scholarly journals Soil thermal properties of forest biogeocenoses in steppe zone as a diagnostic indicator of their soil genesis

2019 ◽  
Vol 19 (1) ◽  
pp. 26-30
Author(s):  
V. A. Gorban
Keyword(s):  
Thermal Conductivity ◽  
Organic Matter ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Steppe Zone ◽  
Thermal Capacity ◽  
Illuvial Horizon ◽  
Soil Genesis ◽  
Silt Fraction ◽  
Soil Features

Soil is a specific natural body, which is characterized by a number of features due to which it differs from living organisms and rocks. One of these features is its thermal properties. The most important thermal properties of the soil are thermal conductivity, thermal capacity and thermal diffusivity, which reflect the specific features of the set of properties inherent in different soils. As a result of the studies, the existence of a direct relationship between the values of thermal conductivity and thermal diffusivity of Calcic Chernozem and the content of the silt fraction in them, as well as between the thermal capacity and the content of organic matter in them. The established relations do not appear clearly in Luvic Chernozem and Chernic Phaeozem. The maximum thermal properties for Luvic Chernozem and Chernic Phaeozem were found in the eluvial horizon, which in the lower part borders on the illuvial horizon. The eluvial horizons of Luvic Chernozem and Chernic Phaeozem are characterized by lower thermal properties compared with the illuvial horizons. The thermal properties of soils can be used to clarify the distribution characteristics of the silt fraction and organic matter along the profile, as well as determination of the intensity of eluvial-illuvial processes. The establishment of these soil features is an important characteristic of their soil genesis, which is especially important for chernozem soils under forest vegetation.

scholarly journals Features of soil thermophysical properties of the southern variant of ravine biogeocenoses of the Ukrainian steppe zone

2020 ◽  
Vol 31 (2) ◽  
pp. 82-86
Author(s):  
V. A. Gorban
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Diffusivity ◽  
Thermophysical Properties ◽  
Organic Matter Content ◽  
Steppe Zone ◽  
Matter Content ◽  
Illuvial Horizon ◽  
Meadow Soil ◽  
The Village

Thermophysical properties are an important characteristic of the general condition of soils, which determine the peculiarities of the distribution of heat flow in them. Today studies of thermophysical properties of soils, including the steppe zone of Ukraine, are practically not performed. This determines the relevance of the work, which is devoted to establishing the characteristics of the thermal properties of various soils. As a result of the study of thermal diffusivity, heat capacity and thermal conductivity of soils of northern and southern exposures, as well as the thalweg of the Voyskovoy Bayrak (located near the village of Voyskovoe Solonyansky district of Dnipropetrovsk region), it was found that the most important soil factors particles of physical clay and organic matter content. It was found that the eluvial horizons of the chernozem of the forest of the northern exposure differ in the reduced values ​​of heat capacity and thermal conductivity in comparison with the illuvial horizons. Eluvial horizons of forest-meadow soil of thalweg are characterized by increased values ​​of thermal diffusivity and thermal conductivity, as well as reduced values ​​of heat capacity compared to illuvial horizons. Eluvial horizons of forest chernozem of southern exposure are characterized by lower values ​​of thermal diffusivity, heat capacity and thermal conductivity compared to illuvial horizons. The most significant boundary between eluvial and illuvial horizons in terms of thermophysical properties is characteristic of the chernozem of forest southern exposure, which is manifested in a sharp increase in the values ​​of thermophysical properties in the first illuvial horizon. Cluster analysis revealed that the most similar in terms of thermal diffusivity are forest chernozems of southern and northern exposures, and in terms of heat capacity and thermal conductivity – forest chernozems of northern exposure and forest-meadow soil of thalweg ravine.

