Thermal Properties of Thin Metallic Layer Deposited on Insulators: Effect of the Interface on the Independent Determination of the Thermal Diffusivity and Conductivity of the Layer

2008 ◽  
Author(s):  
Danie`le Fournier ◽  
Jean Paul Roger ◽  
Christian Fretigny
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Thermal Resistance ◽  
Thermal Contact ◽  
Heat Diffusion ◽  
Metallic Layer ◽  
Good Thermal Contact ◽  
Lateral Heat

Lateral heat diffusion thermoreflectance is a very powerful tool for determining directly the thermal diffusivity of layered structures. To do that, experimental data are fitted with the help of a heat diffusion model in which the ratio between the thermal conductivity k and the thermal diffusivity D of each layer is fixed, and the thermal properties of the substrate are known. We have shown in a previous work that it is possible to determine independently the thermal diffusivity and the thermal conductivity of a metallic layer deposited on an insulator, by taking into consideration all the data obtained at different modulation frequencies. Moreover, it is well known that to prevent a lack of adhesion of a gold film deposited on substrates like silica, an intermediate very thin (Cr or Ti) layer is deposited to assure a good thermal contact. We extend our previous work: the asymptotic behaviour determination of the surface temperature wave at large distances from the modulated point heat source for one layer deposited on the substrate to the two layers model. In this case (very thin adhesion coating whose thermal properties and thickness are known), it can be establish that the thermal diffusivity and the thermal conductivity of the top layer can still be determined independently. It is interesting to underline that the calculus can also be extended to the case of a thermal contact resistance which has often to be taken into account between two solids. We call thermal resistance a very thin layer exhibiting a very low thermal conductivity. In this case, the three parameters we have to determine are the thermal conductivity and the thermal diffusivity of the layer and the thermal resistance. We will show that, in this case, the thermal conductivity of the layer is always obtained independently of a bound of the couple thermal resistance – thermal diffusivity, the thermal diffusivity being under bounded and the thermal resistance lower bounded. Experimental results on thin gold layers deposited on silica with and without adhesion layers are presented to illustrate the method. Discussions on the accuracy will also be presented.

Independent Determination of the Thermal Diffusivity and Conductivity of a Thin Metallic Layer Deposited on Silica

2008 ◽  
Author(s):  
Christian Fretigny ◽  
Jean Paul Roger ◽  
Li Liu ◽  
Danie`le Fournier
Keyword(s):  
Thermal Diffusivity ◽  
Careful Analysis ◽  
Thin Layers ◽  
Heat Diffusion ◽  
Bulk Materials ◽  
Thermal Insulator ◽  
Independent Determination ◽  
Lateral Temperature ◽  
Lateral Heat

It is well known that the thermal parameters of materials confined in thin layers may significantly differ from their bulk value. Lateral heat diffusion thermoreflectance experiment is a very powerful tool for determining directly the thermal diffusivity of bulk materials and of layered structure. Nevertheless, in the latter case, experimental data are fitted with the help of a heat diffusion model in which the layer thermal conductivity and thermal diffusivity are taken together into consideration. In this paper, we show that both parameters can be determined independently, in the case of a thermal conductive layer deposited on a thermal insulator, with a careful analysis of the amplitude and the phase of the lateral temperature field associated to a point source.

The insensitivity of thermal diffusivity of natural sediments to saturation

2018 ◽  
Vol 58 (2) ◽  
pp. 705
Author(s):  
Ayman Ezdini ◽  
James Griffith ◽  
Nick Lange ◽  
Soroush Tehrani ◽  
Hamad Roshan ◽  
...  
Keyword(s):  
Grain Size ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Clay Content ◽  
Heat Diffusion ◽  
Reservoir Properties ◽  
Needle Probe ◽  
Close Relationship ◽  
Porosity And Permeability

This extended abstract presents a ground-breaking study of thermal properties of soils and their dependency on saturation. The paper tries to prove that thermal diffusivity is not significantly dependent on saturation due to its close relationship with saturation-independent parameters such as thermal conductivity and volumetric heat capacity. The investigation is divided into two main scopes of work: the first is to build statistical analysis using the Monte Carlo technique by means of random sampling certain soil thermal properties; and the second is to experimentally validate the statistical models. The experimental framework of the study encompasses the measurement of thermal properties of different soil samples. These samples varied in terms of grain size, percentage clay content, and level of saturation. The experiments were carried out using a KD2-Pro Dual Needle Probe Thermal Properties Analyser. The results demonstrate that saturation has a negligible effect on thermal diffusivity of soils but an inverse relationship exists between diffusivity and clay content. Furthermore, the variation in grain size effect on diffusivity is within 5%. The study shows a correlation between lithology, porosity, and thermal properties. The implications are numerous: from the determination of unwanted heat diffusion of pipelines to the estimation of reservoir properties such as porosity and permeability.

The Simultaneous Measurement of Thermal Conductivity, Thermal Diffusivity, and Perfusion in Small Volumes of Tissue

1984 ◽  
Vol 106 (3) ◽  
pp. 192-197 ◽  
Author(s):  
J. W. Valvano ◽  
J. T. Allen ◽  
H. F. Bowman
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Tissue Perfusion ◽  
Effective Thermal Diffusivity ◽  
Liver Preparation ◽  
Improved Technique ◽  
Power Response

An improved technique is presented for the “in-vivo” determination of thermal conductivity, thermal diffusivity, and perfusion using a self-heated spherical thermistor probe. In the presence of flow, solution of the time-dependent, probe-tissue coupled thermal model allows the measurement of “effective” thermal conductivity and “effective” thermal diffusivity, which represent the thermal properties of the perfused tissue. Perfusion can be quantified from both “effective” thermal properties. In the presence of flow, it has been shown that the transient power response does not follow t−1/2 as has been previously assumed. An isolated rat liver preparation has been developed to validate the measurement technique. Radioactive microspheres are used to determine the true perfusion from the total collected hepatic vein flow. Experimental data demonstrates the ability to quantify perfusion in small volumes of tissue.

