• Elastomers and Composites
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• 제36권3호
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• pp.153-161
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• 2001

궤도차량의 고무패드는 상당한 크기의 진폭과 주파수를 가지고 반복되는 동적 변형을 받고 있으므로, 이로 인하여 열발생과 더불어 상당한 내부온도의 상승을 초래한다. 이러한 열발생은 고무 재료의 점탄성 특성에 기인한 것으로, 점성효과에 의하여 변형시의 기계적 에너지의 일부가 히스테리시스 루프의 면적에 해당되는 열에너지로 변환되기 때문이다. 발생한 열은 발산조건이 충분하지 못할 경우 내부온도의 상승을 초래하며, 온도가 과다할 경우에는 고무제품의 성능이나 수명에 중대한 장애요인으로 작용하게 된다. 본 연구에서는 전차 궤도고무에 작용하는 동적 하중에 근거하여 각 부품별 열발생률을 실험을 통하여 측정하고, 이를 입력자료로 하여 궤도패드에 발생하는 온도분포를 유한요소법으로 해석하였다.

• 한국자동차공학회논문집
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• 제10권3호
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• pp.166-175
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• 2002

Tank track rubbers, which undergo dynamic stresses and strains under various road conditions, leads to a result of considerable internal temperature rise due to the heat generation. Since rubber materials are not fully elastic, a part of the mechanical energy is converted into heat because of the hysteresis loss. Heat generation without adequate heat dissipation leads to heat build-up, i.e. internal temperature rise which, if excessive, exerts a bad influence upon the performance and the life of the tank track rubbers. The purpose of this paper is to predict temperature distributions of the rubber components off tank track subjected to complex dynamic loads under various read conditions. In steady state analysis temperature fields are displayed in contour shapes, and in unsteady analysis the temperature variations of some important nodes are represented graphically with respect to the running time of the tank.

• 한국화재소방학회논문지
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• 제34권2호
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• pp.54-63
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• 2020

전선 접속부 등에서 아산화동(Cu₂O)증식 발열에 의해 화재가 발생하는 것은 화재조사 전문가들에게 널리 알려져 있지만 아산화동증식 발열에 의한 화재사례를 구체적으로 분석하여 소개하는 논문은 거의 없다. 이 논문에서는 전기적인 접속부분의 발열에 의한 화재 통계와 아산화동증식 발열 현상과 특징을 분석한 후 아산화동증식 발열에 의해 대학실험실의 전선 접속부분에서 화재가 발생한 사례에 대해 구체적으로 분석하고 있다. 이 화재사례는 발화개소의 화재패턴 조사, 전선 접속부분에 대한 육안 조사, 3차원 CT 촬영 조사, 전원인가 시험, 실체현미경 조사, SEM과 EDS 분석을 통해서 전선 접속부분에서 아산화동 증식 발열로 인해 화재가 발생한 것으로 결론을 내릴 수 있었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.137-142
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• 1997

From the results of study on the electrical characteristics of heat-generation mortar used graphite as fine aggregates is summerized as following. The primary purpose of this study is the mixing ratio of graphite (35%, 50%/Sg), curing conditions (autoclave, steam, surface, underwater) and shape change (length, section of the electric heat-generation mortar). In case of the test condition with the steam curing condition appearance to most excellent heat-generation reproducibility. And temperature a coefficient of electric heat-generation mortar change from is in inverse proportion to the temperature a coefficient of direct proportion as the ratio of graphite mixing increased.

• 설비공학논문집
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• 제13권5호
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• pp.422-430
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• 2001

In the present study, an evaporative generation process of ammonia-water solution film on the vertical plate was analysed. For the utilization of waste heat, hot water of low temperature was used as the heat source. The continuity, momentum, energy and diffusion equations for the solution film and vapor mixture were formulated in integral forms and solved numerically. Counter-current solution-vapor flow resulted in the refrigerant vapor of the higher ammonia concentration than that of co-current flow. Eve the rectification of refrigerant vapor was observed near the inlet of solution film in counter-current flow. For the optimum operation of generator using hot water, numerical experiments, based on the heat exchange and generation efficiencies. revealed the inter-relationships among the Reynolds number of the solution film and hot water, and the length of generator. Enhancement of heat and mass transport in the solution film was found to be very effective for the improvement of generation performance, especially at high solution flow rate.

