scholarly journals Experimental Investigation on Thermal Conductivity and Thermal Diffusivity of Water-Agar Gel from Room Temperature to –60℃

2020 ◽  
Vol 38 (3) ◽  
pp. 583-589
Author(s):  
Elena Campagnoli ◽  
Valter Valter
Keyword(s):  
Thermal Conductivity ◽  
Experimental Investigation ◽  
Thermal Diffusivity ◽  
Room Temperature ◽  
Agar Gel

scholarly journals Experimental Investigation on Thermal Conductivity and Thermal Diffusivity of Ex-Vivo Bovine Liver from Room Temperature down to −60 °C

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3750
Author(s):  
Elena Campagnoli ◽  
Valter Giaretto
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Room Temperature ◽  
Ad Hoc ◽  
Ex Vivo ◽  
Bovine Liver ◽  
Agar Gel ◽  
Calorimetric Analysis ◽  
Temperature Ranges

Ex vivo animal tissues (e.g., bovine liver) as well as water-agar gel are commonly used to simulate both experimentally and numerically the response of human tissues to cryoablation treatments. Data on the low temperature thermal properties of bovine liver are difficult to find in the literature and very often are not provided for the whole temperature range of interest. This article presents the thermal conductivity and thermal diffusivity measurements performed on ex-vivo bovine liver samples using the transient plane source method. Regression coefficients are provided to determine these properties in different temperature ranges except for the phase transition during which no results were obtained, which suggests an ad hoc calorimetric analysis. A quick procedure is also suggested to determine the water mass fraction in the tissue. Moreover, an attempt to estimate the liver density in the frozen state using measurements performed solely at room temperature is also presented. The measured thermal conductivity and thermal diffusivity values are compared with data reported in literature highlighting a spread up to 40%. Moreover, it emerges that water-agar gel usually made with 2% by weight of agar does not show the same thermal properties as the bovine liver.

Thermal Diffusivity and Conductivity of La0.7Ca0.3-xSrxMnO3 (x=0 to 0.10)

2012 ◽  
Vol 501 ◽  
pp. 319-323
Author(s):  
Hasan A. Alwi ◽  
Lay S. Ewe ◽  
Zahari Ibrahim ◽  
Noor B. Ibrahim ◽  
Roslan Abd-Shukor
Keyword(s):  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Grain Size ◽  
Transition Temperature ◽  
Thermal Diffusivity ◽  
Electrical Properties ◽  
Room Temperature ◽  
Electronic Contribution ◽  
Insulator Metal Transition ◽  
Thermal And Electrical Properties

We report the room temperature thermal conductivity κ and thermal diffusivity α of polycrystalline La0.7Ca0.3-xSrxMnO3 for x = 0 to 0.1. The samples were prepared by heating at 1220 and 1320oC. The insulator-metal transition temperature, TIM and thermal diffusivity increased with Sr content. Phonon was the dominant contributor to thermal conductivity and the electronic contribution was less than 1%. Enhancement of electrical conductivity σ and thermal diffusivity for x ≥ 0.08 was observed in both series of samples. The grain size of the samples (28 to 46 µm) does not show any affect on the thermal and electrical properties.

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.

scholarly journals Lightweight cementitious composites containing cenospheres and polypropylene fibres after exposure to high temperatures

2020 ◽  
Vol 322 ◽  
pp. 01028
Author(s):  
Wojciech Szymkuć ◽  
Piotr Tokłowicz
Keyword(s):  
Thermal Conductivity ◽  
Experimental Investigation ◽  
Compressive Strength ◽  
High Temperatures ◽  
Room Temperature ◽  
Cementitious Composites ◽  
Low Density ◽  
Polypropylene Fibres ◽  
Residual Compressive Strength ◽  
Positive Effect

The paper presents the results of experimental investigation of lightweight cementitious composites with cenospheres (LCCC) exposed to high temperatures. We showed the positive effect of cenospheres on post- fire residual compressive strength in previous papers. This paper focuses on the LCCC with the addition of polypropylene (PP) fibres. Specimens are heated up to 400, 600, 800, 1000 and 1200 °C. Then they are cooled to ambient temperature and their residual flexural and compressive strength is tested. The results are compared with non-heated specimens with compressive strength above 50 MPa. For plain LCCC composites, the results show significant improvement of residual compressive strength in comparison with typical concretes. No significant changes of compressive strength are found after exposure to temperatures up to 600°C – more than 85 % of the residual compressive strength is retained after exposure to this temperature for both mixes. Polypropylene fibres are found to be a successful mean to mitigate spalling without significantly lowering neither ambient nor residual compressive strength. Moreover, designed composite has low density and low thermal conductivity at room temperature.

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.

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.

Effect of Silicon Compounds on the Properties of Pressureless Sintered Aluminum Nitride

2014 ◽  
Vol 602-603 ◽  
pp. 565-569
Author(s):  
Chang Lu Fu ◽  
Shang Hua Wu ◽  
Yan Ling Cheng ◽  
Jun Yu Fu ◽  
Ruo Jun Wu ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Aluminum Nitride ◽  
Fracture Mode ◽  
Room Temperature ◽  
Pressureless Sintering ◽  
Sintering Aids ◽  
Silicon Compounds ◽  
Sintered Aluminum ◽  
Microstructure Density

In this paper, the aluminum nitride (AlN) was fabricated by pressureless sintering with YF3 and various silicon compounds as the sintering aids. The phase, microstructure, density and thermal conductivity were characterized by XRD, SEM and laser thermal diffusivity method. The sample densities were detected varied from 3.17 to 3.30g/cm3 and room-temperature thermal conductivity varied from 196 to 233 W/m·K. Samples sintered with YF3 additives have the highest thermal conductivity. The sintering aids with SiO2, Si3N4 and SiC would decrease the density and the thermal conductivity obviously, and also change the fracture mode from the intergranular to transgranular , which is a key for the toughness of the AlN substrate.

Effects of microstructural evolution on the thermal conductivity of α–Al2O3 prepared from nano-size γ–Al2O3 powder

2000 ◽  
Vol 15 (3) ◽  
pp. 744-750 ◽  
Author(s):  
Eduardo J. Gonzalez ◽  
Grady White ◽  
Lanhua Wei
Keyword(s):  
Thermal Conductivity ◽  
Thermal Diffusivity ◽  
Microstructural Evolution ◽  
Vickers Hardness ◽  
Room Temperature ◽  
Volume Fraction ◽  
Al2o3 Powder ◽  
Α Al2o3 ◽  
Thermal Diffusivities ◽  
Nano Size

The thermal diffusivities (D) of porous α–Al2O3 specimens prepared from nano-size γ–Al2O3 powder and from conventional submicrometer-size alumina powders were measured at room temperature, and the thermal conductivity (κ) was calculated from D. Plots of κ versus the volume fraction of porosity (P) showed that the data from both sets of samples followed similar linear curves. Similarly, data of Vickers hardness versus P obtained from the same specimens also followed a single linear curve. The good correlation of thermal diffusivity with P suggests that grain boundaries have a lesser effect on thermal transport than porosity.

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