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실내실험을 통한 공용중인 철도터널(NATM)의 횡배수관 클로깅 현상 원인 분석
기정서 ( Ki Jung Su ),이민수 ( Lee Min Soo ),박경한 ( Park Kyung Han ),노은철 ( Noh Eun Cheol ) 한국구조물진단유지관리공학회 2019 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.23 No.2
터널은 지하수 처리방법에 따라 배수형 및 비배수 방수형식으로 구분된다. 배수형 방수형식 터널은 콘크리트 라이닝 배면의 지하수에 대한 수압을 고려하지 않으므로 대단면 터널 및 얇은 라이닝 콘크리트 두께 등 터널형상 선정에서 자유롭고 경제적인 장점이 있다. 하지만 터널의 배수시스템에 문제가 생기는 경우 라이닝 콘크리트 배면에 지하수로 인한 수압으로 장기적인 측면에서 터널의 구조적 안전성에 영향을 주기 때문에 터널의 내구연한 동안 배수시스템에 대한 유지관리와 문제 발생 시 적절한 보수, 보강 방법의 적용이 필요한 실정이다.
대체냉매 R430A를 적용한 정수기 냉동시스템의 성능 평가
박기정(Ki-Jung Park),이요한(Yohan Lee),정동수(Dongsoo Jung),김경기(Kyoung-kee Kim) 대한설비공학회 2009 설비공학 논문집 Vol.21 No.2
In this study, thermodynamic performance of R430A is examined both numerically and experimentally in an effort to replace HFC134a used in the refrigeration system of domestic water purifiers. Even though HFC134a is used predominantly in such a system these days, it needs to be phased out in the near future in Europe and most of the developed countries due to its high global warming potential. To solve this problem, cycle simulation and experimental measurements are carried out with a new refrigerant mixture of 76%H152a/24% H600a using actual domestic water purifiers. This mixture is numbered and listed as H430A by ASHRAE recently. Test results show that the system performance with R430A is greatly influenced by the amount of charge due to the small internal volume of the refrigeration system of the domestic water purifiers. With the optimum amount of charge of 21 to 22 grams, about 50% of HFC134a, the energy consumption of R430A is 13.4% lower than that of HFC 134a. The compressor dome and discharge temperatures and condenser center temperature of R430A are very similar to those of HFC134a at the optimum charge. Overall, R430A, a new long term environmentally safe refrigerant, is a good alternative for HFC134a requiring little change in the refrigeration system of the domestic water purifiers.
중성자 핵변환 도핑을 위한 수조 내 수력 회전장치 개념 설계
박기정(Ki-Jung Park),서경우(Kyoungwoo Seo),김성훈(Seong Hoon Kim) 대한기계학회 2018 大韓機械學會論文集B Vol.42 No.7
실리콘의 중성자핵변환도핑(Neutron transmutation doping, NTD)은 연구용 원자로(Research Reactor) 이용의 중요한 아이템 중 하나이다. 고품질의 NTD 조사 웨이퍼를 생산하기 위해서는 NTD 조사 과정에서 NTD 조사체를 일정한 속도로 장시간 회전시키는 것이 필요하다. 본 연구에서는 기존의 많은 연구용 원자로에 적용 중인 모터를 이용한 기계식 회전 방식의 단점을 보완할 수 있는 수력 회전장치(Hydraulic rotation device, HRD)에 대한 개념설계를 수행하였다. 수력회전장치는 유량 공급 펌프를 이용하여 어떠한 기계 구동부 없이 수력을 이용하여 실리콘 잉곳을 일정한 속도로 회전시킬 수 있는 새로운 개념의 회전장치이다. NTD 조사를 위한 수력회전장치는 스러스트 베어링 부분(Thrust bearing part)과 저널 베어링 부분(Journal bearing part) 그리고 임펄스 제트 부분(Impulse jet part)의 세 부분으로 구성된다. 각 부분으로 연결된 노즐에서 형성된 고압의 제트류에 의해 회전체의 안정적인 부상, 지지 및 일정속도의 회전을 구현하도록 설계하였다. 본 연구에서 제안된 수력회전장치 개념은 향후 실제 적용을 위해 제작 및 실험을 통해 추가 검증되어야 한다. Neutron transmutation doping (NTD) of silicon is one of the important items in the utilization of a research reactor. For the production of high-quality NTD silicon, it is necessary to rotate the silicon ingot at a uniform speed and in a certain position in the NTD irradiation sites for uniform irradiation of the NTD during the NTD irradiation process. In this study, a hydraulic-driven rotation system is proposed to make up for the weakness of the motor-driven rotation system as the conventional method, which is needed to enhance the reliability of NTD systems. The hydraulic rotation device (HRD) for the NTD to rotate the silicon ingot at a uniform speed is designed conceptually to apply the new concept of a hydraulic-driven rotation system. The HRD designed for the NTD consists of a thrust bearing part, journal bearing part, and an impulse jet part. High-pressure water jets are supplied through each nozzle. The thrust bearing part is designed for the stable levitation of the silicon ingot and HRD in the pool. The journal bearing part is designed to support the HRD during thrust and rotation. The impulse jet part is designed for uniform rotation of the HRD. Through the proposed design, the potential for application to a new NTD rotation system will be verified.
