• 제목/요약/키워드: Convection condition

검색결과 294건 처리시간 0.028초

열전달을 이용한 엔진오일 열화 감지 방법 (A Method for Detecting Engine Oil Deterioration using Heat Transfer)

  • 김형표
    • 센서학회지
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    • 제13권2호
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    • pp.139-143
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    • 2004
  • This paper presents a method that the engine oil condition is detected using a natural convection heat transfer in a engine oil. A sensor circuit maintains a constant temperature difference between a heat plate and engine oil for detecting a natural convection heat transfer rate on the constant temperature. The natural convection heat transfer rate is measured by a current through the heat plate of the sensor circuit. The sensor is tested by a fresh oil. 6,000 km and 10,000 km driven oil in the oil temperature range from $20^{\circ}C$ to $100^{\circ}C$. In the experimental result, when the current through the heat plate is altered by variation of a engine oil temperature and flows driven oil more than fresh oil, the sensor could inform a engine oil deterioration to a car driver.

일정 열유속 실린더를 갖는 수평 환형 공간에서의 공기의 이중 자연대류 유동 (Dual Natural-Convective Flows of Air in a Horizontal Annulus with a Constant Heat Flux Cylinder)

  • 유주식
    • 한국전산유체공학회지
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    • 제4권2호
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    • pp.1-8
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    • 1999
  • Natural convection in a horizontal annulus with the inner cylinder heated by the application of a constant heat flux and the isothermally cooled outer cylinder is considered, and the transition of flows and the bifurcation phenomenon are numerically investigated for air with Pr=0.7. The zero initial condition always induces a crescent-sheped eddy flow. A bicellular flow in which the fluid descends along the vertical central plane of the annulus can be obtained at high Rayleigh number by introducing artificial numerical disturbances. Dual solutions are found above a certain critical Rayleigh number. Hysteresis phenomena have not been observed.

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담금 냉각되는 LED 조명엔진의 열특성에 대한 연구 (Study on the Thermal Behavior of Immersion Cooled LED Lighting Engines)

  • 김경준
    • 동력기계공학회지
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    • 제18권3호
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    • pp.87-92
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    • 2014
  • This study is aimed at investigating the thermal behavior of immersion-cooled high power LED lighting engines. 3D CFD models have been generated for the numerical analysis. Five cases in terms of the configuration of LED chips have been explored for various passive cooling conditions of the lighting engine, i.e., the natural air convection with a lens, the natural air convection without a lens, the deionized water-immersion cooling condition with a lens. The numerical study reveals that the deionized water-immersion cooled lighting engine has nearly twice better thermal performance than the natural air convection cooled lighting engine containing a lens. The investigation has also demonstrated that the four chips configuration has the better thermal performance than the single chip configuration.

열원이 부착된 수평 평판에서 복합 열전달에 관한 연구 (A Study on the Conjugate Heat Transfer from Horizontal Plate with Protruding Heat Source)

  • 김병철;주동인
    • 설비공학논문집
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    • 제14권6호
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    • pp.512-518
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    • 2002
  • The real chip and similarity model were used to investigate the thermal behavior and velocity distribution of air from the heat source with the location and the amount of heat experimentally and numerically, and compared. The heat generated in the block is not cooled by convection and show the high temperature by the stagnation of heat flow. After maintaining the high temperature of block by the natural convection, the sudden drop of temperature with the air flow was shown in the channel but the decreasing rate was small with the time. The inward block was effected by infinitesimal air flow generated between block and channel and outward block was effected by the entry condition.

발열 전도체가 존재하는 밀폐계 내부의 자연대류 현상에 대한 수치적 연구 (A Numerical Study of Natural Convection in a Horizontal Enclosure with Heat-Generating Conducting Body)

  • 이재룡;하만영
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2004년도 춘계학술대회
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    • pp.1177-1182
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    • 2004
  • The physical model considered here is a horizontal layer of fluid heated below and cooldabove with a heat-generating conducting body placed at the center of the layer. The body genrates a constant amount of heat as initial condition. Two-dimensional solution for unsteady natural convection is obtained using an accurate and efficient Chebyshev spectral methodology for various of Rayleigh number from $10^3$ to $10^6$. Multi-domain Technique is used to handle heat-generating conducting body. The results for the case of heat-generating body are also compared to those of adaibatic body.

