scholarly journals Composites with Excellent Insulation and High Adaptability for Lightweight Envelopes

Energies ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 53 ◽  
Author(s):  
Liang Guo ◽  
Wenbin Tong ◽  
Yexin Xu ◽  
Hong Ye
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Flow Direction ◽  
Base Material ◽  
Core Material ◽  
Insulation Materials ◽  
The Core ◽  
Cross Section Area ◽  
Heat Flow Direction ◽  
Section Area

Lightweight insulation materials are widely used in lightweight buildings, cold-chain vehicles and containers. A kind of insulation composite, which can combine the super insulation of state-of-the-art insulation materials or structures and the machinability or adaptability of traditional insulation materials, was proposed. The composite consists of two components, i.e., polyurethane (PU) foam as the base material and vacuum insulation panel (VIP) or silica aerogel as the core material. The core material is in plate shape and covered with the base material on all sides. The thermal conductivity of the core material is nearly one order lower than that of the base material. The effective thermal conductivity of the insulation composite was explored by simulation. Simulation results show that the effective thermal conductivity of the composite increases with the increase of the thermal conductivity of the core material. The effective thermal conductivities of the composites decrease with the increase of the cross-section area of the core material perpendicular to heat flow direction and the thicknesses of the core material parallel with heat flow direction. These rules can be elucidated by a series-parallel mode thermal resistance network method, which was verified by the measured results. For composite with a VIP as the core material, when the cross-section area and thickness of the VIP are respectively larger than 60% and 21% of the composite, the composite’s effective thermal conductivity can be 50% or less than that of the base material. Simulated heat loss of the envelope adopting the insulation composites with VIP as the core material is nearly a half of that of the envelope adopting traditional insulation materials.

Effective thermal conductivity of open-pore metal foams as a function of the base material

2015 ◽  
Vol 57 (10) ◽  
pp. 825-836 ◽  
Author(s):  
Alexander Martin Matz ◽  
Bettina Stefanie Mocker ◽  
Norbert Jost ◽  
Peter Krug
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Base Material ◽  
Metal Foams

Thermal Properties of Vacuum Insulation Panels with Glass Fiber

2012 ◽  
Vol 446-449 ◽  
pp. 3753-3756 ◽  
Author(s):  
Wang Ping Wu ◽  
Zhao Feng Chen ◽  
Jie Ming Zhou ◽  
Xue Yu Cheng
Keyword(s):  
Thermal Conductivity ◽  
Glass Fiber ◽  
Fiber Diameter ◽  
Core Material ◽  
The Core ◽  
Vacuum Insulation ◽  
Getter Effect ◽  
Porosity Ratio ◽  
Home Appliance ◽  
Heat Flow Meter

The VIPs consist of the glass-fiber core material and two types of envelope film. The glass fiber was fabricated by a centrifugal blowing process. The core material was prepared by the wet method. The thermal conductivities of the core material and VIPs were measured by the heat flow meter. The thermal conductivity for six pieces of 1mm thick core material is less than that for one piece of 6mm thick core material, which is affected by the fiber diameter, porosity ratio and the largest pore size diameter. The VIP for the building material has a low thermal conductivity (<0.008W/mK). The VIP for the home appliance has a lower thermal conductivity (<0.003W/mK). The VIP maintains a high-uniform thermal conductivity values due to the getter effect.

scholarly journals Modelling of Effective Thermal Conductivity of Composites Filled with Core-Shell Fillers

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5480
Author(s):  
Jan Czyzewski ◽  
Andrzej Rybak ◽  
Karolina Gaska ◽  
Robert Sekula ◽  
Czeslaw Kapusta
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Thermal Conduction ◽  
Hexagonal Boron Nitride ◽  
Core Material ◽  
Core Shell ◽  
Glass Spheres ◽  
Materials Modelling ◽  
Properties Of Materials ◽  
Good Agreement

An effective model to calculate thermal conductivity of polymer composites using core-shell fillers is presented, wherein a core material of filler grains is covered by a layer of a high-thermal-conductivity (HTC) material. Such fillers can provide a significant increase of the composite thermal conductivity by an addition of a small amount of the HTC material. The model employs the Lewis-Nielsen formula describing filled systems. The effective thermal conductivity of the core-shell filler grains is calculated using the Russel model for porous materials. Modelling results are compared with recent measurements made on composites filled with cellulose microbeads coated with hexagonal boron nitride (h-BN) platelets and good agreement is demonstrated. Comparison with measurements made on epoxy composites, using silver-coated glass spheres as a filler, is also provided. It is demonstrated how the modelling procedure can improve understanding of properties of materials and structures used and mechanisms of thermal conduction within the composite.