R1234yf와 R1234yf/R134a의 자동차 에어컨 작동 조건에서의 성능 평가
박기정(Ki-Jung Park),이요한(Yohan Lee),최대성(Daeseong Choe),정동수(Dongsoo Jung) 대한설비공학회 2010 설비공학 논문집 Vol.22 No.12
In this study, performance of R1234yf and R1234yf/R134a mixture is measured on a heat pump bench tester in an attempt to substitute R134a used widely in mobile air conditioners (MACs). The bench tester is equipped with a open type compressor providing a nominal capacity of 3.5 ㎾. All tests are conducted under the summer cooling and winter heating conditions of 7/4 5℃ and -7/41℃ in the evaporator and condenser, respectively. For R1234yf/R134a mixture, measurements are made at 5%, 10%, and 15% of R134a by mass. Test results show that the coefficient of performance (COP) and capacity of R1234yf are up to 2.7% and 4.0% lower than those of R134a, respectively. For R1234yf/R134a mixture, the COP and capacity are up to 3.9% lower and 3.6% higher than those of R134a. For R1234yf and R1234yf/R134a mixture, the compressor discharge temperature is 4.1~6.7℃ lower than that of R134a while the amount of charge is reduced up to 11% as compared to R134a. 90%R1234yf/10%R134a is a better refrigerant than pure R1234yf in that it is less flammable and more compatible with existing R134a system. Based upon the results, it is concluded that R1234yf and R1234yf/R134a mixture are long term environmentally friendly solutions to mobile air-conditioners due to their excellent environmental properties with acceptable performance.
박현신(Hyun-Shin Park),박기정(Ki-Jung Park),정동수(Dongsoo Jung) 대한설비공학회 2008 설비공학 논문집 Vol.20 No.2
Flow condensation heat transfer coefficients(HTCs) of R123 and R245fa are measured in a horizontal plain tube. The main test section in the experimental flow loop is made of a plain copper tube of 9.52 ㎜ outside diameter and 530 ㎜ length. The refrigerant is cooled by passing cold water through an annulus surrounding the test section. Tests are performed at a fixed saturation temperature of 50 ± 0.2 ℃ with mass fluxes of 50, 100, 150 ㎏/㎡s and heat flux of 7.3~7.7 ㎾/㎡. Heat transfer data are obtained in the vapor quality range of 10~90%. Test results show that the flow condensation HTCs of R245fa are overall 7.9% higher than those of R123 at all mass fluxes. The pressure drop of R245fa is smaller than that of R123 at the same heat flux. In conclusion, R245fa is a good candidate to replace ozone depleting R123 currently used in chillers from the view point heat transfer and environ-mental properties.
박기정(Ki-Jung Park),정동수(Dongsoo Jung) 대한설비공학회 2008 설비공학 논문집 Vol.20 No.9
In this work, pool boiling heat transfer coefficients(HTCs) of 5 refrigerants of differing vapor pressure are measured on horizontal smooth square surface of 9.52 ㎜ length. Tested refrigerants are R123, R152a, R134a, R22, and R32 and HTCs are taken from 10 ㎾/㎡ to critical heat flux of each refrigerant. Wall and fluid temperatures are measured directly by thermocouples located underneath the test surface and by thermocouples in the liquid pool. Test results show that pool boiling HTCs of refrigerants increase as the heat flux and vapor pressure increase. This typical trend is maintained even at high heat fluxes above 200 ㎾/㎡. Zuber's prediction equation for critical heat flux is quite accurate showing a maximum deviation of 21% for all refrigerants tested. For all refrigerant data up to the critical heat flux, Stephan and Abdelsalam's well known correlation underpredicted the data with an average deviation of 21.3% while Cooper's correlation overpredicted the data with an average deviation of 14.2%. On the other hand, Gorenflo's and lung et al's correlation showed only 5.8% and 6.4% deviations respectively in the entire nucleate boiling range.
박기정(Ki-Jung Park),이철희(Cheol-Hee Lee),정동수(Dongsoo Jung) 대한설비공학회 2008 설비공학 논문집 Vol.20 No.9
In this study, performance of R170/R290 mixtures is measured on a heat pump bench tester in an attempt to substitute R22. The bench tester is equipped with a commercial hermetic rotary compressor providing a nominal capacity of 3.5 ㎾. All tests are conducted under the summer cooling and winter heating conditions of 7/45℃ and -7/41 ℃ in the evaporator and condenser respectively. During the tests, the composition of R170 is varied from 0 to 10% with an interval of 2%. Test results show that the coefficient of performance (COP) and capacity of R290 are up to 15.4% higher and 7.5% lower than those of R22 for both conditions respectively. For R170/R290 mixture, the COP decreases and the capacity increases with an increase in the amount of R170. The mixture of 4%R170/96%R290 shows the similar capacity and COP as those of R22. For the mixture, the compressor discharge temperature is 16~30℃ lower than that of R22. There is no problem with mineral oil since the mixture is mainly composed of hydrocarbons. The amount of charge is reduced up to 58% as compared to R22. Overall, R170/R290 mixture is a good long term 'drop-in'. candidate to replace R22 in residential air-conditioners and heat pumps.