In Situ Testing and Analysis of Thermal Properties of the Ground Formation in Jiangsu, China

2014 ◽  
Vol 933 ◽  
pp. 477-481
Author(s):  
Shuai Chen
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Resistance ◽  
Thermal Response ◽  
Geological Structure ◽  
Ground Source ◽  
In Situ Conditions ◽  
Thermal Conductivity Λ

Ground source heat pump (GSHP) systems exchange heat with the ground, often through a closed-loop, vertical, borehole heat exchanger (BHE). The performance of the BHE depends on the thermal properties of the ground formation, as well as soil or backfill in the borehole. The design and economic probability of GSHP systems need the thermal conductivity of geological structure and thermal resistance of BHE. Thermal response test (TRT) method allows the in-situ determination of the thermal conductivity (λ) of the ground formation in the vicinity of a BHE, as well as the effective thermal resistance (Rb) of this latter. Thermal properties measured in laboratory experiments do not comply with data of in-situ conditions. The present article describes the results of thermal properties of the BHE whose depth is 100m in Yancheng City, Jiangsu Province, China. As shown in these results, λ and Rb of borehole are determined as 1.84(W·m-1·K-1) and 0.121 (m·K·W-1) respectively.

scholarly journals DETERMINATION OF THERMAL PROPERTIES OF COFFEE BEANS AT DIFFERENT DEGREES OF ROASTING

2018 ◽  
Vol 13 (4) ◽  
pp. 498
Author(s):  
Danilo Barbosa Cardoso ◽  
Ednilton Tavares de Andrade ◽  
Renso Alfredo Aragón Calderón ◽  
Mariane Helena Sanches Rabelo ◽  
Camila De Almeida Dias ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Infinite Cylinder ◽  
Element Analysis ◽  
Heating Source ◽  
Mixing Method ◽  
Cylinder Method

<p>The aim of this study was to determine the main thermal properties of the granular mass of coffee (specific heat, thermal conductivity, and thermal diffusivity) for different degrees of roasting, as well as to model and simulate thermal conductivity at different degrees of roasting. For determination of specific heat, the mixing method was used, and for thermal conductivity, the theoretically infinite cylinder method with a central heating source. Thermal diffusivity was simulated algebraically using the results of the properties cited above and of the apparent specific mass of the product. Thermal conductivity was also simulated and optimized through finite element analysis software. At darker roasting, there was an increase in specific heat and a reduction in thermal conductivity and thermal diffusivity. Comparing thermal conductivity determined in relation to simulated and optimized conductivity, the mean relative error was 1.02%, on average.</p>

scholarly journals Determination of Some Selected Thermal Properties of Pumpkin Seeds (Cucurbita pepo)

2021 ◽  
Vol 25 (4) ◽  
pp. 599-604
Author(s):  
M.O. Sunmonu ◽  
M.M. Odewole ◽  
O.A. Adeyinka ◽  
M.S. Sanusi ◽  
S.O. Musa
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Moisture Content ◽  
Specific Heat ◽  
Average Moisture Content ◽  
Pumpkin Seed ◽  
C Value ◽  
Pumpkin Seeds

In this study, some selected thermal properties (specific heat, thermal conductivity and thermal diffusivity) in the moisture content range of 5.0-5.6% or green and 4.80 – 5.20% for white varieties of pumpkin seeds were determined. The specific heat was measured using mixture method while the thermal conductivity was measured by transient technique using the heat line source. The green pumpkin seed has average moisture content of 5.2% higher than moisture content of white pumpkin seed of average 4.8%. The average specific heat values of green pumpkin seed are 6.171kJ/kgK and white pumpkin seed 4.327kJ/kgK. The thermal conductivity values for white pumpkin seed ranged from 0.074 to 0.288 W/m°C while that for green pumpkin seed ranged from 0.079 to 0.433 W/m°C. The thermal diffusivity values for green pumpkin ranged from 0.0011 to 0.06 m2/s while that for white pumpkin seed ranged from 0.01 to 0.06 m2/s. It was concluded that the higher the moisture content (5.2%) the higher the value of specific heat of seed (6.171kJ/kgK). It can also be concluded that the thermal conductivity (0.079 to 0.433 W/m°C) value is higher with high moisture content (5.2%).

Thermal Conductivity and Thermal Diffusivity of Biomaterials: A Simultaneous Measurement Technique

1977 ◽  
Vol 99 (3) ◽  
pp. 148-154 ◽  
Author(s):  
T. A. Balasubramaniam ◽  
H. F. Bowman
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Measurement Technique ◽  
Thermal Model ◽  
In Vitro Measurements ◽  
Made In

A technique is presented for the simultaneous determination of thermal conductivity and thermal diffusivity of biomaterials. Measurements are derived from the transient power supplied to a thermistor probe operated in a self-heated mode. The thermal properties are extracted through the use of an appropriate thermal model. Thermal conductivity is determined through a simple algebraic equation. Thermal diffusivity is determined from a convenient set of nondimensionalized curves. The technique can be used in vivo and in vitro. Measurements can be made in sample volumes of less than 1 cc in less than 30 s.

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