Thermal Properties of Aerogels

Ebert, Hans-Peter

doi:10.1007/978-1-4419-7589-8_23

Cited by 58 publications

(40 citation statements)

References 44 publications

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“…The conductivity of a random 3D cellulose fiber network is therefore determined mainly by gas phase via heat conduction, here being of diffusive nature, since the pores are smaller than a micron and additionally conduction through the solid skeleton. Therefore the overall conductivity can be described by the weighted addition of heat conduction through the gas phase and solid state conduction through the cellulose fibers [32][33][34][35]. Therefore the thermal conductivity should vary linearly with the cellulose content in the range of low cellulose concentrations.…”

Section: Resultsmentioning

confidence: 99%

Production of porous cellulose aerogel fibers by an extrusion process

Karadagli

Schulz

Schestakow

et al. 2015

The Journal of Supercritical Fluids

122

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Section: Resultsmentioning

confidence: 99%

Production of porous cellulose aerogel fibers by an extrusion process

Karadagli

Schulz

Schestakow

et al. 2015

The Journal of Supercritical Fluids

122

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“…where insulation is the apparent thermal conductivity of the insulation material; solid is the thermal conduction through the solid parts in the material; convection is the macroscopic movement of the gas particles; fluid is the gas conduction through the pores; and radiation is the heat radiation passing through the material. 56 As previously mentioned, heat transfer through the solid components of the highly porous materials contributes only one quarter of the total heat transfer. The lower the bulk density of the materials is the smaller the effect of the solid conductivity in the total heat transfer through an insulator.…”

Section: Resultsmentioning

confidence: 96%

“…Commonly in thermal insulation, porous materials play a significant role. Equation simply describes the equivalent thermal conductivity through porous materials, ie,

λ_{insulation} = λ_{solid} + λ_{convection} + λ_{fluid} + λ_{radiation} ([], normalW false/ ((), normalm \cdot normalK)),

where λ insulation is the apparent thermal conductivity of the insulation material; λ solid is the thermal conduction through the solid parts in the material; λ convection is the macroscopic movement of the gas particles; λ fluid is the gas conduction through the pores; and λ radiation is the heat radiation passing through the material …”

Section: Resultsmentioning

confidence: 99%

Polystyrene nanofibers for nonwoven porous building insulation materials

Datsyuk

Trotsenko

Peikert³

et al. 2019

Engineering Reports

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The building industry makes a great effort to reduce energy consumption. The use of nanotechnology is one of the approaches to surpassing the properties of conventional insulation materials. In this work, an industrial cost‐effective method to manufacture highly porous materials with excellent thermal insulation properties is described. The materials are prepared from polystyrene recovered from the building sector and electrospun as nanofiber‐based sheets. Varying electrospinning parameters allow controlling the morphology of the produced materials. The materials are obtained with differences in interfiber and inner‐fiber porosity and morphology. The thermal conductivity of the freestanding and compressed materials is evaluated. Those differences affect the insulation performance: the materials with higher interfiber porosity show better thermal insulation in the freestanding state. An increase of the inner‐fiber porosity leads to better insulation in the compressed samples. Insertion of carbon nanomaterials reduces the effects of the infrared Radiation. Nanofiber‐based insulation materials from the recycled expanded polystyrene (EPS) show thermal conductivity values of 20 to 25 mW/mK (ie, 20% to 30% below the thermal conductivity of the commercial EPS). The effect of integrating polystyrene nanofiber sheets into conventional wall‐building materials is also investigated in terms of thermal insulation. The nanofiber insulation sheets are sandwiched between two pieces of the building materials resulting in a drastic increase of the insulation effect. The materials have a great potential in using, for example, as thermal insulation for the restoration of historic buildings in the narrow central parts of the old towns.

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“…The size of pores (~20 nm) hinders thermal conduction, which is inversely proportional to the diameter of the pores themselves. Moreover, the dimension of the pores prevents the Brownian motion of the air molecules and therefore prevents convective heat exchange [17]. As stated by Baetens [11], if one would be able to find a cheaper manufacturing process, aerogel might become a real alternative to existing building insulating materials.…”

Section: Aerogel For Super-insulationmentioning

confidence: 99%

Modeling of an Aerogel-Based “Thermal Break” for Super-Insulated Window Frames

et al. 2020

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Research activities in the field of innovative fixtures are continuously aiming at increasing their thermal and optical performances to offer optimal exploitation of daylight and solar gains, providing effective climate screen, according to increasing standards for indoor comfort and energy saving. Within this work, we designed an innovative aerogel-based "thermal break" for window frames, so as to consistently reduce the frame conductance. Then, we compared the performance of this new frame both with currently used and obsolete frames, present in most of the existing building stock. Energy savings for heating and cooling were assessed for different locations and confirmed the potential role played by super-insulating materials in fixtures for extremely rigid climates. Buildings 2020, 10, x FOR PEER REVIEW 3 of 15 were studied. The window frame was made of wood and aluminium and an interposed aerogel 92 thermal break was also used. A finite element method analysis of a window frame containing aerogel 93 was carried out, obtaining a high performance level. This innovative window was compared with 94 others, embodying different frames, as explained in the Methodology section, by means of 95 simulations in test rooms within the Energyplus software platform [33]. Energy consumption for 96 heating and cooling was tested within a typical office on all possible exposures, in two locations with 97 very different climates: the Canadian city of Toronto and Bari, in Southern Italy. 98 2. Materials and Methods 99 2.1. Frame and window description100 This innovative window (Figure 1), specifically designed to meet the highest thermal insulation 101 standards, includes a three-pane glazing. The internal glazing embodied a low emittance coating 102 (ε=0.21) deposited on face 5, i.e., the outer face of the internal pane. The aerogel section (the red part 103 in Figure 2) was conveniently surrounded by a thin acrylonitrile-butadienestyrene (ABS) skin (2 mm 104 thick), and embodied granular aerogel within the frame section, thus behaving like a super-insulating 105 "thermal break", between the external aluminium frame and the internal wooden frame. The same 106 ABS skin is generally adopted in existing commercial frames using the same technology, to embody 107 expanded polystyrene (Isover EPS 035) insulating material. Cabot Enova IC3100 granular aerogel 108 was used, with granule size spanning between 2 and 40 μm, a thermal conductivity of 0.012 W/m•K 109 at ambient temperature, and very low density, ranging from 120 to 150 kg/m 3 according to technical 110 specifications of the material. The coupling between the aerogel section and the wooden frame was 111 made by using a stripe of aerogel blanket, Pyrogel-XTE by Aspen, with comparable thermal 112 conductivity (less than 0,02 W/m•K) suitably glued and mechanically fixed to the frame. 113 114 below, the wooden profile, facing the indoor space.118 2.2. Finite element method 119 The thermal heat loss due to the transmission through windows is strongly affected by the 120 technical f...

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Thermal Properties of Aerogels

Cited by 58 publications

References 44 publications

Production of porous cellulose aerogel fibers by an extrusion process

Production of porous cellulose aerogel fibers by an extrusion process

Polystyrene nanofibers for nonwoven porous building insulation materials

Modeling of an Aerogel-Based “Thermal Break” for Super-Insulated Window Frames

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