scholarly journals Development and experimental studies of heat insulating coatings of basalt and glass-fiber tubing

2019 ◽  
Author(s):  
M.A. Komkov ◽  
Yu.Z. Bolotin ◽  
T.V. Vasiljeva ◽  
O.V. Zarubina
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Thermal Conductivity Coefficient ◽  
Heat Insulation ◽  
Unit Length ◽  
Experimental Studies ◽  
Low Density ◽  
Basalt Fibers ◽  
Insulating Materials ◽  
Insulation Wall

The study shows that in order to significantly reduce the thermal conductivity coefficient of heat insulating materials made of staple basalt raw fibers, it is necessary to grind and clean them from impurities by liquid method. Within the research, we found that tubing heat insulating coating has the insulation wall thickness and mass per unit length limitations. In this paper we give the results of studying high-temperature and low-density heat insulation of short basalt fibers and alumina bundles.

scholarly journals ТЕПЛОФИЗИЧЕСКИЕ ХАРАКТЕРИСТИКИ И ТЕРМОЭРОЗИОННАЯ СТОЙКОСТЬ КЕРАМИЧЕСКОГО МАТЕРИАЛА НА ОСНОВЕ КАРБИДА БОРА

2020 ◽  
pp. 136-145
Author(s):  
Юрий Игоревич Евдокименко ◽  
Ирина Александровна Гусарова ◽  
Геннадий Александрович Фролов ◽  
Вячеслав Михайлович Кисель ◽  
Сергей Васильевич Бучаков
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Heat Resistance ◽  
Specific Heat ◽  
Thermal Conductivity Coefficient ◽  
Erosion Resistance ◽  
Combustion Products ◽  
Structural Ceramics ◽  
Radiation Coefficient ◽  
Temperature Dependences

A study of the thermophysical characteristics, heat resistance, and thermal erosion resistance of high-temperature structural ceramics (SC), which was developed at NTUU "I. Sikorsky Kyiv Polytechnic Institute" under the supervision of Corresponding Member of the National Academy of Sciences of Ukraine, Professor P. I. Loboda was made. This high-temperature structural ceramics is intended for use in aerospace engineering, in particular - for the manufacture of aerodynamic surfaces of reusable hypersonic aircraft and heat-stressed elements of the gas-dynamic paths of their engines. The samples of B4C-SiC-B6Si ceramics of two compositions (No. 1 and No. 2) were studied, which differ in the mass content of the initial components. Temperature dependences of the specific heat and thermal conductivity of the spacecraft, radiation coefficient, heat resistance in an oxidizing environment, and the thermal erosion resistance in supersonic flow of combustion products of an air-kerosene fuel mixture were determined. The temperature dependence of the specific heat was determined using an IT-c-400 instrument (in the range of 40 °C - 440 °C) and by the calculation of the temperature dependences of the specific heat capacity of the system components following the Reno rule (up to 2100 °C). The temperature dependence of the thermal conductivity coefficient of the SC of composition No. 1 was determined by solving the inverse heat conduction problem on a computer model based on experimental data. Temperature fields and heat fluxes were obtained under conditions of one-sided heat-ing with a reducing flame of a propane-oxygen welding burner. The thermal conductivity coefficient of SC composition No. 1 increases from 11 W/(m×K) at 20 °С to 25 W/(m×K) at 1400 °С. Its radiation coefficient in the temperature range 1000 °С - 1400 °С is ε = 0.96 ± 0.02. Heat resistance of SC of both compositions in the oxidizing flame of an oxygen welding burner at a surface temperature of 1400 °C has demonstrated that after two hours of heating, the average values of mass ablation for the two tested samples of compositions №1 and № 2 respectively 2.1% and 1.4% (a sample thickness of 4 mm). Tests in the supersonic flow of combustion products at the same surface temperature confirm the high resistance of the material to thermoerosion in the oxidizing medium. The change in the morphology of the heated surface of the sample after six five-minute heating cycles was manifested only by an increase in its roughness without visible oxidation. High thermal conductivity, heat and thermoerosion resistance, radiation coefficient of the studied SC at a temperature of 1400 °C in combination with low density (2.7 g / cm3) make this high-temperature structural material of aerospace technology promising for use.

