• 수산해양기술연구
• /
• 제27권3호
• /
• pp.184-192
• /
• 1991

In many combustion systems, swirling combustion air is extensively applied as an aid for stabilization of high intensity combustion pocesses. Swirl, generally, causes significant effects on the flow field which, in turn, determines the size, shape, and stability of flames, and combustion intensity. The purpose of this study is to investigate the effect of swirls on flames produced from a model combustor designed in this paper. In order to impart swirls to the combustion air, a movable block swirl generator was used. Temperature distribution and radiative heat flux along the centerline of the swirling flame were measured. Data obtained from these swirl flows can be used as design data for high intensity or high efficiency combustion systems. The results obtained are summarized as follows: 1. Flame temperature profiles were measured at various swirl number. 2. The axial distance for maximum temperature from the centerline of burner increased as the swirl number increased. 3. Radiative heat flux increased as the swirl number and axial distance from burner increased.

• Journal of Mechanical Science and Technology
• /
• 제16권10호
• /
• pp.1346-1354
• /
• 2002

The purpose of this work is to study the effects of specularly reflecting wall under the combined radiative and laminar free convective heat transfer in an infinite square duct. An absorbing and emitting gray medium is enclosed by the opaque and diffusely emitting walls. The walls may reflect diffusely or specularly. Boussinesq approximation is used for the buoyancy term. The radiative heat transfer is evaluated using the direct discrete ordinates method. The parameters under considerations are Rayleigh number, conduction to radiation parameter, optical thickness, wall emissivity and reflection mode. The differences caused by the reflection mode on the stream line, and temperature distribution and wall heat fluxes are studied. Some differences are observed for the categories mentioned above if the order of the conduction to radiation parameter is less than order of 10$\^$-3/ fer the range of Rayleigh number studied. The differences at the side wall heat flux distributions are observed as long as the medium is optically thin. As the top wall emissivity decreases, the differences between these two modes are increased. As the optical thickness decreases at the fixed wall emissivity, the differences also increase. The difference of the streamlines or the temperature contours is not as distinct as the side wall heat flux distributions. The specular reflection may alter the fluid motion.

• 대한설비공학회지:설비저널
• /
• 제17권4호
• /
• pp.435-441
• /
• 1988

The purpose of this study is to apply the zone method expressions for a gray, absorbing, emitting, and linearly anisotropic scattering medium enclosed in an infinite plane layer to evaluate heat transfer applications. The medium is assumed to be homogeneous and has a refractive index of unity. The boundary surfaces are opaque and gray, diffusely emitting and reflecting at a constant temperature. Radiative equilibrium condition, combined conductive and radiative heat transfer, and thermal ignition are studied in terms of the governing parameters, and the results are compared with previous studies. Wall heat flux results agree well with those of others. Except for the minor discrepancies observed for some cases, temperature results also agree well with those of previous studies. Good agreement with results from other methods indicates the accuracy of the zone method as well as its compatibility with other modes of heat transfer.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 춘계학술대회
• /
• pp.1370-1375
• /
• 2004

This article investigates the heat transfer characteristics in a RTA system for LCD manufacturing and suggests a way to evaluate the quality of a poly-Si film from the thin film optics analysis. The transient and one-dimensional conductive/radiative heat transfer equation considering wave interference effect is solved to predict surface temperatures of thin films. In dealing with radiative heat transfer, a one-dimensional two-flux method is used and the ray tracing method is also utilized to account for the wave interference effects. It is assumed that each interface is assumed diffusive but the spectral radiative properties are included. It is found that the selective heating region exists for various wavelengths and consequently may contribute to heat the poly-Si film. Using the formalism of the characteristic transmission matrix, the lumped structure reflectance, transmittance, and absorptance are calculated and they are compared with experimental data of the poly-Si film during the SPC process via the FE-RTA (Field-Enhanced RTA) technology.

• 생물환경조절학회지
• /
• 제22권2호
• /
• pp.108-115
• /
• 2013

본 연구의 목적은 일중피복온실의 피복재에 대하여 우리나라 환경에 적합한 관류열전달계수를 산정하는 방법을 찾아내고 검증하여 다양한 온실조건 및 환경조건에서 관류열전달계수를 산정할 수 있는 모델을 제시하는 것이다. 온실내부 및 외부온도와 피복재 표면온도와의 상관관계를 분석한 결과 주간 및 야간 온도를 모두 고려하였을 때보다 야간온도만을 고려하였을 경우가 상관성이 훨씬 더 높은 것으로 나타났다. 피복재의 표면온도가 온실의 외부온도보다는 내부온도와 상관성이 더 높은 것으로 나타났다. 관류열전달계수를 산정하는데 사용된 5가지 종류의 대류 및 복사열전달계수 산정식을 비교한 결과 Kittas가 제안한 대류 및 복사열전달계수 산정식이 가장 적합한 것으로 나타났다. 피복재 표면온도의 측정값과 계산 값의 상관성을 분석한 결과 직선의 기울기는 1.009이고 절편은 0.001이며 결정계수가 0.98로 나타나 본 연구에서 제시된 관류열전달계수 산정모델이 신뢰성이 있음을 확인할 수 있었다. 온실내부로부터 피복재 내부표면으로 전달되는 열흐름량의 경우 모든 풍속구간에 대해 대류열전달량이 복사열전달량보다 더 컸으며 풍속이 증가할수록 그 차이가 증가하였다. 외부표면에서 손실되는 열흐름량의 경우 풍속이 낮을 때에는 대류열전달량에 비해 복사열전달량이 더 컸으나 풍속이 증가함에 따라 그 차이는 점점 줄어들어 풍속이 높을 때에는 대류열전달량이 더 커지는 것으로 나타났다. 피복재 외부 표면의 대류열전달량은 내부표면의 대류열전달량에 직선적으로 비례하여 증가하는 것으로 나타났다. 풍속이 증가함에 따라 관류열전달계수는 증가하고 피복재의 표면 온도는 감소하는 것을 확인할 수 있었고, 변화추세를 보면 관류열전달계수는 거듭제곱함수와 그리고 표면온도는 로그함수와 잘 일치하였다.

