• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.3 no.2
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• pp.147-156
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• 1999

A numerical simulation has been carried out for the performance characterization of heat sinks in electronic equipment. Heat transfer characteristics have been analyzed for various design parameters including the shape of heat sink, thickness of fin base and fin pitches. A commercial program called Flotherm has been employed for the numerical calculation. Optimal design of the heat sink has been persued which is closely related with the reduction of heat resistance involved in conduction and convection of heat.

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.5
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• pp.1706-1716
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• 1991

본 연구에서는 혼합대류하는 연직원통휜 열전달에 미치는 복사효과에 Rossel- and 근사해법을 도입한 층류 경계층방정식과 휜 전도방정식을 동시에 해석하여 복사 -전도매개변수(radiation-conduction parameter) M, 대류-전도 매개변수(convectionc- onduction parameter) N$_{c}$, 부력매개변수(buoyancy force parameter) R$_{i}$ 그 리고 횡곡률 매개변수(transverse curvature parameter) .lambda.를 계산 파라미터로 하여 휜 최적설계의 기본이 되는 총열전단률, 무차원 국소등가열전달계수, 무차원 국소열플 럭스 및 휜온도분포를 계산할 수 있는 일반성있는 algorithm을 개발하고 휜 성능에 관 한 결과들을 제공함으로써, 좀 더 완전한 복사 열플럭스를 도입한, 다음 연구를 위한 범용의 기초자료를 얻는데 본 연구의 목적이 있다.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.6
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• pp.1178-1185
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• 2011

In the present study, a recuperator is suggested to improve the thermal efficiency of a micro gas turbine. Primary design parameters of the recuperator are determined from the ideal cycle analysis. The counter flow plate-fin heat exchanger with offset strip fins is chosen as the type of the recuperator. In order to satisfy the design constraints which are the minimum effectiveness and the maximum pressure drop, the optimization for the internal structure of the recuperator is performed with varying the fin spacing and the fin height of offset strip fins. Also the effects of the thermal conductivity of fins and separation plates and the longitudinal heat conduction on the thermal performance of the recuperator are investigated.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.2
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• pp.279-286
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• 1987

An numerical and experimental study has been performed on natural convection heat transfer from a horizontal heat exchanger tube with a fin. At s bare tube, by increasing $C_{T}$ (tube conduction parameter), mean Nusselt number and outer wall temperature are apparently increased at $C_{T}$.leq.300, slightly increased at $C_{T}$>300 and they can be represented in an exponential function of $C_{T}$. Natural convection heat transfer characteristics for the tube with a fin at given Rayleigh number are well agreed by those for an isothermal cylinder at a modified Rayleigh number. The local fin Nusselt number of the tube with a downward fin is much higher than that of the tube with an upward fin. The comparisons between numerical and experimental results showed good agreement.reement.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.798-803
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• 2009

In this study, dimensionless correlations of frost properties (i.e. the thickness and surface temperature of frost) on heat exchanger fin with nonuniform temperature distribution are proposed from frosting experiments. We analyzed the local fin temperature distribution, frost thickness and frost surface temperature on a 2D fin; in the airflow direction and the direction perpendicular to airflow. As a result, the frost growth on the fin had a close relation with fin heat conduction. The dimensionless correlations for the average frost properties were expressed as a function of dimensionless temperature, humidity ratio, Reynolds number, and Fourier number. These correlations agreed well with experimental data with the error less than 14%.

• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.1
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• pp.1-9
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• 2003

The rectangular profile annular fin with fixed volume is optimized using 2-dimensional analytic method. For a base boundary condition, convection from fluid within the pipe to the inside wall of the pipe and conduction from the inside wall of the pipe to the fin base are considered. Heat loss from the fin tip radius is not ignored. The maximum heat loss, the optimum fin tip radius and the optimum fin half thickness corresponding to the maximum heat loss are presented as a function of fin base radius, Biot number over the fin surface and Biot number within the pipe. Results show 1) the maximum heat loss increases as both Biot number over the fin surface and Biot number within the pipe increase and as fin base radius decreases 2) the optimum fin thickness increases as Biot number within the pipe decreases or as fin base radius and Biot number over the fin surface increase.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.6
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• pp.1621-1628
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• 1990

Numerical solutions are presented for the heat transfer from radiating and convecting fins. Consideration is given to thin, annular fins attached to a tube surface for which the temperature is constant. Fin to fin, fin to base, and fin to environment radiative interactions are considered. It is assumed that the radiating surface is diffuse-gray, the environment is black, and the surrounding fluid is transparent. The radiation terms are formulated by using Poljak's net-radiation methoad. The mathematical description of the simultaneously heat transport by conduction, convection, and radiation leads to a nonlinear integro-differential equation. This has been solved for a wide range of the pertinent physical parameters by using finite difference method and iteration method based on the Newton-Raphson technique. The temperature distributions, heat transfer rates, fin efficiencies, and fin effectivenesses are presented in dimensionless form. The results definitely indicate that the use of fins leads to a significant increase in heat transfer compared with the unfinned tube.

• Solar Energy
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• v.6 no.1
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• pp.60-69
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• 1986

Two-dimensional finite difference numerical analysis is used to study conjugate natural convection heat transfer from a horizontal conducting tube with one vertical axial fin. By increasing dimensionless fin length ($L_F$), the mean total Nusselt number of the upward fin is slightly less than that of the downward fin at $L_F\;{\le}\;0.18$ and is higher than that of the downward fin at $L_F\;>\;0.18$. However comparing the upward fin and the downward fin with the no fin, the mean total Nusselt numbers of downward fin and upward fin at $L_F=0.30$ are increased approximately 4.01% and 5.51%, respectively. As Rayleigh number, Prandtl number and Biot number increase, the mean total and the mean tube Nusselt numbers are increased, but as wall thickness increases, the mean total and the mean tube Nusselt numbers are decreased. As the fin conduction parameter increases, the mean total Nusselt number is slightly increased because of increasing the mean fin Nusselt number.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.2
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• pp.382-390
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• 1992

The problem of natural convection from a vertical fin is solved by coupling the thermal diffusion equation in the fin to the constitutive equations of the ambient medium involving the radiation of the medium. The analysis is accomplished by employing an integral method. The governing equations for the problem are solved by shooting method based on the Runge-Kutta Scheme at Pr= 0.7. For the range of values of the fin parameter and the radiation-conduction parameter in the analysis, the numerical results show that the radiation effects play an important role in the heat transfer and enhance the heat transfer.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.256-261
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• 2008

In this study, frost behavior on two dimensional fins of a heat exchanger was experimentally investigated. Temperature distribution on a 2-D fin surface and frost properties were measured in the directions perpendicular to and parallel to airflow. The results indicated that the temperature gradient in the direction perpendicular to airflow was large because of fin heat conduction, while that in the direction parallel to airflow was very small. Frost thickness in the airflow direction decreased from the leading edge towards the trailing edge of the fin due to leading edge effect. The reduction rate of frost thickness in the airflow direction, however, was very small compared with that in the direction perpendicular to the airflow, as affected by the temperature distribution.