Effective Thermal Conductivity and Viscosity of Nanofluids

2005 ◽  
Author(s):  
S. M. S. Murshed ◽  
K. C. Leong ◽  
C. Yang
Keyword(s):  
Thermal Conductivity ◽  
Experimental Investigation ◽  
Aluminum Oxide ◽  
Effective Thermal Conductivity ◽  
Titanium Oxide ◽  
Present Model ◽  
Geometrical Structure ◽  
Dispersion Of Nanoparticles

This paper presents a model to determine the effective thermal conductivity (ETC) of nanofluids. The model was developed by considering the geometrical structure of dispersed nanoparticles in base fluids. For the experimental investigation, nanofluids were prepared by suspending aluminum oxide (Φ80 nm) and titanium oxide (Φ15 nm and Φ10×40 nm) nanoparticles in deionized (DI) water and taken through longtime (8–10 hours) sonication for proper mixture of nanoparticles. Cetyltrimethylammoniumbromide (CTAB) surfactant was used to ensure better stability and dispersion of nanoparticles in the base fluids. The thermal conductivity and viscosity of the nanofluids were measured and compared with the predictions by various models. The present model gives better prediction of the effective thermal conductivity of nanofluids compared to existing models.

Evaluation of the Temperature Oscillation Technique to Calculate Thermal Conductivity of Water and Systematic Measurement of the Thermal Conductivity of Aluminum Oxide – Water Nanofluid

2004 ◽  
Author(s):  
P. Bhattacharya ◽  
S. Nara ◽  
P. Vijayan ◽  
T. Tang ◽  
W. Lai ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Aluminum Oxide ◽  
Effective Thermal Conductivity ◽  
Base Fluid ◽  
Suspended Solid ◽  
Temperature Oscillation ◽  
Solid Particles ◽  
Systematic Measurement ◽  
Experimental Setup ◽  
Suspended Solid Particles

A nanofluid is a fluid containing suspended solid particles, with sizes of the order of nanometers. The nanofluids are better conductors of heat than the base fluid itself. Therefore it is of interest to measure the effective thermal conductivity of such a nanofluid. We use temperature oscillation technique to measure the thermal conductivity of the nanofluid. However, first we evaluate the temperature oscillation technique as a tool to measure thermal conductivity of water. Then we validate our experimental setup by measuring the thermal conductivity of the aluminum oxide-water nanofluid and comparing our results with previously published work. Finally, we do a systematic series of measurements of the thermal conductivities of aluminum oxide-water nanofluids at various temperatures and explain the reasons behind the dependence of the enhancement in thermal conductivity of the nanofluid on temperature.

Experimental Investigation of Effective Thermal Conductivity for LHP Wicks

2010 ◽  
Author(s):  
Gongming Xin ◽  
Kehang Cui ◽  
Yan Chen ◽  
Wenjing Du ◽  
Yong Zou ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Experimental Investigation ◽  
Effective Thermal Conductivity ◽  
Pure Copper ◽  
Pure Nickel ◽  
Loop Heat Pipe ◽  
Porosity Level ◽  
Nickel Powders ◽  
Copper Powders ◽  
Reasonable Prediction

In this study, the effective thermal conductivity (ETC) of sintered loop heat pipe wicks, with pure nickel powders, pure copper powders, Ni-10wt%Cu powders and Ni-20wt%Cu powders were experimentally investigated. The ETC of sintered Ni-Cu wicks is found less than those of sintered pure nickel wick and sintered pure copper wicks. In the same porosity level, addition of copper into nickel will reduce ETC of the sintered Ni-Cu wicks. The sintered Ni-20wt%Cu wick presents the lowest ETC among the tested wick samples. Compared to experimental results, Alexander model can provide a reasonable prediction in some wick samples.

Energy Partition to the Workpiece for Grinding with Aluminum Oxide and CBN Abrasive Wheels

1995 ◽  
Vol 117 (2) ◽  
pp. 160-168 ◽  
Author(s):  
S. Kohli ◽  
C. Guo ◽  
S. Malkin
Keyword(s):  
Thermal Conductivity ◽  
Experimental Investigation ◽  
Aluminum Oxide ◽  
Lower Energy ◽  
Energy Input ◽  
Thermal Damage ◽  
Cubic Boron Nitride ◽  
Energy Partition ◽  
Abrasive Wheel ◽  
Very High

An experimental investigation is reported of the energy partition to the workpiece for grinding of steels with aluminum oxide and cubic boron nitride (CBN) abrasive wheels. The energy input to the workpiece was obtained by measuring the temperature distribution in the workpiece using an embedded thermocouple technique and matching the results with analytically computed values. It was found that 60-75 percent of the grinding energy is transported to the workpiece as heat with an aluminum oxide abrasive wheel, as compared to only about 20 percent with CBN wheels. An analysis of the results indicates that the much lower energy partition to the workpiece with CBN can be attributed to its very high thermal conductivity whereby a significant portion of the grinding heat is transported to the abrasive instead of to the workpiece. The much lower energy partition to the workpiece with CBN wheels results in much lower grinding temperatures and a greatly reduced tendency for thermal damage to the workpiece.

Porosity and Effective Thermal Conductivity of Wire Screens

1990 ◽  
Vol 112 (1) ◽  
pp. 5-9 ◽  
Author(s):  
Won Soon Chang
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Theoretical Model ◽  
Effective Thermal Conductivity ◽  
Present Model ◽  
Model Based ◽  
Wire Screen ◽  
Simple Theoretical Model ◽  
Parallel Conduction ◽  
The Wire

A simple theoretical model based on combined series and parallel conduction for the effective thermal conductivity of fluid-saturated screens has been developed. The present model has been compared with the existing correlations and experimental data available in literature, and it has been found that the model is effective in predicting thermal conductivity. The study also demonstrates that it is important to include the actual thickness of the wire screen in order to calculate the porosity accurately.

Experimental Investigation of a Three-Layer Oscillating Heat Pipe

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
C. D. Smoot ◽  
H. B. Ma
Keyword(s):  
Thermal Conductivity ◽  
Experimental Investigation ◽  
Heat Pipe ◽  
Effective Thermal Conductivity ◽  
Heat Transport ◽  
Total Power ◽  
Oscillating Heat Pipe ◽  
Layer Effect ◽  
Layering Effect ◽  
Heat Transport Capability

An experimental investigation of a compact, triple-layer oscillating heat pipe (OHP) has been conducted to determine the channel layer effect on the heat transport capability in an OHP. The OHP has dimensions 13 mm thick, 229 mm long, and 76 mm wide embedded with two-independent closed loops forming three layers of channels. The unique design of the investigated OHP can be readily used to explore the channel layering effect on the heat transport capability in the OHP. The experimental results show that the addition of channel layers can increase the total power and at the same time, it can increase the effective thermal conductivity of the OHP. When the OHP switches from one layer of channels to two layers of channels, the highest effective thermal conductivity can be increased from 5760 W/mK to 26,560 W/mK. At the same time, the dryout limit can be increased. With three layers of channels, the OHP investigated herein can transport a power up to 8 kW with a heat flux level of 103 W/cm2 achieving an effective thermal conductivity of 33,170 W/mK.

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