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일정 열 유속으로 냉각되는 안쪽 실린더를 갖는 수평 환형 공간에서의 공기의 자연 대류 (Natural Convection of Air in a Horizontal Annulus with the Inner Cylinder Cooled by Constant Heat Flux)

  • 유주식;엄용균;김용진
    • 설비공학논문집
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    • 제12권8호
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    • pp.755-762
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    • 2000
  • Natural convection of air in a horizontal annulus with the inner cylinder cooled by the application of a constant heat flux and the isothermally heated outer cylinder is considered. The bifurcation phenomenon of flow patterns and the heat transfer characteristics are numerically investigated. The zero initial condition induces a unicellular flow in a half annulus. A bicellular flow consisting of two counter-rotating eddies in a half annulus can be obtained above a certain critical Rayleigh number. A transition from the bicellular to the unicellular flow occurs with a decrease in Rayleigh number. Hysteresis phenomena have not been observed. In the regime of dual flows, the overall Nusselt number of the bicellular flow is greater than that of the unicellular flow.

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일정 열유속으로 가열되는 수직원통 주위의 유체에서의 자연대류에 관한 연구 (On the Study of the Natural Convection in the Fluid near a Vertical Cylinder Heated with Uniform Heat Flux)

  • 이철재;김시범
    • 대한설비공학회지:설비저널
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    • 제17권4호
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    • pp.426-434
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    • 1988
  • Series expansion is applied to solve the laminar boundary layer equations for the problem of natural convection from vertical cylinder with uniform surface heat flux. The series in terms of transverse curvature parameter ${\xi}$ is extended to five terms and is well converged by applying the Shanks transform twice. In case of natural convection from a vertical cylinder heated with uniform surface heat flux, it is possible to consider the vertical cylinder as vertical plate under the condition of D/L${\geq}$A/$(Gr_L^*)^{1/5}$, where A is in the range of 5.7~55.2. Also, mean Nusselt number ${\overline{Nu_L}}$ can be represented as $C_1(Ra_L^*)^{1/5}$, where $C_1$ is a constant which depends on Pr and is in the range of 0.5~0.8.

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반도체 표면처리공정용 대면적 히터 플레이트의 열전달 특성에 관한 연구 (A Study on the Heat Transfer Characteristics of the Large Dimension Heater Plate for a Semiconductor Process)

  • 이윤용;강환국;문석환
    • 한국표면공학회지
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    • 제43권6호
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    • pp.309-314
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    • 2010
  • The numerical study for the effect of various factors that affect the temperature distribution of the process glass installed above the large rectangular heater plate was carried out. For the calculation, heat flux, distance between heat source and process glass plate, effect of vacuum condition and convection in a chamber were considered as important factors. The results showed that the temperature gradient on the glass was increased at the natural convection because of the buoyancy force increases due to the heated air. Also, the more heat flux and distance between the heater plate and glass increases, the more increasing the temperature gradient was. In the case of isothermal heating wall, the temperature variation was smaller than the uniform heat flux condition.

용접코팅된 연속주조 몰드의 열해석 (Thermal Analysis of Continuous Casting Welding-Coated Mold)

  • 이종선;김세환
    • 한국산학기술학회논문지
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    • 제2권1호
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    • pp.7-12
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    • 2001
  • 본 연구에서는 제철소에서 활발히 사용되고 있는 연속주조 몰드에 대하여 용접코팅을 실시한 후 주조시 열적거동을 규명하는 열해석을 수행하였다. 열해석을 수행하기 위하여 상용 유한요소해석 코드인 ANSYS를 활용하였으며 주조속도, 냉각조건, 막 열전도계수, 대류열복사, 하중조건 등을 고려하여 몰드 표면의 온도분포를 구하였다.

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Study on Flow Mixing Effects in a High-Speed Journal Bearing

  • Chun, Sang-Myung
    • KSTLE International Journal
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    • 제1권2호
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    • pp.76-82
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    • 2000
  • Turbulence in journal bearing operation is examined and the thermal variability is studied for isothermal, convective and adiabatic conditions on the walls under aligned and misaligned conditions. Also, the effects of a contraction ratio at the cavitation region and the mixing between re-circulating oil and inlet oil on the fluid field of oil film are included. An algorithm for the solution of the coupled turbulent Reynolds and energy equations is used to examine the effects of the various factors. Heat convection is found to play only a small role in determining friction and load under no mixing condition. However, under realistic mixing condition, the heat convection cannot be ignored. The wall temperature and heat transfer have been found to be of secondary important factors to the mixing effectiveness at the groove and the final mixture temperature.

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