Thermal Insulative Performance of Bamboo Leaf Aerogel Opacified Using Activated Carbon Compared with Carbon Black

2014 ◽  
Vol 941-944 ◽  
pp. 2482-2485
Author(s):  
Kien Woh Kow ◽  
Rozita Yusoff ◽  
A. R. Abdul Aziz ◽  
E. C. Abdullah
Keyword(s):  
Thermal Conductivity ◽  
Activated Carbon ◽  
Carbon Black ◽  
Silica Aerogel ◽  
Radiative Heat ◽  
Radiative Heat Loss ◽  
Insulating Material ◽  
Thermal Insulating ◽  
Different Temperatures ◽  
Carbon Loading

Silica aerogel with extremely low thermal conductivity has great potential to be used as thermal insulating material. Opacification using carbon black is normally applied to reduce radiative heat loss in silica aerogel. This work attempted to replace carbon black with activated carbon as opacifer. Both the silica aerogel and activated carbon were synthesized via bamboo leaf. Effects of carbon loading and temperatures on the thermal conductivity of opacified aerogel were studied. The results show that an optimal carbon loading that minimized the thermal conductivity present at different temperatures. Such optimal loading increased as temperature applied to the opacified aerogel increased. Properties of aerogels opacified with activated carbon were also compared with aerogels opacified with carbon black.

A Novel Poly(Ionic Liquid) as the Thermal Insulating Material

2020 ◽  
Vol 13 (3) ◽  
pp. 241-247
Author(s):  
Wenxin Wei ◽  
Guifeng Ma ◽  
Hongtao Wang ◽  
Jun Li
Keyword(s):  
Thermal Conductivity ◽  
Ionic Liquid ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Flame Resistance ◽  
Insulating Material ◽  
Low Thermal Conductivity ◽  
Thermal Insulating ◽  
Poly Ionic Liquid

Objective: A new poly(ionic liquid)(PIL), poly(p-vinylbenzyltriphenylphosphine hexafluorophosphate) (P[VBTPP][PF6]), was synthesized by quaternization, anion exchange reaction, and free radical polymerization. Then a series of the PIL were synthesized at different conditions. Methods: The specific heat capacity, glass-transition temperature and melting temperature of the synthesized PILs were measured by differential scanning calorimeter. The thermal conductivities of the PILs were measured by the laser flash analysis method. Results: Results showed that, under optimized synthesis conditions, P[VBTPP][PF6] as the thermal insulator had a high glass-transition temperature of 210.1°C, high melting point of 421.6°C, and a low thermal conductivity of 0.0920 W m-1 K-1 at 40.0°C (it was 0.105 W m-1 K-1 even at 180.0°C). The foamed sample exhibited much low thermal conductivity λ=0.0340 W m-1 K-1 at room temperature, which was comparable to a commercial polyurethane thermal insulating material although the latter had a much lower density. Conclusion: In addition, mixing the P[VBTPP][PF6] sample into polypropylene could obviously increase the Oxygen Index, revealing its efficient flame resistance. Therefore, P[VBTPP][PF6] is a potential thermal insulating material.

Thermographic Studies of Aerogel Composites

2020 ◽  
Vol 15 (2) ◽  
Author(s):  
K. Keerthi Sanghamitra ◽  
A. Yamini ◽  
A. Venu Vinod ◽  
Neha Hebalkar
Keyword(s):  
Thermal Conductivity ◽  
Silica Aerogel ◽  
Cold Water ◽  
High Porosity ◽  
Fiber Mats ◽  
Aerospace Applications ◽  
Thermal Insulating ◽  
Wide Range ◽  
Composite Form ◽  
Insulation Performance

