• 설비공학논문집
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• 제19권12호
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• pp.874-882
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• 2007

The effects of a guide fin blade on the flow characteristics in a ventilating axial fan were investigated experimentally. The guide fins were setup onto the pressure surface of the blade, and their effects on the flowrate were evaluated. Two types of the guide fin blade were designed. One is the stem fin blade, and the other is the radial fin blade. The stem fin is designed normal to the circumference of a circle, and the radial fin is designed along the circumference of a circle. The results from the guide fin blade fans are compared with that of the blade without guide fins. The position and the geometry of the radial fin setting up on the blade have an effect on the increase of flowrate with the minor sacrifice of rotational speed of the blades. The radial fin positioning at 0.84 times blade diameter shows highest performance in the flowrate. The increase of the blade weight resulting from applying the guide fins shows minor effect on the variation of rotational speed of the blades.

• 태양에너지
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• 제2권1호
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• pp.24-32
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• 1982

In this paper, temperature distributions in radial fin of rectangular profile for steady-state with no heat generation are obtained by one-dimensional analytical method, finite difference method and experiment respectively. Heat flow rate and fin efficiency from the fin model are obtained by analytical method. Consequently, temperature distributions in radial fin can certify that are similar to exact solution. From theoretical analysis, the effects according to heat flow rate and fin efficiency are related to variation of parameters which are fin thickness ${\delta}_o$, fin base temperature $T_o$, thermal conductivity K with same basic dimensions and the effects are studied and compared.

• 대한설비공학회지:설비저널
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• 제11권3호
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• pp.9-17
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• 1982

In this paper, temperature distributions in radial fin of hyperbolic profile for steady -state with no heat generation are obtained by one-dimensional analytical method, finite difference method and experiment respectively. Heat flow rate and fin efficiency from the fin model are obtained by analytical method. To compare the exact solutions obtained by theoretical analysis with the results obtained by finite difference method, cylindrical shape is selected. Particularly, equations of finite difference method for cylindrical shape with irregular boundary are rearranged and formulated. Consequently, temperature distributions in radial fin can certify that are similar to exact solutions. From theoretical analysis, the effects according to heat flow rate and fin efficiency are related to variation of parameters which are fin thickness ${\delta}_o$, fin base temperature $T_o$, thermal conductivity K with same basic dimensions and the fleets are studied and compared.

• 한국전산유체공학회지
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• 제18권1호
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• pp.63-68
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• 2013

The purpose of this study is to investigate the cooling performance of radial heat sink used for high power LED lightings by natural convection cooling with surrounding air. Experimental and numerical analyses are carried out together. Parametric studies are performed to compare the effects of geometric parameters in radial heat sink such as the number of fins, fin height, fin length, and thickness of fin base as well as the surface coatings of radial heat sink. In this study, the cooling of 60 W LED lamp is examined with radiative heat transfer considered as well as natural convection. Numerical results show the optimum condition when the number of fin is 40, heat sink height is 120 mm, fin length is 15 mm, and fin base thickness is 3 mm. The difference in temperature of the LED metal PCB is within $1^{\circ}C$ between numerical analyses and experimental results. Also, the CNT coating on the heat sink surface is found to increase the cooling performance significantly.

• 대한기계학회논문집B
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• 제36권4호
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• pp.385-390
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• 2012

본 연구는 LED 조명기구에 적합한 원형 히트싱크의 최적설계를 수행하였다. DTRM 복사 모델을 이용하여 자연대류와 복사 열전달을 수치적으로 해석하였고, 수치모델을 실험을 통하여 검증하였다. 휜 개수, 긴 휜 길이, 중간 휜 길이가 전체 열저항 및 복사 열전달에 미치는 영향을 조사하였고, 그 결과 방사율이 증가할수록 복사 열전달의 크기는 증가하여 열저항은 감소하지만, 인자 변화에 따른 전체 열저항의 경향성은 거의 일정하였다. 원형 히크싱크의 최적화를 수행하였고, 최적화된 긴 휜의 개수는 19~28 개, 긴 휜의 길이는 히트 싱크의 반지름의 1/2 이고, 휜의 길이 비는 0.4~0.7 사이의 값을 얻었다.

• 설비공학논문집
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• 제1권3호
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• pp.244-251
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• 1989

A numerical study has been performed on the natural convection heat transfer from a conducting tube with two axial fins to a surrounding cylinder. As increasing dimensionless fin length ($L_F$), the center of flow moves to the bottom of annulus and the recirculating flow rate is decreased. The maximum local Nusselt number of conducting tube appears at ${\theta}=180^{\circ}$ for $L_F=0.0$, but at ${\theta}=130^{\circ}$ for $L_F{\geq}0.3$ and that of outer cylinder appears at ${\theta}=13^{\circ}$ for $L_F{\leq}0.6$ but at ${\theta}=33^{\circ}$ for $L_F=1.0$. The fin temperature is decreased by increasing radial distance and the temperature distribution of the downward fin is generally less than that of the upward fin. By increasing fin length, the local Nusselt number of the upward fin appears negative values for $L_F=1.0$, but appears positive values for $L_F<0.8$, and that of the downward fin appears positive values.

