scholarly journals The Thermal Conductivity of Periodic Particulate Composites as Obtained from a Crystallographic Mode of Filler Packing

2018 ◽  
Vol 2 (4) ◽  
pp. 71
Author(s):  
John Venetis ◽  
Emilio Sideridis
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Thermomechanical Properties ◽  
Influential Factors ◽  
Particulate Composites ◽  
Closed Form Expression ◽  
Form Expression ◽  
Theoretical Predictions ◽  
Advanced Model ◽  
Theoretical Results

In this paper, an icosahedral non-body-centered model is presented to simulate the periodic structure of a general class of homogeneous particulate composites, by predicting the particle arrangement. This model yielded three different variations, which correspond to three different deterministic particle configurations. In addition, the concept of a boundary interphase between matrix and inclusions was taken into account. In this framework, the influence of particle vicinity on the thermomechanical properties of the overall material was examined in parallel with the concept of boundary interphase. The simultaneous consideration of these two basic influential factors constitutes the novelty of this work. Next, by the use of this advanced model, the authors derived a closed-form expression to estimate the thermal conductivity of this type of composite. To test the validity of the model, the theoretical predictions arising from the proposed formula were compared with experimental data found in the literature, together with theoretical results obtained from several accurate formulae derived from other workers, and an adequate accordance was observed.

scholarly journals The Thermal Conductivity of Periodic partIculate Composites as Obtained from a Crystallographic Mode of Particle Packing

2018 ◽  
Author(s):  
John Venetis ◽  
Emilio Paul Sideridis
Keyword(s):  
Thermal Conductivity ◽  
Periodic Structure ◽  
Thermomechanical Properties ◽  
Particle Packing ◽  
Particulate Composites ◽  
Form Expression ◽  
Particle Arrangement ◽  
Theoretical Predictions

In this paper, an icosahedral non – body centered model to simulate the periodic structure of homogeneous particulate composites, by predicting the particle arrangement, is presented. This model has yielded three different variations which correspond at three different deterministic particle configurations.  In addition, the concept of boundary interphase between matrix and inclusions was taken into account. Thus, the influence of particle vicinity was examined in parallel with the interphase concept on the thermomechanical properties of the overall material. Next, by the use of this model the authors derived a closed – form expression to estimate the thermal conductivity of this type of composites. To test the validity of the model, the theoretical values arising from the proposed formula were compared with other theoretical predictions obtained from several accurate formulae found in the literature and an adequate accordance was observed.

Effective Thermal Conductivity of Composites Reinforced with Curvilinearly Anisotropic Inclusions with Kapitza Contact Resistance

2006 ◽  
Vol 306-308 ◽  
pp. 775-780
Author(s):  
Tung Yang Chen
Keyword(s):  
Thermal Conductivity ◽  
Contact Resistance ◽  
Closed Form ◽  
Effective Thermal Conductivity ◽  
Thermal Contact Resistance ◽  
Thermal Contact ◽  
Transversely Isotropic ◽  
Closed Form Expression ◽  
Form Expression ◽  
Micromechanical Models

Effective thermal conductivities of composites consisting of curvilinearly anisotropic inclusions with Kapitza thermal contact resistance between the constituents are considered. We show that the effect of these curvilinearly anisotropic inclusions can be exactly simulated by certain equivalent isotropic or transversely isotropic inclusions. Three different micromechanical models are employed to estimate the effective thermal conductivity of the composite. Interestingly, all these methods result in the same simple, closed-form expression.

Thermal Behavior and Friction in Journal Bearings

1970 ◽  
Vol 92 (3) ◽  
pp. 373-380 ◽  
Author(s):  
Al. Nica
Keyword(s):  
Experimental Data ◽  
Thermal Behavior ◽  
Heat Dissipation ◽  
Journal Bearings ◽  
Friction Torque ◽  
Operating Characteristics ◽  
Lubricant Flow ◽  
Theoretical Predictions ◽  
Theoretical Results ◽  
Good Agreement

This paper deals with friction and the field of temperature in the lubricant film of journal bearings. Theoretical results regarding the thermal behavior are checked with experimental data and good agreement is found. Emphasis is put on the variation of temperature and lubricant flow with the operating characteristics of the bearing and it is seen that theoretical predictions for minima of friction torque are backed by temperature measurements. Further on, the friction torque and the mechanism of heat dissipation in bearings are dealt with, in order to verify the assumptions used in the calculation schemes. The means of efficiently cooling the bearing are also discussed, as well as the part played by the divergent zone in this process.

