scholarly journals Accurate thermal analysis considering nonlinear thermal conductivity

2006 ◽  
Author(s):  
A. Ramalingam ◽  
F. Liu ◽  
S.R. Nassif ◽  
D.Z. Pan
Keyword(s):  
Thermal Conductivity ◽  
Thermal Analysis ◽  
Nonlinear Thermal Conductivity

scholarly journals 3D Printing of PDMS-Like Polymer Nanocomposites with Enhanced Thermal Conductivity: Boron Nitride Based Photocuring System

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 373 ◽  
Author(s):  
Lorenzo Pezzana ◽  
Giacomo Riccucci ◽  
Silvia Spriano ◽  
Daniele Battegazzore ◽  
Marco Sangermano ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Analysis ◽  
Boron Nitride ◽  
Thermal Analyses ◽  
Tensile Tests ◽  
Morphological Characterization ◽  
Digital Light Processing ◽  
Form Complex ◽  
K Value ◽  
Enhanced Thermal Conductivity

This study demonstrates the possibility of forming 3D structures with enhanced thermal conductivity (k) by vat printing a silicone–acrylate based nanocomposite. Polydimethylsiloxane (PDSM) represent a common silicone-based polymer used in several applications from electronics to microfluidics. Unfortunately, the k value of the polymer is low, so a composite is required to be formed in order to increase its thermal conductivity. Several types of fillers are available to reach this result. In this study, boron nitride (BN) nanoparticles were used to increase the thermal conductivity of a PDMS-like photocurable matrix. A digital light processing (DLP) system was employed to form complex structures. The viscosity of the formulation was firstly investigated; photorheology and attenuate total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) analyses were done to check the reactivity of the system that resulted as suitable for DLP printing. Mechanical and thermal analyses were performed on printed samples through dynamic mechanical thermal analysis (DMTA) and tensile tests, revealing a positive effect of the BN nanoparticles. Morphological characterization was performed by scanning electron microscopy (SEM). Finally, thermal analysis demonstrated that the thermal conductivity of the material was improved, maintaining the possibility of producing 3D printable formulations.

Improvement of Thermal Conductivity for Carbon Fabric Composites Base on the Fabric Structure

2021 ◽  
Vol 1037 ◽  
pp. 161-166
Author(s):  
Phone Thant Kyaw ◽  
Pyae Phyo Maung ◽  
Galina V. Malysheva
Keyword(s):  
Thermal Conductivity ◽  
Thermal Analysis ◽  
Thermal Load ◽  
Thermal Conduction ◽  
Thermal Calculation ◽  
Carbon Fabric ◽  
Fabric Structure ◽  
Fabric Composites ◽  
Load Calculation ◽  
Fabric Structures

This paper presents the development of methods for improving the thermal conductivity of fiber reinforcing materials based on the fabric structures. The thermal analysis of fabric structure in thermal load calculation is performed by Fourier’s Law of Thermal Conduction and Steady-State Thermal calculation in Siemens NX. This study leads to the development of thermal conductivity in manufacturing technology of fiber reinforcing materials. Keywords: Thermal conductivity, fabric structure, polymer composite materials

Single-Crystal Aluminum Nitride Substrate Preparation from Bulk Crystals

2001 ◽  
Vol 680 ◽  
Author(s):  
J. Carlos Rojo ◽  
Leo J. Schowalter ◽  
Kenneth Morgan ◽  
Doru I. Florescu ◽  
Fred H. Pollak ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Analysis ◽  
Dislocation Density ◽  
Single Crystal ◽  
High Strain ◽  
Bulk Crystals ◽  
Scanning Thermal Microscopy ◽  
Substrate Preparation ◽  
X Ray ◽  
Differential Expansion

ABSTRACTLarge (15mm diameter) single-crystal AlN boules have been prepared using sublimationrecondensation growth. X-ray topography shows that the dislocation density averages less than 103 cm2 in some of the substrates but also that the dislocations are not uniformly distributed. Also, strain due to the differential expansion with the crucible walls seems to cause severe cracking in the periphery of the crystal and high-strain regions. Thermal analysis using the Scanning Thermal Microscopy (SThM) reveals a thermal conductivity of 3.4 ± 0.2 W/K-cm, which is the largest value ever reported for AlN.

