• Title/Summary/Keyword: Constant wall heat flux

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A Low-Reynolds Number Second Moment Closure for Turbulent Heat Fluxes (저레이놀즈수 2차 모멘트 난류 열유속모형 개발에 관한 연구)

  • 신종근;최영돈;이건휘
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.12
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    • pp.3196-3207
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    • 1993
  • A second moment turbulent closure for the turbulent heat flux near a wall is developed by modification of model constants in pressure interaction term as the variables of the turbulent Reynolds number using the universal properties of turbulent heat flux near the wall. The present model shows that model constant for the wall reflection term in pressure interaction is most important in modelling of the near wall heat flux. Fully developed pipe flows with constant wall heat flux are tested to validate the proposed model. In most of calculation region, the predicted turbulent properties agree better with the experimetal data than the results from standard algebraic heat flux model which use the uniform model constants.

Study on the Heat Flux Using Instantaneous Temperature as Height of Probe in the Combustion Chamber (연손실 순간온도 측저에 있어서 돌출높이에 따른 실험적 연구)

  • 이치우;김지훈;김시범
    • Journal of Advanced Marine Engineering and Technology
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    • v.25 no.2
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    • pp.395-402
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    • 2001
  • The gasoline engine tends to high performance, fuel economy, small-sized. Therefore, it is necessary to solve the problems on thermal load, abnormal combustion, etc, in the engine, Thine film instantaneous temperature measurement probe was made. And the manufactural method of probe was established. The instantaneous surface temperatures in the constant volume combustion chamber were measured by this probe and the heat flux was obtained by Fourier analysis. The authors measured the wall temperature of combustion chamber and computed the heat flux through the cylinder wall in order to understand the combustion characteristics depending on height of probe. For achieving this goal, the thin film instantaneous temperature probe was developed for analyzing the instantaneous surface wall temperature and unsteady heat flux on the constant volume combustion chamber.

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Combined Radiation and Natural Convection Heat Transfer in an Enclosure with a Constant Heat Flux at the Bottom (밑면에 균일 열유속이 존재하는 밀폐공간에서의 복사 - 자연대류열전달)

  • Kwon, Sun-Sok;Kwon, Yong-Il
    • Solar Energy
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    • v.12 no.2
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    • pp.28-42
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    • 1992
  • This investigation is carried out numerically for the two dimensional natural convection and surface radiation heat transfer in a square enclosure. The bottom wall is a constant heat flux at hot temperature and also top wall is isothermal at cold temperature whereas the left and right side walls are adiabatic except a transparent window on the right side partially. The exchange of radiant energy is obtained by the net radiation method and the shape factor by the crossed string method. The change in temperature and Nusselt number distributions of the walls due to the effect of the wall emissivity for various emissivities and for various dimensionless insolation energies are investigated. The dimensionless local convective heat flux and local radiative heat flux distributions in the wall except an adiabatic wall are also compared.

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Experimental Study of Collision Angle Effects on Heat Transfer During Droplet-wall Collision in Film Boiling Regime (막비등 영역에서 액적-벽면 충돌 시 충돌각도가 열전달에 미치는 영향에 관한 실험적 연구)

  • Park, Junseok;Kim, Hyungdae
    • Journal of ILASS-Korea
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    • v.22 no.3
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    • pp.129-136
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    • 2017
  • Effects of collision angle on heat transfer characteristics of a liquid droplet impinging on a heated wall above the Leidenfrost point temperature were experimentally investigated. The heated wall and droplet temperatures were $506^{\circ}C$ and $100^{\circ}C$, respectively, and the impact angle varied from $20^{\circ}$ to $90^{\circ}$ while the normal collision velocity was constant at 0.27 m/s. The droplet collision behaviors and the surface temperature distribution were measured using synchronized high-speed video and infrared cameras. The major physical parameters influencing upon droplet-wall collision heat transfer, such as residence time, wall heat flux, effective heat transfer area, heat transfer amount, were analyzed. It was found at the constant normal collision velocity that the residence time, wall heat flux and effective heat transfer area were hardly not changed, resulting in the almost constant heat transfer amount.

