소형 연소기를 위한 재생냉각의 선행연구

장동욱(Dongwuk Jang),조성권(Sungkwon Jo),조황래(Hwangrae Cho),방정석(Jeongseok Bang),권세진(Sejin Kwon) 한국추진공학회 2011 한국추진공학회 학술대회논문집 Vol.2011 No.11

2,500 N급 과산화수소/케로신 이원 추력기의 성능 향상 및 다양한 임무에 적용하기 위하여 재생냉각의 적용가능성을 검토하였다. 1-D 계산을 통해 과산화수소를 냉각제로 하는 경우에 대한 계산을 수행하였다. 설계된 재생냉각 연소기의 노즐 목에서의 열 유속은 18~20 MW/m2 로 예측되었으며, 그에 따른 유로의 너비는 2.5 mm 높이는 0.45 mm로 설계 되었다. 설계된 유로형상을 바탕으로 냉각 유로 내에서의 압력강하를 예측하기 위한 평판형 모델을 제작하여 실험을 진행하였고, 수치해석결과와 비교를 수행하였다. 그 결과, 수치해석과 실험결과와의 최대 오차는 약 13%, 평균 오차는 약 5%로 계산되었다. Applicability of regenerative cooling in 2,500 N-class bipropellant thruster using hydrogen peroxide and kerosene was considered for improvement performance and application in various missions. Calculation was performed by one dimensional approach using hydrogen peroxide as a coolant. In designed regenerative cooling thruster, heat flux at nozzle throat was estimated at 18 ~ 20 MW/m2. Designed cooling channel width and height were 2.5 mm and 0.5 mm, respectively. Based on designed cooling channel configuration, flat plate model was manufactured and tested for estimation of pressure drop in cooling channel, and CFD analysis was compared with the test result. The maximum error between CFD analysis and experimental result was approximately 13% and average error was approximately 5%.

오블리크 핀을 적용한 확대채널 배터리 냉각판의 효과

최홍석(Hongseok Choi),한욱민(Ukmin Han),이호성(Hoseong Lee) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11

In this paper, the effects of the diverging channel design cooling plate for improving temperature uniformity of high energy density lithium-ion battery (LIBs) are examined. A large capacity NMC (Nickel Manganese Cobalt: LiNiMnCoO2) battery with 355Wh/L is used. To verify the cooling simulation model, the battery module cooling experiments is discharged with 0.33 current-rate (C-rate) are proceeded using cooling plates with straight channels and diverging channels. With the verified cooling model, the thermal effects of the diverging channel cooling plate with oblique fins are examined especially in perspective to the uniformity of battery temperature. In addition, scale-up and simulations of the cooling plate for battery pack are progressed. As a result, the diverging channel cooling plate with oblique fins shows more enhanced effects on the battery temperature distribution than the straight channel cooling plate for the battery pack.

이차유동의 방향이 막냉각 효율에 미치는 영향

박세진(Sehjin Park),최석민(Seok Min Choi),손호성(Ho-seong Sohn),정희윤(Heeyoon Chung),조형희(Hyung Hee Cho) 대한기계학회 2013 大韓機械學會論文集B Vol.37 No.7

막냉각에 관한 많은 연구들은 주유동과 이차유로가 평행한 형태로 연구가 이루어졌다. 하지만 실제 터빈 블레이드에서 이차유로의 방향은 일반적으로 주유동의 방향에 수직한 형태이다. 그래서 본 연구에서는 이차유동의 방향이 이중분사 막냉각의 효율에 미치는 영향을 수치해석을 통해 알아보고자 한다. 분사율은 1, 2이고 횡방향 분사각은 22.5°이다. 분사율이 1일 때 평행 형상에서는 안티키드니 와류가 잘 형성되어 막냉각 효율이 수직 형상의 경우보다 더 높다. 반면에 분사율이 2일 때 수직 형상의 막냉각 효율은 평행 형상보다 향상되었다. 많은 유량의 제트가 서로 반대 방향으로 분사되기 때문에 두 형상 모두 막냉각 효율이 높게 나타난다. 하지만 안티키드니 와류의 영향은 다른 분사율보다 상대적으로 작다. Several studies of film cooling were accomplished with a secondary flow channel parallel to the main flow. In real turbine blades, however, the direction of the secondary flow channel is generally normal to the main flow. Thus, this study performs a numerical analysis to investigate the effects of the direction of secondary flow on the effectiveness of double-jet film cooling. The blowing ratio is 1 and 2, and the lateral injection angle is 22.5°. The parallel channel case creates a well-developed anti-kidney vortex with a blowing ratio of 1, and the laterally averaged film cooling effectiveness of the parallel channel is enhanced compared to the normal channel. The normal channel shows higher performance with a blowing ratio of 2. Both cases show high film cooling effectiveness. These phenomena can be attributed to a high blowing ratio and flow rate rather than an anti-kidney vortex.