Adaptive Thermal Conductivity Metamaterials: Enabling Active and Passive Thermal Control

2018 ◽  
Vol 10 (5) ◽  
Author(s):  
Austin A. Phoenix ◽  
Evan Wilson
Keyword(s):  
Thermal Conductivity ◽  
Thermal Management ◽  
Passive Control ◽  
Coefficient Of Thermal Expansion ◽  
Thermal Strain ◽  
Thermal Control ◽  
Variable Thermal Conductivity ◽  
Highly Nonlinear ◽  
Wide Range ◽  
Nonlinear Thermal Conductivity

The novel adaptive thermal metamaterial developed in this paper provides a unique thermal management capability that can address the needs of future spacecraft. While advances in metamaterials have provided the ability to generate materials with a broad range of material properties, relatively little advancement has been made in the development of adaptive metamaterials. This metamaterial concept enables the development of materials with a highly nonlinear thermal conductivity as a function of temperature. Through enabling active or passive control of the metamaterials bulk effective thermal conductivity, this metamaterial that can improve the spacecraft's thermal management systems performance. This variable thermal conductivity is achieved through induced contact that results in changes in the F path length and the conductive path area. The contact can be generated internally using thermal strain from shape memory alloys, bimetal springs, and mismatches in coefficient of thermal expansion (CTE) or it can be generated externally using applied mechanical loading. The metamaterial can actively control the temperature of an interface by dynamically changing the bulk thermal conductivity controlling the instantaneous heat flux through the metamaterial. The design of thermal stability regions (regions of constant thermal conductivity versus temperature) into the nonlinear thermal conductivity as a function of temperature can provide passive thermal control. While this concept can be used in a wide range of applications, this paper focuses on the development of a metamaterial that achieves highly nonlinear thermal conductivity as a function of temperature to enable passive thermal control of spacecraft systems on orbit.

scholarly journals Measurement of the Thermal Conductivity and Rainwater Resistance of the Stabilized Mound Soil with Cement

2019 ◽  
Vol 9 (2) ◽  
pp. 3174-3179
Keyword(s):  
Thermal Conductivity ◽  
Thermal Analysis ◽  
Thermal Resistance ◽  
Building Materials ◽  
Energy Savings ◽  
Environmental Benefits ◽  
Energy Crisis ◽  
Termite Mound ◽  
Cement Concrete ◽  
Naturally Occurring

This study is the result of experimental work in the field thermal of buildings. The study focuses on mounds termite’s clays. In this study a thermal analysis by the measurement of the thermal conductivity and the thermal resistance is carried out. This approach to determining the characteristics of materials has led to a better understanding of the possible choice of local building materials available in Chad. The estimation of thermal parameters of building materials plays a key role in a large number of scientific and industrial fields. Our choice has been focused on the termite mound soil which is currently of interest as a result of availability, energy crisis and that of housing.Unlike cement concrete, thé soil has long been used as a building material with practically many environmental benefits and considerable energy savings. The results obtained showed that the materials we used have a appreciable thermal properties. Brick from naturally occurring mound termite soil has better thermal resistance than brick made from mound termite soil, which means it is worked in advance. The influence of density on thermal resistance has been demonstrated. The stabilization of the cement reinforced the structure of the material and its resistance to erosion of the rain water

Mortars Based on a Ternary Binder from Lime, Metakaolin and Calcium Hemihydrate

2020 ◽  
Vol 868 ◽  
pp. 105-118
Author(s):  
Vladimír Pavlík ◽  
Alena Struhárová
Keyword(s):  
Thermal Conductivity ◽  
Thermal Analysis ◽  
Drying Shrinkage ◽  
Normal Weight ◽  
Expanded Perlite ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
Humid Atmosphere ◽  
X Ray ◽  
Sand Filler

Normal-weight mortars with quartz sand filler and lightweight mortars with expanded perlite filler were prepared from a lime-metakaolin-gypsum binder. Mortar test samples were cured in a humid atmosphere and also in the laboratory ambient conditions. Development of hardening processes was studied by X-ray diffraction, thermal analysis and SEM-EDS observation. Compressive strength, drying shrinkage, bulk density and thermal conductivity of the mortars were determined. The presence of gypsum binder in the mixtures enabled formation of ettringite that caused expansion and reduced drying shrinkage of mortars with 20% content of gypsum binder.

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