충돌판(衝突板) 근방(近傍)에 배열(配列)된 2차원(次元) rod가 충돌분류(衝突噴流) 열전달(熱傳達)에 미치는 영향(影響)[3] : rod직경변화(直徑燮化)에 대한효과(效果)

김동춘,이용화,서정윤,Kim, D.C.,Lee, Y.H.,Seo, J.H. 대한설비공학회 1990 설비공학 논문집 Vol.2 No.4

The purpose of this study is augmentation of heat transfer without additional power in two-dimensional impinging air jet. The technique of heat transfer augmentation used in this experiment is to place rod bundles in front of the flat heated surface. The effects of rod diameter, nozzle-to-target plate distance and the nozzle exit velocity on heat transfer have been investigated. The main conclusions obtained from this experiment are as follows. High heat transfer augmentation is achieved by means of flow acceleration and thinning of boundary layer by placing rod bundles in front of the flat plate. Average heat transfer coefficient becomes maximum in the case of H/B=10,D=4mm. For H/B=2,D=4mm, maximum heat transfer augmentation has been determined to be about 1.5 times larger than that of the flat plate. Heat transfer augmentation by placing the rod bundles at 12m/s is to be about 2 times more than increasing nozzle exit velocity from 12m/s to 18m/s.

수직원통형 빙축열조내 얼음의 외향용융과정시 전열특성에 관한 실험적 연구

김동환(D.H.Kim),김동춘(D.C.Kim),김일겸(I.K.Kim),김영기(Y.K.Kim),임장순(C.S.Yim) 한국태양에너지학회 1996 한국태양에너지학회 논문집 Vol.16 No.2

본 연구는 수직원통형 빙축열조 내에 상변하물질로서 순수한 물을 -10℃의 초기 과냉온도로 응고시킨 후, 작동유체의 입구온도를 7℃,4℃,1℃로, 작동유체의 유입방향을 상향과 하향으로 각각 변화시키면서 외향용융시켰을 경우, 시간경과에 따른 축열매질의 온도분포, 상경계면의 형상, 용융율, 용융에너지를 실험적으로 구하여 이를 비교·검토한 것이다.<br/> 작동유체의 입구온도가 7℃,4℃의 경우에는 작동유체의 유입방향이 상·하향 모두 물의 최대밀도점인 4℃ 부근에서 일시적으로 온도가 상승하지 않고 일정 시간동안 정체하는 온도정체구간이 나타났다. 또한, 용융이 진행됨에 따라 물이 축열조의 하부에 적체되고, 이에 따라 하부에서의 용융이 활발히 진행됨으로써 상경계면 형상은 전체적으로 종모양 형태의 곡선을 나타낸다. 작동유체의 입구온도가 7℃인 경우, 용융율(Vl/Vtot)과 용융에너지는 작동유체의 유입방향이 상향인 경우가 하향인 경우세어보다 크게 나타난 반면, 작동유체의 입구온도가 4℃,1℃인 경우는 7℃의 경우와는 달리 하향인 경우가 상향인 경우에서보다 큰 것으로 나타났다. This study presents experimental results of heat transfer characteristics of P. C. M. during outward melting process in a vertical cylinder. The experiment was carried out in six conditions, i. e. , three different inlet temperature (7℃, 4℃ and 1℃) and two directions of working fluid (upward and downward). Melting P. C. M. produced a bell-shaped phase change interface. When the inlet temperature was 7℃, the lower region remained at 4℃ until the temperature of upper region reached 4°C. This was due to the state of maximum density of the lower region. When the direction of the working fluid in the case of 7℃, inlet temperature, was upward, the rate of melting and the total melting energy were higher than when it's direction was downward. But the rate of melting and the total melting energy appeared higher value as it's direction was downward when the inlet temperature is 4℃ and 1℃.

충돌분류계에서 WIRE MESH를 이용한 열전달 증진에 관한 연구

금성민,김동춘,유지오,이창언,임장순,Kum, S.M.,Kim, D.C.,Yoo, J.O.,Lee, C.E.,Yim, C.S. 한국태양에너지학회 1997 한국태양에너지학회 논문집 Vol.17 No.2

본 연구는 2차원 충돌공기분류계의 포텐셜코어 영역에서 열전달증진을 목적으로 노즐출구와 전열면사이에 메쉬를 설치한후 노즐출구 속도, 메쉬와 전열면사이의 간극, 노즐출구와 전열면사이의 거리를 변화시킬 때의 열전달특성을 메쉬를 설치하지 않은 경우와 비교 검토한 것으로 메쉬를 설치했을 때에는 분류가 전열면에 충돌하면서 소분류로 분할되어 발생하는 난류에 의해 충돌영역에서 열전달성능이 좋아지며, 또한 벽면분류영역으로 진행하면서 홀과 홀사이의 밑부분에서 일어나는 가속으로 인해 열전달성능이 향상된다. 특히 메쉬와 전열면사이의 간극을 변화시켰을 경우 정체점부근에서는 간극이 클수록, 벽면분류영역에서는 간극이 작을수록 전달성능은 향상되며 U=18m/s, H/B=2, C=1인 경우에는 메쉬를 설치하지 않은 평판보다 평균 약 44%의 열전달증진 효과과 있었다. 그리고 본 실험결과를 기존의 난류촉진체를 이용한 연구결과와도 비교 검토하였다. The objective of this research was to investigate the enhancement of heat transfer by wire mesh in impinging air jet system at the potential core region. The first experiment was carried out without mesh between nozzle exit and flat plate and the second experiment was done with mesh between them. When mesh was installed in front of the plate, heat transfer has been Increased due to the acceleration between rectangular halls and divided small jet In case clearances are changed, heat transfer comes to maximum under the condition of C=1mm, irrespective of nozzle exit velocity and H/B. Also the average heat transfer enhancement rate of a flat plate with mesh has been increased about 44% at maximum under the condition of U=18m/s, H/B=2 and C=1mm, compared to the result of a flat plate without mesh.