Theoretical Analysis on Heat Transfer Characteristics of Metal Rubber

2011 ◽  
Vol 183-185 ◽  
pp. 1696-1700
Author(s):  
Bin Zhu ◽  
Jie Hong ◽  
Yan Hong Ma
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Conductivity Coefficient ◽  
Heat Insulation ◽  
Engineering Application ◽  
Porous Metal ◽  
Transfer Model ◽  
Fourier Law ◽  
Theoretical Support ◽  
Metal Rubber

Based on the basic components of the porous Metal Rubber (MR) materials, all kinds of heat transfer modes were analyzed. Wire helix was considered as the micro-element of Metal Rubber by analyzing the characteristics of processing components of Metal Rubber. According to the acoustoelectric analogy method, the heat transfer model of MR was established on the basis of arrangement of wire helix and Fourier Law. The formula of thermal conductivity coefficient was derived. And the LFA 427 instrument was used to obtain thermal conductivity characteristics of MR experimentally. The results showed that the model had certain application. This model was valuable for the analysis of the thermal properties and the design of Metal Rubber. It provided theoretical support for the further engineering application of Metal Rubber in the field of heat insulation.

Utilization of CaO for Improvement of Durability of Vacuum Insulating Panels (VIP)

2019 ◽  
Vol 296 ◽  
pp. 203-208
Author(s):  
Jiří Zach ◽  
Jitka Peterková ◽  
Vítězslav Novák
Keyword(s):  
Thermal Conductivity ◽  
Construction Industry ◽  
Thermal Conductivity Coefficient ◽  
Main Issue ◽  
Building Structures ◽  
Insulating Materials ◽  
Vacuum Insulation

Vacuum insulation panels (VIP) currently belong to a group of so-called super-insulating materials. These are special products with an extremely low equivalent value of the thermal conductivity coefficient. Despite this fact, the use of VIP in the construction industry is rather problematic. The main issue is the relatively complicated VIP integration into building structures, as well as the limited VIP durability. The issue of durability is also one of the main topics of VIP development and research in this field. The paper describes the possibilities of using CaO to increase the durability of vacuum insulation panels.

High Temperature Thermal Barrier Coating Made by the Solution Precursor Plasma Spray Process

2014 ◽  
Author(s):  
Eric H. Jordan ◽  
Maurice Gell ◽  
Chen Jiang ◽  
Jiwen Wang ◽  
Balakrishnan Nair
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Plasma Spray ◽  
High Hardness ◽  
Temperature Phase ◽  
Low Density ◽  
Solution Precursor Plasma Spray ◽  
Low Thermal Conductivity ◽  
Solution Precursor ◽  
Stress Relieving

Yttrium aluminum garnet (YAG) is well-known to have desirable physical and mechanical properties, including high temperature phase stability, relatively low thermal conductivity, high hardness, and low density. This combination of properties makes it desirable to pursue YAG as an advanced TBC. Unfortunately, thermal cycle durability is poor because it has higher thermal expansion mismatch stresses compared to conventional 7YSZ. Recently, 250 micron thick YAG TBCs have been produced by the solution precursor plasma spray (SPPS) process. These SPPS YAG TBCs exhibit good thermal cycling properties compared to APS 7YSZ because of the presence of stress-relieving, through-thickness cracks. The SPPS YAG TBCs also exhibit low thermal conductivity, low density and high hardness.

scholarly journals Performance of Heat-Insulating Materials Doped with Basalt Fibres for Use in Mines

Polymers ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2057
Author(s):  
Yewei Jiang ◽  
Song Xin ◽  
Hongyu Li ◽  
Long Zhang ◽  
Chuanbin Hou ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Compressive Strength ◽  
High Temperature ◽  
High Strength ◽  
Optimal Combination ◽  
Performance Indices ◽  
Insulating Materials ◽  
Data Analyses ◽  
Insulation Performance ◽  
Orthogonal Tests

To solve high-temperature-induced hazards in mines, heat-insulating materials were prepared by utilising basalt fibres and high-strength ceramsite combined with cementing materials. Through orthogonal tests and data analyses, the optimal combination of the heat-insulating materials doped with basalt fibres was determined as A1B1C1, that is, doping with 45% basalt fibres, a length of the basalt fibres of 6 mm, and doping with 20% ceramsite. The performance indices corresponding to the optimal comprehensive combination of the heat-insulating materials doped with basalt fibres included a density of 1200 kg/m3, thermal conductivity of 0.151 W/(mK), compressive strength of 9.7 MPa, flexural strength of 3.6 MPa, and a water-seepage depth of 25.4 mm. Numerical simulations verified that the materials presented favourable thermal insulation performance.

