Solar Tower용 흡수기의 설치 각도 및 작동 조건 변화에 따른 대류 열손실 분석

강경문(Kang Kyung-Mun),이주한(Lee Ju-Han),김용(Kim Yong),서태범(Seo Tae-Beom),강용혁(Kang Yong-Heack) 한국태양에너지학회 2007 한국태양에너지학회 논문집 Vol.27 No.4

Convective heat loss from solar tower receiver is experimentally investigated in wind tunnel with tilt angles and operating conditions. In order to simulate the receiver, an electric heater, which is made of aluminum (width : 100 ㎜, height : 100㎜) is used and installed in the wind tunnel. The convective heat loss from the receiver is dependent on the direction and the velocity of the wind and the surface temperature of the receiver. The tilt angle and surface temperature of the receiver are varied from 0o(cavity facing straight down) and 90o(cavity aligned horizontally) and from 150℃ to 250℃, respectively. Also, the wind speed is changed from 0 to 4㎧. The convective heat loss is obtained by measuring consumed power to the heater to maintain the desired surface temperature. It is concluded that Nusselt number increases with increasing wind speed for all cases. Especially, it is showed that Nusselt number can be maximized when the tilt angle is 30o.

ZnO 초박막의 두께 변화에 따른 구조적, 전기적, 광학적 특성 변화 연구

강경문,김민재,이홍섭,박형호,Kang, Kyung-Mun,Wang, Yue,Kim, Minjae,Lee, Hong-Sub,Park, Hyung-Ho 한국마이크로전자및패키징학회 2019 마이크로전자 및 패키징학회지 Vol.26 No.2

원자층 증착법(ALD: atomic layer deposition)으로 $150^{\circ}C$에서 성장된 zinc oxide (ZnO) 초박막의 두께 변화에 따른 구조적, 전기적, 광학적 특성을 조사하였다. ZnO 박막을 증착하기 위해 금속 전구체와 반응물로 각각 diethylzinc와 deionized water를 사용하였다. ALD 사이클 당 성장률은 $150^{\circ}C$에서 약 0.21 nm/cycle로 일정 하였으며, 50 사이클 이하의 샘플들은 초기 ALD 성장 단계에서 상대적으로 얇은 두께로 인하여 비정질 성질을 갖는 것으로 보였다. 100 사이클에서 200 사이클로 두께가 증가함에 따라 ZnO 박막의 결정성이 증가하였고 hexagonal wurtzite 구조를 보였다. 또한, ZnO 박막의 입자 크기가 ALD 사이클의 수의 증가에 따라 증가되었다. 전기적 특성 분석 결과 박막 두께의 증가에 따라서 비저항 값이 감소하였으며, 이는 박막 두께 증가에 따른 입자 크기 증가 및 결정성 개선으로 더 두꺼운 ZnO 박막에서 입자 경계의 농도 감소와 상관 관계가 있음을 알 수 있었다. 광학적 특성 분석 결과 근 자외선 영역 (300 nm~400 nm)에서의 밴드 엣지 흡수가 증가 및 이동되었는데 이 현상은 ZnO 박막 두께의 증가에 따른 캐리어 농도의 증가가 기인 한 것으로, 이 결과는 박막 두께의 증가에 따른 저항률 감소와 잘 일치한다. 결과적으로 박막의 두께가 증가하면 막 면의 응력이 완화되어 밴드 갭이 감소하고 결정성 및 전도성이 향상됨을 알 수 있었다. We investigated the structural, electrical and optical properties of zinc oxide (ZnO) ultra-thin films grown at $150^{\circ}C$ by atomic layer deposition (ALD). Diethylzinc and deionized water were used as metal precursors and reactants, respectively, for the deposition of ZnO thin films. The growth rate per ALD cycle was a constant 0.21 nm/cycle at $150^{\circ}C$, and samples below 50 cycles had amorphous properties due to the relatively thin thickness at the initial ALD growth stage. With the increase of the thickness from 100 cycles to 200 cycles, the crystallinity of ZnO thin films was increased and hexagonal wurtzite structure was observed. In addition, the particle size of the ZnO thin film increased with increasing number of ALD cycles. Electrical properties analysis showed that the resistivity value decreased with the increase of the thin film thickness, which is correlated with the decrease of the grain boundary concentration in the thicker ZnO thin film due to the increase of grain size and the improvement of the crystallinity. Optical characterization results showed that the band edge absorption in the near ultraviolet region (300 nm~400 nm) was increased and shifted. This phenomenon is due to the increase of the carrier concentration with the increase of the ZnO thin film thickness. This result agrees well with the decrease of the resistivity with the increase of the thin film thickness. Consequently, as the thickness of the thin film increases, the stress on the film surface is relaxed, the band gap decreases, and the crystallinity and conductivity are improved.

