Fe-Cr-C-Si 계 경면처리 합금의 고압ㆍ수중 마모거동

이권영,이민우,오영민,김영석,김선진,Lee, Kwon-yeong,Lee, Min-Woo,Oh, Young-Min,Kim, Seon-Jin 한국재료학회 2003 한국재료학회지 Vol.13 No.4

The sliding wear behavior of a Fe-base hardfacing alloy was investigated in the temperature range of $25∼250^{\circ}C$ under a contact stress of 15 ksi (103 MPa). The wear loss of this Alloy in pressurized water was less than that of NOREM 02. And galling did not occurred at this alloy in all temperature ranges. It was considered that the wear resistance of this Alloy was attributed to the strain-induced phase transformation from austenite to $\alpha$'martensite during sliding wear.

Fe계 Norem 02 경면처리 합금의 고압.수중 마모거동

이권영,오영민,이민우,김선진,Lee, Kwon-Yeong,Oh, Young-Min,Lee, Min-Woo,Kim, Seon-Jin 한국재료학회 2002 한국재료학회지 Vol.12 No.8

The sliding wear behavior of an iron-base NOREM 02 hardfacing alloy was investigated in the temperature range of $25~250^{\circ}C$ under a contact stress of 103MPa (15ksi). With increasing temperature, the wear loss of Norem 02 in water increased slightly up to $180^{\circ}C$ at which Norem 02 showed the wear loss of 2.1mg. The wear resistance of Norem 02 resulted from the surface hardening due to the strain-induced phase transformation from austenite to $\alpha$'martensite during sliding wear. The wear loss of Norem 02 was smaller in water compared to air at same temperature because the water could be served as a sort of lubricant. The wear mode of NOREM 02 changed abruptly to severe adhesive wear at $190^{\circ}C$ and galling occurred above $200^{\circ}C$. It was caused that the strain- induced phase transformation took place below $180^{\circ}C$ while not above $190^{\circ}C$. Therefore, Norem 02 was considered to be inadequate at high temperature service area.

사이펀 차단기 시뮬레이션 프로그램의 개발 및 활용

이권영(Kwon-Yeong Lee),김완수(Wan-Soo Kim) 한국산학기술학회 2016 한국산학기술학회논문지 Vol.17 No.5

일부 연구용 원자로의 설계조건상 사이펀 현상은 배관 파단 사고 시 수조수의 지속적인 방출을 유발할 수 있다. 사이펀 차단기는 이러한 현상을 효과적으로 제한하기 위한 안전장치로, 유체역학적인 특성상 사이펀 차단 현상 해석을 위해 고려해야 할 변수가 많고 계산이 복잡하다. 이에 사이펀 차단 현상을 쉽게 분석할 수 있는 프로그램을 개발하게 되었다. 윈도 우8 운영체제에서 비쥬얼 스튜디오 2012를 이용하여 MFC프로그래밍으로 개발되었으며, 사용자가 쉽게 사용할 수 있도록 GUI형식으로 개발되었다. 개발된 프로그램은 사용자가 입력한 값으로부터 유체역학적 관계식을 통해 3단계의 연산과정을 거쳐 시뮬레이션을 진행한다. 베르누이 방정식으로부터 유속과 유량을 구하여 수위, 언더슈팅, 압력, 손실계수, 그리고 이상 유동과 관계된 값들을 연산한다. 프로그램에 적용된 이상유동 해석모델은 Chisholm 모델이며, 실제와 유사하게 시뮬레이션 이 가능함을 확인하였다. 시뮬레이션 결과는 그래프를 통해 나타나기 때문에 사용자는 전체적인 차단 현상을 쉽게 파악하는 것이 가능하며, 시뮬레이션 데이터의 저장 또한 가능하다. 따라서 사용자는 사이펀 차단기 시뮬레이션 프로그램의 사용을 통해 사이펀 차단 현상을 쉽게 확인할 수 있으며, 사이펀 차단기의 실제 설계에도 이용할 수 있을 것으로 기대된다. In the design conditions of some research reactors, the siphon phenomenon can cause continuous efflux of water during pipe rupture. A siphon breaker is a safety device that can prevent water efflux effectively. However, the analysis of the siphon breaking is complicated because many variables must be included in the calculation process. For this reason, a simulation program was developed with a user-friendly GUI to analyze the siphon breaking easily. The program was developed by MFC programming using Visual Studio 2012 in Windows 8. After saving the input parameters from a user, the program proceeds with three steps of calculation using fluid mechanics formulas. Bernoulli's equation is used to calculate the velocity, quantity, water level, undershooting, pressure, loss coefficient, and factors related to the two-phase flow. The Chisholm model is used to predict the results from a real-scale experiment. The simulation results are shown in a graph, through which a user can examine the total breaking situation. It is also possible to save all of the resulting data. The program allows a user to easily confirm the status of the siphon breaking and would be helpful in the design of siphon breakers.

