic Hamilton-Crosser model is presented. The model is shown to predict a temperature and particle size dependent thermal conductivity. Comparison between the predicted and experimental results show that the model is able to accurately predict the temperature and volume fraction dependence of the thermal conductivity of water based alumina and gold nanofluids.

Thermodynamic and Transport Properties of CNT-Water Based Nanofluids

2010 ◽  
Vol 11 ◽  
pp. 101-106 ◽  
Author(s):  
J. Ponmozhi ◽  
F.A.M.M. Gonçalves ◽  
A.G.M. Ferreira ◽  
I.M.A. Fonseca ◽  
S. Kanagaraj ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Shear Rate ◽  
Colloidal Stability ◽  
Volume Concentration ◽  
Volume Fraction ◽  
Process Intensification ◽  
Average Concentration ◽  
Water Based ◽  
Different Temperatures ◽  
Device Miniaturization

Carbon nanotubes (CNTs) – perhaps the most enticing class of nano-materials, can be added in small volume fractions to enhance the thermal properties of fluids when process intensification or even device miniaturization is required. This work reports on the results obtained when measuring viscosity, and thermal conductivity of homogenous CNTs – water based nanofluids. The influence of CNTs volume concentration on the nanofluid thermo-physical properties is studied and measurements are undertaken at different temperatures, ranging from 283.15 K to 333.15 K. The nanofluids have been prepared by adding different volume concentrations of treated CNTs to water. The latter has been then sonicated for one hour and the colloidal stability monitored via UV – vis spectrophotometer. The absorbance of the nanofluid was observed at 263 nm, and the average concentration of CNTs was maintained at 9.35 mg/l, even after 200 hours, over 97% when compared with the initial concentration. The viscosity was measured using a controlled stress rheometer, and the measurements were performed in the shear rate ranging from 0 to 600 sec-1. At the same shear rate and temperature, the viscosity was observed to rise with increasing CNTs volume concentration. In what concerns thermal conductivity, it was assessed with a KD2 pro thermal property tester from Decagon Devices and the results clearly show that thermal conductivity rises with CNTs volume fraction, reaching its maximum at 2.5%vol where it represents more than 100% enhancement when the comparison is established with the corresponding value for the base fluid, at the same temperature conditions (i.e. 283.15 – 303.15 K). Furthermore, at higher temperatures (i.e. 313.15 – 333.15 K), the latter, for up to 1%vol concentration represents a 70% enhancement in thermal conductivity.

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