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컴퓨터 CPU 냉각용 방열기 튜브 삽입길이에 따른 열유동 해석
최진태(Jin Tae Choi),권오경(Oh Kyung Kwon),윤재호(Jae Ho Yun),김용찬(Yong Chan Kim) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.2
컴퓨터용 방열기의 헤더부 튜브 삽입길이에 따른 열전달 및 유동특성을 파악하기 위하여 수치해석을 수행하였다. 튜브삽입길이 0, 5, 10㎜의 3가지 해석모델을 선정하였으며 해석결과의 타당성 검증을 위해 삽입길이가 5㎜ 일 때 샘플을 실험결과와 비교하였다. 유량분배의 균일성을 판단하기 위해 각 튜브에서 유량비를 분석하였고, 유량분배 특성을 정량적으로 비교하기 위하여 유량균일도를 정의하였다. 해석결과를 통하여 모든 샘플에서 열전달량과 압력강하는 질량유량이 증가함에 따라 점차 증가하였으며, 튜브삽입길이가 10㎜(h/D=0.5)인 샘플 3의 열전달량과 압력강하는 가장 크게 나타났다. 유량균일도(Stotal)를 조사하였을 때 튜브삽입길이가 0㎜(h/D=0)인 샘플 1이 0.0052로 가장 균일한 유량분포를 보였다. The performance of flat-tube radiators with louvered fins was numerically investigated for different tube insertion lengths. The results of numerical analysis using CFX-11 were compared with experimental results. In this study, three types of flat-tube radiators with louvered fins were considered. An experiment was conducted to validate the numerical results. Flow rate ratio (FR) and Stotal were introduced to understand the uniformity of flow distribution easily. The results of numerical analysis revealed that the heat transfer rate and pressure drop increased as the mass flow rate increased. Further, the results showed that the heat transfer rate of sample 3 with h/D = 0.5 was higher than that of the other samples. The pressure drop increased as the insertion length toward the header part increased, and the pressure drop in the case of sample 3 appeared to be the highest. The factor Stotal showed that the uniformity of the flow distribution in the case of sample 1 with h/D = 0 was higher than that in the case of the other samples.
다중 충돌 공기제트에서 발포 알루미늄 방열기의 방열 특성 실험
이명호,김서영,이관수,Lee, Myeong-Ho,Kim, Seo-Yeong,Lee, Gwan-Su 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.8
The present experiment investigates the effects of pore density f of aluminum foam heat sinks, the jet-to-jet spacing X and the nozzle plate-to-target surface spacing H of 3$\times$3 square impinging arrays on the averaged Nusselt number. The performance of the aluminum foam heat sinks and the rectangular plate heat sink is evaluated in terms of the enhancement factor. /equation omitted/. The multiple impinging jet with X/d=4.0 displays higher Nusselt numbers than single impinging jet for 12.0$\leq$H/d$\leq$20.0. With the variation of the jet-to-jet spacing, the aluminum foam heat sink of 10 PPI show higher Nusselt numbers than the 20 and 40 PPI aluminum foam heat sinks. Further, the 10 PPI aluminum foam heat sink demonstrates 26% higher enhancement factor than the rectangular plate heat sink in the range of 7000$\leq$Re$\leq$11000.
변압기용 방열기의 방열판 형상이 방열특성에 미치는 영향에 관한 수치적 연구
김영주(Y.J. Kim),두정훈(J.H. Doo),하만영(M.Y. Ha),손성완(S.W. Son),김중경(J.K. Kim),이승호(S.H. Lee) 한국전산유체공학회 2015 한국전산유체공학회지 Vol.20 No.1
In this study, the natural convection phenomenon of the air side and the forced convection phenomenon of the oil side were simulated in the radiator through a 3-D numerical analysis, and the total heat released by the oil side into the radiator heating plate and then to the air side was evaluated. Also, a quantitative analysis was carried out on the effect of each thermal resistance on the overall heat transfer coefficient through a 1-D thermal circuit analysis on the heat transfer mechanisms of the radiators considered in this study. In addition, for the diverse shapes of the heating plates considered in this study, the pressure drops of the oil side were quantitatively compared and evaluated. The temperatures at the air side and the oil side outlets of the radiators with 8 different fin shapes considered in this study had almost similar values showing a difference of +/-3% and, accordingly, the total heat transfer also showed similar heat dissipation performance in all the models. As a result of the 1-D hermal circuit analysis, in all the models considered in this study, while the thermal resistance of the air side accounted for 92% to 96% of the total, that of the oil side was 5 to 7%, and that of the heating plate showed a very small value of 0.02%.