AbstractAerogels are regarded as the superior thermal insulating materials for wide range of temperatures, from cryogenic insulation, cold water diving garments to high temperature applications and even to defense and aerospace applications. For most of such applications, the aerogels are used in composite form rather than monolithic form as aerogels are fragile in nature due to its high porosity of up to 98%. These composites constitute aerogel infiltrated fiber mats to give flexibility, on the other hand, compromises on the insulation performance due to reinforcing aerogel with fibers that have comparatively higher thermal conductivity than silica aerogel. To increase the efficiency, density of the fiber mat needs to be reduced to incorporate higher loading of silica aerogel. Many techniques are being used to study the insulation performance of these composites. This paper presents about the study of insulation performance of fibre mats with different aerogel content and composition using a well-known thermography technique. The morphological, compositional, thermal and physical studies of the fiber mats and its composites using FESEM, EDAX, BET, thermal conductivity etc., are discussed.

scholarly journals Effect of Radiative Heat-Loss Function and Finite Larmor Radius Corrections on Jeans Instability of Viscous Thermally Conducting Self-Gravitating Astrophysical Plasma

2012 ◽  
Vol 2012 ◽  
pp. 1-14 ◽  
Author(s):  
Sachin Kaothekar ◽  
R. K. Chhajlani
Keyword(s):  
Thermal Conductivity ◽  
Heat Loss ◽  
Loss Function ◽  
Radiative Heat ◽  
Gravitational Instability ◽  
Mode Analysis ◽  
Instability Criterion ◽  
Larmor Radius ◽  
Astrophysical Plasma ◽  
Radiative Heat Loss

The effect of radiative heat-loss function and finite ion Larmor radius (FLR) corrections on the self-gravitational instability of infinite homogeneous viscous plasma has been investigated incorporating the effects of thermal conductivity and finite electrical resistivity for the formation of a star in astrophysical plasma. The general dispersion relation is derived using the normal mode analysis method with the help of relevant linearized perturbation equations of the problem. Furthermore the wave propagation along and perpendicular to the direction of external magnetic field has been discussed. Stability of the medium is discussed by applying Routh Hurwitz’s criterion. We find that the presence of radiative heat-loss function and thermal conductivity modify the fundamental Jeans criterion of gravitational instability into radiative instability criterion. From the curves we see that temperature dependent heat-loss function, FLR corrections and viscosity have stabilizing effect, while density dependent heat-loss function has destabilizing effect on the growth rate of self-gravitational instability. Our result shows that the FLR corrections and radiative heat-loss functions affect the star formation.

Thermal Instability of Self-Gravitating Partially-Ionized Gaseous Plasma

2011 ◽  
Vol 8 (1) ◽  
pp. 181-187
Author(s):  
Ram K. Pensia ◽  
V. Shrivastava ◽  
Vishal Kumar ◽  
Ashok K. Patidar ◽  
Vikas Prajapat
Keyword(s):  
Magnetic Field ◽  
Thermal Conductivity ◽  
Heat Loss ◽  
Radiative Heat ◽  
Longitudinal Mode ◽  
Thermal Mode ◽  
Radiative Heat Loss ◽  
Gaseous Plasma ◽  
Jeans Instability ◽  
Partially Ionized

The effect of radiative heat-loss function on the Jeans instability of an infinitely conducting, homogeneous partially ionized gaseous plasma is investigated. It is assumed that the medium is carrying a uniform magnetic field in the presence of porosity and thermal conductivity. With the help of relevant linearized perturbation equations of the problem, a general dispersion relation is obtained for a such medium using the normal analysis technique, which is reduced for both the transverse and the longitudinal mode of propagation. The longitudinal mode is found to be modified by Alfven speed and parameter of porosity. The thermal mode is obtained separately having the effects of thermal conductivity and arbitrary radiative heat-loss functions. The effect of collision with neutrals and magnetic field have a stabilizing effect, while thermal conductivity has destabilizing influence on the Jeans instability of gaseous plasma. In the transverse mode of propagation, we find the condition of radioactive instability depends on thermal conductivity, magnetic field and the porosity of the medium.