충돌분류계에서 WIRE MESH를 이용한 열전달 증진에 관한 연구

금성민(S.M.Kum),김동춘(D.C.Kim),유지오(J.O.Yoo),이창언(C.E.Lee),임장순(C.S.Yim) 한국태양에너지학회 1997 한국태양에너지학회 논문집 Vol.17 No.1

본 연구는 2차원 충돌공기분류계의 포텐셜코어 영역에서 열전달증진을 목적으로 노즐출구와 전열면사이에 메쉬를 설치한후 노즐출구 속도, 메쉬와 전열면사이의 간극, 노즐출구와 전열면사이의 거리를 변화시킬 때의 열전달특성을 메쉬를 설치하지 않은 경우와 비교 검토한 것으로 메쉬를 설치했을 때에는 분류가 전열면에 충돌하면서 소분류로 분할되어 발생하는 난류에 의해 충돌영역에서 열전달성능이 좋아지며, 또한 벽면분류영역으로 진행하면서 홀과 홀사이의 밑부분에서 일나는 가속으로 인해 열전달성능이 향상된다. 특히 메쉬와 전열면사이의 간극을 변화시켰을 경우 정체점부근에서는 간극이 클수록, 벽면분류영역에서는 간극이 작을수록 전달성능은 향상되며 U=18m/s, H/B=s, C=1인 경우에는 메쉬를 설치하지 않은 평판보다 평균 약 44%의 열전달증진 효과과 있었다. 그리고 본 실험결과를 기존의 난류촉진체를 이용한 연구결과와도 비교 검토하였다. The objective of this research was to investigate the enhancement of heat transfer by wire mesh in impinging air jet system at the potential core region.<br/> The first experiment was carried out without mesh between nozzle exit and flat plate and the second experiment was done with mesh between them.<br/> When mesh was installed in front of the plate, heat transfer has been increased due to the acceleration between rectangular halls and divided small jet<br/> In case clearances are changed, heat transfer comes to maximum under the condition of C= 1mm, irrespective of nozzle exit velocity and H/B.<br/> Also the average heat transfer enhancement rate of a flat plate with mesh has been increased about 44% at maximum under the condition of U=18m/s, H/B=2 and C=l mm, compared to the result of a flat plate without mesh.

수직원통형 빙축열조내 외향용융과정시 열전달특성에 관한 연구 -작동유체의 유동방향 및 축열조 형상비에 따른 열성능 비교-

김동환,김동춘,김일경,김영기,임장순,Kim, D.H.,Kim, D.C.,Kim, I.G.,Kim, Y.K.,Yim, C.S. 대한설비공학회 1997 설비공학 논문집 Vol.9 No.2

During the day time in summer, peak of air conditing load, and electric power management system lies under overloaded condition. The reason is the enlarged peak load value of electric power caused by increased air-cooling load in summer. To prevent load concentration during day time and overloaded condition of power management system, some energy storage methods are suggested. One of these methods is ice storage system. Water has some good properties as P.C.M.(Phase Chang Material) : Its melting point is the range of required operation temperature. It has large specific latent heat and is chemically stable compared to other organic or inorganic substances. It is cheap and easy to treat. This study represents experimental results of heat transfer characteristics of P.C.M. under the outward melting process in a vertical cylinder. We experimented with twelve combinations of conditions, i.e., three different inlet temperatures($7^{\circ}C,\;4^{\circ}C\;and\;1^{\circ}C$), two working fluid directions(upward and downward), and two aspect ratios, H/R(4 and 2). At the inlet temperature of $7^{\circ}C$ and $4^{\circ}C$, there was temperature stagnation region where the temperature of P.C.M. remains constant at $4^{\circ}C$ regardless of aspect ratio and direction of working fluid. This temperature stagnation occurs as the water, at its maximum density, flows down to the lower region. The phase change interface formed bell-shaped curve as the melting process continued. With a new set of conditions(4H/R, inlet temperature $4^{\circ}C$ and $1^{\circ}C$, downward/upwerd inlet direction), the movement of phase change interface was faster when the working flued inlet direction was downward. With the same set of conditions, melting rate and total melting energy were larger when the working fluid inlet direction was downward. The results were reversed when the other sets of conditions were applied.

