열응답시험 데이터를 이용한 SCW형 지중열교환기 블리딩 효과 분석

장근선,김민준 한국산학기술학회 2020 한국산학기술학회논문지 Vol.21 No.1

Recently, the applications of the standing column well (SCW) ground heat exchanger (GHX) have increased significantly in Korea as a heat transfer mechanism of ground source heat pump systems (GSHP) because of its high heat capacity and efficiency. Among the various design and operating parameters, bleeding was found to be the most important parameter for improving the thermal performance, such as ground thermal conductivity and borehole thermal resistance. In this study, a bleeding analysis model was developed using the thermal response test data, and the effects of bleeding rates and bleeding locations on the thermal performance of anSCW were investigated. The results show that, when the ground water flows into the top of anSCW, the time variation of circulating water temperature decreased with increasing bleeding rate, and the ground thermal conductivity increases by as much as 179% with a 30% bleeding rate. When the ground water flows into the bottom of the SCW, the circulating water temperatures become almost constant after the increase in the beginning time because the circulating water exchanges heat with the ground structure before mixing with the ground water at the bottom. 개방형 지중열교환기(SCW)는 수직 밀페형 지중열교환기에 비해 높은 용량과 효율을 갖고 있어 최근에 우리나라에서 많이 보급되고 있는 추세이다. SCW형 지중열교환기의 여러 설계 및 운전변수 중 블리딩 운전이 지중 열전도율, 보어홀 열저항 등 열성능 개선에 가장 효과가 큰 것으로 보고되고 있다. 본 연구에서는 SCW형 지중열교환기가 설치된 현장의 열응답시험 결과를 기반으로 블리딩해석 모델을 정립하고 블리딩율 및 지하수 유입수의 위치변화가 SCW형 지중열교환기 열성능에 미치는 영향을 수치해석을 통하여 고찰하였다. 해석결과 지하수가 지중열교환기 상부에서 유입될 경우 지중열교환기 순환수의 시간에 따른 온도증가는 블리딩율이 증가함에 따라 낮아지는 경향을 보였으며, 지중 열전도율은 30% 블리딩율에서 179% 증가하는 결과를 보였다. 반면에 지하수가 지중열교환기 하부에서 유입될 경우 지중열교환기 순환수는 지중과 먼저 열교환을 한 후 유입수와 하단에서 혼합되기 때문에 지중열교환기 순환수의 온도증가는 상부 유입의 경우보다 적으며 블리딩율이 약 10%를 초과하면 일정하게 유지되는 경향을 보였다.

The Effect of Sample Size and Computation method on turbulent acales

장근선 선문대학교 중소기업기술지원연구소 1997 선문공대 연구/기술 논문집 Vol.2 No.1

본 논문에서는 난류 요동속도 데이터의 표본크기와 계산방법이 난류성분에 미치는 영향을 고찰하였다. 난류 제트가 제한된 자유 유동장으로 수직으로 분사될 때 생성되는 유동장을 본 분석의 대상으로 선택하였다. 난류성분으로서 Autocorrelation 함수, 난류적분 길이 및 Taylor 미소길이를 순간 속도성분으로부터 직접 Fourier 변환방법과 일반적인 평균법을 사용하여 구하였으며, 이 두 가지 계산방법은 다양한 데이터 표본크기에 대해 상호 비교하였다. 분석결과 이 두 가지 다른 계산방법에 의한 난류 성분 값은 표본수가 증가할수록 일치하는 경향을 보이나 직접 Fourier 변환방법에 의한 값이 평균법에 의해 구한 값보다 항상 크게 나타나고 있음을 보여 주고 있다. This paper presents effects of sample size of the turbulent fluctuating velocity data and the computation method on the determination of turbulent scales. The flow field created by a turbulent jet vertically discharging into a confined crossflow is selected for this investigation. Turbulent information such as the autocorrelation function, integral length scale and Taylor microscale is constructed from the instantaneous velocity components using the direct Fourier transform method and the conventional averaging technique, and these two computation methods are compared with each other for the various number of sample size. Results show that the direct Fourier transform method consistently yields the turbulent scale values larger than the results from the averaging technique, although the values between two methods become closer as the number of sample size increase.