• 대한기계학회논문집
• /
• 제12권3호
• /
• pp.551-560
• /
• 1988

본 연구에서는 해석하려는 시스템의 유동 및 열전달 현상의 개념도를 Fig.1 에 나타내었다. 고체 입자는 윗부분 홈으로부터 분사되어, 선택적 투과면을 통해서 입사되는 복사열을 흡수 하며, 기체는 아래 또는 위의 홈 부분으로부터 들어와서 고체 입자와의 대류열전달로 가열이 된다. 기차게 아래 홈에서부터 분사되는 경우 대류에 의해 가열된 기체가 역성층화로 인해 부력을 받게 되어, 고체 입자의 하강 속도가 감 소할 때 입자의 체류 시간의 증가에 따른 복사열의 흡수효과에 대하여 고찰하였으며 입자의 크기, 투사 복사량, 분사속도, 입자의 질량유량 등을 파라미터로 하여 이들의 변화에 따른 영향을 규명하였다. 2-방연계를 고려한 2-방정식 모델을 구성하고 고체 입자에 대하여는 Lagrangian 방법으로 기술하였으며 수치해석에 있어 유한차분법을 도 입하고 두 상간의 상호연계는 PSI-Cell 방법을 이용하였고 복사 열유속은 2-유속 모델 (two-flux model)을 도입하여 계산하였다.

• 한국표면공학회지
• /
• 제46권5호
• /
• pp.208-215
• /
• 2013

The aim of the present study was to improve the radiative heat dissipation of aluminum alloy, Al 1050. Resin/CuO coating and Cu/CuO composite plating were applied on aluminum alloy to improve the radiative heat dissipation. Resin/CuO coating was made using thermosetting silicon resin and Cu/CuO composite plating was made in pyrophosphate copper plating bath. Radiant heat flux($W/m^2$) was measured by self-produced radiant heat measurement device to compare each specimen. The cross section of specimen and chemical bonding of surface were analyzed by FE-SEM, XPS and FT-IR. As a result, radiant heat of Resin/CuO coating was higher than Cu/CuO composite plating due to the adhesion with aluminum plate and the difference in chemical bonding. But, Both of them were higher than aluminum alloy. In order to confirm the result of experiment, aluminum plate, Resin/CuO coating and Cu/CuO composite plating sample were applied LED and measured the LED temperature. As a result, LED temperature of samples were matched previous results and confirmed coated samples were lower about 10 degrees than the aluminum alloy.

• 한국연소학회지
• /
• 제10권2호
• /
• pp.18-25
• /
• 2005

An experimental study has been conducted to evaluate the effects of reburning on $NO_x$ reduction and also to examine heat transfer characteristics from LPG flame. Experiments were performed in flames stabilized by a co-flow swirl burner, which was mounted at the bottom of the furnace. Tests were conducted using LPG gas as main fuel and also as reburn fuel. The effects of reburn fuel fraction and injecting location of reburn fuel are studied. The paper reports data on flue gas emissions, temperature distribution in furnace and various heat fluxes at the wall for a wide range of experimental conditions. In a steady state, the total as well as radiative heat flux from the flame to the wall of furnace has been measured using a heat flux meter. Temperature distribution and emission formation in furnace have been also measured and compared.

• Journal of Biosystems Engineering
• /
• 제31권5호
• /
• pp.395-402
• /
• 2006

Mixed heat transfer in an indirected NIR (Near Infrared Ray) dry chamber was investigated numerical analysis. It is Important that the miked heat transfer effects on double parameters which the Reynolds number and the position of emit lamp. Reynolds number are based on the outer diameter of the cylinder range from 103 to $30{\times}105$. Four difference heat transfer regimes of behavior are apparent: forced convection and radiation on the outer surface of the cylinder, pure conduction, pure natural convection and radiation between lamp surface and inner surface of the cylinder. The temperature and flow patterns are illustrated by iso-contour lines for the double parameters. Also presented are results on the convective heat transfer flux and the radiative heat transfer flux as increased with Reynolds number.

• 대한기계학회논문집
• /
• 제16권10호
• /
• pp.1955-1962
• /
• 1992

본 연구에서는 무한 원형관 안의 복사에 참여하는 참여가스에 면을 도입시키 면, 참여가스로부터 원형관 벽면으로의 복사 열유속(radiatve heat flux)이 증진 또는 감소되는 현상을 연구하는 데 있다. 참여가스는 흡수, 방사 특성이 온도와 파장에 변하지 않는 회체가스(gray gas)이거나, 화석 연료 연소시 연소가스의 성분이며, 복사 에 참여하는, 수증기와 이산화탄소의 혼합물이다. 편의상, 이 가스를 실제가스(real gas)라 부르기로 한다.도입면은 동축 무한 원형관(coaxial Infinite cylinder)이다. 참여가스의 성분, 계의 직경, 동축 무한 원형관 사이의 직경비, 면의 방사율, 면과 가 스의 온도가 열전달 증진에 미치는 영향을 연구하고자 한다.