scholarly journals Thermoactivated heat transfer mechanism in molecular crystals: Thermal conductivity of benzophenone single crystals

AIP Advances ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 015121 ◽  
Author(s):  
A. Jeżowski ◽  
M. A. Strzhemechny ◽  
A. I. Krivchikov ◽  
O. S. Pyshkin ◽  
O. O. Romantsova ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Single Crystals ◽  
Molecular Crystals ◽  
Transfer Mechanism ◽  
Heat Transfer Mechanism

scholarly journals Design and Implementation of a Laboratory Equipment for Studying Heat Transfer by Conduction

2019 ◽  
Vol 11 (1) ◽  
pp. 153-156
Author(s):  
István Padrah ◽  
Judit Pásztor ◽  
Rudolf Farmos
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Conduction ◽  
Thermal Conduction ◽  
Transfer Mechanism ◽  
Measuring Instrument ◽  
Heat Transfer Mechanism ◽  
Laboratory Equipment ◽  
Insulating Materials ◽  
Design And Implementation

Abstract Thermal conduction is a heat transfer mechanism. It is present in our everyday lives. Studying thermal conductivity helps us better understand the phenomenon of heat conduction. The goal of this paper is to measure the thermal conductivity of various materials and compare results with the values provided by the manufacturers. To achieve this we assembled a measuring instrument and performed measurements on heat insulating materials.

scholarly journals Change in Conductive–Radiative Heat Transfer Mechanism Forced by Graphite Microfiller in Expanded Polystyrene Thermal Insulation—Experimental and Simulated Investigations

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2626
Author(s):  
Aurelia Blazejczyk ◽  
Cezariusz Jastrzebski ◽  
Michał Wierzbicki
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Thermal Insulation ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Expanded Polystyrene ◽  
Transfer Mechanism ◽  
Total Thermal Conductivity ◽  
Heat Transfer Mechanism

This article introduces an innovative approach to the investigation of the conductive–radiative heat transfer mechanism in expanded polystyrene (EPS) thermal insulation at negligible convection. Closed-cell EPS foam (bulk density 14–17 kg·m−3) in the form of panels (of thickness 0.02–0.18 m) was tested with 1–15 µm graphite microparticles (GMP) at two different industrial concentrations (up to 4.3% of the EPS mass). A heat flow meter (HFM) was found to be precise enough to observe all thermal effects under study: the dependence of the total thermal conductivity on thickness, density, and GMP content, as well as the thermal resistance relative gain. An alternative explanation of the total thermal conductivity “thickness effect” is proposed. The conductive–radiative components of the total thermal conductivity were separated, by comparing measured (with and without Al-foil) and simulated (i.e., calculated based on data reported in the literature) results. This helps to elucidate why a small addition of GMP (below 4.3%) forces such an evident drop in total thermal conductivity, down to 0.03 W·m−1·K−1. As proposed, a physical cause is related to the change in mechanism of the heat transfer by conduction and radiation. The main accomplishment is discovering that the change forced by GMP in the polymer matrix thermal conduction may dominate the radiation change. Hence, the matrix conduction component change is considered to be the major cause of the observed drop in total thermal conductivity of EPS insulation. At the microscopic level of the molecules or chains (e.g., in polymers), significant differences observed in the intensity of Raman spectra and in the glass transition temperature increase on differential scanning calorimetry(DSC) thermograms, when comparing EPS foam with and without GMP, complementarily support the above statement. An additional practical achievement is finding the maximum thickness at which one may reduce the “grey” EPS insulating layer, with respect to “dotted” EPS at a required level of thermal resistance. In the case of the thickest (0.30 m) panels for a passive building, above 18% of thickness reduction is found to be possible.

A New Theoretical Equation for Effective Thermal Conductivity of Cellular Concrete

2011 ◽  
Vol 71-78 ◽  
pp. 1228-1232
Author(s):  
Xiang Yu Li ◽  
Xiao Long Zhao ◽  
Xiang Yong Guo ◽  
Li Qiang Cao
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Property ◽  
Effective Thermal Conductivity ◽  
Transfer Mechanism ◽  
Theoretical Equation ◽  
Heat Transfer Mechanism ◽  
Two Phase ◽  
New Equation ◽  
Cellular Concrete

A new theoretical equation that represents the thermal conductivity of two-phase composite has been proposed. The Cheng-Vachon equation has been modified by introducing a new parameter that is the corrected porosity. It was found that the new equation can describe the thermal conductivity of cellular concrete very accurately. Development of the equation is helpful to understanding heat transfer mechanism and improving thermal property of cellular concrete.

Influence of Density on the Thermal Conductivity of Fiberglass Felt

2012 ◽  
Vol 628 ◽  
pp. 33-36 ◽  
Author(s):  
Yong Yang ◽  
Xue Yu Cheng ◽  
Zhao Feng Chen ◽  
Ren Li Fu ◽  
Zhou Chen ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Porous Materials ◽  
Transfer Mechanism ◽  
Low Density ◽  
Measuring Instrument ◽  
Heat Transfer Mechanism ◽  
Coefficient Of Thermal Conductivity

The influence of density on the thermal conductivity of fiberglass felt is studied by experiment.Experimental data obtained using the coefficient of thermal conductivity measuring instrument(Germany Netzsch HFM 436).The results show that the thermal conductivity of the low-density fiberglass felt increases with the increasing of density，when the density of fiberglass felt is below a certain value,the thermal conductivity is tend to a stable value.At last the conclusion that using the heat-transfer mechanism of the porous materials explains this phenomenon has also been drawn by experiment.

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