The Effect of Lightweight Concrete Cores on the Thermal Performance of Vacuum Insulation Panels

The performance of vacuum insulation panels (VIPs) is strongly affected by several factors, such as panel thickness, design, quality of vacuum, and material type. In particular, the core materials inside VIPs significantly influence their overall performance. Despite their superior insulation performance, VIPs are limited in their widespread use as structural materials, because of their low material strength and the relatively expensive core materials. As an alternative core material that can compensate these limitations, foamed concrete, a type of lightweight concrete with very low density, can be used. In this study, two different types of foamed concrete were used as VIP core materials, with their effects on the thermal behavior of the VIPs having been evaluated using experimental and numerical methods. To confirm and generate numerical models for VIP analysis, micro-computed tomography (micro-CT) was utilized. The obtained results show that insulation effects increase effectively when panels with lightweight concrete are in a vacuum, and both foamed concrete types can be effectively used as VIP core materials.

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

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.415-417.859 ◽

2011 ◽

Vol 415-417 ◽

pp. 859-864 ◽

Cited By ~ 1

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.

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Vacuum insulation panel core materials and modelling the thermal conductivity of granular materials

10.31274/etd-180810-4365 ◽

2015 ◽

Author(s):

Boyce Sek Koon Chang

Keyword(s):

Thermal Conductivity ◽

Granular Materials ◽

Vacuum Insulation ◽

Vacuum Insulation Panel ◽

Core Materials

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Preparation and characterization of vacuum insulation panels with super-stratified glass fiber core material

Energy ◽

10.1016/j.energy.2015.08.105 ◽

2015 ◽

Vol 93 ◽

pp. 945-954 ◽

Cited By ~ 32

Author(s):

Zhou Chen ◽

Zhaofeng Chen ◽

Zhaogang Yang ◽

Jiaming Hu ◽

Yong Yang ◽

...

Keyword(s):

Glass Fiber ◽

Core Material ◽

Fiber Core ◽

Vacuum Insulation

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Thermal insulation properties of green vacuum insulation panel using wood fiber as core material

BioResources ◽

10.15376/biores.14.2.3339-3351 ◽

2019 ◽

Vol 14 (2) ◽

pp. 3339-3351 ◽

Cited By ~ 1

Author(s):

Baowen Wang ◽

Zhihui Li ◽

Xinglai Qi ◽

Nairong Chen ◽

Qinzhi Zeng ◽

...

Keyword(s):

Thermal Conductivity ◽

Bulk Density ◽

Thermal Insulation ◽

Wood Fiber ◽

Core Material ◽

High Porosity ◽

Total Thermal Conductivity ◽

Wood Fibers ◽

Vacuum Insulation ◽

Vacuum Insulation Panel

Wood fibers were prepared as core materials for a vacuum insulation panel (VIP) via a dry molding process. The morphology of the wood fibers and the microstructure, pore structure, transmittance, and thermal conductivity of the wood fiber VIP were tested. The results showed that the wood fibers had excellent thermal insulation properties and formed a porous structure by interweaving with one another. The optimum bulk density that led to a low-cost and highly thermally efficient wood fiber VIP was 180 kg/m3 to 200 kg/m3. The bulk density of the wood fiber VIP was 200 kg/m3, with a high porosity of 78%, a fine pore size of 112.8 μm, and a total pore volume of 7.0 cm3·g-1. The initial total thermal conductivity of the wood fiber VIP was 9.4 mW/(m·K) at 25 °C. The thermal conductivity of the VIP increased with increasing ambient temperature. These results were relatively good compared to the thermal insulation performance of current biomass VIPs, so the use of wood fiber as a VIP core material has broad application prospects.

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Fibers Networks as a New Type of Core Material. Processing and Mechanical Properties

MRS Proceedings ◽

10.1557/proc-1188-ll02-02 ◽

2009 ◽

Vol 1188 ◽

Author(s):

Laurent Mezeix ◽

Christophe Bouvet ◽

Serge Crézé ◽

Dominique Poquillon

Keyword(s):

