Fractal structure reconstruction for alumina-silicate refractory fiber and simulation of the thermal conductivity

Recent developments in liquid technology have created a new class of fluids called “nanofluids” which are two-phase mixtures of a non-metal-liquid matrix and addon particles usually less than 100 nm in size. It is reputed that such liquids have a great potential for application. Indeed, many tests have shown that their thermal conductivity can be increased by almost 20% compared to that of the base fluids for a relatively low particle loading (of 1 up to 5% in volume). It is confirmed by experimental data and simulation results. In this study, the author considers an effect of impurity clustering by liquid density fluctuations as a natural mechanism for stabilizing microstructure of the colloidal solution and estimates the effect of fractal structure of colloidal particles on thermal conductivity of water. The results of this study may be useful for motivating choosing the composition of heat-transfer suspension and developing technology for making the appropriate nanofluid.

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Preparation of Refractory Fiber Cardboard for Building Insulation

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.357-360.1295 ◽

2013 ◽

Vol 357-360 ◽

pp. 1295-1299 ◽

Cited By ~ 1

Author(s):

Sha Wang ◽

Chuan Shan Zhao ◽

Dai Qi Wang ◽

Wen Jia Han

Keyword(s):

Thermal Conductivity ◽

Raw Materials ◽

Mass Ratio ◽

Bonding Agents ◽

Physical Strength ◽

Refractory Fiber ◽

Building Insulation ◽

Alumino Silicate ◽

Sepiolite Fiber ◽

Pva Fiber

A kind of refractory fiber cardboard functioning as building insulation materials was developed. To improve the cardboard abilities to bear high temperature, sepiolite and alumino-silicate fibers were chosen as the raw materials for making refractory fiber carboard. In addition, inorganic adhesives and PVA fiber were used as bonding agents to enhance the physical strength of cardboard. The effect of bonding agents amount on tensile strength of the cardboard were investigated. When choosing inorganic adhesives and PVA fibers as the adhesives, the optimum condition is that amount of aluminum sol and PVA fibers is 30%and 3%-4% by weight, respectively; The best technical conditions for making the refractory fiber cardboard were determined. When the mass ratio of alumino-silicate fibers, sepiolite fiber, PVA fibers is 90: 6: 4, the physical strength of refractory fiber cardboard can be up to 1.556N·m/g. When the bulk density of the cardboard is 305.8kg/m3, the thermal conductivity of insulation cardboard at 200°C is very low, which is only 0.065W/m·K.

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Study of the reconstruction of fractal structure of closed-cell aluminum foam and its thermal conductivity

Journal of Thermal Science ◽

10.1007/s11630-012-0521-x ◽

2012 ◽

Vol 21 (1) ◽

pp. 77-81 ◽

Cited By ~ 3

Author(s):

Dehong Xia ◽

Shanshan Guo ◽

Ling Ren

Keyword(s):

Thermal Conductivity ◽

Aluminum Foam ◽

Fractal Structure ◽

Closed Cell

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The thermal conductivity of refractory fiber products

Refractories ◽

10.1007/bf01284706 ◽

1975 ◽

Vol 16 (7-8) ◽

pp. 408-413 ◽

Cited By ~ 1

Author(s):

I. I. Vishnevskii ◽

E. I. Akselrod ◽

N. D. Talyanskaya ◽

A. D. Melentev ◽

D. B. Glushkova

Keyword(s):

Thermal Conductivity ◽

Refractory Fiber

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Numerical Study of Thermal Properties of a Silica Aerogel Fractal Material

Journal of Heat Transfer ◽

10.1115/1.4049275 ◽

2020 ◽

Author(s):

Amal Maazoun ◽

Abderrazak Mezghani ◽

Ali Ben Moussa

Keyword(s):

Heat Transfer ◽

Thermal Conductivity ◽

Silica Aerogel ◽

Fractal Structure ◽

Numerical Study ◽

Solid Particles ◽

Conductive Heat ◽

Equivalent Thermal Conductivity ◽

Random Fractal ◽

Type Boundary

Abstract Silica Aerogel is material with a special structure consisting of interconnected solid particles of SiO2 forming the skeleton that enclose nano-pores filled with confined air and occupying more than 90% of the volume. It is characterised by a thermal conductivity that can reach lower values than any other material. Our aim was to explain the causes of the super-insulation of this material with the use of a calculating method of conductive heat transfer flux in an aerogel structure and determine the equivalent thermal conductivity. For this purpose, numerical specific software was developed to generate random fractal structure of silica aerogel with pre-defined concentration of solid particles and properties of both skeleton and confined air. Calculation of the conductivity at any point in the confined gas domain shows variable values as a function of the pore size and the location of the point in the pore. Heat transfer through the aerogel in the unsteady state as well as in the steady state was simulated by imposing a Dirichlet-type boundary conditions for each side of the domain of the aerogel structure. A new developed numerical method was used to calculate the equivalent thermal conductivity of the whole fractal structure. Concentration of solid particles has proved not to be the only parameter in which depend on the thermal conductivity of silica aerogel and the influence of tortuosity has been demonstrated. A correlation linking thermal conductivity to both concentration of solid particles and tortuosity of the material was suggested.

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