Thermal Characterization of Carbon-Carbon Composites

2011 ◽  
Author(s):  
Messiha Saad ◽  
Darryl Baker ◽  
Rhys Reaves
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Critical Role ◽  
Carbon Composite ◽  
Flash Method ◽  
Carbon Composites ◽  
Energy Storage Devices ◽  
Graphitized Carbon

Thermal properties of materials such as specific heat, thermal diffusivity, and thermal conductivity are very important in the 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 and solar cells. Thermal conductivity plays a critical role in the performance of materials in high temperature applications. Thermal conductivity is the property that determines the working temperature levels of the material, and it is an important parameter in problems involving heat transfer and thermal structures. The objective of this research is to develop thermal properties data base for carbon-carbon and graphitized carbon-carbon composite materials. The carbon-carbon composites tested were produced by the Resin Transfer Molding (RTM) process using T300 2-D carbon fabric and Primaset PT-30 cyanate ester. The graphitized carbon-carbon composite was heat treated to 2500°C. The flash method was used to measure the thermal diffusivity of the materials; this method is based on America Society for Testing and Materials, ASTM E1461 standard. In addition, the differential scanning calorimeter was used in accordance with the ASTM E1269 standard to determine the specific heat. The thermal conductivity was determined using the measured values of their thermal diffusivity, specific heat, and the density of the materials.

Experimental Study on Thermal Properties of Hollow Sphere Structures

2021 ◽  
Vol 407 ◽  
pp. 185-191
Author(s):  
Josef Tomas ◽  
Andreas Öchsner ◽  
Markus Merkel
Keyword(s):  
Thermal Conductivity ◽  
Experimental Study ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Hollow Sphere ◽  
Plane Source ◽  
Source Method ◽  
Transient Plane Source ◽  
Transient Plane Source Method

Experimental analyses are performed to determine thermal conductivity, thermal diffusivity and volumetric specific heat with transient plane source method on hollow sphere structures. Single-sided testing is used on different samples and different surfaces. Results dependency on the surface is observed.

scholarly journals Application of sonication and freezing as initial treatments before microwave-vacuum drying of cranberries

2019 ◽  
Vol 2 (22) ◽  
pp. 151-167 ◽  
Author(s):  
Izabela Staniszewska ◽  
Szymon Staszyński ◽  
Magdalena Zielińska
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Physical Properties ◽  
Color Change ◽  
Vacuum Drying ◽  
Drying Time ◽  
Dried Fruits ◽  
Microwave Vacuum Drying ◽  
Drying Kinetic

The aim of study was to determine the influence of sonication and freezing on the kinetic of the microwave-vacuum drying, energy consumption and physical properties of whole cranberries as well as evaluate the applicability of sonication instead of freezing in order to change their physical properties and the drying kinetic of whole cranberries. Microwave-vacuum drying of whole cranberries with/without initial treatments took from 12 ± 1 to 14.5 ± 0.5 minutes. All of treatments did not significantly shorten the drying time of cranberries. However, they increased SMER values even by 31%. Despite of cryogenic freezing, all of treatments significantly increased the values of Dew. Sonication combined with drying allowed to obtain dried berries characterized by the lowest cohesiveness (0.19±0.02), springiness (0.62±0.02) and chewiness (3.4±0.8 N), while cryogenic freezing combined with drying allowed to obtain dried fruits characterized by highest springiness (0.75±0.03) and low chewiness (3.3±0.5 N). The highest lightness (32.2±0.7), redness (32.6±0.8), and yellowness (11.1±0.7) were found for fruits subjected to initial convective freezing before drying. The efficiency of sonication in color change was comparable to cryogenic freezing and much lower than convective freezing. All of initial treatments increased such thermal properties of dried cranberries as thermal conductivity and thermal diffusivity.

Influence of Mesocarp Fibre Inclusion on Thermal Properties of Foamed Concrete

2021 ◽  
Vol 87 (1) ◽  
pp. 1-11
Author(s):  
Siti Shahirah Suhaili ◽  
Md Azree Othuman Mydin ◽  
Hanizam Awang
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Volume Fraction ◽  
Thermal Constant ◽  
Volume Fractions ◽  
Foamed Concrete