• 대한기계학회논문집B
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• 제35권5호
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• pp.467-472
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• 2011

본 연구는 LED 조명기구와 같은 원형 모양에 적합한 원형 히트싱크의 주위의 열유동을 실험 및 해석적으로 분석하였다. 기존 복사 열전달을 고려하지 않은 상관식을 이용하여, 추가적으로 복사 열전달을 해석적으로 계산하였다. 본 해석 모델의 타당성을 실험적으로 확인하였다. 이 모델을 바탕으로 휜의 형상 및 열유속을 인자로 하여 히트싱크 평균 온도의 변화를 살펴보았다. 그 결과 열전달 성능을 최대로 할 수 있는 최적 휜의 길이가 존재하였고, 방사율이 클수록 형상 인자의 변화가 복사 열전달 변화에 미치는 영향이 상대적으로 감소하였다.

• 한국연소학회지
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• 제1권1호
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• pp.19-29
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• 1996

This study is to investigate the characteristics of heat transfer of a horizontal tube, with radial fins of various configuration, immersed in a high temperature fluidized bed. The experimental heat transfer variation is compared with that of a smooth tube. The finned tubes and smooth tube, with outside and inside diameter of 48.6mm and 30.6mm, are made of steel tubes. The depth of the fin is 5mm, the rake angles of fin are $25^{\circ},\;35^{\circ},\;45^{\circ}$ and the widthes of fin for each rake angle are 0mm, 1mm, 2mm and 3mm. A bed temperature is fixed at $880\;{\pm}\;10^{\circ}C$. A granular refractory(silica sand) is used as a bed material with mean particle diameters of 1.22mm and 1.54mm. The maximum heat transfer coefficient is achieved with the rake angle of $25^{\circ}$ and the width of 0mm for the mean particle size 1.22mm. The coefficient is 2.14 times larger than that for a smooth tube. The rake angle for the maximum heat transfer coefficient depends on the particle size of bed material. Also the transfer coefficient decreases as the width of fin increases.

• 대한기계학회논문집B
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• 제40권5호
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• pp.339-345
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• 2016

본 연구에서는 천공과 유동 가이드를 활용한 방사형 히트싱크의 자연대류 열전달 향상에 관해 수치적으로 탐구하였다. 천공과 침니 기반의 유동 가이드를 활용한 개선된 형상의 방사형 히트싱크의 성능을 평가하고, 기존의 방사형 히트싱크와 열 성능을 비교하였다. 연구 결과, 천공형 히트싱크는 연구범위 내에서 천공의 개수와 직경이 클수록 열 성능이 좋아짐을 알 수 있었다. 침니 기반의 유동 가이드를 활용한 히트싱크에 대해서는, 핀의 개수, 침니와 바닥면 사이의 거리의 영향을 분석하였다. 그 결과 핀의 개수와 침니와 바닥면 사이의 거리에 최적화된 값이 있다는 것을 확인할 수 있었다. 또한 히트싱크의 방향이 상 방향($0^{\circ}$)에서 최고의 열 성능을, 측 방향($90^{\circ}$)일 때 최악의 열 성능이 나타나는 것을 알 수 있었다. 천공형 히트싱크와 최적의 구조를 갖는 유동 가이드를 갖는 히트싱크는 기존의 방사형 히트싱크와 비교하였을 때, 각각 최대 17%, 20% 개선된 열 성능을 가짐을 알 수 있었다. 본 논문은 공학과 관련한 획기적인 아이디어를 제시함으로써 창업기술개발, 벤처 및 기업가정신 함양에도 중요한 의미를 지닐 수 있다.

• 소성∙가공
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• 제8권2호
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• pp.143-151
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• 1999

The twisting and extrusion process of the product with trapezoidal helical fin from the round billet is developed by the upper bound analysis. The twisting of extruded product is caused by the twisted die surface connecting the die entrance section and the die exit section linearly. In the analysis, the rotational velocity in angular direction is assumed by the multiplication of radial distance and angular velocity. The angular velocity is increased linearly by axial distance from the die entrance. The increase rate of angular velocity is determined by the minimization of plastic work. The results of the analysis show that the angular velocity of the extruded product increases with the die twisting angle, the reduction of area, and decreases with the die length, the friction condition.