평행관 모델링을 통한 보일러 화로벽관 내 밀도파 불안정의 해석

김진일(Jinil Kim),최상민(Sangmin Choi) 대한기계학회 2013 大韓機械學會論文集B Vol.37 No.2

화력발전용 관류보일러 화로벽관에서의 밀도파 불안정 예측을 목적으로 수치모델을 개발하였다. 시간 도메인에서 1 차원 유한체적법을 적용하여 관내 비정상상태의 유동장을 계산하였으며, 화로벽관의 평행관 연결을 모사하기 위해 헤더의 모델도 포함하였다. 평행관들 가운데 하나의 관에 열 섭동을 부가 후 관 입출구 유량의 변동을 관찰함으로써 밀도파 불안정을 찾았다. 개발된 모델은 문헌의 실험결과와 검증을 거쳐 700MW 보일러 화로벽관에 적용하였다. 그 결과 Takitani 의 실험결과에서는 평행으로 연결된 우회 유량이 줄어들수록 불안정 경계 열량이 상승하는 경향이 있었던 반면, 보일러 화로벽관의 경우에는 평행관 모델링에 크게 영향을 받지 않음을 확인하였다. A numerical model was developed to predict the density wave oscillation (DWO) in the furnace wall tubes of a fossil-fired once-through boiler. The transient flow fields in the tubes were obtained using a 1D finite volume method in the time domain. A header model was also implemented to simulate the parallel tube connection of the wall tubes. The inlet and outlet mass flow variation in one of the parallel tubes was examined after a heat perturbation to find the DWO. After successful verification with experimental results reported in literature, the developed model was applied to the wall tubes of a 700-MW boiler furnace. In contrast to the simulation of Takitani’s experiment, in which the unstable power thresholds tended to rise in the reduced bypass channel flow, no remarkable changes were observed in the power thresholds in the parallel channel modeling of the wall tubes of the boiler furnace.

유로형상 및 운전조건에 따른 고분자 전해질 연료전지의 성능 특성

이필형(Pil-Hyong Lee),조선아(Son-Ah Cho),한상석(Sang-Seok Han),황상순(Sang-Soon Hwang) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5

For proton exchange membrane fuel cell, it is very important to design the flow channel on separation plate optimally to maximize the current density at same electrochemical reaction surface and reduce the concentration polarization occurred at high current density. In this paper, three dimensional computation model including anode and cathode domain together was developed to examine effects of flow patterns and operation conditions such as humidity and operating temperature on performance of fuel cell. Results show that voltage at counter flow condition is higher than that at coflow condition in parallel and interdigitated flow pattern. And fuel cell with interdigitated flow pattern which has better mass transport by convection flow through gas diffusion layer has higher performance than with parallel flow pattern but its pressure drop is increased such that the trade off between performance and pressure drop should be considered for selection of flow pattern of fuel cell.

평행평판 간극에서 전기장의 강도변화에 따른 분산계 ER유체의 유량-압력강하 특성

장성철,염만오,김도태 한국공작기계학회 2003 한국생산제조학회지 Vol.12 No.1

Electro-rheological(ER) fluids are suspensions in which rheological properties show an abrupt change with variation of electric fields. We modeled the parallel-plates relating to ER-Valve system and yielded shear stress according to the strength of electric field. The purpose of the present study is to examine the flow characteristics of ER fluids according to the strength of electric field between parallel-plates. Then the steady relationship between pressure drop and flow rate of the ER fluids between parallel-plates under application of an electric fields for steady flow were measured. For the experiment, we used the ER fluids, 35w% zeolite having hydrous particles and differential pressure gauge. This test reviewed experiment for the special changes of ER fluids in the steady flow condition.