대용량 인휠 모터 냉각유로의 유동 특성 및 형상 최적화

임동현(Dong Hyun Lim),신윤혁(Yoon Hyuk Shin),김대건(Dae Geon Kim),김성철(Sung Chul Kim),김동현(Dong-Hyun Kim),김영광(Young-Kwang Kim) 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11

For the proper cooling of oil-cooled motor, the cooling channel should have the characteristics which are low pressure drop and adequate supply to motor part. In this paper, the cooling channel in hollow shaft of in-wheel motor is optimized by Taguchi method and flow analysis. The pressure drop and outlet flow rate of the initial model were calculated using CFD(Computational fluid dynamics). Also, the design parameters of cooling channel were derived by CFD result. Through the changing of design parameters, 9models were made, flow characteristics of the models were evauated in simulation. The simulation results applied to L9 Taguchi test matrix, it can be found the main effect of each design parameters and optimal design level. In addition, the flow characteristics of optimized model was evaluated using flow analysis. As the result, the optimized model has low pressure drop(0.3 bar) and high oil flow rate for motor part(0.203 lpm) than the initial model.

소형 이원추진제 추력기를 위한 재생냉각 유로형상 설계에 대한 선행연구

장동욱(Dongwook Jang),조성권(Sungkwon Jo),조황래(Hwangrae Cho),방정석(Jeongseok Bang),권세진(Sejin Kwon) 한국추진공학회 2012 한국추진공학회지 Vol.16 No.2

Applicability of regenerative cooling in 2,500 N-class bipropellant thruster using hydrogen peroxide and kerosene was considered for improvement of performance and application in various missions. Calculation was performed by one dimensional approach using hydrogen peroxide as a coolant. The heat flux of thruster at nozzle throat was estimated at 18 ~ 20 ㎿/㎡ . Designed cooling channel width and height were 2.5 ㎜ and 0.5 ㎜, respectively. Based on designed cooling channel configuration, flat plate model was manufactured and tested for estimation of pressure drop in cooling channel, and CFD analysis was compared with the test result. The maximum error between CFD analysis and experimental result was approximately 13% and average error was approximately 5%.

병렬 사형유로를 채택한 냉각판을 통한 고분자 전해질 연료전지의 균일 냉각에 대한 전산유체역학 해석 연구

류승호(Seung Ho Yu),백승만(Seung Man Baek),남진현(Jin Hyun Nam),김찬중(Charn-Jung Kim) 대한기계학회 2010 大韓機械學會論文集B Vol.34 No.10

고분자 전해질 연료전지(PEMFC)의 열관리는 성능 향상과 내구성 측면에서 중요한 문제이다. 일반적으로 냉각수 순환 유로를 가진 냉각판이 여러 개의 단전지 사이에 삽입되어 PEMFC 내부에서 발생하는 반응열을 외부로 배출한다. 본 연구에서는 개선된 병렬 사형유로(MPSFF)를 향상된 냉각성능을 가진 냉각판 유로형상으로 제안하고, 이를 전산유체역학(CFD) 해석을 통하여 평가하였다. 비교를 위하여 냉각수 유로로 일반적으로 사용되는 사형유로 및 병렬형유로의 냉각성능에 대한 계산도 수행하였다. CFD 결과는 개선된 병렬 사형유로가 냉각판 표면에서의 온도의 비균일도를 상당히 감소시키고, 따라서 PEMFC의 내구성과 성능을 향상시킬 수 있음을 보여주었다. Thermal management is important for enhancing the performance and durability of polymer electrolyte membrane fuel cells (PEMFCs) and is taken into account in the design of PEMFCs. In general, cooling pates with circulating liquid coolant (water) are inserted between several unit cells to exhaust the reaction heat from PEMFCs. In this study, computational fluid dynamics (CFD) simulations were performed to characterize the uniform cooling performance of parallel multipass serpentine flow fields (MPSFFs) that were used as coolant flow channels in PEMFCs. The cooling performances of conventional serpentine and parallel flow fields were also evaluated for the purpose of comparison. The CFD results showed that the use of parallel MPSFFs can help reduce the temperature nonuniformity, and thus, can favorably enhance the performance and durability of PEMFCs.

이차유동의 방향이 막냉각 효율에 미치는 영향

박세진(Sehjin Park),최석민(Seok Min Choi),손호성(Ho-seong Sohn),정희윤(Heeyoon Chung),조형희(Hyung Hee Cho) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11

In real turbine blades, the direction of secondary flow channel is generally perpendicular to the direction of main flow. Thus, this study performs the numerical analysis to investigate the effects of the direction of secondary flow on the film cooling effectiveness of double-jet film cooling. The secondary flow is fed from two different directions, one is parallel and the other is normal to the direction of main stream. The blowing rate is 1 and the lateral injection angle is 22.5°. The numerical analysis is performed by using CFX, and the k-ε model is used for the turbulence model. When the secondary flow is supplied from the normal channel, blowing rates of both holes are different. Blowing rate of first hole is bigger than blowing rate of second hole. However, both blowing rates of holes are similar in the parallel secondary flow channel case. The asymmetrical film cooling effectiveness is obtained from the normal channel case because of different blowing rate. Similar blowing rates in the parallel channel case make anti-kidney vortex well, so the laterally averaged film cooling effectiveness of the parallel channel case is bigger than of the normal channel case.

