Estimation of thermal conductivity of PP/Al(OH)3/Mg(OH)2 composites

2012 ◽  
Vol 32 (6-7) ◽  
pp. 401-406
Author(s):  
Ji-Zhao Liang
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Volume Fraction ◽  
Measured Data ◽  
Measuring Instrument ◽  
Conductivity Equation ◽  
Experimental Conditions ◽  
Thermal Conductivity Equation ◽  
Pp Composites

Abstract The thermal conductivity of polypropylene (PP) composites filled with Al(OH)3 and Mg(OH)2 was measured by means of the stable flat measuring instrument at different testing temperatures. The effective thermal conductivity of the composites was estimated by applying the thermal conductivity equation proposed previously, and the estimations were compared with the experimental measured data under the same experimental conditions. The results showed that the calculations and measurements of the effective thermal conductivity were close to each other when the volume fraction of the Al(OH)3/Mg(OH)2 powder was <10.4%. Moreover, the effective thermal conductivity of the composites was estimated using the Russell model and the Maxwell-Eucken model, and the predictions were compared with the experimental data and the estimations of this equation. It was found that the estimations of this equation were closer to the experimental data than those of the Russell model and Maxwell-Eucken model.

Two-dimensional lattice Boltzmann modeling for effective thermal conductivity in carbon black filled composites

2017 ◽  
Vol 52 (15) ◽  
pp. 2047-2053 ◽  
Author(s):  
Yong-Jun Kim ◽  
Yu-Fei Tan ◽  
Sok Kim
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Carbon Black ◽  
Effective Thermal Conductivity ◽  
Lattice Boltzmann ◽  
Volume Fraction ◽  
Effective Properties ◽  
Lattice Boltzmann Model ◽  
Two Dimensional ◽  
Boltzmann Model

Polymer composites filled with thermally conductive particles are widely used in thermo-electronic industry, and the prediction of effective properties is still important for design and use of composites. Thus, we propose a lattice Boltzmann model to predict the effective thermal conductivity of composites filled with carbon black. First, a method for reconstructing numerical material having filler distribution characteristic similar to that of actual material is introduced, and the process for obtaining the phase function and the volume fraction of grain filler is described. The energy transport governing equation is then solved through the two-dimensional discrete structure by using a lattice Boltzmann model. The effective thermal conductivity of two-phase composite is expressed by the conductivity of each phase and the temperature distribution in discrete rectangle. The resultant prediction is compared with theoretical and experimental data and indicates good agreement with experimental data.

The Simulation of Discrete Vessel Effects in Experimental Hyperthermia

1994 ◽  
Vol 116 (3) ◽  
pp. 256-262 ◽  
Author(s):  
R. J. Rawnsley ◽  
R. B. Roemer ◽  
A. W. Dutton
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Blood Vessel ◽  
Effective Thermal Conductivity ◽  
Blood Vessels ◽  
Temperature Data ◽  
Experimental Temperature ◽  
Conductivity Equation ◽  
Thermal Models ◽  
Thermal Conductivity Equation

The ability of two simple thermal models to predict experimentally measured in vivo temperature profiles was compared. These comparisons were done both with and without the inclusion of separate, discrete blood vessels. The two tissue models were: 1) Pennes’ Bio-Heat Transfer equation (BHTE), and 2) an effective thermal conductivity equation (ETCE). The experimental temperature data were measured (Moros, 1990; Moros et al., 1993) in the thighs of anesthetized greyhound dogs under hyperthermic conditions generated by scanned focused ultrasound. Blood vessels were added to the thermal models in counter-current pairs transiting the model domain. The blood vessels in both models were assumed to have a constant heat transfer coefficient, and an axially varying mixed mean temperature. The vessel locations were determined a posteriori, via inspection of the experimental temperature data. Least square error fits of the predicted model temperatures to the experimental temperature data were obtained by adjusting both (a) the mass flow rate within and (b) the position of each blood vessel, and (c) the value of either the perfusion parameter (W) in the BHTE or the effective thermal conductivity parameter (Keff) in the ETCE. When small numbers (3-4) of blood vessel pairs were included, both of the models showed significant improvement in their ability to predict the experimental temperatures. Although both models performed well in terms of predicting temperatures near large vessels, the BHTE had a statistically significant better ability to predict the complete set of measured temperatures at all locations.

THERMAL CONDUCTIVITY OF SOLIDS AT HIGH TEMPERATURES AND HIGH PRESSURES

2007 ◽  
Vol 21 (25) ◽  
pp. 4419-4427 ◽  
Author(s):  
S. K. SHARMA ◽  
S. K. SRIVASTAVA ◽  
B. S. SHARMA
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
High Temperatures ◽  
High Pressures ◽  
Equations Of State ◽  
Conductivity Equation ◽  
Thermoelastic Properties ◽  
Thermal Conductivity Equation ◽  
Wide Range ◽  
Low Pressures

In the present study, we have extended the model due to Tang1 based on the thermal conductivity equation due to Leibfried and Schlomann12 so as to make it applicable for a wide range of pressures and temperatures. We have used the Stacey14,15 equations of state (EOS) for determining the thermoelastic properties of NaCl , KCl and Al 2 O 3 at high pressures and high temperatures. These are used to estimate the variations of thermal conductivity with the change in pressure along different isotherms at selected temperatures. The results thus obtained are compared with the values derived from relations, which reproduced available experimental data well at low temperatures and low pressures. Experimental data at high temperatures and high pressures are not available. A close agreement between the two sets of data reveals the validity of the present work.