scholarly journals Mechanical Properties and Thermal Conductivity of Aerogel-Incorporated Alkali-Activated Slag Mortars

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Levent Bostanci ◽  
Ozlem Celik Sola
Keyword(s):  
Thermal Conductivity ◽  
Compressive Strength ◽  
Thermal Conductivity Coefficient ◽  
Experimental Studies ◽  
Strength Test ◽  
Strength Increase ◽  
Alkali Activated Slag ◽  
Compressive Strength Test ◽  
Activated Slag ◽  
Alkali Activated

Compressive strength, thermal conductivity coefficient, and porosimetric properties of alkali-activated slag (AAS) mortars containing silica aerogel were investigated experimentally in this study. For this purpose, slag mortar mixtures at 0.75% and 1.0% aerogel content ratios were prepared, and these mortar mixtures were activated with lithium carbonate (Li2CO3) at 0.03% and 1.50% dosage rates. Mortar samples were exposed to curing process in water for 2, 7, and 28 days, and the samples, which completed the curing stage, were subjected to the compressive strength test. The porosimetry test and the thermal conductivity coefficient measurement were carried out following the compressive strength test on 28-day samples. The varying aerogel content rate in the mixtures and the effects of the dosage of Li2CO3 on the gel, capillary, and macropore distributions, and the effect of changing porosimetric properties on compressive strength and thermal conductivity coefficient were analyzed in detail. Experimental studies have shown that AAS mortars including an optimum 0.75% aerogel content rate and 0.03% Li2CO3 activation provided a compressive strength of 34.1 MPa and a thermal conductivity coefficient of 1.32 W/mK. Aerogel addition provides a partial compressive strength increase at 7- and 28-day samples while it also causes maximum strength loss of 5.0% at 2-day samples.

scholarly journals Influence of Surface Emissivity and of Low Emissivity Shields on the Thermal Properties of Low Density Insulating Materials

2011 ◽  
Author(s):  
Mariacarla Arduini ◽  
Manuela Campanale ◽  
Lorenzo Moro
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Test Temperature ◽  
Transfer Factor ◽  
Thermal Characteristics ◽  
Expanded Polystyrene ◽  
Low Density ◽  
Insulating Materials ◽  
Insulating Material ◽  
Radiation Extinction

The theory of heat transfer through low density insulating materials explains the importance of thermal radiation in the overall heat transfer. As a matter of fact, in many semitransparent insulating materials, radiation has a considerable influence on measured thermal conductivity. In this work we continue the investigation (both experimentally and theoretically) on the heat transfer through low density insulating materials that we started some years ago and whose results have been presented in some International Conferences. Test have been done on low density insulating materials: expanded polystyrene with a density of 10 kg/m3 and polyester fibres with a density of 9 kg/m3 (these last tests are not yet completed and will not be discussed in this paper). The transfer factor T was measured in the heat flow meter apparatus of our laboratory [1]. The first measurements have been done with the two surfaces of the apparatus uncoated (emissivity ε = 0.91) at a mean test temperature of 283 K (10 °C) and then with the specimens enclosed in the aluminium foils (emissivity ε = 0.045) at the same mean test temperature. The results obtained from the measurements of the transfer factor T pointed out that a change of the emissivity ε of the surfaces from 0.91 to 0.045 caused a considerable decreasing of the transfer factor. Then the same panels have been cut into two slices and the aluminium foil has been interposed also between the slices, as shield, and the transfer factor was measured again in both cases: at first with the surfaces of the apparatus uncoated and then with the surfaces of the apparatus coated with the aluminium foils. In both cases the decreasing of the transfer factor τ was not negligible. The radiation extinction parameters have been then measured with a spectrometer and a model has been found to predict the transfer factor T in function of the testing conditions. We can conclude that in presence of a thin reflective metal cover placed on a low density insulating material, the thermal conductivity decrease immediately (about 7%) with a significant improvement of the thermal characteristics of the insulating material. If we put then some low emissivity foils between the slices of the material, another considerable decreasing of the thermal conductivity can be obtained (about 10%) and in presence of both aluminum foils (inside and outside). This fact confirms the importance of the contribution of radiation in thermal transmissivity of low density insulating materials and gives the possibility to reduce and to predict the thermal performances of such a material.

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