• Title/Summary/Keyword: 일정열유속

Search Result 72, Processing Time 0.027 seconds

Heat transfer of Mixed convection in rectangular space with constant heat flux (일정 열유속의 열원을 갖는 사각공간의 혼합대류 열전달)

  • 조대환
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.23 no.4
    • /
    • pp.552-558
    • /
    • 1999
  • Ventilation of the marine engine room is very important for the health of the workers as well as the normal operation of machines. To find proper ventilation conditions of this engine room numerical simulation with a standard k-$\varepsilon$model was carried out. In the present study the marine engine room is considered as a closed space with a heat source and forced ventilation ducts. The injection angle of air supply is found to be important. Injection with a downward angle depresses recirculation flow causing a strong stream in the wider space of the room Ventilation and removal of the released heat are promoted with this pattern, There is a possibility of local extreme heating at the upper surface of the engine when supply and exhaust ports of air are in bilateral symmetry.

  • PDF

Numerical Study on Pulsatile Flow and Heat Transfer in a Curved Tube with Constant Heat Flux (일정 열유속을 받는 곡관내에서의 맥동 열유동에 관한 수치적 연구)

  • 백영렬;이재헌;오명도
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.18 no.4
    • /
    • pp.1031-1038
    • /
    • 1994
  • Characteristics of pulsatile flow and heat transfer have been studied numerically in the constant heat flux curved tube with periodic pressure gradient. As the Womersley number increases, the phase difference between the pressure gradient and the cross section averaged axial velocity becomes larger. In case of the Womersley number $\beta = 2$, when cross section averaged axial velocity reaches periodic state with time, the reverse and the natural flow coexist at phase angle, $\lambda = 1.44\pi$ and $\lambda =1.96\pi$. For all the Womersley numbers of present investigation, the time variation of wall temperature near inner wall is higher than that of near outer wall, independent of phase angle.

Heat Dissipation of Cylinder Head of Reciprocating Internal Combustion Engine (왕복동 내연기관 실린더 헤등의 방열에 관한 연구)

  • Kim, K. C.
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.8 no.1
    • /
    • pp.71-78
    • /
    • 1984
  • 본 논문은 왕복동 내연기관의 방열에 관한 연구의 하나로서 디이젤 기관 실린더 헤드와 흡 배기 밸브의 온도 분포와 열유속의 분포를 구한 것이다. 방열 해석은 기관의 정상 작동된 다음의 실린 더 헤드의 열부하가 일정하다고 생각하여 실린더 헤드의 밸드 시이트 양단의 온도와 연소 가스 배출 온도, 흡기 및 냉각수 온도를 측정하고 온도분포 및 열유속을 유한요소법을 적용하여 구하 였다. 본 연구의 결과 실린더 헤드 및 밸브의 과부하는 밸브의 경우에는 밸브 헤드 중심과 밸브 헤드 중심 부근에서 일어나며, 실린더 헤드의 경우에는 헤드 중심부 표면에서 발생하였다. 흡 배 기 밸브 및 물재킷부의 온도 분포 및 열유속의 분포를 주어진 냉각수 온도 조건에 대하여 구한 후 이들을 비교 검토 하였다.

단상 열사이폰 루프의 작동특성에 관한 연구

  • 이진호;김태열;설신수
    • Transactions of the Korean Society of Mechanical Engineers
    • /
    • v.14 no.4
    • /
    • pp.960-970
    • /
    • 1990
  • 본 연구에서는 단상 밀폐 사각형 열사이폰 루프에서 가열부는 일정 열유속으 로 가열되고 냉각부는 일정온도로 냉각될 경우에 대해 루프 경사각도, 종횡비, 작동유 체 종류 및 관 직경변화에 대한 유동 및 온도변동 특성과 이에따른 전열성능 및 안정 작동범위를 실험적으로 조사하였다.