단양지역 층리평행전단구조의 운동학적 특성과 지체구조적 의미

소진현,김고은,서여은,배상열,최호석,김영석 대한지질학회 2023 지질학회지 Vol.59 No.4

옥천대의 주요 구조선인 옥동단층과 각동충상단층 사이에 분포하는 태백형 조선누층군을 따라 층리평행 전단구조가 보고되어 있어 해당 구조에 대한 운동학적 특성을 파악하기 위해 연구를 수행하였다. 이를 위해 단양지역에서 이러한 전단구조가 인지되는 노두들에 대해 야외조사를 수행하였으며, 운동학적 지시자를 식별하여운동감각을 알아내고 C′ 엽리를 이용한 소용돌이도 분석을 통해 운동학적 특성을 알아냈다. 그 결과 엽상규산염광물이 풍부한 묘봉층, 화절층, 두무골층에서 우수향 주향이동을 지시하는 C′ 엽리가 다수 관찰되었다. 또한좌수향 주향이동을 지시하는 전단습곡이 일부 나타나는데 이는 우수향 C′ 엽리를 변형시키고 있어 우수향 전단이후에 발생한 것으로 보인다. 운동특성을 이해하기 위하여 우수향을 지시하는 C′ 엽리에 대해 평균 운동학적소용돌이수(Wm) 분석을 실시하였으며, 그 결과 옥동단층과 가까운 묘봉층은 0.738~0.813의 값이 나타나 단순전단이 우세하지만, 옥동단층과 먼 화절층과 두무골층은 0.170~0.466 사이의 값을 보여주어 순수전단이 우세하게 나타났다. 이는 옥동단층을 가로지르는 방향으로 변형분할(strain partitioning)이 발생하였음을 지시하는것으로 보인다. 층리평행 전단구조의 운동감각과 Wm 변화양상은 해당구조가 옥동단층과 연관이 있음을 보여주며, 변형분할 양상과 최소순간신장축(minimum instantaneous stretching axes; ISA3)은 옥동단층이 전달압축환경(WNW-ESE 압축)에 놓여있었음을 지시한다. 또한 Wm을 바탕으로 도출한 고수렴각(paleo-convergence angle)은 옥동단층으로부터 멀어질수록 ENE-WSW에서 WNW-ESE방향으로 회전하는 것으로 나타났으며, 이는 각동충상단층과의 운동학적 연관성을 시사하는 것으로 해석된다. Layer-parallel shearing has been reported along the Taebaek-type Joseon Supergroup, which is distributed between the Okdong Fault and the Gakdong Thrust, which are the major tectonic lines along the Okcheon Belt. We conducted a study to understand the kinematics of these structures. We identified several shear indicators through field surveys in the Danyang area, providing information on the sense of shear and the vorticity analysis using C′ foliations. As a result, a number of C′ foliations, indicating right-lateral sense, were observed in the Myobong Formation, Hwajeol Formation, and Dumugol Formation, which are phyllosilicate rich layers. In contrast, there are also some shear folds indicating left-lateral shear, which deformed the right-lateral C′ foliations, suggesting that it occurred after the right-lateral shear. The mean kinematic vorticity number (Wm) derived from the right-lateral C′ foliations, range from 0.738 to 0.813 in the Myobong Formation near the Okdong Fault, indicating prevalent simple shear. In contrast, they range from 0.170 to 0.466 in the Hwajeol and Dumugol Formations farther from the Okdong Fault, indicating predominance of pure shear. This may indicate stress change and strain partitioning between the Okdong fault. The kinematics and changes of the Wm across the Okdong fault indicate that they are strongly associated with the movement of the Okdong fault, and the minimum instantaneous stretching axes (ISA3) and the strain partitioning indicates that the Okdong fault experienced transpressional stress (WNW-ESE compression) condition. In addition, the paleo-convergence angle based on Wm was rotated clockwise from ENE-WSW toward the WNW-ESE with distance from the Okdong Fault, which may suggest a kinematic relation with the Gakdong Thrust.

열간 분지 삽입물 형태가 2열/4패스 평행류 열교환기의 냉매 분배에 미치는 영향

변호원(Ho-Won Byun),정영빈(Young-Bin Jeong),김내현(Nae-Hyun Kim) 대한설비공학회 2015 대한설비공학회 학술발표대회논문집 Vol.2015 No.11

메탄올 Fuel Cell 내의 유로 형상에 대한 열유동해석

백수홍,이동렬 한국기계기술학회 2015 한국기계기술학회지 Vol.17 No.6

This research is to investigate the performance analysis of methanol fuel cell for flow channel with four different types of the channel (Serpentine I, II, Inter-digitated, Parallel) in the fuel cell stack. Velocity, pressure, temperature and density distributions of fluid over the flow domain of the flow channel are numerically calculated for the optimum design of flow channel with uniform inlet velocity. According to better water discharge and mutual gas reaction with low pressure drop and high density difference between inlet and outlet in the flow channel, Serpentine I type is of highest performance of the flow channel shapes in the present methanol fuel cell models.

메탄올 Fuel Cell 내의 유로 형상에 대한 열유동해석

백수홍,이동렬 한국기계기술학회 2015 한국기계기술학회지 Vol.17 No.6

This research is to investigate the performance analysis of methanol fuel cell for flow channel with four different types of the channel (Serpentine I, II, Inter-digitated, Parallel) in the fuel cell stack. Velocity, pressure, temperature and density distributions of fluid over the flow domain of the flow channel are numerically calculated for the optimum design of flow channel with uniform inlet velocity. According to better water discharge and mutual gas reaction with low pressure drop and high density difference between inlet and outlet in the flow channel, Serpentine I type is of highest performance of the flow channel shapes in the present methanol fuel cell models.

평행유동 공랭식 구조를 가진 함탑재장비의 방열성능에 관한 연구

나선근(Sun-Geun Na),김병준(Byung-Jun Kim) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11

산소극 가습도 변화에 따른 고분자 전해질 연료전지의 성능변화에 대한 3차원 수치해석적 연구

이필형(Pilhyong Lee),한상석(Sangseok Han),이재영(Jaeyoung Lee),박창수(Changsoo Park),황상순(Sangsoon Hwang) 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

Flow configuration and operating condition such as cell temperature, humidity at each cell, stoichiometric number is very crucial for improving its performance. Too many flow channels could enhance the performance resulting in high parasite loss. Therefore trade off between pressure drop and efficiency of fuel cell should be considered for optimum design. This work focus on numerical simulation the effects of operating condition, especially cathode humidity, with simple parallel now channel. It is known that humidity at cathode becomes very important for predicting performance of fuel cell because fully humidified condition was normally set at anode. Results show the maximum power density can be obtained under 20~30% humidified condition at cathode where oxygen concentration is moderate high maintaining high thermal conductivity at a membrane.

평행유동 공랭식 구조를 가진 함탑재장비의 방열성능에 관한 연구

나선근(Sun-Geun Na),김병준(Byung-Jun Kim) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11