• Journal of Aerospace System Engineering
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• v.13 no.2
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• pp.66-72
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• 2019

The observation satellites which uses high heat-dissipating equipment such as synthetic aperture radar (SAR) satellites require a radiator to transmit heat from the equipment into outer space. However, during cold conditions it requires a heater to maintain the temperature of equipment within the allowable minimum limit when it is not in operation. In this study, we proposed a variable conductivity radiator that changes its thermal conductivity value through movement of the liquid metal between two reservoirs based on the temperature condition. This reduces the power consumption of the heater by limiting heat transfer path to the radiator in cold condition, while effectively transferring heat to the radiator during hot condition. The feasibility of the proposed radiator was validated through comparison of the thermal control performance with the conventional fixed conductivity radiator via a thermal analysis.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.10
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• pp.933-940
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• 2013

In this study, we evaluated the heat release performance of two extruded-type and two swaged-type heat sinks used in an inverter for solar power generation. The number of fins and heat transfer areas of the two swaged-type heat sinks, namely S-62 and S-98, are 62 and 98 and $2.8m^2$ and $5.3m^2$, respectively. Those for the two extruded-type heat sinks, namely, E-38 and E-47, are 38 and 47 and $1.8m^2$ and $1.9m^2$, respectively. The heat release fractions of S-62 and S-98 were measured as 82.7 % and 86.3 %, respectively. Those of E-38 and E47 were measured to be 79.6 % and 81.6 %, respectively. In this experiment, despite the mass flow rates of air entering the heat sinks being almost the same, the heat release fractions increased with heat transfer area. Furthermore, despite S-62's heat transfer area being 47.4 % higher than that of E-47, its heat release fraction was higher by only 1.3 %. We believe that this indicates the better heat transfer property of the extruded-type heat sink. S-98's heat release is only 4.4 % higher than that of S-62, but its heat transfer area is 89.3 % higher; this suggests that its heat transfer area need to be optimized.

• Journal of Energy Engineering
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• v.4 no.1
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• pp.31-41
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• 1995

본 연구에서는 일반 가정에서 많이 쓰이고 있는 15,000 Kcal/hr용량의 유류 보일러에 대한 제반 실험을 통하여 보일러 운전자료를 제공함은 물론 방열코일의 열교환 실험을 통하여 시중에 유통되고 있는 방열코일의 방열량 비교와 공기와 냉각수와의 열관류율을 비교함으로서 보일러 시공에 필요한 기초 자료를 얻었다. 연소에 필요한 급기량은 매연농도가 문제시 되지 않는 Smoke Scale No.가 1 이하인 공기비 1.45 이상으로 운전이 되어야 하며 송수온도는 t2=-0.0781XGw+85($^{\circ}C$)의 실험식으로 표시할 수 있다. 공기중에서 코일의 방열량은 X-L관이 외경의 차이로 인해 동관보다 높게 나타났다.

• Journal of Biosystems Engineering
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• v.14 no.1
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• pp.24-32
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• 1989

고밀도(高密度)의 열(熱)에너지를 저장(貯藏)하기 위(爲)한 잠열축열장치를 설계(設計), 제작(製作), 작동(作動)하는 경우 잠열축열장치의 사용목적(使用目的)에 적합(適合)한 최적설계(最適設計)와 그 효율적(效率的)인 이용(利用)을 위(爲)해서는 그 부열특성(傅熱特性)이 규명(糾明)되어야 한다. 본(本) 연구(硏究)에서는 실용화(實用化)에 필요(必要)한 이중관형(二重管形) 잠열축열장치의 방열과정(放熱過程)에서의 부열특성(傅熱特性)을 이차원적(二次元的)으로 실험(實驗) 분석(分析)하였으며, 시간변화(時間變化)에 따른 잠열재의 온도변화(溫度變化)와 응고율(凝固率)이 실험분석치(實驗分析値)와 이론분석치(理論分析値)에 있어서 잘 일치하였다. 한편 응고율(凝固率), 방열율(放熱率), 물의 온도변화(溫度變化)에 대(對)한 분석(分析)을 하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.8
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• pp.4749-4755
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• 2014

In this study, to maximize the heat release from the heat generating environment, such as a high-capacity inverter, the heat release performance of the extruded-type heat sinks with the variation of the base thickness were investigated using the experimental and numerical methods. The base thickness was varied from 5 to 14 mm. The heat release was characterized by the amount of heat released through the heat sink, the surface temperature of heat sink base between the heat sources, and temperature of heat sources. The surface temperatures between heat sources and the amounts of heat release were improved more as the base thickness was decreased. In contrast, the temperatures of the heat sources decreased with increasing base thickness. Based on the case study of these heat sinks, it is believed that a heat sink with a 9.5mm-thick base was optimized for the heat release.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.9
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• pp.3141-3147
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• 2010

