• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.3
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• pp.163-172
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• 2017

Porous insulation have been frequently used in a number of industries by minimizing thermal insulation space because of excellent performance of their thermal insulation. This paper devices an effective thermal conductivity prediction model. First of all, we perform literature survey on traditional effective thermal conductivity prediction models and compare each other model with heat transfer experimental results. Furthermore this research defines advanced effective thermal conductivity prediction models model based on heat transfer experimental results, the Zehner-Schlunder model. Finally we verify that the newly defined effective thermal conductivity prediction model has better performance prediction than other models. Finally, this research performs a transient heat transfer analysis of thermal protection system with a porous insulation using the finite element method and confirms validity of the effective thermal conductivity prediction model.

• Journal of Aerospace System Engineering
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• v.10 no.4
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• pp.26-34
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• 2016

In a number of industries, porous insulations have been frequently used, reducing thermal insulation space through excellent performance of the thermal insulation's characteristics. This paper suggests an effective thermal conductivity prediction model. Firstly, we perform a literature review of traditional effective thermal conductivity prediction models and compare each model with experimental heat transfer results. Furthermore, this research defines the effectiveness of thermal conductivity prediction models using experimental heat transfer results and the Zehner-Schlunder model. The newly defined effective thermal conductivity prediction model has been verified to better predict performance than other models. Finally, this research performs a transient heat transfer analysis of a thermal protection system with a porous insulation in a high speed vehicle using the finite element method and confirms the validity of the effective thermal conductivity prediction model.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.3
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• pp.53-59
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• 2006

This paper presents the IR-Lamp test results of evaluating heat protection performance and measuring of mechanical/thermal properties in the heat protection material of missile external surface. The results showed that increasing the contents of microballoons improved the heat protection performance, but the mechanical properties were deteriorated. Among the kinds of microballoons, Epoxy/Phenolic Microballoons mixture showed the best mechanical properties and low thermal conductivity. Epoxy/Cork mixture showed the best heat protection in the IR-Lamp test, though it has low mechanical properties and high thermal conductivity.

• Composites Research
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• v.20 no.5
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• pp.20-25
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• 2007

Cyclic heating method is useful method for measuring the thermal diffusivity of porous materials. The main object of this paper is to develop and verify the thermal diffusivity measuring system of porous materials under vacuum condition. To verify this method, thermal diffusivities of the alumina ($Al_2O_3$) specimen and polystyrene foam were measured. Thermal diffusivities of these specimens were agreed with reference values. Thermal diffusivities of carbon/epoxy and porous insulation material were measured at atmospheric room temperature condition and vacuum condition respectively. Thermal diffusivities of carbon/epoxy and porous insulation material under vacuum are reduced by 66.4% and 64.9% compared to the thermal diffusivities under the atmospheric condition. These differences are considered the effect of the porous insulation material with an air.

• Journal of Institute of Convergence Technology
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• v.8 no.1
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• pp.21-25
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• 2018

We developed nano-porous $TiO_2-SiO_2$ composites (commercial name : PTI, porous titania insulator) with low thermal conductivity as thermal insulating material as well as function of photocatalyst. The objectives of this paper are, firstly, to evaluate of the thermal conductivity of the PTI powder in the temperature range from -160 to $250^{\circ}C$, secondly to evaluate of thermal conductivities of insulation materials that is applied PTI powder. The structure of the PTI powder that has the pores size of 20-30 nm and the particle diameter of 2-10 nm. The PTI had a high surface area of $400m^2/g$ and a mean pore size of $45{\AA}$, which was fairly uniform. The thermal conductivity was measured by GHP(guarded hot plate) method and HFM(heat flux method). The PTI structure is a three-dimensional network nano-structures composed by a pearl-necklace that involved a precious stone in the center of the necklace. The thermal conductivities of PTI-PX powder by the GHP and HFM were 0.0366 W/m.K, 0.0314 W/m.K at $20^{\circ}C$, respectively. This is similar to values that are proportional to the square of the absolute temperature of the thermal conductivity of static air. The thermal conductivities of insulating sheets coated with PTI powder were similar results with that of the PTI powder.