A Study of Heat Flux According to the Initial Temperature of Combustion Chamber and Blight of Probe in a Constant Volume Combustion Chamber (돌출높이와 초기온도 변화에 따른 연소실 벽면에서의 열유속에 관한 연구)

  • Lee Chi-Woo
    • Journal of Advanced Marine Engineering and Technology
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    • v.28 no.7
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    • pp.1055-1062
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    • 2004
  • As for the Production of internal combustion engines there has been further movement toward development of high Performance engines with improved fuel efficiency as well as a lightweight and a small size. These tendencies help to solve the problems in engines for example, such as thermal load. abnormal combustion and so on. In order to investigate these Problems, a thin film-type probe for measuring instantaneous temperature has been suggested. A method for manufacturing such a probe was established in this study The instantaneous surface temperature of a constant volume combustion chamber was measured by using this probe and the heat flux was obtained through Fourier analysis In order to thoroughly understand the characteristics of combustion. authors measured wall temperature of combustion chamber and calculated heat flux through a cylinder wall while varying the protrusion height of probe. For these Purposes, the instantaneous surface temperature probe was developed. thereby making possible the analysis of instantaneous temperature of wall surface and the detection of unsteady heat flux in the constant volume combustion chamber.

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
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    • v.18 no.4
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    • pp.1031-1038
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    • 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.

A Study of Hear Flux and Instantaneous Temperature According to the Initial Tamperature of Combustion Chamber in a Constant Volume Combustion Chamber (연소실 초기온도 변화에 따른 순간열유속에 관한 연구)

  • Lee, Chi-Woo
    • Journal of the Korean Society of Industry Convergence
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    • v.6 no.3
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    • pp.193-200
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    • 2003
  • In the production of internal combustion engines, there has been a move towards the development of high performance engines with improved fuel efficiency, lighter weight and smaller sizes. These trends help to answer problems in engines related to thermal load and abnormal combustion. In order to investigate these problems, a thin film-type probe for instantaneously measuring temperatures has been suggested. A method for manufacturing such a probe was established in this study. The instantaneous surface temperature of a constant volume combustion chamber was measured by this probe and the heat flux was obtained through Fourier analysis. In order to thoroughly understand the characteristics of combustion, the authors measured the wall temperature of the combustion chamber and computed heat flux through a cylinder wall while varying the protrusion height of the probe. For achieving the above goals, a instantaneous temperature probe was developed, thereby making possible the analysis of the instantaneous temperature of wall surface and the detection of unsteady heat flux in the constant volume combustion chamber.

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A Study of Heat Flux on the Height of an Instantaneous Temperature Probe in a Constant Volume Combustion Chamber (정적 연소기에서 순간온도 프로브의 돌출높이에 따른 열유속에 관한 연구)

  • Lee, C.W.
    • Journal of the Korean Society for Heat Treatment
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    • v.16 no.4
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    • pp.216-223
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    • 2003
  • In the production of internal combustion engines, there have been trends to develop the high performance engines with improved fuel efficiency, lighter weights and smaller sizes. This trends help to answer problems related to thermal load and abnormal combustion, etc. in these engines. In order to investigate these problems, a thin film-type probe and its manufacturing method for instantaneously measuring surface-temperatures have been proposed in this study, Instantaneous surface temperature of a constant volume combustion chamber was measured by this probe and heat flux was obtained by Fourier analysis. In order to thoroughly understand the characteristics of combustion, the authors measured the wall temperature of the combustion chamber and computed heat flux through a cylinder wall while varying the protrusion height of the probe have been measured. To achieve the above goals, a instantaneous temperature probe was developed, thereby making possible the analysis of the instantaneous temperature of wall surface and the detection of unsteady heat flux in the constant volume combustion chamber.

Heat Transfer Characteristics of Micro-encapsulated Phase-Change-Material Slurry (잠열 마이크로캡슐 슬러리의 열전달 특성)

  • Kim, Myoung-Jun;Park, Ki-Won
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.18 no.6
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    • pp.518-525
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    • 2006
  • The present experiments have been performed for obtaining the melting heat transfer characteristics of micro-encapsulated solid-liquid phase-change material and water mixture slurry flow in a circular tube heated with constant wall heat flux. The phase change material having a low melting point was selected for a domestic cooling system in the present study. The governing parameters were found to be latent heat material concentration, heat flux, and the slurry velocity. The experimental results revealed that the increase of tube wall temperature of latent microcapsule slurry was lower than that of water caused by the heat absorption of fusion.

Heat Transfer Characteristics of Micro-encapsulated Phase Change Material Slurry (잠열 마이크로캡슐 슬러리의 열전달 특성)

  • Park, Ki-Won;Kim, Myoung-Jun
    • Proceedings of the SAREK Conference
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    • 2005.11a
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    • pp.193-198
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    • 2005
  • The present experiments have been performed for obtaining the melting heat transfer characteristics of micro-encapsulated solid-liquid phase change material and water mixed slurry flow in a circular tube heated with constant wall heat flux. The phase change material having a low melting point was selected for a domestic cooling system in the present study. The governing parameters were found to be latent heat material concentration, heat flux, and the slurry velocity. The experimental results revealed that the increase of tube wall temperature of latent microcapsule slurry was lower than that of water caused by the heat absorption of fusion.

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