터빈 기익 선단부에 설치된 냉각유로에서의 요철배열에 따른 열전달 특성

이동현(Dong Hyun Lee),김경민(Kyung Min Kim),이동호(Dong Ho Rhee),조형희(Hyung Hee Cho) 한국유체기계학회 2005 유체기계 연구개발 발표회 논문집 Vol.- No.-

The present study investigates the heat transfer characteristics of a triangular channel. Three different rib configurations are tested. The ribs are installed on two sides of the channel. The rib height (e) to channel hydraulic diameter is 0.079 and the rib-to-rib pitch (p) is 8 times of the rib height. The rotation number ranges from 0.0 to 0.1 while the Reynolds number is fixed at 10,000. The copper blocks with heaters are installed on the channel walls to measure the regionally averaged heat transfer coefficients. For the stationary 45° and 135° ribbed channels, a pair of counter rotating vortices is induced by the angled rib arrangements, and high heat transfer coefficients are obtained on the regions near the inner wall for the 45° ribbed channel and near the leading edge for the 90° ribbed channel. The heat transfer coefficients of angled ribbed channels are changed little with rotation, whereas those of the transverse ribbed channel are changed significantly with rotation.

4:1 종횡비를 갖는 가스터빈 블레이드 냉각 유로에서의 립-딤플 복합 냉각 특성 연구

최용덕(Yong Duck Choi),김석범(Seok Beom Kim),이용진(Yong Jin Lee),김진곤(Jin Kon Kim),곽재수(Jae Su Kwak) 한국추진공학회 2010 한국추진공학회 학술대회논문집 Vol.2010 No.5

본 연구에서는 딤플이 설치된 유로, 립이 설치된 유로, 립과 딤플이 함께 설치된 유로에서의 열전달 성능을 천이액정법을 이용하여 측정하였다.. 실험에 사용된 유로의 종횡비(W/H)는 4이고, 립의 높이는 6 mm, 립 간 거리(P/e)는 10, 립이 설치된 각도는 60°이며, 딤플의 직경은 6 mm, 딤플 중심간 거리(s/D)는 1.2로 하였다. 레이놀즈 수는 30000-50000에 대해 실험을 수행하였다. 립이 설치된 유로에서는 경사 립에 의해 발생된 이차유동이 열전달 계수를 증가시켰고, 립과 딤플이 함께 설치된 유로에서는 립 사이에 설치된 딤플이 열전달 계수를 더욱 증가시켰다. 열전달계수는 립과 딤플이 복합 적용된 유로, 립이 적용된 유로, 딤플이 적용된 순으로 나타났고, 열성능계수도 립과 딤플이 복합 적용된 유로에서 크게 나타났다. Heat transfer coefficients in a dimpled channel, a ribbed channel, and a rip-dimple compound channel were measured by the transient liquid crystal technique. The channel aspect ratio, the rib height, the rip pitch, and the rib angle were 4:1, 6 mm, 60 mm and 60°, respectively. The dimple diameter and the center-to-center distance were 6mm and 7.2 mm, respectively, and the Reynolds number range was 30,000-50,000. Results showed that the heat transfer coefficients were increased by the angled rib. For the dimple-rib compound cooling cases, the heat transfer coefficients were further augmented and the thermal performance factor for the case was the highest.

4:1 종횡비를 갖는 가스터빈 블레이드 냉각 유로에서의 립-딤플 복합 냉각 특성 연구

최용덕(Yong Duck Choi),김석범(Seok Beom Kim),이용진(Yong Jin Lee),김진곤(Jin Kon Kim),곽재수(Jae Su Kwak) 한국추진공학회 2010 한국추진공학회지 Vol.14 No.4

Heat transfer coefficients in a dimpled channel, a ribbed channel, and a rip-dimple compound channel were measured by the transient liquid crystal technique. The channel aspect ratio, the rib height, the rip pitch, and the rib angle were 4:1, 6 ㎜, 60 ㎜ and 60°, respectively. The dimple diameter and the center-to-center distance were 6㎜ and 7.2 ㎜, respectively, and the Reynolds number range was 30,000-50,000. Results showed that the heat transfer coefficients were increased by the angled rib. For the dimple-rib compound cooling cases, the heat transfer coefficients were further augmented and the thermal performance factor for the case was the highest.