원자력 발전용 고온고압 시험장치 내 배수라인 오리피스 개념 설계

박기정(Ki-Jung Park),이선일(Sunil Lee),박주현(Joo Hyun Park),최용석(Yong-Seok Choi) 한국유체기계학회 2021 한국유체기계학회 학술대회 논문집 Vol.2021 No.12

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.

수조형 연구용 원자로의 운전모드에 따른 수조 냉각을 위한 열교환기 성능 예측

박기정(Ki-Jung Park),박홍범(Hong Beom Park) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.11

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.

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.

수평 평활관내 R245fa의 흐름 응축 열전달 특성

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.

임계 열유속 근방까지의 풀 비등 열전달계수

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.

R170/R290 혼합냉매 적용 히트펌프 성능 평가

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.

연구용 원자로의 정상 정지 후 노심 붕괴열을 고려한 수조냉각계통 유량 설계

박기정(Ki-Jung Park),박홍범(Hong Beom Park),서경우(Kyoungwoo Seo) 대한기계학회 2022 대한기계학회 춘추학술대회 Vol.2022 No.6

개방 수조형 연구용 원자로의 조사체 냉각 계통 개념 설계

박기정(Ki-Jung Park),정민규(Minkyu Jung),서경우(Kyoungwoo Seo),김성훈(Seong-Hoon Kim) 대한기계학회 2019 대한기계학회 논문집. Transactions of the KSME. C, 산업기술과 혁신 Vol.7 No.2

연구용 원자로는 핵분열 연쇄 반응으로 발생한 중성자를 기초 연구에서 산업 및 공학적 응용 연구까지의 광범위한 분야에 걸쳐 이용하는 원자로이다. 이 중성자를 이용하는 가장 중요한 분야 중 하나는 매우 다양하게 사용되는 동위 원소 생산 분야이다. 여러 동위 원소 중 Mo-99는 전 세계적으로 의학 진단 등의 의료 분야에서 많이 사용되고 있으며, 이에 대한 수요가 해마다 증가하고 있다. Mo-99 조사시 발생하는 열량은 핵연료에서 발생하는 열량과 비슷한 수준으로 안정적인 Mo-99 생산을 위해서는 충분한 냉각 시스템 설계가 동반되어야 한다. 특히 외부 반사체에서 Mo-99 타깃을 조사할 경우 Mo-99 냉각을 위한 별도의 냉각 계통이 설계되어야 한다. 외부 반사체 내에서의 냉각수 흐름 방향에 따라 냉각계통 설계가 크게 달라지게 되며, 각 유동 방향에 따른 장단점을 분석하여 계통 설계에 적용해야 한다. 본 연구에서는 Mo-99를 포함한 조사체 냉각 계통 설계에 적용 가능한 냉각 계통 개념을 제안하였으며, 이를 바탕으로 개방 수조형 연구용 원자로의 조사체 냉각 계통 개념 설계를 수행하였다. Research reactors are nuclear reactors that utilize fission chain reactions for a wide range of applications, from basic research to industrial and engineering applications. One of the most important application areas is the radioisotope production area. Mo-99 is widely used in medical fields such as medical diagnosis and the demand for Mo-99 is increasing every year. The heat generated by Mo-99 irradiation is similar to that from nuclear fuel, so sufficient cooling system design must be accompanied by stable Mo-99 production. In particular, when Mo-99 target is irradiated on an out-core reflector, an independent cooling system for Mo-99 should be designed. The design of the cooling system depends on the flow direction of the cooling water in the out-core reflector. The characteristic of each flow direction should be analyzed and applied to the conceptual design. In this study, the applicable conceptual design of irradiation targets cooling system of open pool research reactor was proposed.