Thermal Conductivity Equations Based on Brownian Motion in Suspensions of Nanoparticles (Nanofluids)

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Bao Yang
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Brownian Motion ◽  
Relaxation Time ◽  
Kinetic Theory ◽  
Significant Role ◽  
Particle Velocity ◽  
Long Time ◽  
Theoretical Results ◽  
Enhanced Thermal Conductivity

Thermal conductivity equations for the suspension of nanoparticles (nanofluids) have been derived from the kinetic theory of particles under relaxation time approximations. These equations, which take into account the microconvection caused by the particle Brownian motion, can be used to evaluate the contribution of particle Brownian motion to thermal transport in nanofluids. The relaxation time of the particle Brownian motion is found to be significantly affected by the long-time tail in Brownian motion, which indicates a surprising persistence of particle velocity. The long-time tail in Brownian motion could play a significant role in the enhanced thermal conductivity in nanofluids, as suggested by the comparison between the theoretical results and the experimental data for the Al2O3-in-water nanofluids.

scholarly journals Upper Bound of the Generalized p Value for the Population Variances of Lognormal Distributions with Known Coefficients of Variation

2017 ◽  
Vol 2017 ◽  
pp. 1-9
Author(s):  
Rada Somkhuean ◽  
Sa-aat Niwitpong ◽  
Suparat Niwitpong
Keyword(s):  
Upper Bound ◽  
Closed Form Expression ◽  
P Value ◽  
Form Expression ◽  
Lognormal Distributions ◽  
Coefficients Of Variation ◽  
The Difference ◽  
Generalized P Value ◽  
The One ◽  
Theoretical Results

This paper presents an upper bound for each of the generalized p values for testing the one population variance, the difference between two population variances, and the ratio of population variances for lognormal distribution when coefficients of variation are known. For each of the proposed generalized p values, we derive a closed form expression of the upper bound of the generalized p value. Numerical computations illustrate the theoretical results.

The Effective Thermal Conductivity of Composite Materials with Spherical Dispersed Phase

2011 ◽  
Vol 239-242 ◽  
pp. 1870-1874 ◽  
Author(s):  
Bin Wan ◽  
Kai Yue ◽  
Lian Cun Zheng ◽  
Xin Xin Zhang
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Composite Materials ◽  
Theoretical Result ◽  
Effective Thermal Conductivity ◽  
Integration Method ◽  
Dispersed Phase ◽  
Porous Composite ◽  
Resistance Model ◽  
Theoretical Results

The derivation of effective thermal conductivity (ETC) for composite materials is a long-standing thermal transport problem. Based on the thermal resistance model and integration method, two analytical solutions of the ETC of composite materials, in which the dispersed phase consists of spheres in cubic arrangements, were derived either neglecting or considering the effect of radiation. As the effect of radiation in porous composite materials is considered, the theoretical result indicates that the effect of radiation cannot be neglected as the temperature or porosity of composite materials is high. The differences between the theoretical results and experimental data of the ETC of porous composite materials are acceptable.

Comparison Between Theoretical Predictions of Wave Resistance and Experimental Data for the Wigley Hull

1983 ◽  
Vol 27 (04) ◽  
pp. 215-226
Author(s):  
C. Y. Chen ◽  
F. Noblesse
Keyword(s):  
Experimental Data ◽  
Froude Number ◽  
Resistance Coefficient ◽  
Wave Resistance ◽  
Number Range ◽  
Theoretical Predictions ◽  
Wigley Hull ◽  
Sinkage And Trim ◽  
Theoretical Results ◽  
Good Agreement

A number of theoretical predictions of the wave-resistance coefficient of the Wigley hull are compared with one another and with available experimental data, to which corrections for sinkage and trim are applied. The averages of eleven sets of experimental data (corrected for sinkage and trim) and of eleven sets of theoretical results for large values of the Froude number, specifically for F 0.266, 0.313, 0.350, 0.402, 0.452, and 0.482, are found to be in fairly good agreement, in spite of considerable scatter in both the experimental data and the numerical results. Furthermore, several sets of theoretical results are fairly close to the average experimental data and the average theoretical predictions for these large values of the Froude number. Discrepancies between theoretical predictions and experimental measurements for small values of the Froude number, specifically for F = 0.18, 0.20, 0.22, 0.24, and 0.266, generally are much larger than for the above-defined high-Froude-number range. However, a notable exception to this general finding is provided by the first-order slender-ship approximation evaluated in Chen and Noblesse [1],3 which is in fairly good agreement with the average experimental data over the entire range of values of Froude number considered in this study.