• Journal of the Korea Institute of Building Construction
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• v.16 no.6
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• pp.529-534
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• 2016

Calcium silicate inorganic insulating material is a porous material which is made of 90 wt% of cement. Unlike existing inorganic insulation materials, it is produced without high temperature curing process and also it costs much less than existing inorganic insulation materials. It is an innovative insulation material that supplemented disadvantages of conventional inorganic insulation material. Researches and developments about inorganic insulation materials have been actively researched abroad. Calcium silicate insulation has $0.13g/cm^3$ of specific gravity. Its heat conductivity is under 0.050W/mK, which it similar to conventional inorganic insulation. However, it has weak compressive strength compared to other inorganic insulation. The point of this research is to manifest that calcium silicate inorganic insulating material can have certain compressive strength after curing process with high insulating performance and to find out the proper curing methods and period.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.4
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• pp.182-189
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• 2021

Porous ceramics were manufactured using the foaming method for the development of inorganic insulating materials. Silica fume and SiO₂ were used as main raw materials, and bentonite was used as a rapid setting agent for uniform structure formation of porous ceramics. The porous ceramics were sintered at 1200℃, and porosity, density, compressive strength, microstructure and thermal conductivity were analyzed. As the content of silica fume to SiO₂ of the porous ceramics increased 70 to 90 %, the specific gravity increased from 0.63 to 0.69, and the compressive strength increased from 9.41 Mpa to 12.86 Mpa. But, the porosity showed a tendency to decrease from 72.07 % to 70.82 %, contrary to the specific gravity. As a result of measuring the thermal conductivity, the porous ceramic with a silica fume content of 70 % showed a thermal conductivity of 0.75 to 0.72 W/m·K at 25 to 800℃, respectively, and, another that a silica fume content of 90 % showed a 0.66~0.86 W/m·K. So the lower the silica f ume content, the lower the thermal conductivity, which was conf irmed to be consistent with porosity result. As a result of microstructure analysis using SEM (Scanning Electron Microscope), pores in the range of tens to hundreds ㎛ were observed inside and outside the porous ceramic, and it was confirmed that the pore distribution was relatively uniform.

• Applied Chemistry for Engineering
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• v.22 no.5
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• pp.501-507
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• 2011

To develop environmental-friendly insulating composite materials, natural cellulose and porous ceramic balls were used as core materials and activated Hwangtoh was used as a binder. Various specimens were prepared with different water/binder ratios and core material/binder ratios. The physical properties of these specimens were then investigated through compressive strengths, flexural strengths, absorption test, hot water resistance test, pore analysis, thermal conductivity, and observation of micro-structures using scanning electron microscope. Results showed that the maximum compressive strength varied appreciably with the water/binder ratios and core material/binder ratios, but the flexural strength increased with the core material/binder ratios regardless of water/binder ratios. The compressive strength and the flexural strength measured after the hot water resistance test decreased remarkably compared to those measured before test. The pore analysis measured after the hot water resistance test showed that total pore volume, porosity and average pore diameter decreased, while bulk density increased by the acceleration of hydration reaction of binder in the hot water. The thermal conductivity decreased gradually with an increase of core material/binder ratios. It can be evaluated that the composite insulation materials having good insulating properties and mechanical strengths can be used in the field.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.5
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• pp.543-551
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• 2015

Polyurethane Foam(PUF), a outstanding thermal insulation material, is used for various structures as being composed with other materials. These days, PUF composed with glass fiber, Reinforced PUF(R-PUF), is used for a insulation system of LNG Carrier and performs function of not only the thermal insulation but also a structural member for compressive loads like a sloshing load. As PUF is a porous material made by mixing and foaming, mechanical properties depend on volume fraction of voids which is a dominant parameter on density. Thus, In this study, density is considered as the effect parameter on mechanical properties of Polyurethane Foam, and mechanical behavior for compression of the material is described by using modified Gurson damage model.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.5
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• pp.437-445
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• 2016

Recently, polyurethane foam has been used in various industry fields to preserve temperature environment of structures, and a wide range of loads from the static to the dynamic are imposed on the material during a life period. The biggest characteristic of polyurethane foam is porosity as being polymeric material, and it is generally known that insulation performance of the material strongly depends on internal void size. In addition, polyurethane foam's mechanical behavior has high dependence on strain rate and temperature as well as being highly non-linear ductile for compression. In the non-linear compressive behavior, volume fraction of voids and elastic modulus decrease as strain increases. Therefore, in this study, temperature-dependent viscoplastic-damage constitutive model was developed to describe the non-linear compressive behavior with the aforementioned features of polyurethane foam.