Calculation of Mass Transfer Rates in the Cylindrical Tank

장근선 선문대학교 첨단과학기술연구소 1997 첨단과학기술연구소 논문집 Vol.2 No.-

This article is designed to examine the development of two trends in Korean Ak-Jang Literature. The main findings of this study are as follows. 1. There have been two ways of development in the origin of Korean Ak-Jang Literature. The one was the autogenous Ak-Jang Literature, which was not named Ak-Jang but originated from the flow of Korean ethnic ceremonial music(Ye-Ak). The other was the foreign Ak-Jang Literature originated from China, which were based on Chinese ceremonial music and imported during Koryo Dynasty. These two forms of Ak-Jang, in conflict one time and in fusion another, have given and taken influence each other. 2. The origin of the autogenous Ak-Jang Literature was the Guk-Joong festival, which was the memorial ceremony for Heaven in ancient society. It has been developed to such Korean national ceremonies as the Poong-Wol ceremony of Hwa-Rang Circle in Silla Dynasty and Pal-Kwan Hoe in Koryo Dynasty, which dedicated to peace, well-being of the people, and long life of the King. 3. The form of the foreign Ak-Jang Literature was originated from the model of Ak-Jang Literature in Chinese antiquity. Its existence explained that China was the center of the world in East Asia and Korea tried to build a cultural community with China. Ak-Jang Literature in the early Chosun Dynasty followed the universal form of East Asian Ak-Jang style on the one hand, and succeeded to make an original form Korean Ak-Jang style on the other. 4. The reason why different dynasties in Korean history tried to do their best in fabricating their own Ak-Jang was, in the first place, to enhance their status as cultural country and to join medieval East Asian cultural sphere willingly and harmoniously. The Chinese written Ak-Jang in the early Chosun Dynasty was formed with Korean original poetic style, and escaped from typical Chinese formula. The foreign Ak-Jang Literature in Korea was not the copy of Chinese Ak-Jang, but the independent trial of expressing Korean cultural tradition. In conclusion, Korean Ak-Jang Literature can be appreciated and its value would be estimated not from the superficial viewpoint of copy or flattery to Chinese culture, but from the standpoint of the sharing of East Asian universality and the originality of Korean culture.

완전 발달된 관류 유동장에서의 비정상 열전달

장근선 선문대학교 첨단과학기술연구소 1996 첨단과학기술연구소 논문집 Vol.1 No.1

본 연구에서는 유한 길이를 지닌 원형관에서 입구 온도가 급격히 변하는 과도시( transient) 비정상 열전달 현상은 수치 해석을 이용하여 분석하였다. 관내의 속도장은 정상 상태인 power-law분포로 가정하였으며 관외부 열전달 경계 조건은 일부 영역에 대해 대류 열전달 조 건을 주고 나머지 부분에 대해서는 단열 조건을 주었다. 지배 방정식은 이완 격자 구조로된 제어 체적에 대해 2차원 유한 차분 방정식으로 표현하였으며 계산은 SIMPLER 알고리즘을 사용하였다. 계산 결과는 다양한 입구 온도 빛 입구 유량 조건에 대해 시간 변화에 따른 축방향 Nusselt 수 분포, 반경 방향 온도 분포, 평균 온도 분포 등을 구하였다. Numerical results arc presented for the transient heal transfer of the finite length pipe flow with step change in the inlet temperature. Velocity field inside the pine is assumed to be Power-law distribution and heat transfer boundary conditions outside the pipe are given partially by the convection heat transfer conditions and partially by insulated conditions. Governing equations are expressed by the two-dimensional finite-difference formulations for the staggered grid control volumes and calculation results are obtained using the SIMPLER algorithm. Results presented include the time variant axial Nusselt number distribution, radial temperature distribution and average temperature distribution for the various inlet temperatures and flow rates.