Thermal Conductivity of Composites with Carbon Nanotubes: Theory and Experiment

2012 ◽  
Vol 1479 ◽  
pp. 101-106
Author(s):  
J. Ordonez-Miranda ◽  
C. Vales-Pinzon ◽  
J. J. Alvarado-Gil
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Carbon Nanotubes ◽  
Theoretical Model ◽  
Size Effects ◽  
Polyester Resin ◽  
Thermal Design ◽  
Theoretical Predictions ◽  
Theory And Experiment ◽  
Composite Samples

ABSTRACTIn this work, the thermal conductivity of composites made up of carbon nanotubes embedded in a polyester resin is investigated by comparing experimental data with theoretical predictions. The composite samples were prepared with a random and aligned distribution of carbon nanotubes. Its thermal conductivity is then measured by using the photothermal radiometry technique. The obtained experimental data is accurately described by the proposed theoretical model, which takes into account the size effects of the nanotubes. It is expected that the obtained results can provide useful insights on the thermal design of composites based on carbon nanotubes.

Physically based closed-form expression for the bimodal unsaturated hydraulic conductivity function

2013 ◽  
Vol 68 (2) ◽  
pp. 328-334
Author(s):  
Shiyu Liu ◽  
Noriyuki Yasufuku ◽  
Qiang Liu ◽  
Hazarika Hemanta
Keyword(s):  
Experimental Data ◽  
Hydraulic Conductivity ◽  
Closed Form ◽  
Characteristic Curve ◽  
Complex Structure ◽  
Closed Form Expression ◽  
Form Expression ◽  
Unsaturated Hydraulic Conductivity ◽  
Physically Based ◽  
Conductivity Function

Simulation of flow and contaminant transport through the vadose zone requires accurate parameterization of the soil hydraulic properties. This requirement is particularly important for soils with a complex structure. In the present study, a physically based closed-form expression for the bimodal unsaturated hydraulic conductivity function is proposed for soils with bimodal pore-size distribution. It combines the bimodal representation of the soil-water characteristic curve (SWCC) function of Liu with the conductivity representation model of Mualem. The proposed equations are defined by parameters that have physical significance, which can be related to the properties of the materials. Experimental data for the representation of bimodal SWCCs and corresponding hydraulic conductivity curves were used to demonstrate the applicability of the proposed functions. The proposed approaches resulted in good agreement with experimental data. These functions can potentially be used as an effective tool for identifying hydraulic porosities in mediums with a complex structure.

TWO-LEVEL TUNNELLING MODEL DESCRIPTION OF THERMAL CONDUCTIVITY FOR CuxSn1-x METALLIC GLASSES AT LOW TEMPERATURE

2003 ◽  
Vol 17 (11) ◽  
pp. 2259-2271
Author(s):  
G. M. BHUIYAN ◽  
MD. SHAHJAHAN ◽  
ISSAM ALI ◽  
S. M. MUJIBUR RAHMAN
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Low Temperature ◽  
Metallic Glasses ◽  
Model Description ◽  
Recent Experimental Data ◽  
Model Parameters ◽  
Scattering Mechanism ◽  
Fitting Procedure ◽  
Theoretical Results

The two level tunnelling model is applied to analyze recent experimental data on low temperature thermal conductivity of Cu x Sn 1-x metallic glasses. An extra scattering mechanism due to Rayleigh is introduced to describe three characteristic regions of conductivity. Model parameters are determined using least-squares fitting procedure. Results derived from the parameters allow one to predict several interesting low temperature properties of metallic glasses in particular the characteristic plateau of conductivity. Theoretical results are also compared and contrasted with those of other metallic and non-metallic systems, and both common and uncommon features that exist between them are discussed.

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