수직관 내 비응축가스 존재 하에서의 층류 막응축에 관한 수치적해석

이권영(Kwon-Yeong Lee),김무환(Moo Hwan Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11

A theoretical model has been developed to study the local heat transfer coefficient of a condensing vapor in the presence of a noncondensable gas inside a vertical tube. The gas/vapor mixture side is modeled using the analogy between heat and mass transfer. Interface roughness, developing flow, and suction effect are considered. In the laminar liquid film side, a comparative study of the condensate mass flow rate and the heat transfer coefficient has been made with various film thickness models, film heat transfer models, and friction factor correlations. The best model will be used to the analysis of the PRHRS condensation heat exchanger in SMART.

태양에너지를 활용한 소형 초임계 이산화탄소 사이클의 실험 연구

이원구(Wonkoo Lee),이권영(Kwon-yeong Lee) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11

Renewable energy are in the spotlight in the field of power generation with international demands for green energy transformation and carbon net zero. Research on the supercritical carbon dioxide cycle is being conducted as one of CCU (Carbon Capture and Utilization) technologies without converting CO2 gas. While many studies are being conducted using carbon dioxide as a working fluid of a large Brayton cycle based on the nuclear field, there are lack of research in the renewable energy field such as solar energy. In this study, an experimental study on the supercritical carbon dioxide cycle using solar energy as a heat source was conducted. The experiment was conducted through a small-scaled experimental facility manufactured with 12 kW thermal capacity, and the power generation efficiency was evaluated by analyzing the experimental results. The thermal efficiency that was theoretically analyzed in the basic design stage was compared with the value obtained as a result of the experiment. The reason of the difference between two efficiency and the method for improving the experimental facility were presented.

노후화된 대학 건물의 단열성능 향상 실험 및 경제성 평가

이정민(Jeongmin Lee),소원호(Wonho So),조경찬(Kyungchan Cho),최동녁(Dongnyeok Choi),이권영(Kwon-yeong Lee) 한국산학기술학회 2020 한국산학기술학회논문지 Vol.21 No.8