• 비파괴검사학회지
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• 제29권1호
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• pp.10-14
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• 2009

초음파 적외선 비파괴 열화상 검사기술의 발열 메커니즘은 정확히 규명되지 않았으나, 열-기계 연성효과와 결함 계면 사이의 마찰효과가 주요한 원인인 것으로 추정되고 있다. 본 논문에서는 피로균열을 갖는 알루미늄 합금 시험편에서 결함을 검출하고, 실험조건으로부터 각각의 메커니즘에 따라 온도 변화를 수치 예측하였다. 시험결과와 수치예측 결과로부터 발열의 주요한 원인이 마찰이라는 것을 밝혔다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2005년도 춘계 학술기술논문발표대회 논문집
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• pp.9-12
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• 2005

This paper investigated the temperature history of mass concrete mock up structure considering different heat generation by varying with mixture proportion. Setting time difference between high early strength mixture (E-P) and retarding mixture (R-F30) was 14.5hours. Incorporation of $30\%$ of fly ash contributed to $10^{\circ}C$ of hydration heat reduction. In generally used C and D combination, bottom concrete shows earlier hydration, while E-J combination showed reverse tendency and thus, this method can reduce the crack occurrence. Therefore, heat generation difference method has beneficial effect on reducing crack induced by hydration heat resulting from heat generation difference between surface and center section.

• 전기학회논문지
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• 제62권5호
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• pp.596-603
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• 2013

The increase of distributed power generation is closely related to interest in microgird including renuable energy sources such as photovoltaic (PV) systems and fuel cell. By the growing interest of microgrid all over the world, many studies on microgrid operation are being carried out. Especially operation technique which is core technology of microgrid is to supply heat and electricity energy simultaneously. Optimal microgrid scheduling can be established by considering CHP (Combined Heat and Power) generation because it produce both heat and electricity energy and its total efficiency is high. For this reason, CHP generation in microgrid is being spotlighted. In the near future, wide application of microgrid is also anticipated. This paper proposes a mathematical model for optimal operation of microgrid considering both heat and power. To validate the proposed model, the case study is performed and its results are analyzed.

• Korean Chemical Engineering Research
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• 제52권3호
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• pp.294-301
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• 2014

This study focuses on analysis and comparison of entropy generation in various cross-sectional ducts along with fully developed laminar flow and constant uniform wall heat flux. The obtained results were compared in ducts with circular, semicircular, and rectangular with semicircular ends, equilateral triangular, and square and symmetrical hexagonal cross-sectional areas. These results were separately studied for aspect ratio of different rectangular shapes. Characteristics of fluid were considered at average temperature between outlet and inlet ducts. Results showed that factors such as Reynolds number, cross section, hydraulic diameter, heat flux and aspect ratio were effective on entropy generation, and these effects are more evident than heat flux and occur more in high heat fluxes. Considering the performed comparisons, it seems that semicircular and circular cross section generates less entropy than other cross sections.

• Journal of Electrochemical Science and Technology
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• 제13권3호
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• pp.323-338
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• 2022

Heat generation and temperature of a battery is usually presented by an equation of current. This means that we need to adopt time domain calculation to obtain thermal characteristics of the battery. To avoid the complicated calculations using time domain, 'state of charge (SOC)' can be used as an independent variable. A SOC based calculation method is elucidated through the comparison between the calculated results and experimental results together. Experiments are carried for rapid resistive discharge of a large-capacitive lithium secondary battery to evaluate variations of cell potential, current and temperature. Calculations are performed based on open-circuit cell potential (SOC,T), internal resistance (SOC,T) and entropy (SOC) with specific heat capacity.