• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.182-187
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• 2006

This research presented the heat resistance characteristics of heat sink which is newly designed through the experiment. For the same volume and base plate of heat sinks, the experiment of heat transfer characteristics was conducted for forced convection of layered type heat sink. The heat transfer and pressure drop characteristics of the layered type heat sink were compared for the various kinds of fin pitches, fin heights and heights of heat sink. The results show that thermal resistance is decreased as the height of heat sink increases and the fin height and fin pitch decrease, From the experimental data of layered type heat sink, the correlation equation of Nusselt number was obtained as follows ; $$Nu=0.845{\cdot}Re^{0.393}{\cdot}(\frac{f_h}{D_h})^{0.160}{\cdot}(\frac{f_p}{D_h})^{0.372}{\cdot}(\frac{H_{hs}}{D_h})^{-0.942}$$

• Advances in aircraft and spacecraft science
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• v.5 no.4
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• pp.411-430
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• 2018

This computational study examines the augmentation of classic 2-D Rayleigh-$B{\acute{e}}nard$ convection by the addition of periodically-spaced transverse fins. The fins are attached to the heated base of the cavity and serve to partition the cavity into 'units' with different aspect ratios. The respective impacts upon heat transfer of the fin configuration parameters - including spacing, height, thickness and thermal conductivity - are systematically examined through numerical simulations for a range of laminar Rayleigh numbers (0 < Ra < $2{\times}10^5$) and reported in terms of an average Nusselt number. The selection of the low Rayleigh number regime is linked to likely scenarios within aerospace applications (e.g. avionics cooling) where the cavity length scale and/or gravitational acceleration is small. The net heat transfer augmentation is found to result from a combination of competing fin effects, most of which are hydrodynamic in nature. Heat transfer enhancement of up to $1.2{\times}$ that for a Rayleigh-$B{\acute{e}}nard$ cavity without fins was found to occur under favorable fin configurations. Such configurations are generally characterized by short, thin fins with half-spacings somewhat less than the convection cell diameter from classic Rayleigh-$B{\acute{e}}nard$ theory. In contrast, for unfavorable configurations, it is found that the introduction of fins can result in a significant reduction in the heat transfer performance.

• 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.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.1
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• pp.117-123
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• 2001

In present study a methodology has been developed and applied for the optimum design and performance evaluation of microchannel heat sinks. The optimum design parameters include channel number and fin thickness. For a trial model of 127mm in length, 52.5mm in width, 16mm in height and 2.5mm in base thickness, the optimum channel number and the fin thinckness have been determined to be of 194 and 0.08359mm, respectively in laminar flow region. Performance of the optimally designed microchannel heat sinks has been compared with those having 50% and 150% of the number of channels. The results showed that the 50% and 150% designs increased the pumping power by 200% and 150%, respectively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.4
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• pp.343-350
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• 2015

The natural convection heatsink is the most commonly used cooling device, especially for high-power LED lights, because of its reliability and low long-term cost. High power LED lights are generally used in an inclined configuration for street lamps and security lamps. However, it was difficult to estimate the thermal performance of an inclined heatsink, because the results from previous studies are not applicable to the inclined configuration. In this study, we measured the thermal performance of an inclined cylindrical heatsink with plate fins. Various fin numbers, fin heights, base temperatures, and inclination angles ($30^{\circ}$ and $60^{\circ}$) were examined. Based on the experimental results, the Nusselt number correlation is presented. This correlation is applicable when the Rayleigh number, ratio of the fin height to cylinder diameter, and fin number are in the ranges 100,000-600,000, 1/6-1/2, and 9-72, respectively.

• Korean Journal of Ichthyology
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• v.19 no.1
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• pp.57-65
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• 2007

A new species of the rajid genus Okamejei is described from a single specimen (295 mm TL) from off Shantou, Gwangdong in the South China Sea. The new species differs from all other congeners in the following combination of characters: snout pointed, dorsal head length 6.7 times interorbital width, tail moderately wide and long, its length 48.5% TL, interdorsal distance less than length of first dorsal fin base, postdorsal tail short as 5.8% TL, small evenly distributed dark brownish spots, without ocelli on dorsal surface of disc, pores of ampullae of Lorenzini on ventral surface distributed from snout tip to distal end of metapterygium, scapulocoracoid high, its height about 1.4 times rear corner height, trunk vertebrae 23, predorsal tail vertebrae 50 and pectoral fin radials 96.