수소 도핑효과에 의한 ZnO 맴트랜지스터 소자특성

손기훈,강경문,박형호,이홍섭,Son, Ki-Hoon,Kang, Kyung-Mun,Park, Hyung-Ho,Lee, Hong-Sub 한국마이크로전자및패키징학회 2020 마이크로전자 및 패키징학회지 Vol.27 No.1

원자층 증착법(ALD: atomic layer deposition)으로 성장된 ZnO n-type 산화물반도체를 이용하여 three terminal memristor (memtransistor) 소자를 제작하여 습도에 따른 그 특성을 관찰하였다. 40 nm 두께의 ZnO 박막을 이용하여 channel width 70 ㎛, length 5 ㎛, back gate 구조의 memtransistor 소자를 제작하여 습도에 (40%, 50%, 60%, 70%) 따른 gate tunable memristive 특성변화를 관찰하였다. 습도가 높아질수록 electron mobility와 gate controllability가 감소하여 수소도핑효과에 의한 carrier 농도가 증가하는 거동의 output curve가 관찰되었다. 60%, 70%의 습도에서 memristive 거동이 관찰되었으며 습도가 높아질수록 on/off ratio는 증가하는 반면 gate controllability가 감소하였다. 60% 습도에서 가장 우수한 특성의 gate tunable memristive 특성을 얻을 수 있었다. This study demonstrates metal-oxide based memtransistor device and the gate tunable memristive characteristic using atomic layer deposition (ALD) and ZnO n-type oxide semiconductor. We fabricated a memtransistor device having channel width 70 ㎛, channel length 5 ㎛, back gate, using 40 nm thick ZnO thin film, and measured gate-tunable memristive characteristics at each gate voltage (50V, 30V, 10V, 0V, -10V, -30V, -50V) under humidity of 40%, 50%, 60%, and 70% respectively, in order to investigate the relation between a memristive characteristic and hydrogen doping effect on the ZnO memtransistor device. The electron mobility and gate controllability of memtransistor device decreased with an increase of humidity due to increased electron carrier concentration by hydrogen doping effect. The gate-tunable memristive characteristic was observed under humidity of 60% 70%. Resistive switching ratio increased with an increase of humidity while it loses gate controllability. Consequently, we could obtain both gate controllability and the large resistive switching ratio under humidity of 60%.

인공지능 모델에 의한 지하수위 모의결과의 적절성 판단을 위한 허용가능한 예측오차 범위의 추정

신문주,문수형,문덕철,류호윤,강경구,Shin, Mun-Ju,Moon, Soo-Hyoung,Moon, Duk-Chul,Ryu, Ho-Yoon,Kang, Kyung Goo 한국수자원학회 2021 한국수자원학회논문집 Vol.54 No.7

Groundwater is an important water resource that can be used along with surface water. In particular, in the case of island regions, research on groundwater level variability is essential for stable groundwater use because the ratio of groundwater use is relatively high. Researches using artificial intelligence models (AIs) for the prediction and analysis of groundwater level variability are continuously increasing. However, there are insufficient studies presenting evaluation criteria to judge the appropriateness of groundwater level prediction. This study comprehensively analyzed the research results that predicted the groundwater level using AIs for various regions around the world over the past 20 years to present the range of allowable groundwater level prediction errors. As a result, the groundwater level prediction error increased as the observed groundwater level variability increased. Therefore, the criteria for evaluating the adequacy of the groundwater level prediction by an AI is presented as follows: less than or equal to the root mean square error or maximum error calculated using the linear regression equations presented in this study, or NSE ≥ 0.849 or R² ≥ 0.880. This allowable prediction error range can be used as a reference for determining the appropriateness of the groundwater level prediction using an AI.

위치추적 센서를 이용한 터널의 실시간 시공관리

이강현,김대원,문성모,조훈희,강경인,이인모,Lee, Kang-Hyun,Kim, Dae-Won,Mun, Sung-Mo,Cho, Hun-Hee,Kang, Kyung-In,Lee, In-Mo 한국터널지하공간학회 2011 한국터널지하공간학회논문집 Vol.13 No.2

Construction sites are becoming larger and complex with the growth of national economy. Accordingly, it is important to identify real-time information about materials, equipments, and manpower during construction at sites. Even though research utilizing position tracking sensors has been conducted in architectural engineering fields, this area of research is almost nil in civil engineering fields. Therefore, a feasibility study to find a way to apply position tracking sensors to an in-situ tunnel construction site adopting conventional tunnelling method is performed in this study. A methodology is proposed that the progress management of the tunnelling work can be monitored by checking construction materials needed at job site and the safety management system can be assessed by checking distance between in-situ workers and construction equipments. The most representative materials were identified so that IT technology can be applied by attaching and monitoring sensors to the selected materials. Also, time of arrival (TOA) for a position determination technology along with a wireless network technology was chosen and build wireless network system. The adopted methodology was applied to an in-situ tunnelling site, and verified the usefulness of the proposed system. 국가 경제규모의 성장과 더불어 단위 건설현장도 대형화, 복합화 되어 가고 있는 추세이다. 이에 따라 건설현장에서는 효율적인 프로젝트 관리를 위하여 자재, 장비, 인력 등의 자원에 관한 실시간 정보파악의 요구가 증가하고 있다. 최근 건축분야에서는 다양한 위치추적 센서를 활용한 시공관리에 대한 연구가 이루어지고 있다. 하지만 토목분야에서는 이러한 연구가 거의 전무한 실정이다. 따라서 본 연구에서는 터널 시공 방법 중 NATM 공법을 대상으로 위치추적이 가능한 센서를 활용하여 자재를 이용한 진도관리와 장비와 인력간의 안전관리에 있어서 실제 현장에 활용 가능한 방법을 제시하였다. 각 공정의 자재를 이용한 진도관리 방안과 사람과 장비의 거리를 통한 안전관리 방안을 제시하였다. 센서를 부착할 진도관리용 자재를 선정하고, 위치좌표를 계산하기 위한 TOA방식의 무선측위기술과 무선랜을 이용하여 터널 현장에 무선 네트워크 시스템을 구축하였다. 이를 바탕으로 터널 현장에 적용 가능한 모델을 제시하였으며, 현장 예비 시험과 현장시험을 통하여 시스템을 검증하였다.

