scholarly journals Experimental Validation of Formula for Calculation Thermal Diffusivity in Superlattices Performed Using a Combination of Two Frequency-Domain Methods: Photothermal Infrared Radiometry and Thermoreflectance

2021 ◽  
Vol 11 (13) ◽  
pp. 6125
Author(s):  
Michał Pawlak ◽  
Timo Kruck ◽  
Nikolai Spitzer ◽  
Dariusz Dziczek ◽  
Arne Ludwig ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Diffusivity ◽  
Thermal Transport ◽  
Theoretical Formula ◽  
Elastic Continuum ◽  
Frequency Domain Methods ◽  
Different Temperatures ◽  
Infrared Radiometry

In this paper, we validate two theoretical formula used to characterize thermal transport of superlattices at different temperatures. These formulas are used to measure cross-plane thermal conductivity and thermal boundary resistance, when it is not possible to obtain heat capacity or thermal diffusivity and in-plane thermal conductivity. We find that the most common formula for calculating thermal diffusivity and heat capacity (and density) can be used in a temperature range of −50 °C to 50 °C. This confirms that the heat capacity in the very thin silicon membranes is the same as in bulk silicon, as was preliminary investigated using an elastic continuum model. Based on the obtained thermal parameters, we can fully characterize the sample using a new procedure for characterization of the in-plane and cross-plane thermal transport properties of thin-layer and superlattice semiconductor samples.

scholarly journals Comparative study of thermal transport in Zea mays straw and Zea mays heartwood (cork) boards

2010 ◽  
Vol 14 (1) ◽  
pp. 31-38 ◽  
Author(s):  
Sunday Etuk ◽  
Louis Akpabio ◽  
Ita Akpan
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Zea Mays ◽  
Thermal Diffusivity ◽  
Comparative Study ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Thermal Transport ◽  
Insulation Material ◽  
Thermal Absorptivity

Thermal conductivity values at the temperature of 301-303K have been measured for Zea mays straw board as well as Zea mays heartwood (cork) board. Comparative study of the thermal conductivity values of the boards reveal that Zea mays heartwood board has a lower thermal conductivity value to that of the straw board. The study also shows that the straw board is denser than the heartwood board. Specific heat capacity value is less in value for the heartwood board than the straw board. These parameters also affect the thermal diffusivity as well as thermal absorptivity values for the two types of boards. The result favours the two boards as thermal insulators for thermal envelop but with heartwood board as a preferred insulation material than the straw board.

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%.

Study of the Thermophysical Characteristics of Steel Fiber Reinforced Concrete

2020 ◽  
Vol 992 ◽  
pp. 41-47
Author(s):  
I.L. Shubin ◽  
V.A. Dorf ◽  
R.O. Krasnovskij ◽  
D.E. Kapustin ◽  
P.S. Sultygova
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Reinforced Concrete ◽  
Thermal Diffusivity ◽  
Fire Resistance ◽  
Steel Fiber ◽  
Fiber Reinforced Concrete ◽  
Steel Fiber Reinforced Concrete ◽  
Thermophysical Characteristics ◽  
Volumetric Content

The number of researches on steel fiber reinforced concrete (SFRC) fire resistance is insignificant. For the calculation of building structures for fire resistance, it is necessary to use the thermophysical characteristics of concrete: thermal conductivity, heat capacity and thermal diffusivity. The physicomechanical characteristics of SFRC depend on the volumetric content of the fiber in it. This paper presents the results of studies of thermophysical properties of SFRC. The studied SFRC had a high-strength self-compacting cement-sand matrix and a different percentage of fiber content (from 0 to 6%). The experiments were carried out for SFRC with steel wavy fiber 15 mm long and 0.3 mm in diameter. As a result of experimental studies, it was discovered that with an increase in the volumetric content of the fiber, a decrease in the values of heat flow, thermal conductivity and thermal diffusivity coefficients, specific heat capacity is observed and the thermal resistance of SFRC increases.

scholarly journals Applying the EDPS Method to the Research into Thermophysical Properties of Solid Wood of Coniferous Trees

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Ľuboš Krišťák ◽  
Rastislav Igaz ◽  
Ivan Ružiak
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Diffusivity ◽  
Moisture Content ◽  
Thermophysical Properties ◽  
Solid Wood ◽  
Plane Source ◽  
Coniferous Trees ◽  
Extended Dynamic ◽  
Dynamic Plane

The results of using the EDPS (extended dynamic plane source) method to determine thermophysical properties of solid wood of coniferous trees growing in Slovakia with 0% and 12% equilibrium moisture content are presented in the paper. Solid wood of two different tree species: Norway spruce (Picea abies L.) and Scots pine (Pinus sylvestris L.) was used in the research. The research was carried out independently in three anatomical planes. Coefficients of thermal conductivity, thermal diffusivity, and specific heat capacity were determined following the research. Comparing the research results to the values determined by other authors and already published models to calculate individual parameters, the fact that the data gathered using the EDPS method can be accepted in case of all studied thermophysical properties can be stated.

scholarly journals Thermophysical properties of BiFeO3/REE multiferroics in a wide temperature range

2020 ◽  
Vol 10 (01n02) ◽  
pp. 2060019
Author(s):  
Sidek Khasbulatov ◽  
Suleiman Kallaev ◽  
Haji Gadjiev ◽  
Zairbek Omarov ◽  
Abumuslim Bakmaev ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Rare Earth ◽  
High Temperature ◽  
Thermal Diffusivity ◽  
Rare Earth Elements ◽  
Wide Temperature Range ◽  
Thermophysical Properties ◽  
Multiferroic Bifeo ◽  
Comprehensive Study

The paper presents the results of a comprehensive study of the thermophysical properties (thermal conductivity, thermal diffusivity, heat capacity) of high-temperature multiferroic BiFeO3 modified with rare-earth elements (REEs) (La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Lu). The regularities of the formation of the mentioned characteristics were established. The assumptions about the nature of the observed phenomena were suggested.

Effect of timeliness on the thermal properties of paraffin-based Al2O3 nanofluids

2019 ◽  
Vol 33 (05) ◽  
pp. 1950051
Author(s):  
Yangyang Wu ◽  
Baichao Wang ◽  
Dong Li ◽  
Changyu Liu
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Volume Concentration ◽  
Volume Fraction ◽  
Thermal Conversion ◽  
Volumetric Heat Capacity ◽  
Energy Storage Material ◽  
Over Time

Paraffin is an excellent photo-thermal conversion phase change energy storage material, and extensively used in the thermal storage field at the medium-low temperature. However, the low thermal conductivity of paraffin restricts its application in practice. Adding nanoparticles into paraffin is one of the effective methods to improve its thermal conductivity. Nevertheless, the thermal diffusivity, specific heat and volumetric heat capacity of paraffin as well as timeliness were affected after the addition of nanoparticles. In this paper, the influences of volume fraction of Al2O3 nanoparticle and timeliness on these thermal parameters of paraffin were investigated. The results show that the thermal conductivity of paraffin-based Al2O3 nanofluids increases first and then decreases with time, and the maximum thermal conductivity is 0.34 W/[Formula: see text] for volume fraction 1% on third day. The higher volume concentration, the lower specific heat and volumetric heat capacity, all present downtrend over time, until stable in the range of 0.3 MJ/[Formula: see text] and 0.4 MJ/[Formula: see text]. The average enhancement rate of specific heat and volumetric heat capacity are concentrates on −6% to 9%, −10% to 0%, respectively. While increasing the volume concentration, the thermal diffusivity has no obvious regularity, and presents undulatory property over time.

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