An experimental investigation and fractal modeling on the effective thermal conductivity of novel autoclaved aerated concrete (AAC)-based composites with silica aerogels (SA)

Qu, Ming-Liang; Tian, Shuai-Qi; Fan, Li‐Wu; Yu, Zi‐Tao; Ge, Jian

doi:10.1016/j.applthermaleng.2020.115770

Cited by 31 publications

(15 citation statements)

References 52 publications

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“…The thermal conductivity, one of the most important physical properties of AAC, is widely considered by researchers [ 41 , 42 , 43 , 44 , 45 , 46 , 47 ]. Many factors may affect the thermal conductivity coefficient of AAC.…”

Section: Resultsmentioning

confidence: 99%

Waste Originating from the Cleaning of Flue Gases from the Combustion of Industrial Wastes as a Lime Partial Replacement in Autoclaved Aerated Concrete

Różycka

Kotwica

2022

Materials

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This paper aims to study the suitability of partial replacement of lime by waste originating from the cleaning of flue gases from the combustion of industrial wastes in the production of autoclaved aerated concrete (AAC). The compressive strength, bulk density, pore structure, phase composition, and microstructure of hydration products of the AAC were analyzed. According to the results, the addition of the waste can effectively enhance the mechanical properties of AAC due to the differences in morphology of hydration product—1.1 nm tobermorite and related dense microstructure. The pore size distribution was significantly influenced by waste addition, which was one of the main reasons for the increase in thermal conductivity. The XRD and SEM results showed that foreign ions introduced with the wastes affect the synthesis of 1.1 nm tobermorite. Moreover, it was shown that waste containing a high content of CaO can be used as lime replacement, which allows reducing CO2 emissions during the AAC production process.

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Section: Resultsmentioning

confidence: 99%

Waste Originating from the Cleaning of Flue Gases from the Combustion of Industrial Wastes as a Lime Partial Replacement in Autoclaved Aerated Concrete

Różycka

Kotwica

2022

Materials

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“…As indicated in our former study, 21 it is found that aerogels are 3‐D networks comprising of spherical like colloids, so nevertheless, investigation of aerogels structure will become complicated. Therefore, to simplify theoretical investigation considering novolac aerogel disarranged nature, much attention has been paid to the fractal analysis of cubes such as colloids 7,23 . In this state, a cube represents novolac aerogel, for which next to each colloid cube, there is a hollow cube to describe porosity.…”

Section: Theory: Heat Transfer Of Nanoporous Novolac Aerogel‐npcmsmentioning

confidence: 99%

“…Therefore, to simplify theoretical investigation considering novolac aerogel disarranged nature, much attention has been paid to the fractal analysis of cubes such as colloids. 7,23 In this state, a cube represents novolac aerogel, for which next to each colloid cube, there is a hollow cube to describe porosity. Subsequently, solid and gas phases unimodal distribution suggested heat transfer model with the main concept of NPCMs replacement instead of a specific number of novolac aerogel cubic colloids, for which model assumptions and limitations are presented as follows:…”

Section: Novolac Aerogel-npcms Thermal Modelmentioning

confidence: 99%

“…By virtue of internal nanoporous microstructure, it would be hardly possible to predict, design, and optimize such microstructure heat transfer phenomena to attain precise thermal analysis to a large extent. To achieve a deep understanding of the mathematical relation among insulation properties, thermal diffusion, and aerogels microstructure, thermal conductivity prediction models such as experimental, 6 quasi‐experimental, 7 numerical, and analytical 8 have been proposed. General practical heat transfer models have suggested that an analytical model is one of the appropriate ones that predict aerogels thermal characteristics based on equivalent structural units such as cubic‐like, spherical, and cylindrical with least experimental constants utilization 7,9 .…”

Section: Introductionmentioning

confidence: 99%

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Novolac aerogel thermal diffusion and efficiency enhancement using paraffin wax core/polyurethane shell phase‐change material nanocapsules