Epoxy Resin ◽

Carbon Fibers ◽

Sandwich Panels ◽

Open Architecture ◽

Core Material ◽

Cross Linking ◽

Damping Capacity ◽

The Core ◽

Water Accumulation ◽

Core Materials

AbstractMany different sandwich panels are used for aeronautical applications. Open and closed cell structured foam, balsa wood or honeycomb are often used as core materials. When the core material contains closed cells, water accumulation into the cell has to be taken into account. This phenomenon occurs when in service conditions lead to operate in humidity atmosphere. Then, water vapor from air naturally condenses on cold surfaces when the sandwich panel temperature decreases. This water accumulation might increase significantly the weight of the core material. Core with a ventilated structure helps to prevent this phenomenon. Periodic cellular metal (PCM) has been motivated by potential multifunctional applications that exploit their open architecture as well as their apparent superior strength and stiffness: pyramidal, lattice, Kagome truss or woven. One of the drawbacks of these materials is the expensive cost of the manufacturing. Recently, a novel type of sandwich has been developed with bonded metallic fibers as core material. This material presents attractive combination of properties like high specific stiffness, good damping capacity and energy absorption. Metal fibers bonded with a polymeric adhesive or fabricated in a mat-like form consolidated by solid state sintering. Entangled cross-linked carbon fibers have been also studied for using as core material by Laurent Mezeix. In the present study, ventilated core materials are elaborated from networks fibers. The simplicity of elaboration is one of the main advantages of this material. Multifunctional properties are given by mixing different sorts of fibers, by example adding fibers with good electrical conduction to give electrical conductivity properties. In this study network fibers as core material are elaborated using carbon fibers, glass fibers and stainless steel fibers. In aeronautical skins of sandwich panels used are often carbon/epoxy prepreg, so epoxy resin was used to cross-link fibers. The core thickness was chosen at 30 mm and fibers length was chosen at 40 mm. Entanglement, separation of filaments and cross-linking are obtained in a specific blower room. Fibers are introduced in the blower room, compressed air is applied and in same time epoxy resin is sprayed. Indeed one of the sandwich core material properties required is low density, so yarns size need to be decreased by separating filaments. Network fibers are introduced in a specific mould and then are compressed. The density obtained before epoxy spaying is 150 kg/m3. Finally samples are polymerized at 80°C for 2 hours in a furnace under laboratory air. Compressive behavior is study to determinate the influence of fibers natures and the effect of cross-linking. Reproducibility is also checked.

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Evaluation of fire performance of lightweight concrete wall panels using finite element analysis

Journal of Structural Fire Engineering ◽

10.1108/jsfe-10-2020-0030 ◽

2021 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Irindu Upasiri ◽

Chaminda Konthesingha ◽

Anura Nanayakkara ◽

Keerthan Poologanathan ◽

Brabha Nagaratnam ◽

...

Keyword(s):

Finite Element ◽

Lightweight Concrete ◽

Lightweight Aggregate ◽

Lightweight Aggregate Concrete ◽

Fire Performance ◽

Concrete Wall ◽

Aggregate Concrete ◽

Content Type ◽

Wall Panels ◽

Foamed Concrete

Purpose In this study, the insulation fire ratings of lightweight foamed concrete, autoclaved aerated concrete and lightweight aggregate concrete were investigated using finite element modelling. Design/methodology/approach Lightweight aggregate concrete containing various aggregate types, i.e. expanded slag, pumice, expanded clay and expanded shale were studied under standard fire and hydro–carbon fire situations using validated finite element models. Results were used to derive empirical equations for determining the insulation fire ratings of lightweight concrete wall panels. Findings It was observed that autoclaved aerated concrete and foamed lightweight concrete have better insulation fire ratings compared with lightweight aggregate concrete. Depending on the insulation fire rating requirement of 15%–30% of material saving could be achieved when lightweight aggregate concrete wall panels are replaced with the autoclaved aerated or foamed concrete wall panels. Lightweight aggregate concrete fire performance depends on the type of lightweight aggregate. Lightweight concrete with pumice aggregate showed better fire performance among the normal lightweight aggregate concretes. Material saving of 9%–14% could be obtained when pumice aggregate is used as the lightweight aggregate material. Hydrocarbon fire has shown aggressive effect during the first two hours of fire exposure; hence, wall panels with lesser thickness were adversely affected. Originality/value Finding of this study could be used to determine the optimum lightweight concrete wall type and the optimum thickness requirement of the wall panels for a required application.

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Prediction of thermal performance of vacuum insulation panels (VIPs) with micro-fiber core materials

Materials Today Communications ◽

10.1016/j.mtcomm.2019.100786 ◽

2020 ◽

Vol 22 ◽

pp. 100786 ◽

Cited By ~ 2

Author(s):

Shang Mao ◽

Anakang Kan ◽

Zipei Huang ◽

Wenbing Zhu

Keyword(s):

Thermal Performance ◽

Fiber Core ◽

Vacuum Insulation ◽

Core Materials

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Impact of aeration and deaeration of switchable vacuum insulations on the overall heat conductivity using different core materials and filling gases

International Journal of Energy and Environmental Engineering ◽

10.1007/s40095-020-00356-y ◽

2020 ◽

Vol 11 (4) ◽

pp. 395-404

Author(s):

Lars Erlbeck ◽

S. Sonnick ◽

D. Wössner ◽

H. Nirschl ◽

M. Rädle

Keyword(s):

Silica Gel ◽

Heat Conductivity ◽

High Heat ◽

Vacuum Insulation ◽

Aeration Time ◽

Helium Gas ◽

New Type ◽

Insulation Effect ◽

Backbone Structure ◽

Core Materials

Abstract Investigating switchable vacuum insulation panels might lead to a new type of insulation, which can be switched on to enable a low heat flow when a good insulation effect is desired and switched off when exchange with the environment is requested, during a cold summer night, for example. For this reason, different core materials for vacuum insulations as typical silica powder were investigated as well as silica agglomerates and silica gel. These materials were checked for the necessary time of aeration and evacuation and the corresponding change of heat conductivity along with the change of gas-pressure. Silica gel in combination with helium as filling gas showed best results corresponding to a high difference of the heat conductivities evacuated and aerated. Beside the solid backbone structure of the silica gel, this is caused by the high heat conductivity and small kinetic atomic diameter of the helium gas. Silica agglomerates decreased the aeration time as well as the deaeration time, but the improvement was neglected because of a lower change of heat conductivity during pressure drop or rise. Nevertheless, a good switchable vacuum insulation can be produced using silica gel and helium, for example.

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