Figure of Merit-Based Optimization Approach of Phase Change Material-based Composites for Portable Electronics Using Simplified Model

2021 ◽  
Author(s):  
Ayushman Singh ◽  
Srikanth Rangarajan ◽  
Leila Choobineh ◽  
Bahgat Sammakia
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Phase Change ◽  
Effective Thermal Conductivity ◽  
Phase Change Material ◽  
Figure Of Merit ◽  
Volume Fraction ◽  
Simplified Model ◽  
Transient Temperature ◽  
Change Material

Abstract This work presents an approach to optimally designing a composite with thermal conductivity enhancers (TCEs) infiltrated with phase change material (PCM) based on figure of merit (FOM) for thermal management of portable electronic devices. The FOM defines the balance between effective thermal conductivity and energy storage capacity. In present study, TCEs are in the form of a honeycomb structure. TCEs are often used in conjunction with PCM to enhance the conductivity of the composite medium. Under constrained composite volume, the higher volume fraction of TCEs improves the effective thermal conductivity of the composite, while it reduces the amount of latent heat storage simultaneously. The present work arrives at the optimal design of composite for electronic cooling by maximizing the FOM to resolve the stated trade-off. In this study, the total volume of the composite and the interfacial heat transfer area between the PCM and TCE are constrained for all design points. A benchmarked two-dimensional direct CFD model was employed to investigate the thermal performance of the PCM and TCE composite. Furthermore, assuming conduction-dominated heat transfer in the composite, a simplified effective numerical model that solves the single energy equation with the effective properties of the PCM and TCE has been developed. The effective thermal conductivity of the composite is obtained by minimizing the error between the transient temperature gradient of direct and simplified model by iteratively varying the effective thermal conductivity. The FOM is maximized to find the optimal volume fraction for the present design.

A Simplified Model for Effective Thermal Conductivity of Highly Porous Ceramic Fiber Insulation

2015 ◽  
Vol 7 (4) ◽  
Author(s):  
Nicholas P. G. Lumley ◽  
Emory Ford ◽  
Eric Minford ◽  
Jason M. Porter
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Natural Convection ◽  
Effective Thermal Conductivity ◽  
Research Effort ◽  
Porous Ceramic ◽  
Ceramic Fiber ◽  
Chemical Process Industry ◽  
Thermophysical Model ◽  
Highly Porous

Highly porous ceramic fiber insulations are beginning to be considered as a replacement for firebrick insulations in high temperature, high pressure applications by the chemical process industry. However, the implementation of such materials has been impeded by a lack of experimental data and predictive models, especially at high gas pressure. The goal of this work was to develop a general, applied thermophysical model to predict effective thermal conductivity, keff, of porous ceramic fiber insulation materials and to determine the temperature, pressure, and gas conditions under which natural convection is a possible mode of heat transfer. A model was developed which calculates keff as the sum of conduction, convection, and radiation partial conductivities. The model was validated using available experimental data, including laboratory measurements made by this research effort. Overall, it was concluded that natural convection is indeed possible for the most porous insulations at pressures exceeding 10 atm. Furthermore, keff for some example insulations was determined as a function of temperature, pressure, and gas environment.

Thermal Conductivity of Metal-Oxide Nanofluids: Particle Size Dependence and Effect of Laser Irradiation

2006 ◽  
Vol 129 (3) ◽  
pp. 298-307 ◽  
Author(s):  
Sang Hyun Kim ◽  
Sun Rock Choi ◽  
Dongsik Kim
Keyword(s):  
Thermal Conductivity ◽  
Particle Size ◽  
Effective Thermal Conductivity ◽  
Laser Irradiation ◽  
Volume Fraction ◽  
Suspended Particle ◽  
Titanium Dioxide Nanoparticles ◽  
Size Change ◽  
Conductivity Enhancement ◽  
Wide Range

The thermal conductivity of water- and ethylene glycol-based nanofluids containing alumina, zinc-oxide, and titanium-dioxide nanoparticles is measured using the transient hot-wire method. Measurements are performed by varying the particle size and volume fraction, providing a set of consistent experimental data over a wide range of colloidal conditions. Emphasis is placed on the effect of the suspended particle size on the effective thermal conductivity. Also, the effect of laser-pulse irradiation, i.e., the particle size change by laser ablation, is examined for ZnO nanofluids. The results show that the thermal-conductivity enhancement ratio relative to the base fluid increases linearly with decreasing the particle size but no existing empirical or theoretical correlation can explain the behavior. It is also demonstrated that high-power laser irradiation can lead to substantial enhancement in the effective thermal conductivity although only a small fraction of the particles are fragmented.

An Analytical Modeling for Effective Thermal Conductivity of Multi-Phase Transversely Isotropic Fiberous Composites Using Generalized Self-Consistent Method

2012 ◽  
Vol 249-250 ◽  
pp. 904-909 ◽  
Author(s):  
Syed Aadil Hassan ◽  
Hassaan Ahmed ◽  
Asif Israr
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Composite System ◽  
Volume Fraction ◽  
Transversely Isotropic ◽  
Balance Principle ◽  
Isotropic Composite ◽  
Self Consistent ◽  
Consistent Method ◽  
Multi Phase

In this paper a theoretical relationship for the effective thermal conductivity of a multiphase transversely isotropic composite system is obtained. The Generalized Self-Consistent Method and simple energy balance principle is employed to derive a more appropriate model. In the derivation, it is assumed that the orientation of fiber within the transversely isotropic composite system is unidirectional and surrounded by two different phases of porous and matrix phase. A combined effect of these three different phases on the effective thermal conductivity of the composite system in transverse direction is studied. The effect of the interfacial contact conductance between the fibers and porous medium is also considered. Results of effective thermal conductivity are plotted against volume fraction and conductance which shows extremely good agreement.

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