Abdeali

Bahramian

2021

Intl J of Energy Research

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Summary Aerogels are one of the most promising nano‐dimension open‐cell foams with considerably varied characteristics such as high porosity, super large specific surface area, low density, and super low thermal conductivity. Aerogel's high porosity and microstructure consisting of micro‐ and nanoparticles as well as pores in nanometer dimension are the origin of distinctive properties. However, the main challenge of aerogels is their low density (0.05−0.50 gcm3), which leads to equal thermal diffusion (normalα×10−7) compared with general thermal insulators. To minimize aerogel thermal diffusion and to enhance thermal insulation, replacing some aerogel colloids with phase‐change material nanocapsules (NPCMs) (while aerogel IUPAC definition and at least porosity of 80% is preserved) is proposed in this work. While NPCMs undergo a physical change during phase transfer, temperature becomes persistent, and as a consequence, specific heat capacity (Cp) getting close to an infinite number and thermal diffusion (normalα=knormalρCp) will tend to very low values. Results have demonstrated that by only applying 4.5 wt.% of paraffin wax core /polyurethane shell (PW/PU) NPCMs instead of some novolac aerogel colloids, aerogel has experienced temperature decrement as well as stability. During NPCMs' melting process, thermal diffusivity has reached 2.5×10−12 and temperature increment delay rate has become 40%.

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“…The infiltration also causes increased moisture movement through the wall, which may contribute to water condensation [9,10]. The water present in building structures due to the phenomenon of condensation is an energy carrier and a key factor that decreases the thermal properties of porous materials [11][12][13] but also leads to the mechanical [14,15] and microbiological deterioration of the materials [16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Heat Losses Caused by the Temporary Influence of Wind in Timber Frame Walls Insulated with Fibrous Materials

et al. 2020

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The paper presents the results of research concerning three fiber materials—mineral wool, hemp fiber and wood wool—as loose-fill thermal insulation materials. The analysis used the material parameters determined in previous works conducted by the authors, such as thermal conductivity and air permeability in relation to bulk density. These materials exhibit open porosity; thus, convection is an essential phenomenon in the heat transfer process. The paper aimed at conducting thermal simulations of various frame wall variants which were filled with the above-mentioned insulation materials. The simulations were performed with the Control Volume Method using the Delphin 5.8 software. The studies accounted for the effect of wind pressure and the time of its influence on a wall insulated by means of fiber material with a thickness of 150 as well as 250 mm. The simulation enabled us to obtain such data as maximal R-value reduction and time to return to equilibrium after filtration for the analyzed materials. The study proved that heat transfer in these insulations strongly depends on the bulk density, thickness of the insulation and wind pressure. The decrease in R is reduced as the density increases. This results from the decreased air permeability characterizing the material. Wind washing causes lower R reduction than air filtration in all models. The greater the thickness, the longer it takes for the models to return to the equilibrium state following air filtration (and wind washing). This period is comparable for air filtration and wind washing. Hemp fibers were characterized with the strongest susceptibility to air filtration; in the case of wood wool, it was also high, but lower than for hemp fibers, while mineral wool was characterized with the lowest.

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An experimental investigation and fractal modeling on the effective thermal conductivity of novel autoclaved aerated concrete (AAC)-based composites with silica aerogels (SA)

Cited by 31 publications

References 52 publications

Waste Originating from the Cleaning of Flue Gases from the Combustion of Industrial Wastes as a Lime Partial Replacement in Autoclaved Aerated Concrete

Waste Originating from the Cleaning of Flue Gases from the Combustion of Industrial Wastes as a Lime Partial Replacement in Autoclaved Aerated Concrete

Novolac aerogel thermal diffusion and efficiency enhancement using paraffin wax core/polyurethane shell phase‐change material nanocapsules

Heat Losses Caused by the Temporary Influence of Wind in Timber Frame Walls Insulated with Fibrous Materials

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