• The Korean Journal of Ceramics
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• 제5권1호
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• pp.78-81
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• 1999

Aluminium titanate is highly anisotropic in thermal expansion. As a result, thermal stresses build up in the material and intergranular cracks can develop. Both the outstanding thermal shock resistance and the low mechanical strength of aluminium titanate ceramics are a result of intergranular microcracking. The authors have previously identified a possibility of remarkably increasing fracture toughness of aluminium titanate without excessive penalty on strength. The paper shows that sintered density and porosity measurements can be used for optimizing the sintering and microstructure of aluminium titanate for an ideal balance between toughness and strength and, hence, the best thermal shock resistance.

• 한국주조공학회지
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• 제39권6호
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• pp.103-109
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• 2019

Cu-added SKD11 was manufactured through the casting process and the effects of Cu addition with different contents (0, 1, 2 and 3 wt%) and aging treatment on microstructure, mechanical characteristics such as tensile strength and hardness, and thermal conductivity were investigated. The microstructure was analyzed by FE-SEM and XRD, the mechanical characteristics by Rockwell hardness tester and Tensile tester, and the thermal conductivity by Laser flash. As a result, SKD11 containing Cu had higher hardness than as-received SKD11. The hardness of as-cast SKD11 containing 1 wt% Cu was 42.4 HRC, whereas the hardness of asreceived SKD11 cast alloy was 19.5 HRC, indicating that the hardness was greatly improved when Cu was added. In the case of tensile strength, Cu-added SKD11 cast alloy had lower tensile strength than as-received SKD11, and the tensile strength tended to increase as Cu content increased. After heat treatment, however, tensile strength of as-received SKD11 was significantly increased, whereas in the case of Cu-added SKD11, as the Cu contents increased, the tensile strength increased less and even reduced at 3 wt% Cu. The thermal conductivity of Cu-added SKD11 cast alloy was about 13 W m^-1 K^-1, which was lower than that of the asreceived SKD11 cast alloy (28 W m^-1 K^-1). After the heat treatment, however, the thermal conductivity of as-received SKD11 was reduced, while the thermal conductivity of the SKD11 added with Cu was increased. Thermal conductivity was generally larger with less Cu content, and this tendency became more pronounced after heat treatment.

• 설비공학논문집
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• 제26권10호
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• pp.460-466
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• 2014

This paper uses in-situ thermal response tests to present the characteristics of the ground thermal conductivities of three different SCW GHX. These SCW GHXs were installed in the same site in Seojong City. The three different cases are distinguished by the flow direction and the presence of a filler. The first type (A) is constructed for water to flow downstream. The second (B) and third (C) types are designed for water to flow upstream, and a filler is additionally inserted into the third type. The results of the in-situ thermal response tests, indicate that the ground thermal conductivity for types (A), (B) and (C) are of $4.84W/m{\cdot}K$, $3.40W/m{\cdot}K$, and $11.62W/m{\cdot}K$, respectively.

• 대한기계학회논문집B
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• 제33권8호
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• pp.573-579
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• 2009

A thermal mass air flow sensor, which consists of a micro-heater and thermal sensors on the silicon-nitride thin membrane structure, is micro-fabricated by MEMS processes. Three thermo-resistive sensors, one for the measurement of microheater temperature, the others for the measurement of membrane temperature upstream and downstream of the micro-heater respectively, are used. The micro-heater is operated under the constant temperature difference mode via a real time controller, based on inlet air temperature. Two design models for microfabricated flow sensor are compared with experimental results and confirmed their applicabilities and limitations. The thermal characteristics are measured to find the best flow indicator. It is found that two normalized temperature indicators can be adopted with some advantages in practice. The flow sensor with this control mode can be adopted for wide capability of high speed and sensitivity in the very low and medium velocity ranges.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.1912-1914
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• 2005

The electrical, chemical and mechanical characteristics in transformer insulations are changed due to thermal stress. It is known that characteristics of transformer insulations is deteriorated such as decrease of dielectric strength, deterioration of dielectric constant and tensile strength of paper as transformer oil and paper are aged by thermal stress. Furthermore, chemical characteristics of them are deteriorated as like increment of moisture contents and dissolved by-products in oil, etc. In this paper we have been investigated chemical characteristics of transformer by accelerated thermal aging. For this working we have made experimental test cell and aged at a temperature up to $140^{\circ}C$ for 500 hours. The oil-paper insulation samples have been measured at intervals of 100 hours. For analysis we used Karl-Fisher titration method and high performance liquid chromatography (HPLC).