고로슬래그 기반의 고칼슘 플라이애시 치환비율에 따른 물리적 특성

조성우(Cho, Seong Woo),강경모(Kang, Kyung mo),문경주(Mun, Kyoung Ju),형원길(Hyung, Won Gil) 한국콘크리트학회 2019 한국콘크리트학회 학술대회 논문집 Vol.31 No.2

전산유체역학을 이용한 태양열 화학반응기에서의 열전달 특성 해석

고요한(Johan Ko),강경문(Kyung-Mun Kang),서태범(Tae-Beom Seo) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5

This paper describes the experiment and simulation results of a heat transfer in the SCR (solar chemical reactor). The SCR is installed on the dish type solar collector, Inha Dish-1 in Songdo, Incheon. Dish type solar collector which has operation temperature above 1000℃ is normally classified in high temperature process in solar thermal engineering. With this high operation temperature, convective heat loss, thermal fracture are important features for designing SCR. In this paper, temperature distribution of the SCR is measured and compared with simulation result. SCR is made of SUS304 and the receiver diameter is 10㎝ and 6 sheets of 10㎜ thickness porous metals are laminated inside the receiver. Irradiation from Inha Dish-1 is about 5㎾. Simulation result and measured temperature shows similar inclination through the center line of the SCR.

전산유체역학을 이용한 직접 접촉식 히트파이프의 응축부 형상에 따른 성능비교

고요한(Ko Yo-han),강경문(Kang Kyung-Mun),서태범(Seo Tae-Beom) 한국태양에너지학회 2008 한국태양에너지학회 학술대회논문집 Vol.- No.-

The purpose of this study is to compare the different shapes of condenser of the direct contact heat transfer from the heat pipe condenser to the receiving water using CFD. The heat transfer from the working fluid of the heat pipe to receiving fluid flows through the manifolder is one of the important part in evacuated solar collector system. The retrenchment of the thermal resistance between the heat pipe and the manifolder could increase the thermal performances of the whole system. Recently, direct heat transfer from the heat pipe condenser wall to the receiving water was suggested and accompanied experiments were achieved. This experiment shows the better performances of the direct contact hear transfer analogically. Preceding calculations are carried out for the performance comparison: mesh dependence test, discretization method test and equation model test. with these preceding tests, 4 different shapes of condenser are compared and each case were set up for the same heat flux at the condenser wall. The calculation result shows that the efficiency of the extended surface condenser shape is 10% higher then the that of the others.

연료전지 채널 내 균일한 유량분배를 위한 연료전지 스택의 매니폴드 디자인 최적화 연구

조아래(A-Rae Jo),강경문(Kyung-Mun Kang),오성진(Sung-Jin Oh),주현철(Hyun-chul Ju) 한국유체기계학회 2012 한국유체기계학회 논문집 Vol.15 No.5

고온 태양열 공기식 흡수기의 충진재 변화에 따른 열전달 및 압력강하 성능 분석

조자현(Ja Hyun Cho),이주한(Ju Han Lee),강경문(Kyung Mun Kang),서태범(Tae Beom Seo) 대한설비공학회 2008 설비공학 논문집 Vol.20 No.11

The characteristics of heat transfer and pressure drop of several different porous materials which can be used as inserts inside solar volumetric air receivers were experimentally investigated. Generally, porous materials were inserted into solar volumetric air receivers to increase the thermal performance. In the present work, honeycomb (diameter: 100 ㎜, thickness: 30 ㎜), laminated mesh (diameter: 100 ㎜, thickness: 1 ㎜) are considered as the inserts for the experiment. The experimental apparatus consists mainly of a cylindrical ceramic duct as a receiver and an electric heater as an energy source. This system is an intake open loop, which used as air of working fluid. The temperatures inside the ceramic tube are measured by thermocouples, which are installed at each layer of the porous materials. The pressure-drop experimental apparatus is fabricated alike the above experimental equipment. An acrylic tube is used like as the ceramic tube, which has the same specifications of the ceramic tube. The pressure drop of porous materials inserted in the acrylic tube is measured between front and rear of those by transmitter. The results show that the laminated mesh surpasses the honeycomb of heat transfer and pressure drop increase as the porous material thickness and Reynolds number.