이영춘(Young-Chun Lee),김광석(Kwang-Seuk Kim) 산업기술교육훈련학회 2012 산업기술연구논문지 (JITR) Vol.17 No.2
Industrial development and income increase causes rapid increase in using fossil energy like coal, petroleum and natural gas, and it results in accelerating environmental pollution owing to the increase in emission of air pollution substance. Specially, fresh water like stream and river water is acidified and specific resistance is decreased. Therefore, corrosion damage is accelerated in radiator for automobile that is using acidified water and specific resistance is decreased water. Generally, material for radiator of automobile is composed of Al-alloy, but part of radiator material is still composed of Cu and stainless. Specially, Al-alloy replaces Cu and Cu-alloy as cooling and heating system material for light weight. Therefore, galvanic electronic cell is formed between Al-alloy, Cu and stainless for automobile radiator material, and Al-alloy corrosion is accelerated. So, in this study, galvanic corrosion test of Al-alloy coupling with stainless was carried out in distilled water, tap water, polluted environment. And thus corrosion potential and galvanic current density of Al-alloy with stainless is investigated.
국한 충돌공기제트에 의한 발포 알루미늄 방열기의 열전달 특성
황준,김서영,강병하,Hwang, Jun,Kim, Seo-Young,Kang, Byung-Ha 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.4
An experimental study has been performed on thermal transport from an aluminum foam heat sink under a confined impinging air jet. Three kinds of aluminum foam heat sinks with 10, 20 and 40 PPI and a conventional pin-fin heat sink are tested in the present study. The jet Reynolds number is varied in the range of Re=667~5672 The effect of the confinement disk diameter and the distance between the confinement disk and the heater surface on the averaged Nusselt number is investigated in detail. The results are also compared with those of the unconfined impinging air jet. The critical distance, at which thermal performance shows a minimum compared to the unconfined jet impinging, will be described in terms of the Reynolds number and the pore density of the aluminum foam.
자연대류를 이용한 변압기용 방열기의 채널 구조가 방열성능에 미치는 영향
김다은(D. E. Kim),강상모(S. Kang),서용권(Y. K. Suh) 한국전산유체공학회 2014 한국전산유체공학회지 Vol.19 No.4
Increased demand of power-transformer’s capacity inevitably results in an excessive temperature rise of transformer components, which in turn requires improved radiator design. In this paper, numerical simulation of the cooling performance of an ONAN-type (Oil Natural Air Natural) radiator surrounded by air was performed by using CFX. The natural convection of the air was treated with the full-model. The present parametric study considers variation of important variables that are expected to affect the cooling performance. We changed the pattern and cross-sectional area of flow passages, the fin interval, the flow rate of oil and shape of flow passages. Results show that the area of flow passage, the fin interval, the flow rate of oil and shape of flow passages considerably affect the cooling performance whereas the pattern of flow passages is not so much influential. We also found that for the case of the fin interval smaller than the basic design, the temperature drop decreases while a larger interval gives almost unchanged temperature drop, indicating that the basic design is optimal. Further, as the flow rate of oil increases, the temperature drop slowly decreases as expected. On the other hand, when the shape of flow passages are changed, temperature drop is increased, indicating that the cooling performance is enhanced thereupon.
충돌제트 열전달에 발포알루미늄 방열기의 높이와 노즐의 크기가 미치는 영향
김서영,백진욱,강병하,Kim, Seo-Yeong,Baek, Jin-Uk,Gang, Byeong-Ha 대한기계학회 2001 大韓機械學會論文集B Vol.25 No.9
An experimental study is carried out for an aluminum foam heat sink attached to an isolated heat source to evaluate high potential of aluminum foam as a heat sink with impinging jets. The effects of the pore density and the height of the aluminum foam heat sink, the jet Reynolds number, and the nozzle diameter are delineated in comparison with a conventional pin type heat sink. It is found that the aluminum foam with small pores is inefficient for the heat transfer enhancement due to the large flow friction at the given porosity. In the parameter ranges of the present study, the change in the nozzle diameter shows no significant effects on the surface temperature of the aluminum foam heat sink at a given Reynolds number. The heat transfer enhancement is strongly dependent on the jet Reynolds number and shows a maximum value at a moderate Reynolds number.
차동안(Dong-An Cha),권오경(Oh-Kyung Kwon),윤재호(Jae-Ho Yun) 대한설비공학회 2011 설비공학 논문집 Vol.23 No.1
The performance of louver-finned flat-tube and fin and tube radiators for computer CPU liquid cooling was experimentally investigated. In this study, 7 samples of radiators with different shape and pass number (1, 2, 10) were tested in a wind tunnel. The experiments were conducted under the different air velocity ranged from 1 to 4 ㎧. The water flow rate through a pass was 1.2 LPM. Inlet temperatures of air and water were 20℃ and 30℃ respectively. It was found that the best performance was observed in the louver-finned flat-tube sample considering pressure drop and heat transfer coefficient.