• Title/Summary/Keyword: Thermal Estimation

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Degradation Estimation Of Material by Barkhausen Noise Analysis (바크하우젠 노이즈 해석에 의한 재료의 열화도 평가)

  • Lee Myung Ho
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.14 no.3
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    • pp.38-46
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    • 2005
  • The destructive method is reliable and widely used for the estimation of material degradation but it have time-consuming and a great difficulty in preparing specimens from in-service industrial facilities. Therefore, the estimation of degraded structural materials used at high temperature by nondestructive evaluation such as electric resistance method, replica method, Barkhausen noise method, electro-chemical method and ultrasonic method are strongly desired. In this study, various nondestructive evaluation(NDE) parameters of the Barkhausen noise method, such as MPA(Maximum Peak Amplitude), RMS, IABNS(Internal Area of Barkhausen Noise on Signal) and average amplitude of frequency spectrum are investigated and correlated with thermal damage level of 2.25cr-1.0Mo steel using wavelet analysis. Those parameters tend to increase while thermal degradation proceeds. It also turns out that the wavelet technique can help to reduce experimental false call in data analysis.

Characteristics of Thermo-Acoustic Emission from Composite Laminates during Thermal Load Cycles

  • Kim, Young-Bok;Park, Nak-Sam
    • Journal of Mechanical Science and Technology
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    • v.17 no.3
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    • pp.391-399
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    • 2003
  • The thermo-acoustic emission (AE) technique has been applied for nondestructive characterization of composite laminates subjected to cryogenic cooling. Thermo-AE events during heating and cooling cycles showed a Kaiser effect. An analysis of the thermo-AE behavior obtained during the 1st heating period suggested a method for determining the stress-free temperature of the composite laminates. Three different thermo-AE types classified by a short-time Fourier transform of AE signals enabled to offer a nondestructive estimation of the cryogenic damages of the composites, in that the different thermo-AE types corresponded to secondary microfracturing in the matrix contacting between crack surfaces and some abrasive contact between broken fiber ends during thermal load cycles.

Unsteady heat exchange at the dry spent nuclear fuel storage

  • Alyokhina, Svitlana;Kostikov, Andrii
    • Nuclear Engineering and Technology
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    • v.49 no.7
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    • pp.1457-1462
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    • 2017
  • Unsteady thermal processes in storage containers with spent nuclear fuel were modeled. The daily fluctuations of outer ambient temperatures were taken into account. The modeling approach, which is based on the solving of conjugate and inverse heat transfer problems, was verified by comparison of measured and calculated temperatures in outer channels. The time delays in the reaching of maximal temperatures for each spent fuel assembly were calculated. Results of numerical investigations show that daily fluctuation of outer temperatures does not have a large influence on the maximal temperatures of stored spent fuel, so that fluctuation can be neglected and only daily average temperature should be considered for safety estimation using the "best estimation" approach.

Thermal Lifetime Estimation of Coil Used for Dry-type Transformer (건식변압기 코일의 열적 수명평가)

  • Kim, M.K.;Huh, D.H.;Kim, I.S.;Jang, J.Y.;Moon, B.C.;Go, J.C.
    • Proceedings of the KIEE Conference
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    • 2008.05a
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    • pp.131-132
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    • 2008
  • This paper describes a method to estimate the thermal lifetime of coil used in the dry-type molded transformer which is widely used in the domestic distribution system. In order to reduce the testing time, temperature accelerated aging test is planned. Finally, the thermal lifetime estimation method is composed of a temperature aging test and a cyclic test of temperature, humidly and lightning impulse voltage withstand test.

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Estimation of Empirical Equation on Thermal Conductivity (열전도계수 경험식의 국내 적용성에 관한 평가)

  • Kim, Hak-Seung;Lee, Jang-Guen;Kim, Young-Seok;Kang, Jae-Mo;Hong, Seung-Seo
    • Proceedings of the Korean Geotechical Society Conference
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    • 2010.09a
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    • pp.1151-1155
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    • 2010
  • Frost depth is one of important factors to design roadway structure, and it can be estimated with numerical simulation on thermal distribution through subgrade soils. Thermal conductivity is a key parameter for accurate prediction on thermal distribution, but there are few studies on thermal conductivity of subgrade soils in Korea. Thermal conductivity can be affected by several factors such as dry density, moisture content, and saturation degree based on previous researches. Two empirical equations to estimate thermal conductivity are applied to access the accuracy of these equations with experimental data. Results indicate that the equation can be used to estimate thermal conductivity with proper quartz fraction.

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Thermal Characteristic Estimation of NC Machining Center Bed following Rib Structure (리브 구조에 따른 머시닝센터 베드의 열적 특성 평가)

  • Kim, Yang-Jin
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.19 no.6
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    • pp.746-752
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    • 2010
  • Rib structure has been used to bed and column of machine tool to heighten weight stiffness ratio, cost performance and weight saving. In this paper the bed rib structure was estimated with thermal characteristics. Using superposition principle, machine tool designer can describe every complicated heat generation in the machine tool thermal source. As thermal characteristics, thermal deformation of guide rail and column and Maximum-minimum temperature variation were selected. The size, configuration and direction against the thermal loading surface operated to the thermal characteristics. The DB chart was made following rib structure estimating thermal characteristics. With superposition principle and DB chart, machine tool designer can prognosticate the thermal characteristics without FEM analysis to every bed rib structure.

Development of the Soil Thermal Property and Temperature Measurement System for the Real-time Ampacity Estimation of Underground Power Cables (실시간 지중 전력케이블 용량 평가를 위한 토양 열 특성 및 온도 측정 시스템 개발)

  • Jeong, Seong-Hwan;Kim, Dae-Kyeong;Choi, Sang-Bong
    • Proceedings of the KIEE Conference
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    • 2002.07a
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    • pp.22-24
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    • 2002
  • This paper introduces the real-time soil thermal property analyzer and temperature measuring system which is combined with radio telecommunication technique. To measure the thermal parameters in real-time, the radio telecommunication technique are used the personal communication service (PCS) which is in the world-wide serviced commercially firstly by CDMA. The thermal property analyzer has an ability of measuring thermal resistivity, thermal diffusivity and thermal stability. To estimate the soil thermal properties, the curve fitting algorithm by means of the least square method are used. TCP/IP protocol and MTM are used to install the real-time soil thermal property and temperature measurement system at multiple locations along routes of the underground power cables and to reduce the cost of telecommunication.

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An Estimation of the Temperature-dependent Thermal Conductivity for Hybrid-fiber Reinforced Shield Tunnel Lining (하이브리드 섬유보강 쉴드터널 라이닝의 온도의존적 열전도도 추정)

  • Lee, Chang Soo;Kim, Yong Hyok
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.16 no.4
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    • pp.99-106
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    • 2012
  • This study presents estimation method of temperature-dependent thermal conductivity by using solution of inverse heat conduction problem. Time and depth temperature distribution data from full-scale fire test were used for estimating temperature-dependent thermal conductivity on hybrid-fiber reinforced shield tunnel lining. At short heating time, estimated thermal conductivity sharply decreased within $100^{\circ}C$. On the other hand, it reflected thermal properties of concrete and effect of steel fiber at heating time of measured maximum heating temperature. Thus arbitrary time should be determined to estimate temperature-dependent thermal conductivity in time zone of measured maximum heating temperature. Estimated temperature-dependent thermal conductivity is similar to results of other study.