Spectrometric Radiation Measurements of Nanoporous Insulation Materials

2012 ◽  
Vol 486 ◽  
pp. 437-443 ◽  
Author(s):  
Xu Ji Fan

For the measurement of radiation heat transfer in the low-density nanoporous insulation material at extreme temperature environment, this paper describes in detail on how the experimental optical system is established, and the way and method of measurements are presented .A Silica Aerogel nanoporous insulation plate specimen is experimented and its result is compared with the analytical result, their discrepancies are analyzed. This work is intended to give reference to the development of new types of thermal protection system (TPS) with low density microporous material insulations.

2018 ◽  
Vol 281 ◽  
pp. 131-136
Author(s):  
Shi Chao Zhang ◽  
Wei Wu ◽  
Yu Feng Chen ◽  
Liu Shi Tao ◽  
Kai Fang ◽  
...  

With the increase of the speed of vehicle, the thermal protection system of its powerplant requires higher insulation materials. Phase change materials can absorb large amounts of heat in short time. So the introduction of phase change materials in thermal insulation materials can achieve efficient insulation in a limited space for a short time. In this paper, a new phase change thermal insulation material was prepared by pressure molding with microporous calcium silicate as matrix and Li2CO3 as phase change material. The morphology stability, exudation and heat insulation of the materials were tested. The results show that the porous structure of microporous calcium silicate has a good encapsulation when the phase transition of Li2CO3 is changed into liquid. And the material has no leakage during use. The thermal performance test also shows that the insulation performance of the material has obvious advantages in the short term application.


Polymers ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1899 ◽  
Author(s):  
Haiwei Yang ◽  
Zongqian Wang ◽  
Zhi Liu ◽  
Huan Cheng ◽  
Changlong Li

Aerogel fiber, with the characteristics of ultra-low density, ultra-high porosity, and high specific surface area, is the most potential candidate for manufacturing wearable thermal insulation material. However, aerogel fibers generally show weak mechanical properties and complex preparation processes. Herein, through firstly preparing a cellulose acetate/polyacrylic acid (CA/PAA) hollow fiber using coaxial wet-spinning followed by injecting the silk fibroin (SF) solution into the hollow fiber, the CA/PAA-wrapped SF aerogel fibers toward textile thermal insulation were successfully constructed after freeze-drying. The sheath (CA/PAA hollow fiber) possesses a multiscale porous structure, including micropores (11.37 ± 4.01 μm), sub-micron pores (217.47 ± 46.16 nm), as well as nanopores on the inner (44.00 ± 21.65 nm) and outer (36.43 ± 17.55 nm) surfaces, which is crucial to the formation of a SF aerogel core. Furthermore, the porous CA/PAA-wrapped SF aerogel fibers have many advantages, such as low density (0.21 g/cm3), high porosity (86%), high strength at break (2.6 ± 0.4 MPa), as well as potential continuous and large-scale production. The delicate structure of multiscale porous sheath and ultra-low-density SF aerogel core synergistically inhibit air circulation and limit convective heat transfer. Meanwhile, the high porosity of aerogel fibers weakens heat transfer and the SF aerogel cellular walls prevent infrared radiation. The results show that the mat composed of these aerogel fibers exhibits excellent thermal insulating properties with a wide working temperature from −20 to 100 °C. Therefore, this SF-based aerogel fiber can be considered as a practical option for high performance thermal insulation.


2020 ◽  
Author(s):  
Luc Yannick Andréas Randriamarolaza ◽  
Enric Aguilar ◽  
Oleg Skrynyk