본 연구는 노후화된 대학 건물의 내부 단열 성능 향상에 대한 것으로, 대학교 건물 내 재실자의 생산성을 높이고 노후화된 건물의 단열효과를 높이기 위해 진행됐다. 본 논문은 한동대학교 느헤미야홀 건물 내 오피스 재실자의 단열성능 향상에 대한 지속적인 요청에 응답하여 문제해결을 위해 진행된 연구라는 차별성을 가지고 있으며, 내부온도가 인접건물의 내부온도와 비교했을 때 낮음을 확인하여 연구 필요성에 대한 타당성을 검증하였다. 학교라는 건물의 특성을 고려해 내외부 단열 중 내부 단열을 주제로 단열재를 선택했다. 대학교 교수 오피스를 소형화시킨 모형 방을 만들어 시장에서 사용되는 내부 벽면 단열재를 설치해 실험을 진행했다. 실험 결과를 바탕으로 가열 시간과 실제 열전달 계수를 측정하여 단열효과를 분석하는 경제성 평가를 실시했다. 경제성 평가는 실험과 이론에 의해, 겨울철과 여름철 기준으로 각각 실시되었다. 연구결과, 느헤미야홀 60 개의 오피스에 아이소핑크(30 T)를 내 단열재로 도입하였을 때, 한 달에 겨울철에는 최대 총 1,071,600 원을 절약 할 수 있으며, 여름철에는 총 109,200 원을 절약할 수 있다. This study examined ways of improving the internal insulation performance of aging university buildings, and to enhance the convenience of occupants in university buildings and the insulation effect of aging buildings. This research was conducted to solve the problem of continuous requests for improving the insulation performance of office workers in the Nehemiah Hall building of Handong University. The results showed that the internal temperature of Nehemiah Hall was low compared to the internal temperature of the adjacent building. Considering the characteristics of the building, the university chose insulating materials under the theme of internal insulation. The experiment was conducted by installing internal wall insulation used in the market by producing a model room that miniaturized the university professor"s office. Based on the experimental results, an economic evaluation was conducted to analyze the insulation effect by measuring the heating time and actual heat transmission coefficient. An economic evaluation was conducted by experiment and theory and on a winter and summer basis. According to the research, when an Isopink (30 T) was introduced as an internal insulation material in 60 offices of Nehemiah Hall, it could save up to 1,071,600 won in total during the winter season and 109,200 won during the summer season.

태양에너지를 활용한 소형 초임계 이산화탄소 사이클의 실험 연구

이원구(Wonkoo Lee),이권영(Kwon-yeong Lee) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11

Renewable energy are in the spotlight in the field of power generation with international demands for green energy transformation and carbon net zero. Research on the supercritical carbon dioxide cycle is being conducted as one of CCU (Carbon Capture and Utilization) technologies without converting CO2 gas. While many studies are being conducted using carbon dioxide as a working fluid of a large Brayton cycle based on the nuclear field, there are lack of research in the renewable energy field such as solar energy. In this study, an experimental study on the supercritical carbon dioxide cycle using solar energy as a heat source was conducted. The experiment was conducted through a small-scaled experimental facility manufactured with 12 kW thermal capacity, and the power generation efficiency was evaluated by analyzing the experimental results. The thermal efficiency that was theoretically analyzed in the basic design stage was compared with the value obtained as a result of the experiment. The reason of the difference between two efficiency and the method for improving the experimental facility were presented.

In-Line Recondenser와 Pre-cooler가 적용된 LNG선 연료관리 시스템 설계

이원구(Wonkoo Lee),선현준(Hyunjun Sun),이권영(Kwon-Yeong Lee) 한국산학기술학회 2023 한국산학기술학회논문지 Vol.24 No.3

