• 제목/요약/키워드: Unsteady-State Temperature

검색결과 93건 처리시간 0.026초

MOSS형 LNG 선박의 열공학적 특성에 관한 연구 (A study on the thermal characteristics of MOSS type LNG carrier)

  • 이세동;송성옥;이종원;김춘식;최두열
    • Journal of Advanced Marine Engineering and Technology
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    • 제22권1호
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    • pp.28-34
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    • 1998
  • This paper introduced the thermal characteristics of Moss Rosenberg Verft spherical tank type LNG Carrier. Especially described the temperature variation during cooling down condition. It is not easy task to calculate the temperature variation because of unsteady state condition. In this paper, computer simulation program is developed by using a Tomas Algorithm on unsteady state condition and compared with calculation results and experimental results on existing LNG Carrier voyage.

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탄소발열체의 외부유속 및 직경변화에 대한 비정상상태에서의 수치해석적 연구 (Numerical Analysis in Unsteady State on variation of Diameter and Environmental Velocity of Carbon Heating Source)

  • 배강열;이윤환;이상용;이칠순;김봉곤;이상철
    • 동력기계공학회지
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    • 제10권4호
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    • pp.25-30
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    • 2006
  • This paper represents the numerical analysis in unsteady state on the variation of diameter and environmental velocity of carbon heating source. In general heating system, the oil and sheath heater is widely used, but these systems have many problems. So, the heating source with carbon ingredient has been researched in many country about manufacture, thermal and electrical properties. In this research, the carbon heating source was studied through numerical analysis on several conditions of unsteady state, heat generation, diameter and environmental velocity. The temperature distributions at steady state are appeared as a non-proportional linear pattern with variations of environmental velocity due to the Nesselt number with convective heat flux is proportioned to 0.805 of Reynolds number. As the radius is increasing, the temperature distributions is appeared the minus tilt because of the environmental condition is cooling by constant temperature. So, the correlation equation between temperature at steady state and environmental velocity was obtained.

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케로신 동축 와류형 분사기의 정상 및 비정상 상태 화염구조 해석 (The steady and unsteady state computations on the flame structure for a Kerosene coaxial swirl injector)

  • 한상훈;김성구;김종규;최환석
    • 한국추진공학회:학술대회논문집
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    • 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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    • pp.31-34
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    • 2012
  • 케로신을 연료로 하는 동축 스월 분사기에 대해 정상 상태 및 비정상 상태의 연소 해석을 수행하였다. 난류연소 모델로 화학평형 상태로 가정하는 Non-premixed equilibrium 모델을 이용하였고, 고압의 조건에서 실제유체의 거동을 다룰 수 있도록 상태방정식으로 SRK(Soave-Redlich-Kwong) 상태방정식을 적용하였다. 해석을 통해 온도분포, OH 질량분율 등 정상 상태의 계산 결과와 시간 평균된 비정상 상태의 계산 결과를 비교하였고, 이들 간의 화염 구조가 서로 상이함을 확인할 수 있었다.

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드럼 브레이크 시스템의 비정상 열전달 해석 (Unsteady State Heat Transfer Analysis of Drum Brake System)

  • 이계섭;국종영;천인범
    • 한국자동차공학회논문집
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    • 제7권9호
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    • pp.172-181
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    • 1999
  • The brakes employed on commercial vehicles must be able to withstand three types of demanding services which are use-emergency stops from high speed, many repeated stops as in a delivery or bus route, and speed control in mountain descents. Two type of friction brakes are in use ; drum breaks and disc brakes. Drum brakes are of the internally expanding type in which two shoes fitted externally with friction material are forced outward against the inside of a rotating drum on the wheel unit. In this case, the Braking power is produced by the friction force between a drum and a lining, and is converted into heat. In this research an unsteady state heat transfer analysis for drum brake system of heavy truck has been performed by ABAQUS/standard code in the case of single-braking and the repeated braking condition. The temperature histories obtained by the finite Element analysis have been compared with the result calculated by the simplified formulation and the result obtained by the experiment of real vehicle conditions.

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정상 및 비정상 온도변화에 따른 린번 천연가스 자동차용 촉매의 정화성능 (Conversion Efficiency of Catalyst for Lean-bum Natural Gas Vehicles with Steady and Unsteady State Temperature Change)

  • 최병철;정우남;박봉애;이춘희;이장희;윤 정 의
    • 한국자동차공학회논문집
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    • 제13권3호
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    • pp.123-130
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    • 2005
  • In this study, we evaluated the CH4 and CO conversion efficiencies over the oxidation catalysts for natural gas vehicle with lean-burn system. On the fresh catalyst, the conversion efficiency was increased when the loading of precious metal was increased. On the aged catalyst, the conversion efficiency was decreased as increasing the excess air ratio. We could confirm the measuring conversion efficiency of the unsteady state with the FTIR and that of steady state with the GC The temperature increasing ratio of unsteady state is acceptable from 3$^{\circ}C$/min. to 15$^{\circ}C$/min. for the evaluation of catalyst conversion performance , which has within the 4$\%$ of the difference of conversion efficiency. We observed a physical behavior of the thermal aged catalyst's surface using TEM and BET device. It was found that the precious metal was grown to the micro-scopic size by thermal aging process.