습표면 조건에서 슬릿 핀-튜브 열교환기의 열전달 및 압력강하 특성

장근선,Thanh-Long Phan 대한설비공학회 2007 설비공학 논문집 Vol.19 No.1

Water condensate accumulated on the surface of a fin-and-tube heat exchanger significantly affects its thermal and hydraulic performance. The purpose of this study is to investigate the effect of condensate retention on the air-side heat transfer performance and flow friction. Total 12 samples of slit and plate fin-and-tube heat exchangers with varying fin spacing and number of tube rows are tested under dry and wet conditions. The thermal fluid measurements are made using a psychometric calorimeter. Frontal air velocity varies in the range from 0.7m/s to 1.5m/s. Using the experimental data, presented are the heat transfer coefficients in terms of Colburn -factor and friction factor.

ASHRAE 2002 winter meeting 신기술동향 - IAQ and Comfort / Ventilation 분야 -

장근선 대한설비공학회 2002 대한설비공학회 학술발표대회논문집 Vol.2002 No.-

Scaling-Law를 이용한 원자력 발전소 개념설계

장근선 선문대학교·중소기업기술지원연구소 1998 선문공대 연구/기술 논문집 Vol.3 No.1

신형원자로를 개발하는데 있어서 가장 핵심적인 과제는 개념설계의 정립이라 할 수 있다 개념설계가 적절히 수립되고 발전소 주요 설계변수가 결정되어야 이후 필요한 개발업무가 순조롭게 이루어 질 수 있다 한편, 급변하는 에너지 수급변화에 신속하게 대처하기 위해서는 노형 개발보다는 기존의 안전성과 경제성이 입증된 발전소의 용량을 증가시키거나 감소시키는 신축성 있는 개발전략이 요구된다 본 연구에서는 참조 발전소의 설계로부터 개발하고자 하는 발전소의 주요설계변수를 Scaling-law를 이용하여 결정하는 기법을 제시하였다 Establishment of conceptual design is the most important task in the development of new nuclear power plant(NPP) Based on the conceptual design, major design parameters can be determined and the successive development tasks are satisfactorily progressed In the meanwhile, in order to cope with rapidIy changing energy needs, scale-up or down of existing NPP with proven safety and economy may be the preferred approach rather than developing new type of NPP In this study, a conceptual design of the target NPP is performed using the scaling-law from the design of reference plant.

An Experimental Study on the Thermal Performance Evaluation of SCW Ground Heat Exchanger

장근선,김민준,김영재 대한설비공학회 2017 International Journal Of Air-Conditioning and Refr Vol.25 No.1

In recent years, application of the standing column well (SCW) ground heat exchanger (GHX) has been noticeably increased as a heat transfer mechanism of ground source heat pump (GSHP) systems with its high heat capacity and efficiency. Determination of the ground thermal properties is an important task for sizing and estimating cost of the GHX. In this study, an in situ thermal response test (TRT) is applied to the thermal performance evaluation of SCW. Two SCWs with different design configurations are installed in sequence to evaluate their effects on the thermal performance of SCW using a single borehole. A line source method is used to derive the effective thermal conductivity and borehole thermal resistance. Effects of operating parameters are also investigated including bleed, heat injection rate, flow rate and filler height. Results show that the effective thermal conductivity of top drawn SCW (Type A) is 11.7% higher than that of bottom drawn SCW (Type B) and of operating parameters tested bleed is the most significant one for the improvement of the thermal performance (40.4% enhanced in thermal conductivity with 10.9% bleed).

2000 ASHRAE winter meeting의 신기술동향 - 열펌프 및 신냉매 분야 -

장근선 대한설비공학회 2000 대한설비공학회 학술발표대회논문집 Vol.2000 No.-

원전 수명 연장에 대한 기술 현안 분석

장근선,정지환,박윤원,이승혁,김효정 한국원자력산업회의 2002 원자력산업 Vol.22 No.6