Thermophysical Properties of Germanium for Thermal Analysis of Growth from the Melt

1981 ◽  
Vol 9 ◽  
Author(s):  
Roger K. Crouch ◽  
A. L. Fripp ◽  
W. J. Debnam ◽  
R. E. Taylor ◽  
H. Groot
Keyword(s):  
Thermal Conductivity ◽  
Thermal Analysis ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Thermophysical Properties ◽  
Room Temperature ◽  
Bridgman Method ◽  
The Other ◽  
Temperature Range ◽  
Diffusivity Measurements

ABSTRACTThe thermal diffusivity of Ge has been measured over a temperature range from 300° C to 1010° C which includes values for the melt. Specific heat has been measured from room temperature to 727° C. Thermal conductivity has been calculated over the same temperature range as the diffusivity measurements. These data are reported along with the best values from the literature for the other parameters which are required to calculate the temperature and convective fields for the growth of germanium by the Bridgman method. These parameters include the specific heat, the viscosity, the emissivity, and the density as a function of temperature.

scholarly journals Phonon hydrodynamics and ultrahigh–room-temperature thermal conductivity in thin graphite

Science ◽  
2020 ◽  
Vol 367 (6475) ◽  
pp. 309-312 ◽  
Author(s):  
Yo Machida ◽  
Nayuta Matsumoto ◽  
Takayuki Isono ◽  
Kamran Behnia
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Wide Temperature Range ◽  
Room Temperature ◽  
Phonon Dispersion ◽  
High Conductivity ◽  
Temperature Range ◽  
A Value ◽  
Out Of Plane ◽  
Intimate Link

Allotropes of carbon, such as diamond and graphene, are among the best conductors of heat. We monitored the evolution of thermal conductivity in thin graphite as a function of temperature and thickness and found an intimate link between high conductivity, thickness, and phonon hydrodynamics. The room-temperature in-plane thermal conductivity of 8.5-micrometer-thick graphite was 4300 watts per meter-kelvin—a value well above that for diamond and slightly larger than in isotopically purified graphene. Warming enhances thermal diffusivity across a wide temperature range, supporting partially hydrodynamic phonon flow. The enhancement of thermal conductivity that we observed with decreasing thickness points to a correlation between the out-of-plane momentum of phonons and the fraction of momentum-relaxing collisions. We argue that this is due to the extreme phonon dispersion anisotropy in graphite.

Thermal Properties of Tungsten SRM’S 730 and 799

1978 ◽  
Vol 100 (2) ◽  
pp. 330-333 ◽  
Author(s):  
R. E. Taylor
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
Thermal Properties ◽  
High Temperature ◽  
Thermal Diffusivity ◽  
Thermophysical Properties ◽  
Room Temperature ◽  
Standard Material ◽  
International Program ◽  
Sintered Tungsten

Samples of sintered and arc-cast tungsten are available from NBS as thermal conductivity (SRM 730) and electrical resistivity (SRM 799) standards for the temperature range from 4 to 3000K. NBS recommended values for these properties above room temperature are based on results of various researchers during a previous international program which included arc-cast and sintered tungsten. The sintered tungsten used in this program was found to be unsuited for use as a standard material due to inhomogeneity and high temperature instability. The present paper gives results at high temperatures for thermal conductivity, electrical resistivity, specific heat, thermal diffusivity and Wiedemann-Franz-Lorenz ratio for a sample of the NBS sintered tungsten using the Properties Research Laboratory’s multiproperty apparatus. These results are compared to values recommended by the Thermophysical Properties Research Center, NBS, and an international program.

Thermal Transport Properties of Multi-Walled Carbon Nanotube Arrays

2007 ◽  
Author(s):  
Huaqing Xie ◽  
An Cai ◽  
Xinwei Wang
Keyword(s):  
Thermal Conductivity ◽  
Carbon Nanotube ◽  
Thermal Diffusivity ◽  
Room Temperature ◽  
Infrared Detector ◽  
Laser Flash ◽  
Temperature Range ◽  
Nanosecond Pulsed Laser ◽  
Multi Walled Carbon Nanotube ◽  
Individual Cnts