Measurement of Critical Heat Flux Using the Transient Inverse Heat Conduction Method in Spray cooling (비정상 열전도 역산법에 의한 분무냉각 임계열유속(CHF)의 측정에 관한 연구)

  • Kim, Yeung Chan
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.40 no.10
    • /
    • pp.653-658
    • /
    • 2016
  • A study on the measurement of critical heat flux using the transient inverse heat conduction method in spray cooling was performed. The inverse heat conduction method estimates the surface heat flux or temperature using a measured interior temperature history. The effects of the measuring time interval and location of temperature measurement on the measurement of critical heat flux were primarily investigated. The following results were obtained. The estimated critical heat flux decreased as the time interval of temperature measurement increased. Meanwhile, the effect of measurement location on critical heat flux was not significant. It was also found, from the experimental results, that the critical superheat increased as the measurement location of thermocouple neared the heat transfer surface.

Experimental Investigation of the LRE Thrust Chamber Regenerative Cooling(II) (액체로켓엔진 추력실의 재생냉각에 관한 실험적 연구(II))

  • Kim Jung-Hun;Jeong Hae-Seung;Park Hee-Ho;Chung Yong-Gab;Kim Sun-Jin
    • Journal of the Korean Society of Propulsion Engineers
    • /
    • v.8 no.3
    • /
    • pp.1-9
    • /
    • 2004
  • We conducted the firing test with the regenerative cooling LRE and calculated the heat flux from measured coolant temperature, that was compared with the heat flux predicted by previously developed numerical analysis method. The difference between the measured heat flux and the numerical calculation value was within nine percents. Therefore, developed numerical analysis method can be applied to the design/fabrication of a real LRE system. and, it was investigated that combustion pressure and mixture ratio have an Influence on the heat flux with a constant relation.

Transient Analysis of Pressure Behavior of Cryogenics in Closed Vessel (극저온 저장용기의 내부압력 거동에 대한 비정상해석)

  • 강권호;김길정;박영무
    • Journal of Energy Engineering
    • /
    • v.5 no.1
    • /
    • pp.19-27
    • /
    • 1996
  • Self-pressurization of cylindrical container of cryogen is numerically analyzed. The container is axi-symmetric and heated from side wall with constant heat flux. Natural convection by external heat flux is studied numerically using finite difference method. Oxygen, nytrogen and hydrogen are working fluids in this paper. Liquid is considered incompressible fluid and vapor is assumed to behave as gas meeting with virial equation of gas. The Second virial coefficients of gas are obtained from Lennard-jones model. The important variables which have effects on self-pressurization are external heat flux, heat capacity of wall and initial ullage in container. The most important variable of them is external heat flux. The pressure rise calculated from the virial gas model is slightly different from that calculated using Ideal gas model for oxygen.

  • PDF

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

  • Yoo Joo-Sik
    • Journal of computational fluids engineering
    • /
    • v.4 no.2
    • /
    • pp.1-8
    • /
    • 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.

  • PDF

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

  • 유주식;엄용균;김용진
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
    • /
    • v.12 no.8
    • /
    • pp.755-762
    • /
    • 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.

  • PDF

Effect of Fire Fighters' Turnout Gear Materials Air Gap on Thermal Protective Performance (소방보호복 소재의 공기간극이 열보호 성능에 미치는 영향)

  • Lee, Jun-Kyoung;Kwon, Jung-Suk
    • Fire Science and Engineering
    • /
    • v.28 no.4
    • /
    • pp.97-103
    • /
    • 2014
  • To ensure adequate protection from the risk of burns, fire fighter's turnout has a composite of more than three components and air gaps between layers of materials. During the flame exposure, radiation and convection heat transfer occurs in the air gap, thus the air gap acts as a thermal resistance with non-linear characteristics. Therefore, in this study, the experiments were performed to identify the effect of various air gap width (0~7 mm) on the thermal protective performance of fire fighter's clothing. The temperatures on each layer and RPP (Radiant Protective Performance, the most effective index representing the thermal protective performance) were measured with various incident radiant heat fluxes. The temperature at the rear surface of the garment decreased and RPP increased with increasing air gap width because the thermal resistance increased. Especially, it could be found that RPP value and air gap width has almost linear relation for the constant incident heat flux conditions. Thus relatively simple RPP predictive equation was suggested for various incident heat flux and air gap conditions.