New Thermal Insulating Material Based on Geocement

2013 ◽  
Vol 838-841 ◽  
pp. 183-187 ◽  
Author(s):  
Vít Petranek ◽  
Sergii Guzii ◽  
Pavel Krivenko ◽  
Konstantinos Sotiriadis ◽  
Anastasiia Kravchenko
Keyword(s):  
Thermal Conductivity ◽  
Heat Flow ◽  
External Heat ◽  
Great Scientist ◽  
Insulating Material ◽  
Average Temperature ◽  
Thermal Insulating ◽  
The Matrix ◽  
Birthday Anniversary ◽  
Alkali Activated

A new thermal insulating material was developed on the basis of a geocement, formulated as Na2OAl2O36SiO220H2O. Ground limestone and aluminosilicate pellets were used as fillers for its production (composition: geocement 64.29 wt. [%]; fillers 35.71 wt. [%]). This material, which is applied having a thickness of 3.0-4.5 mm, swells when it is exposed to an external heat flow of 1273 K average temperature. Swelling is due to the matrix phases and filler dehydration, which include heulandite, ussingite, sodium zeolite and other phases. As a result, a finely porous glassy aluminosilicate frame of jadeite-albite composition is formed, which is characterized by low thermal conductivity (0.09-0.175 Wm-1K-1). The developed material can be used to protect and to insulate wooden, metal and concrete surfaces from an one-sided heat source.The paper is dedicated to the great scientist of the XXI century in the field of alkali-activated cements and materials based on them, Pavlo Kryvenko, in honor of his 75thbirthday anniversary.

High Temperature Thermal Conductivity Measurements of Quasicrystalline Al70.8Pd20.9Mn8.3

2000 ◽  
Vol 626 ◽  
Author(s):  
Philip S. Davis ◽  
Peter A. Barnes ◽  
Cronin B. Vining ◽  
Amy L. Pope ◽  
Robert Schneidmiller ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Radiative Heat ◽  
Accurate Determination ◽  
Fourth Power ◽  
Radiative Effects ◽  
Radiative Heat Loss ◽  
3Ω Method ◽  
Temperature Range

ABSTRACTWe report measurements of the thermal conductivity on a potential high temperature thermoelectric material, the quasicrystal Al70.8Pd20.9Mn8.3. Thermal conductivity is determined over a temperature range from 30 K to 600 K, using both the steady state gradient method and the 3ω method. Measurements of high temperature thermal conductivity are extremely difficult using standard heat conduction techniques. These difficulties arise from the fact that heat is lost due to radiative effects. The radiative effects are proportional to the temperature of the sample to the fourth power and therefore can lead to large errors in the measured thermal conductivity of the sample, becoming more serious as the temperature increases. For thermoelectric applications in the high temperature regime, the thermal conductivity is an extremely important parameter to determine. The 3ω technique minimizes radiative heat loss terms, which will allow for more accurate determination of the thermal conductivity of Al70.8Pd20.9Mn8.3 at high temperatures. The results obtained using the 3ω method are compared to results from a standard bulk-thermal-conductivity-technique on the same samples over the temperature range, 30 K to 300 K.

scholarly journals Mathematical Model for Analyzing Heat Transfer Characteristics of Ablative Thermal Insulating Material

2020 ◽  
Vol 2020 ◽  
pp. 1-19
Author(s):  
Junjie Gao ◽  
Haitao Han ◽  
Daiying Deng ◽  
Jijun Yu
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Mathematical Model ◽  
Size Distribution ◽  
Distribution Area ◽  
Heat Transfer Characteristics ◽  
Equivalent Thermal Conductivity ◽  
Insulating Material ◽  
Transfer Characteristics ◽  
Thermal Insulating

A mathematical model based on minimal thermal resistance and equal law of specific equivalent thermal conductivity is developed to discuss the heat transfer characteristics of ablative thermal insulating material from the mesoscopic scale. Based on the statistical results of mesoscopic parameters, the microstructure unit cell model was established to analyze the influence rule of mesoscopic parameterization which includes the size, distribution, and positional relation of microsphere and fiber. The results show that the equivalent thermal conductivity decreases with the density, size, distribution area, and distance of microsphere and the space distance and volume fraction of fiber decreasing. Besides, the equivalent thermal conductivity will become larger when more quality of heat transfers along the fiber direction. Exploring the relationship between the macroscopic heat transfer process and the microstructure is meaningful for exploring the heat transfer behavior of thermal insulating material and improvement of the processing technology.

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