The most important cause for shortening LED lighting efficiency and life is the junction temperature rises and, to solve this problem, various studies such as thermally efficient packaging, highly conductive material development, contact resistance improvement or heat sink optimization have been studied. However, most studies so far assumed that the LED lights are in the atmosphere, and thermal performance has not been therefore reported when the LED lights are mounted on the ceiling with ceiling unit. Thus, this study investigates the variation of junction temperature of the MR16 LED light under actual installation conditions and more accurate thermal design for the efficiency and life of LED lights is therefore achieved.

• Food Science and Preservation
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• v.6 no.2
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• pp.143-147
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• 1999

Onions were subject to quality evaluation from the physiological and physicochemical points of view during storage under different conditions, which were low temperature (2-4$^{\circ}C$, 80% RH), pit temperature (3-15$^{\circ}C$, 75-85% RH), room temperature (10-23$^{\circ}C$, 75-98% RH) and ambient temperature (2-25$^{\circ}C$, 62-72% RH). Sprouting were dereloped from the 11th month of storage in low temperature. Rotting was quickly occurred from the 7th month of storage excepting onions in room temperature. Low temperature storage showed the least weight change. Moisture content increased with the lapse of storage time at both low temperature and pit temperature storage conditions, but decreased with the lapse of storage time at room and ambient temperature conditions. Total and reducing sugars decreased with the storage time, while vitamin increased in stored onions at low temperature.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.50.2-50.2
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• 2009

지구관측위성의 광학탑재체 내부에 장착된 초점면결상장치(FPA, Focal Plane Assembly)는 영상촬영시 많은 열을 발생하며, 최상성능획득을 위해서는 온도가 좁은 온도범위 내에서 유지되어야 한다. 초점면결상장치가 짧은 시간 동안 많은 열을 발생할 때, 이를 효과적으로 냉각시키기 위해 보통 히트파이프와 복사방열판을 이용한다. 이번 연구에서는 초점면결상장치의 최대상승온도를 낮추고, 영상촬영대기시 최적온도유지를 위한 히터작동율을 낮추기 위해 초점면결상장치와 복사방열판 사이에 열완충질량(TBM, Thermal Buffer Mass)을 적용하였는데, 이를 통해 얻을 수 있는 열설계 개선효과에 대해서 기술한다.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.7
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• pp.868-876
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• 2014

The objective of this study is focused on the analyzing combustion, carbon monoxide and hydrocarbon emission characteristics of marine diesel oil, utilized for naval propulsion engine, with varying pre-post injection timing of an optically accessible single cylinder engine. And also the combustion process is analyzed by means of a high speed camera visualization. On the result of retarding pre-injection timing toward main injection timing, the mean effective pressure and maximum pressure of combustion chamber are increased; however, the heat release rate is decreased. Furthermore, the emission rates of carbon monoxide and hydrocarbon are reduced in this case. In hence, when a post-injection timing is advanced, the mean effective pressure and maximum pressure are increased, because the combustion has been performed under the high temperature and high pressurized environment during main injection time, and the emission rates of carbon monoxide and hydrocarbon are increased. From the experimental results, it considered that retarding of pre-injection timing affects to shorten the ignition delay of main injection clearly, and to raise the flame intensity comparing to the advanced state. The ignition delay during post-injection is not appeared at any post-injection time, but the flame intensity has been weakened gradually according to the retarding of post-injection timing.

• Journal of the Korean Electrochemical Society
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• v.5 no.3
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• pp.125-130
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• 2002

An attempt was made for the application of porous reticular metal to a heat dissipation material in semiconductor process. For this aim, the electrodeposition of Fe/Ni alloy on the porous reticular Cu has been performed to minimize the thermal expansion mismatch between Cu skeleton and electronic chip. Preliminary tests for the electrodeposition of Fe/Ni alloy layer were conducted by using standard Hull Cell to examine the effect of current density on the composition of alloy layer. It seemed that mass transfer affected significantly the composition of Fe/Ni layer due to anomalous codeposition in the electrodeposition of Fe/Ni alloy. A paddle type stirring bath, which was employed to control the mass transfer of electrolyte in the work, was found to allow the electrodeposition Fe/Ni with a precise composition. result showed that the thermal expansion of Fe/Ni alloy layer was much lower than that of pure copper. From the tests of heat dissipation by using the apparatus designed in the work the heat dissipation material fabricated in the work showed the excellent heat dissipation capacity, namely, more than two times as compared to that of pure copper plate.