Forming Simulation of EV Motor Hairpin with Polymer Coated Copper Wire

D. C. Kim(김동춘),Y. J. Lim(임윤재),I. S. Oh(오인석),M. G. Lee(이명규) 한국소성가공학회 2022 한국소성가공학회 학술대회 논문집 Vol.2022 No.12

고분자 필름 및 구리선 이종 물성을 고려한 EV모터용 헤어핀 성형 공정 해석

김동춘(D. C. Kim),임윤재(Y. J. Lim),백민광(M. Baek),이명규(M. G. Lee),오인석(I. S. Oh) 한국소성·가공학회 2023 소성가공 : 한국소성가공학회지 Vol.32 No.3

As electric vehicles (EV) have increasingly replaced the conventional vehicles with internal combustion engines (ICE), most of automotive makers are actively devoting to the technology development of EV parts. Accordingly, the manufacturing process for power source has been also shifting from engine/transmission to EV motor/reducer system. However, lack of experience in developing the EV motor still remains as a technical challenge. In this paper, we employed the forming simulation based on finite element modeling to solve this problem. In particular, in order to increase the accuracy of the forming simulation, we introduced the elastic-plastic constitutive model parameters for polymer-copper hybrid wire by investigating the individual strain-stress curves, and elastic modulus of polymer and copper. Then, the reliability of modeling procedure was confirmed by comparing the simulated results with experiments. Finally, the identified mechanical properties and finite element modeling were applied to a hairpin forming process, which involves multiple deformation paths such as bending, pressing, widening, and twisting. The proposed numerical approach can replace common experience or experiment based trials by reducing production time and cost in the future.

직육면체형 잠열축열조내 상변화물질의 열전달특성에 관한 연구

임장순(C.S.Yim),최국광(K.K.Choi),김준근(J.K.Kim),김영기(Y.K.Kim),김일겸(I.G.Kim),김동춘(D.C.Kim) 한국태양에너지학회 1995 한국태양에너지학회 논문집 Vol.15 No.3

본 연구는 상변화물질로써 무기염수화물계 물질인 피로인산나트륨(Na₄P₂O_7·10H₂O)이 채워져있는 직육면체형 잠열축열조 내에서 축열과정시 일어나는 상변화물질의 온도특성, 열전달현상, 축열량 등을 실험적으로 측정하고 그 결과들을 수치해석 결과들과 비교·검토한 것이다. 축열과정시 상변화물질인 피로인산나트륨은 용융상태가 액체상태가 아닌 gel상태이므로 액체상태에서의 주된 열전달현상으로 나타나는 자연대류 유동현상이 일어나지 않아 전도에 의한 열전달현상이 지배적인 것으로 나타났다. 무기염수화물계 상변화물질은 공극율(공기 함유율)이 작을수록 열용량이 커지므로 축열과정시 공극율이 큰 경우보다 온도가 서서히 상승되었으며, 실험으로 측정된 온도값과 수치해석적인 방법으로 계산된 온도감ㅅ은 최대 15%의 차이가 났다. This study presents experimental and numerical results of the temperature characteristics, the heat transfer phenomema, and the heat storage quantity during the heat storage process with sodium phyrophosphate decahydrate (Na₄P₂O_7·10H₂O)-Phase Change Material (PCM) in a latent heat storage tank (cubic type). It was proved that heat transfer by conduction was dominant because PCM (Na₄P₂O_7o 10H₂O) during heating processes was gel phase, not liquid phase. The gap ratio (rate of air content) of PCM became smaller, the thermal capacity of PCM became larger, therefore the temperature distribution of PCM slowly increased than that of large gap ratio. There was maximum 15% difference between measured temperatures and calculated temperatures.

Ice on Coil형 저온 잠열 축열시스템에서의 용융과정시 열전달에 관한 실험적 연구

김영기(Y.K.Kim),김동춘(D.C.Kim),김일겸(I.G.Kim),최국광(K.K.Choi),임장순(C.S.Yim) 한국태양에너지학회 1999 한국태양에너지학회 논문집 Vol.19 No.1

가스보일러 코일형 열교환기의 열전달 특성에 관한 실험적 연구

홍성혁,김영기,김일겸,김동춘,이창언,임장순,Hong, S.H.,Kim, Y.K.,Kim, I.G.,Kim, D.C.,Lee, C.E.,Yim, C.S. 한국태양에너지학회 1997 한국태양에너지학회 논문집 Vol.18 No.4

The performance of gas-fired boilers were experimentally investigated. The heat exchanger used for the experiments consisted of circular tube with longitudinal fins for the gas side and a spiral coil for the water side. The burner was located at the top of the heat exchanger, and the burned gas flowed down to the exit. The experiments carried out for different water flow rates, the heat capacities of the boiler and the number of baffle. The thermal efficiency of the upward flow was higher than that of the downward flow of the water in the heat exchanger. As the boiler capacity increased, the thermal efficiency decreased. As the number of the baffles increase, the thermal efficiency increased and the increasing rate of the efficiency decreased. The gas-side overall heat transfer coefficient was independent of the flow rate of the water. The effect of the number of the baffles on the heat transfer coefficient was greater than that of the boiler capacity.