<p>Madagascar is an Island in Western Indian Ocean Region. It is mainly exposed to the easterly trade winds and has a rugged topography, which promote different local climates and biodiversity. Climate change inflicts a challenge on Madagascar socio-economic activities. However, Madagascar has low density station and sparse networks on observational weather stations to detect changes in climate. On average, one station covers more than 20 000 km<sup>2</sup> and closer neighbor stations are less correlated. Previous studies have demonstrated the changes on Madagascar climate, but this paper contributes and enhances the approach to assess the quality control and homogeneity of Madagascar daily climate data before developing climate indices over 1950 – 2018 on 28 synoptic stations. Daily climate data of minimum and maximum temperature and precipitation are exploited.</p><p>Firstly, the quality of daily climate data is controlled by INQC developed and maintained by Center for Climate Change (C3) of Rovira i Virgili University, Spain. It ascertains and improves error detections by using six flag categories. Most errors detected are due to digitalization and measurement.</p><p>Secondly, daily quality controlled data are homogenized by using CLIMATOL. It uses relative homogenization methods, chooses candidate reference series automatically and infills the missing data in the original data. It has ability to manage low density stations and low inter-station correlations and is tolerable for missing data. Monthly break points are detected by CLIMATOL and used to split daily climate data to be homogenized.</p><p>Finally, climate indices are calculated by using CLIMIND package which is developed by INDECIS<sup>*</sup> project. Compared to previous works done, data period is updated to 10 years before and after and 15 new climate indices mostly related to extremes are computed. On temperature, significant increasing and decreasing decade trends of day-to-day and extreme temperature ranges are important in western and eastern areas respectively. On average decade trends of temperature extremes, significant increasing of daily minimum temperature is greater than daily maximum temperature. Many stations indicate significant decreasing in very cold nights than significant increasing in very warm days. Their trends are almost 1 day per decade over 1950 – 2018. Warming is mainly felt during nighttime and daytime in Oriental and Occidental parts respectively. In contrast, central uplands are warming all the time but tropical nights do not appear yet. On rainfall, no major significant findings are found but intense precipitation might be possible at central uplands due to shortening of longest wet period and occurrence of heavy precipitation. However, no influence detected on total precipitation which is still decreasing over 1950 - 2018. Future works focus on merging of relative homogenization methodologies to ameliorate the results.</p><p>-------------------</p><p>*INDECIS is a part of ERA4CS, an ERA-NET initiated by JPI Climate, and funded by FORMAS (SE), DLR (DE), BMWFW (AT), IFD (DK), MINECO (ES), ANR (FR) with co-funding by the European Union (Grant 690462).</p>


2014 ◽  
Vol 602-603 ◽  
pp. 624-627 ◽  
Author(s):  
Shi Chao Zhang ◽  
Guang Hai Wang ◽  
Wei Wu ◽  
Yu Feng Chen ◽  
Hao Ran Sun

Tris (hydroxymethyl) ethane (PG) as a phase change material, micro-porous xonotlite (CS) as matrix, PG/CS composite PCMs were prepared by melt-soaking method, and the effect of micro-porous structure of xonotlite on heat absorption capacity, bending strength and insulation performance of composites, and the exudation of PG was studied. Otherwise, for the work environment and characteristics of propulsive device of vehicle, this paper explored the feasibility that phase change materials (PCMs) worked as the insulation material in short-time insulation system of the vehicle. Experimental results show that, when the most probable pore diameters of xonotlite was not less than 63nm, the composites presented better and almost same absorption capacities of matrix (CS) to PCM (PG) in different composites; when up to 85nm, the composite exhibited the lowest leakage rate (less than 5%), the optimal mechanical property and thermal insulation performance. This Study proposed a new idea for the design of the insulation material in the thermal protection system of propulsive device of vehicle.


2019 ◽  
Vol 827 ◽  
pp. 159-164 ◽  
Author(s):  
Janis Andersons ◽  
Mikelis Kirpluks ◽  
Ugis Cabulis

Rigid low-density closed-cell polyurethane (PU) foams are used primarily as a thermal insulation material. The foams have to possess a sufficient strength and stiffness in order to ensure their mechanical integrity and dimensional stability in service. The mechanical characteristics of foams are enhanced by adding cellulose nanofibers to the polyol system, which both modify the foaming process and act as a reinforcement of cell struts and walls. A model of composite foam strength is developed based on a regular unit cell and assuming the onset of strut failure as the foam fracture criterion. The load-bearing capacity of foam struts is estimated by the modified Fukuda and Chou model considering the orientation of nanofibers along the strut axis. The model developed is shown to provide a reasonably accurate prediction for the nanofiber loading effect on the strength of composite foams.


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