A laser flash technique was applied to measure the thermal diffusivity along a multi-walled carbon nanotube (CNT) array in temperature range of −55∼200 °C. In the measurements, a nanosecond pulsed laser was used to realize noncontact heating and the temperature variations were recorded by an infrared detector. The experimental results show that the thermal diffusivity of the CNT array increases slightly with temperature in the −55∼70 °C temperature range and exhibits no obvious change in the −75∼200 °C temperature range. The CNT array has much larger thermal diffusivity than several known excellent thermal conductors, reaching about 4.6 cm2s−1 at room temperature. The mean thermal conductivity (λ) of individual CNTs was further estimated from the thermal diffusivity, specific heat (Cp), and density (ρ) by using the correlation of λ = αρCp. The thermal conductivity of individual CNTs increases smoothly with the temperature increase, reaching about 750 Wm−1K−1 at room temperature.

scholarly journals Determination of thermophysical properties of cupuassu (Theobroma grandiflorum) dry almonds

2021 ◽  
Vol 7 (2) ◽  
Author(s):  
Elisa Santana Cunha ◽  
Geovana Pires Araújo Lima ◽  
Jorge Henrique Oliveira Sales ◽  
Elizama Aguiar de Oliveira
Keyword(s):  
Thermal Conductivity ◽  
Activation Energy ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Thermophysical Properties ◽  
Effective Diffusivity ◽  
Theobroma Grandiflorum

In comparison to cocoa, little has been reported on the drying of cupuassu almonds that can be used to produce cupulate, a chocolate type product. Thus, in this study thermophysical properties of cupuassu dry almonds (moisture = 9.68 % d.b.) were determined as: thermal conductivity (k) of 0.14 kW/(m.K), specific heat (cp) of 2.86 kJ/(kg.K), thermal diffusivity (?) of 4.8·10-5 m²/s, effective diffusivity (Deff) of 9.94·10-10 - 6.29·10-10 m²/s and activation energy (Ea) of 14.90 kJ/mol. These results showed a similarity of values between cupuassu and cocoa and allows to perform more specific studies for the development of dryers for the cupuassu almonds.

Fundamental Study on Laser Interactions With Nanoparticles-Reinforced Metals—Part I: Effect of Nanoparticles on Optical Reflectivity, Specific Heat, and Thermal Conductivity

2016 ◽  
Vol 138 (12) ◽  
Author(s):  
Chao Ma ◽  
Jingzhou Zhao ◽  
Chezheng Cao ◽  
Ting-Chiang Lin ◽  
Xiaochun Li
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Specific Heat ◽  
Thermophysical Properties ◽  
Room Temperature ◽  
Al2o3 Nanoparticles ◽  
Fundamental Study ◽  
Optical Reflectivity ◽  
Theoretical Results ◽  
Laser Interactions

It is of tremendous interest to apply laser to process nanoparticles-reinforced metals for widespread applications. However, little fundamental understanding has been obtained on the underlining physics of laser interactions with nanoparticles-reinforced metals. In this work, fundamental study was carried out to understand the effects of nanoparticles on the optical and thermophysical properties of the base metal, the corresponding heat transfer and melt pool flow processes, and the consequent surface property in laser melting. Part I presents both experimental and theoretical results on the effects of nanoparticles on the optical reflectivity, specific heat, and thermal conductivity. Electrocodeposition was used to produce nickel samples with nanoparticles. Using a power meter, the reflectivity of Ni/Al2O3 (1.8 vol. %) was measured to be 65.8% while pure Ni was at 67.4%, indicating that the Al2O3 nanoparticles did not change the reflectivity substantially. Differential scanning calorimetry was used to determine the heat capacity of the nanocomposites. The specific heat capacities of the Ni/Al2O3 (4.4 vol. %) and Ni/SiC (3.6 vol. %) at room temperature were 0.424 ± 0.013 J/g K and 0.423 ± 0.014 J/g K, respectively, close to that of pure Ni, 0.424 ± 0.008 J/g K. An experimental setup was developed to measure thermal conductivity based on the laser flash method. The thermal conductivities of these Ni/Al2O3 and Ni/SiC nanocomposites at room temperature were 84.1 ± 3.4 W/m K and 87.3 ± 3.4 W/m K, respectively, less than that of pure Ni, 91.7 ± 2.8 W/m K. Theoretical models based on the effective medium approximation theory were also used to predict the heat capacity and thermal conductivity of the nanoparticles-reinforced nickel. The theoretical results match well with the measurements. The knowledge of the optical and thermophysical properties of nanoparticles-reinforced metals would provide valuable insights to understand and control laser processing of metal matrix nanocomposites.