The addition of mesocarp fibre as a bio-composite material in foamed concrete can be well used in building components to provide energy efficiency in the buildings if the fibre could also offer excellent thermal properties to the foamed concrete. It has practical significance as making it a suitable material for building that can reduce heat gain through the envelope into the building thus improved the internal thermal comfort. Hence, the aim of the present study is to investigate the influence of different volume fractions of mesocarp fibre on thermal properties of foamed concrete. The mesocarp fibre was prepared with 10, 20, 30, 40, 50 and 60% by volume fraction and then incorporated into the 600, 1200 and 1800 kg/m3 density of foamed concrete with constant cement-sand ratio of 1:1.5 and water-cement ratio of 0.45. Hot disk thermal constant analyser was used to attain the thermal conductivity, thermal diffusivity and specific heat capacity of foamed concrete of various volume fractions and densities. From the experimental results, it had shown that addition of mesocarp fibre of 10-40% by volume fraction resulting in low thermal conductivity and specific heat capacity and high the thermal diffusivity of foamed concrete with 600 and 1800 kg/m3 density compared to the control mix while the optimum amount of mesocarp fibre only limit up to 30% by volume fraction for 1200 kg/m3 density compared to control mix. The results demonstrated a very high correlation between thermal conductivity, thermal diffusivity and specific heat capacity which R2 value more than 90%.

scholarly journals Characterization of the Petrophysical Properties of the Timahdit Oil Shale Layers in Morocco

Geosciences ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 337
Author(s):  
Hanane Sghiouri El Idrissi ◽  
Abderrahim Samaouali ◽  
Younes El Rhaffari ◽  
Salah El Alami ◽  
Yves Geraud
Keyword(s):  
Thermal Conductivity ◽  
Organic Matter ◽  
Thermal Diffusivity ◽  
Oil Shale ◽  
Velocity Ratio ◽  
Organic Matter Content ◽  
Matter Content ◽  
S Wave ◽  
Wave Velocities ◽  
The Impact

In this work, we study the variability of the lithological composition and organic matter content of samples were taken from the different layers M, X and Y of the Timahdit oil shale in Morocco, in order to experimentally analyze the impact of this variability on petrophysical measurements. The objective of this study is to predict the properties of the layers, including their thermal conductivity, thermal diffusivity, porosity and P and S wave velocities. The results of the study of the impact of the organic matter content of the samples on the petrophysical measurements show that, regardless of the organic matter content, thermal conductivity and diffusivity remain insensitive, while P and S wave velocities decrease linearly and porosity increases with increasing organic matter content. On the other hand, the study of the organic matter variability content is consistent with the velocity ratio, so can be used as an organic matter indicator of the layers. Conductivity and thermal diffusivity are almost invariant to the variability of the organic matter.

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.

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.

The Study on Physical and Thermal Properties of Geopolymer Pastes

2017 ◽  
Vol 751 ◽  
pp. 538-543 ◽  
Author(s):  
Pongsak Jittabut
Keyword(s):  
Thermal Conductivity ◽  
Compressive Strength ◽  
Thermal Properties ◽  
Water Absorption ◽  
Sodium Hydroxide ◽  
Bulk Density ◽  
Rice Husk ◽  
Rice Husk Ash ◽  
Weight Ratio ◽  
Thermal Capacity

This research was aimed to a present the physical and thermal properties of geopolymer pastes made of fly ash (FA) and bagasse ash (BA) with rice husk ash (RHA) containing at the doses of 0%, 2%, 4%, 6%, 8% and 10% by weight. The sodium hydroxide concentration of 15 molars, sodium silicate per sodium hydroxide by weight ratio of 2.0, the alkaline liquid per binder at the ratio of 0.60 and curing at ambient temperature were used at the to mix all mixtures to gether for 7 and 28 days. The properties analysis of the geopolymer pastes such as compressive strength, bulk density, water absorption, thermal conductivity, thermal diffusivity and thermal capacity were tested. The results were indicated that geopolymer pastes that containing rice husk ash 2% by weight for 28 days of curing gave the maximum compressive strength of 84.42 kg/cm2, low water absorption of 1.16 %, low bulk density of 2,065.71 kg/cm3, lower thermal conductivity of 1.1173 W/m.K, lower thermal diffusion of 6.643 µm2/s and lower thermal capacity of 1.6819 MJ/m3K, respectively. The utilization of waste from agriculture industry via geopolymer pastes for green building materials can be achieved. For this research, physical properties and thermal insulation of geopolymer pastes were siqnificantly improved.

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