Effects of Surface Radiation on the Unsteady Natural Convection in a Rectangular Enclosure

  • Baek, Seung-Wook;Kim, Taig-Young
    • International Journal of Aeronautical and Space Sciences
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    • 제3권1호
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    • pp.95-104
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    • 2002
  • Numerical solution of the full Navier-Stokes equation as well as the energy equation has been obtained for the unsteady natural convection in a rectangular enclosure. One side wall was maintained at very high temperature simulating fires. Especially the effect of surface radiation was taken into account. While the enclosed air was assumed to be transparent, the internal walls directly interacted one another through the surface radiation. Due to a significant temperature difference in the flow field, the equation of state was used instead of the Boussinesq approximation. It was found that the rapid heating of the adiabatic ceiling and floor by the incoming radiation from the hot wall made the evolution at thermo-fluid field highly unstable in the initial period. Therefore, the secondary cells brought about at the floor region greatly affected the heat transfer mechanism inside the enclosure. The heat transfer rate was augmented by the radiation, resulting in requiring less time for the flow to reach the steady state. At the steady state neglecting radiation two internal hydraulic jumps were clearly observed in upper/left as well as in lower/right comer. However, the hydraulic jump in the lower/right comer could not be observed for the case including radiation due to its high momentum flow over the bottom wall. Radiation resulted in a faster establishment of the steady state phenomena.

유리용융로의 시간종속 자연대류 (Time-dependent natural convection in a glass melting furnace)

  • 임광옥;이관수
    • 대한기계학회논문집B
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    • 제21권7호
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    • pp.919-927
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    • 1997
  • The main purpose of this study is to determine bifurcation as the primary instability of a glass melting furnace. Steady-state and unsteady characteristics of natural convection in the partially open cavity as appeared in a glass melting furnace is investigated by using numerical analysis. Three types of convection, such as steady laminar, unsteady periodic or unsteady quasi-periodic convection may occur according to the temperature difference between upper two isothermal surfaces along the depth of cavity in a glass melting furnace. In the temperature difference of 150-900 K between batch and free surface, the larger the temperature difference, the weaker the convection strength and unsteadiness. Since the glass viscosity is increasing exponentially in the lower temperature, the batch freezes the thermofluidic field especially below the surface of it. If the depth of cavity is 0.5 m, the bifurcation to time-dependent natural convection may occur in the range of 60-650 K. If that is 1.0 m, it may occur in the whole range of temperature difference.

RTS-SAREK을 이용한 사무용 건물의 나이트 퍼지 성능 평가 (Night Purge Evaluation Using the RTS-SAREK in Office Buildings)

  • 신동신;박성근;박영수;박지수;이진영
    • 설비공학논문집
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    • 제27권12호
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    • pp.633-638
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    • 2015
  • This study evaluates the capacity of night purging in office buildings to reduce the cooling load. RTS-SAREK is used to estimate the performance of night purging on the steady state. To overcome steady state RTS program limitations, we added unsteady heat transfer equations. When the ACH (Air Change per Hour) increases, the wall temperature decreases in both the steady and unsteady states. The unsteady heat transfer rate is different from the steady transfer rate, which validates the unsteady calculation. When ACH is low, the heat transfer rate increases continuously with time. When ACH becomes higher, the heat transfer rate increases and decreases with time. When ACH is quite high, there exists a large difference in the heat transfer rate between the steady and unsteady calculations, which emphasizes the importance of the unsteady calculation.

FEM APPROACH TO ONE DIMENSIONAL UNSTEADY STATE TEMPERATURE DISTRIBUTION IN HUMAN DERMAL PARTS WITH QUADRATIC SHAPE FUNCTIONS

  • Gurung, D. B.;Saxena, V. P.;Adhikary, P. R.
    • Journal of applied mathematics & informatics
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    • 제27권1_2호
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    • pp.301-313
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    • 2009
  • This paper presents a Finite Element Method (FEM) application to thermal study of natural three layers of human dermal parts of varying properties. This paper carries out investigation of temperature distributions in these layers namely epidermis, dermis and under lying tissue layer. It is assumed that the outer skin is exposed to atmosphere and the loss of heat due to convection, radiation and evaporation of water have also been taken into account. The computations are carried out for one dimensional unsteady state case and the shape functions in dermal parts have been considered to be quadratic. A Finite Element scheme that uses the Crank-Nicolson method is used to solve the problem and the results computed have been exhibited graphically.

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전기장 변화에 따른 3차원 비정상 상태 열전달 연계 해석에 관한 연구 (A Study on the 3-D Unsteady State Heat Transfer Coupled by Conductive Currents)

  • 곽이구;김홍건
    • 한국공작기계학회논문집
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    • 제17권1호
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    • pp.29-34
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    • 2008
  • A modeling technique for the 2-way coupling of heat transfer and conduction currents has been performed to inspire a combined analytical simulation. The 3-D finite element method is used to solve steady conduction currents and heat generation in an aluminum film deposited on a silicon substrate. The model investigates the temperature in the device after the current is applied. The conservation equation of energy, the Maxwell equations for conduction currents, the unsteady state heat transfer equation and the Fourier's law for heat transfer are implemented as a bidirectionally coupled problem. It is found that the strongly coupled temperature and time dependent heat equations give a reasonable results and an explicit solving technique.