Thermal Properties Measurement of Particulate Fouling Samples of Air-Cooled Heat Exchangers Using Laser Flash Method

2020 ◽  
Author(s):  
Arjun Sharma ◽  
M. D. Islam ◽  
Ebrahim Al Hajri
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Middle East ◽  
Specific Heat ◽  
Thermophysical Properties ◽  
Heat Exchangers ◽  
Laser Flash ◽  
Flash Method ◽  
Particulate Fouling ◽  
Major Factors

Abstract Fouling is one of the major factors that drastically affects heat exchanger performance. Especially in Middle East where most of the heat exchangers are air cooled due to scarcity of water. As these heat exchangers are placed in a harsh climate, they are at high risk of low performance due to dusty/sticky particulate fouling. In order to identify possible active/passive methods to control or ideally eliminate particulate fouling, it is desirable to know exact thermophysical properties of such particulate fouling. This study presents thermophysical property characterization of selected fouling samples from eight different fin fan heat exchangers installed in an oil & gas facility in the Middle East. Laser flash Analysis (LFA) method is a well-known technique for measurement of the thermophysical properties: thermal diffusivity, specific heat and thermal conductivity of materials. A new technique was developed to prepare powder particulate fouling samples to make them as disc shaped samples while maintaining the range of ± 12 mm diameter and ± 2 mm thickness. The LFA measurements was conducted using LFA 447 Nano Flash Netzsch over the temperature range from 25 °C to 125°C. The thermal diffusivity was measured with an accuracy of ± 3% and the specific heat capacity with an accuracy of ± 5%. As the thermal conductivity is a product of these two measured values, is calculated with an accuracy of ± 5.8% and the measurement repeatability was within 2%.

Thermophysical Characterization of Genipap Pulp

2010 ◽  
Vol 6 (3) ◽  
Author(s):  
Normane Mirele Chaves da Silva ◽  
Renata Cristina Ferreira Bonomo ◽  
Luciano Brito Rodrigues ◽  
Modesto Antonio Chaves ◽  
Rafael da Costa Ihéu Fontan ◽  
...  
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Water Content ◽  
Thermophysical Properties ◽  
Empirical Models ◽  
Influence Of Temperature ◽  
Thermophysical Characterization

The influence of temperature and water content on thermophysical properties (density, thermal diffusivity, thermal conductivity and specific heat) of genipap (Genipa americana, L) pulp at medium maturity were studied. The thermophysical properties were determined at concentrations between 6.0% m/m and 24.0% m/m of water content and temperatures range of 5 to 80°C. The density decreased with increase in temperature and water content, while the thermal diffusivity and conductivity increased as temperature and water content increased. The specific heat decreased with the moisture content. Empirical models were fitted to the experimental data for each property and the accuracy of those models was checked.

Thermophysical Properties of AS4/3501-6 Carbon-Epoxy Composite

2013 ◽  
Author(s):  
Amber Vital ◽  
Bradley Doleman ◽  
Messiha Saad
Keyword(s):  
Thermal Conductivity ◽  
Composite Materials ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Thermophysical Properties ◽  
Critical Role ◽  
Flash Method ◽  
Energy Storage Devices ◽  
Temperature Levels ◽  
American Society

As today’s technology continues to develop at a rate that was once unimaginable, the demand for new materials that will outperform traditional materials also increases dramatically. To meet these challenges, monolithic materials are being combined to develop new unique materials called composites. Thermophysical properties of composite materials such as thermal conductivity, diffusivity, specific heat, and thermal expansion are very important in engineering design process and analysis of aerospace vehicles as well as space systems. These properties are also important in power generation, transportation, and energy storage devices including fuel cells. Thermal conductivity is the property that determines the working temperature levels of a material and plays a critical role in the performance of materials in high temperature applications. This parameter is important in problems involving heat transfer and thermal structures. The objective of this paper is to develop a thermal properties database for the carbon-epoxy AS4/3501-6 composite. The AS4 carbon fiber used is a unidirectional continuous PAN based fiber, and the 3501-6 epoxy resin is amine cured and provides low shrinkage during the curing process while maintain resistance to chemicals and solvents. The thermophysical properties of the AS4 composite have been investigated using experimental methods. The flash method was used to measure the thermal diffusivity of the composite based on the American Society for Testing and Materials standard, ASTM E1461. In addition, the Differential Scanning Calorimeter was used in accordance with the ASTM E1269 standard to measure the specific heat. The measured thermal diffusivity, specific heat, and density were used to compute the thermal conductivity, thus adding to the currently insufficient database for composite materials and foams.

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