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제33회 춘계학술대회 개최
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• pp.114-114
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• 2001

The thermal and friction characteristics of phenolic resin and model friction materials were investigated with the content of acrylonitrilebutadienerubber(NBR). The thermal characteristics of material was performed by dynamic mechanical thermal analysis and differential scanning calorimetry. The friction and wear characteristics of the material were determined by using friction material testing machine. The results show that with the more content of rubber, the loss modulus of friction material was increased. The friction coefficient and the specific wear rate with various NBR contents were reported.

• 한국산학기술학회논문지
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• 제14권12호
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• pp.6098-6105
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• 2013

본 연구에서는 해수용 열교환기 적용을 위한 열분사코팅의 종류에 따른 부식특성 및 열전도 성능을 조사하기 위해 실험이 수행되었다. 코팅은 아연과 알루미늄을 열분사코팅한 뒤 실리콘 및 에폭시 수지를 추가 도포한 시편을 선정하였다. 코팅의 부식특성 변화를 관찰하기 위하여 사이클릭 선도변화 측정 및 SEM촬영을 이용하였다. 시편의 열전도 성능을 측정하기 위해서 레이저 확산법을 이용하여 열전도도를 비교하였으며 추가도포를 실리콘으로 한 경우 3 ~ 4% 에폭시로 한 경우 70 ~ 75%의 열전도도 하락이 발생하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.235-239
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• 2005

We analyzed the thermal and mechanical behaviors of micro reformer for the purpose of design verifications and modification of micro channels. The reformer designed for hydrogen generation from methanol is essential to PEM(Proton Exchange Membrane) type fuel cell. For the mobile applications, the size and the simplicity would be the most critical issues. We utilized silicon process for micro reformer to obtain the thickness thinner than 2 mm thick. We have used commercial simulation software, IDEAS, to analyze the thermal and mechanical characteristics of micro reformer structure. The heat generation rates of heaters, heat transfer rates, and fluid temperatures are derived from thermal equilibrium relation and these values were used for thermal boundary conditions. We also analyzed the thermal stresses, thermal deformations to examine the possibility of failure.

• 한국군사과학기술학회지
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• 제22권5호
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• pp.644-653
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• 2019

With the development of themal observatory device(TOD), thermal camouflage system has been applied not only to the weapon system but also to the combat suit for soldiers. In this paper, the characteristic of thermal radiation of human body depending on the clothing material properties was analyzed through numerical simulations. The bioheat equation with thermoregulatory model was solved to obtain the realistic surface temperature of human body and these results are combined with the emissivity of human skin and clothing in order to calculate the thermal signature from the human body. According to each thermal resistance of clothing, the optimal background radiance which makes contrast radiance intensity(CRI) be lowest is different. Also, the average CRI variation per thermal resistance change is about twice as much as the case of evaporative resistance change.

• 대한기계학회논문집
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• 제18권9호
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• pp.2486-2493
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• 1994

Transient heat transfer characteristics in th radiant heating panel with heat diffusion fin were predicted by numerical analysis. Thermal behaviors of panel, such as temperature distributions in panel and convective and radiative heat fluxes in panel surface with advance of time, were obtained for several important parameters. The performance and thermal comfort of heating panel were studied and compared for various design conditions, such as pipe pitch, area ratio and thermal conductivity of optimal design of the new heating panels with heat diffusion fin. It was concluded that the efficient area ratio of heat diffusion fin is about 0.5, and the greater the thermal conductivity of fin is, the better the performance of panel is.