Effect of Envelope Films on Thermal Properties of Vacuum Insulation Panels with Glass Fiber

2011 ◽  
Vol 415-417 ◽  
pp. 859-864 ◽  
Author(s):  
Wang Ping Wu ◽  
Zhao Feng Chen ◽  
Jie Ming Zhou ◽  
Xue Yu Cheng
Keyword(s):  
Thermal Conductivity ◽  
Glass Fiber ◽  
Core Material ◽  
Type I ◽  
Type Ii ◽  
The Core ◽  
Vacuum Insulation ◽  
Porosity Ratio ◽  
Thermal Conductivities ◽  
Core Materials

The VIPs consist of the glass-fiber core material and two types of envelope film. The glass fiber was fabricated by a centrifugal blowing process. The core material was prepared by the wet method. The thermal conductivities of the materials were measured by the heat flow meter. The microstructure of the envelope film was observed by scanning electron microscopy. The porosity ratio and largest pore size diameters of the core materials are 92.27% and 20μm, respectively. The thermal conductivity of the VIP is about 8-10 times higher than that of the core materials. The thickness of type I and II envelope films are 45μm and 400μm, respectively. The thermal conductivities of the type I and type II envelope films are 0.11W/(m•K) and 0.69W/(m•K), respectively. The thermal conductivity of the VIP with type II envelope is higher than that of the VIP with type I envelope, which is attributed to the different structures and thickness of the envelope film.

Flammability Limit and Flame Visualization of Gaseous Fuel Combustion Inside Meso-scale Combustor with Different Thermal Conductivity

2014 ◽  
Vol 493 ◽  
pp. 204-209 ◽  
Author(s):  
Lilis Yuliati ◽  
Mega Nur Sasongko ◽  
Slamet Wahyudi
Keyword(s):  
Thermal Conductivity ◽  
Wire Mesh ◽  
Gaseous Fuel ◽  
Flammability Limit ◽  
Rich Mixture ◽  
Flame Holder ◽  
Cross Section Area ◽  
Section Area ◽  
Liquid Petroleum Gas ◽  
Meso Scale

This study experimentally investigated effect of thermal conductivity on the combustioncharacteristics of gaseous fuel inside a meso-scale combustor. Combustion characteristics that wereobserved in this research include flame visualization and flammability limit. Quartz glass, stainlesssteel and copper tubes with inner diameters of 3.5 mm were used as combustors. Stainless steel wiremesh was inserted inside meso-scale combustor as a flame holder. Liquid petroleum gas (LPG),which is common fuel use by Indonesian people, was used as a gaseous fuel. A stable blue flame wasestablished inside meso-scale combustor at the downstream of wire mesh for all combustor withdifferent thermal conductivity. Furthermore, flame color is blue for combustion of fuel lean orstoichiometric mixture, and blue-green for combustion of fuel rich mixture. Meso-scale combustorwith the highest thermal conductivity has the narrowest flame cross section area, especially at lowerreactant velocity. Vice versa, this combustor has the widest flammability limit, mainly at the higherreactant velocity.

scholarly journals Anomalous Thermal Response of Graphene Kirigami Induced by Tailored Shape to Uniaxial Tensile Strain: A Molecular Dynamics Study

Nanomaterials ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 126 ◽  
Author(s):  
Hui Li ◽  
Gao Cheng ◽  
Yongjian Liu ◽  
Dan Zhong
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Heat Flux ◽  
Cross Section ◽  
Structural Deformation ◽  
Uniaxial Tensile ◽  
Mechanical And Thermal Properties ◽  
Atomic Lattice ◽  
Cross Section Area ◽  
Section Area

The mechanical and thermal properties of graphene kirigami are strongly dependent on the tailoring structures. Here, thermal conductivity of three typical graphene kirigami structures, including square kirigami graphene, reentrant hexagonal honeycomb structure, and quadrilateral star structure under uniaxial strain are explored using molecular dynamics simulations. We find that the structural deformation of graphene kirigami is sensitive to its tailoring geometry. It influences thermal conductivity of graphene by changing heat flux scattering, heat path, and cross-section area. It is found that the factor of cross-section area can lead to four times difference of thermal conductivity in the large deformation system. Our results are elucidated based on analysis of micro-heat flux, geometry deformation, and atomic lattice deformation. These insights enable us to design of more efficient thermal management devices with elaborated graphene kirigami materials.

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