• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.5
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• pp.339-345
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• 2016

In this study, we numerically investigate the thermal performance of an enhanced radial heat sink with a perforation and chimney structure. We estimate the thermal performance of the enhanced radial heat sink, and compared it with that of a conventional radial heat sink. The results show that the radial heat sink with perforation has a higher thermal performance when either of the diameter and the number of perforations is high. With regards to the radial heat sink with a chimney structure, we investigate primarily the effect of the fin number, and the spacing between the chimney and the base plate on the thermal performance. The results show that there are optimal values for the fin number and the spacing between chimney and base plate. In addition, the enhanced radial heat sinks have maximum thermal performance when facing upward ($0^{\circ}$), while it has worst performance when facing sideward ($90^{\circ}$). The perforation and chimney are shown to cause thermal performance enhancements of 17% and 20%, respectively, compared with a conventional radial heat sink. The proposed method is useful for starting business, and is useful in terms of venture and entrepreneurship.

• Journal of computational fluids engineering
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• v.18 no.1
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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.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.4
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• pp.385-390
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• 2012

A radial heat sink, adopted to LED(light emitting diode) downlight, was optimized. Discrete transfer radiation model (DTRM) was used to calculate radiation heat transfer, and numerical model was verified with experimental results. The effects of number of fin, long fin length and middle fin length on overall thermal resistance and radiation heat transfer were analyzed. As the emissivity increased, thermal resistance decreased due to the increment of radiation heat transfer. The radial heat sink was optimized and optimum number of long fins is 19~28, optimum length of long fin is about half of radius of heat fink and optimum fin ratio is 0.4~0.7.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1172-1176
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• 2009

In the present study, natural convection over a heat sink with a horizontal circular base and rectangular fins was numerically analyzed. To calculate natural convection heat transfer, the assumptions of ideal gas and laminar flow were made for air. Flow patterns around the heat sink were chimney-like. The resultant temperature distribution on the circular base appeared almost uniform. Parametric studies were performed to compare the effects of fin length, fin height, the ideal number of fins, and heat flux on the average temperature of a heat sink and the average heat transfer coefficient from the heat sink array. Correlation to predict the average Nusselt number was presented.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.5
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• pp.467-472
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• 2011

The heat transfer over a radial heat sink, adapted for LED (light emitting diode) downlights, was experimentally and analytically investigated. We added radiation heat transfer into a previous calculation that neglected this factor. The numerical results agreed well with experimental results. Parametric studies were performed to compare the effects of the geometric parameters (fin length, fin height, ideal number of fins) and the operating parameter (heat flux) on the average heat-sink temperature from the heat-sink array. We found the fin length that maximizes the heattransfer performance. As the emissivity increased, the effect of geometric parameters on the radiation heat transfer decreased.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.1052-1065
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• 2024

Advanced Pressurized Water Reactors (APWRs) and Boiling Water Reactors (BWRs) employ a suppression pool as a heat sink to prevent containment overpressure. Steam can be discharged into the pool through multi-hole spargers or blowdown pipes in both normal and accident conditions. Direct Contact Condensation (DCC) creates sources of momentum and heat. The competition between these two sources determines the development of thermal stratification or mixing of the pool. Thermal stratification is of safety concern as it reduces the cooling capability compared to a completely mixed pool condition. In this work we develop a scaling approach to prediction of the thermal stratification in a water pool induced by steam injection through spargers. Experimental data obtained from large-scale pool tests conducted in the PPOOLEX and PANDA facilities, as well as simulation results obtained using validated codes are used to develop the scaling. Two injection orientations, namely radial injection through multi-hole Sparger Head (SH) and vertical injection through Load Reduction Ring (LRR), are considered. We show that the erosion rate of the cold layer can be estimated using the Richardson number. In this work, scaling laws are proposed to estimate both the (i) transient erosion velocity and (ii) the stable position of the thermocline. These scaling laws are then implemented into a 1D model to simulate the thermal behavior of the pool during steam injection through the sparger.