Thermal transport in nano-porous insulation of aerogel: Factors, models and outlook

Tang, G.H.; Bi, Chen; Zhao, Yue; Tao, Wen‐Quan

doi:10.1016/j.energy.2015.07.109

Cited by 168 publications

(75 citation statements)

References 126 publications

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“…On the other hand, from the calculation using the porosity and the thermal conductivity of air, κ g is 0.0245 mW (m K) −1 , which is 20% higher than the former value. We attribute such a difference in κ g to the Knudsen effect of air molecules in confined space, i.e., small pores inside the PVC aerogels. This Knudsen effect indicates that if the pore size is smaller than or comparable with the traveling mean free path of the gas molecules in free space, the gas molecules would collide with the solid framework before their interactive scattering.…”

Section: Properties Of Pvc Aerogels Prepared With Different Porositiesmentioning

confidence: 99%

Ultralight and Flexible Monolithic Polymer Aerogel with Extraordinary Thermal Insulation by A Facile Ambient Process

Qin

Cui

et al. 2019

Adv Materials Inter

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COMMUNICATION (1 of 7)properties. However, most synthesis methods usually involve chemical reactions in gel preparation and are limited to specific materials. In addition, the manufacturing cost introduced by delicate processes such as supercritical drying in preparing high-quality aerogels requires high pressure equipment and consumes large amount of liquid carbon dioxide can pose challenge for large scale deployment.Here, we develop a facile approach to prepare monolithic polymer aerogel based on poly(vinyl chloride) (PVC) via physical processes at ambient environment. Instead of making porous network via crosslink between different molecular chains or covalent bonding between diffe rent nanoparticles, [8,17] the porous network is formed by polymer chains entanglement between different precipitated polymer clusters. Taking advantage of the flexibility of polymer, the porous network remains robust while drying at ambient environment and shows a very low thermal conductivity approaching the air conductivity. Combing with the porosity and pressure dependent thermal conductivity, the thermal transport mechanism in PVC aerogel is carefully analyzed. Furthermore, superhydrophobicity is observed in these synthesized high porosity PVC aerogels.We developed an ambient synthesis process of PVC aerogel mainly consisting of three steps: gelation, solvent exchange, and drying (Figure 1a). First, the reaction sources, i.e., PVC powder (389 293, Sigma-Aldrich, USA) is mixed with dimethylformamide (DMF) (DX1727, EMD Millipore, Germany) with ratio from 0.2 g/10 mL to 1 g/10 mL at temperature of 60 °C. The porosity of aerogel is controlled by tuning the concentrations of PVC solutions. Second, the solution is sonicated for an hour and exposed to air for 12 h, from which the water vapor is absorbed into DMF/PVC solution. Consequently, the solubility of PVC decreases gradually resulting in the precipitation of polymer particles. Finally, a white and jelly-liked PVC solid was formed. To remove the liquid from the PVC gel while avoiding shrinkage of the porous structure, the solvent is exchanged with ethanol, which has a small surface tension. The solvent exchange process includes five steps each with a time interval of 6 h to gradually increase the volume percentage of ethanol in the solvent from 0%, 25%, 50%, 75%, 87.5% to 93.8%.High performance thermal insulation materials are desired for a wide range of applications in space, buildings, energy, and environments. Here, a facile ambient processing approach is reported to synthesize a highly insulating and flexible monolithic poly(vinyl chloride) aerogel. The thermal conductivity is measured respectively as 28 mW (m K) −1 at atmosphere approaching the air conductivity and 7.7 mW (m K) −1 under mild evacuation condition. Thermal modeling is performed to understand the thermal conductivity contributions from different heat transport pathways in air and solid. The analysis based on the Knudsen effect and scattering mean free paths shows that the thermal insulation performance can be f...

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Section: Properties Of Pvc Aerogels Prepared With Different Porositiesmentioning

confidence: 99%

Ultralight and Flexible Monolithic Polymer Aerogel with Extraordinary Thermal Insulation by A Facile Ambient Process

Qin

Cui

et al. 2019

Adv Materials Inter

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“…By Tang a similar effect was found belonging to the air content. [23] According to Eq. 3 on Figure 2b one can see the moisture absorption curve of the sample.…”

Section: 2the Change In the Effective Thermal Conductivity In Funcmentioning

confidence: 99%

Investigation of the moisture induced degradation of the thermal properties of aerogel blankets: Measurements, calculations, simulations

Lakatos

2017

Energy and Buildings

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Please cite this article as:Ákos Lakatos, Investigation of the moisture induced degradation of the thermal properties of Aerogel blankets: measurements, calculations, simulations, Energy and Buildings http://dx.doi.org/10. 1016/j.enbuild.2017.01.054 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.Investigation of the moisture induced degradation of the thermal properties of Graphical abstractIn the graphical abstract one can see an aerogel blanket between a source (warm, T1) and a sink (cold, T2). The fast ways of the heat through the moist paths of the blanket are visible from wall to wall. These fast ways are representing the moisture increased conductive and convective part of the thermal conductivity of aerogel. The ways of the heat through the dry paths are also visible.

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“…Moreover, data show that the film can reach a thermal insulation up to 95%, and as a result, reduced up to 30-60% energy consumption when used on buildings. That means the vacuum thermal insulation coatings are excellent in both thermal insulation and comprehensive performance due to its special structure [56,57]. And it is considered to be one of the most efficient energy-saving materials with a promising future.…”

Section: Vacuum Thermal Insulation Coatingsmentioning

confidence: 99%

Thermal Insulation Coatings in Energy Saving

Ye¹,

Chen²

2019

Energy-Efficient Approaches in Industrial Applications

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The surface temperature of object rises due to the accumulated heat when it absorbs solar energy, the excessive temperature caused by solar radiation will result in many inconveniences and even troubles in industrial production and daily life; in order to maintain the proper temperature of the object, a large amount of energy is consumed. The development of effective and economic thermal insulation materials is the key to meet the urgent needs for energy saving and emission reduction. In the face of variety of choices of thermal insulation materials, thermal insulation coating become more and more popular due to its good thermal insulation performance, economic, easy to use, and adaptability for a wide range of substrates. With the thermal insulation functional fillers (briefly called fillers in the following text) in coating system, the films can show a certain thermal insulation effect by reflecting, radiating, or isolating heat. As a result, when covered by thermal insulation coatings, the surface temperature of object would be greatly decreased. In this case, a large amount of energy consumed for cooling down the objects exposed to sunlight could be saved, which means the energy consumption can be reduced effectively by just covering with a thermal insulation coating on the surface of object.

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Thermal transport in nano-porous insulation of aerogel: Factors, models and outlook

Cited by 168 publications

References 126 publications

Ultralight and Flexible Monolithic Polymer Aerogel with Extraordinary Thermal Insulation by A Facile Ambient Process

Ultralight and Flexible Monolithic Polymer Aerogel with Extraordinary Thermal Insulation by A Facile Ambient Process

Investigation of the moisture induced degradation of the thermal properties of aerogel blankets: Measurements, calculations, simulations

Thermal Insulation Coatings in Energy Saving

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