액화천연가스(LNG)는 천연가스를 장거리로 운송하는 가장 경제적인 방법이다. LNG 운송 및 저장 과정에서 BOG(Boil Off Gas)가 발생하여 손실을 피할 수 없다. 이러한 손실을 막기 위해 BOG를 연료로 사용하거나 재액화 등의 방식을 취하고 있다. In-line Recondenser(이하 I-Recondenser)는 Static-Mixer와 같은 방식으로 BOG를 LNG에 빠르게 섞어 액화시키는 장치로서, 기존 Packed-Bed 형태 대비 부피는 2%, 무게는 1/15 수준이기 때문에 선박에 탑재하기에 용이하다. 이에 본 연구에서는 LNG 운반 및 추진 선박을 대상으로 I-Recondenser를 활용한 BOG 재액화 장치와 연료공급 시스템(FGSS)을 결합한 형태인 연료관리 시스템(FGMS)을 제안하고 개념설계를 수행하였다. BOG 전량을 액화시킨다는 설계 요건 하에서 Basic 모델과 Pre-cooling 모델로 나뉘어 진행되었다. 시뮬레이션을 통해 실현 가능성을 입증하였는데, 일정한 압력 조건에서 LNG의 질량유량이 증가함에 따라 BOG가 전량 액화되는 지점을 찾았다. 즉, Basic 모델은 LNG/BOG 질량유량 비율이 10일 때, Pre-cooling 모델은 8.22일 때 전량 액화되는 것을 확인하였다. Liquefied natural gas (LNG) is the most economical way to transport natural gas over long distances. In the process of LNG transportation and storage, BOG(Boil Off Gas) is generated, and losses are unavoidable. In order to prevent this loss, methods such as using BOG as fuel or re-liquefying it are being used. A recently proposed in-line recondenser is similar to a static mixer. It has 2% of the volume and 1/15 of the weight compared to an existing packed-bed recondenser, making it easy to mount on a ship. The purpose of this research is to propose a fuel gas management system(FGMS) for LNG ships using the in-line type recondenser and to perform basic design of the system. It was designed under the requirement of liquefying the entire amount of BOG according to the temperature and pressure conditions. The design was divided into a basic model and a pre-cooling model. The feasibility of the design was verified through simulation, and the total amount of liquefaction was realized through a method of increasing the mass flow rate of LNG with a constant pressure. The basic model had a LNG/BOG mass-flow ratio of 10, and the pre-cooling model liquefied BOG when the ratio was 8.22.

차량용 램프 내열 예측 프로그램 개발을 위한 열전달 실험

이재진(Jae-jin Lee),지은찬(Eunchan Ji),우지호(Jiho Woo),최동녁(Dongnyeok Choi),김영완(Youngwan Kim),최승(Seung Choi),박유라(Yura Park),이진구(Jingoo Lee),이권영(Kwon-Yeong Lee) 한국자동차공학회 2020 한국자동차공학회 부문종합 학술대회 Vol.2020 No.7

The heat from bulbs of automotive lamp is transferred to internal materials in the form of conduction, convection and radiation. The transferred heat causes deformation of lamp materials when it exceeds the heat-resistance limits. To reduce the effort from trial and error by failing the heat-resistance test after designing and producing lamps, using a simulation program is necessary at the design stage. A new in-house heat-resistance prediction program with less errors is going to be developed, which covers conduction, convection and radiation based on experiments. The experimental facility is designed, according to variables, such as bulb powers, heat-resistant distance, boundary conditions, etc. Key parameters were set to select and perform experimental cases. The surface average temperatures were calculated, and the temperature distribution patterns of each surface were found. As a result of the experiment, the temperature distribution of all data values was different at temperature, but the shape was very similar. This shows similar heat transfer patterns throughout the data. In the case of forced convection, the temperature distribution was lower depending on the atmosphere temperature, bulb distance, and box size compared to the natural convection. By securing reliable data, algorithm development and verification program based on the experiment is possible.

자동차 헤드램프 온도 예측 시뮬레이션 프로그램 개발

이재진(Jae-Jin Lee),최동녁(Dong-Nyeok Choi),김영완(Young-Wan Kim),최승(Seung Choi),박유라(Yu-Ra Park),이진구(Jingoo Lee),이권영(Kwon-Yeong Lee) 한국자동차공학회 2020 한국자동차공학회 부문종합 학술대회 Vol.2020 No.7

The heat generated from the heat source of an automotive headlamp, is transferred to the lamp’s reflector and lens in the form of conduction, convection and radiation. The transferred heat causes deformation of lamp’s materials when it exceeds the heat-resistance limits of its material, thus the design needs to be done in the range of the limits. In case of failing the heat-resistance test after designing and producing a headlight, the design process should start all over again, requiring a lot of time and cost. However, when the design is proceeded with the simulation results using a temperature prediction program, the time and cost spent on the production would be reduced. The previous data based program showed large errors. Accordingly, new prediction program based on three heat transfer mechanisms has to be developed, which should be similar to CFD results but fast. The Beta version was made covering for a simplified cuboid headlamp. With the help of CFD, the simulation is being updated, minimizing the difference between the result of CFD and simulation in order to get reliability.