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A Study of the Thermal Performance of Batch-Type Passive Solar Hot Water Systems
Chun, Won-Gee 濟州大學校 工科大學 産業技術硏究所 1998 尖端技術硏究所論文集 Vol.9 No.1
Three batch-type passive water heating systems, which serve the dual function of absorbing solar energy and storing the heated water, have been designed and fabricated for the purpose of side-by-side tests at KIER. The batch systems evaluated are classified according to the design of the box and the arrangement of the storage tanks. Experimental and numerical results given here show the transient performance of these devices. It is also shown that enough hot water could be available in the early morning if the glazing is covered overnight by appropriate insulation. From this study a design has been selected for commercial development in Korea.
A Study on Dispersed Phases in a DCHX for Solar Application
Chun, Won-Gee,Kim, Sin,Lee, Heon-Ju,Lee, Yoon-Joon,Kang, Yong-Heack 제주대학교 공과대학 첨단기술연구소 2001 尖端技術硏究所論文集 Vol.12 No.2
The present study has been carried out to examine the formation and movement of dispersed phases in DCHXs as this dictates the performance of any heat recovery systems including solar thermal energy systems. Different types of DCHXs are introduced and their operating principles are reviewed in view of fluid mechanical characteristics of dispersed phases. Different cases of DCHXs using two immiscible liquids are considered as these cases offer good examples in capturing and image processing of dispersed phases by using such a technique as electric tomography(ET) without undue difficulties. Also considered is the case of three-phase problem that needs further investigation to resolve the complicated physical phenomena involved with the operation of such DCHXs.
AN EXPERIMENTAL STUDY ON THE FORMATION OF METHANE HYDRATES
Chun, Won-Gee,Kim, Chong-Bo 제주대학교 공과대학 첨단기술연구소 2002 尖端技術硏究所論文集 Vol.13 No.1
Gas(methane) hydrates are solid solutions when water molecules are linked through hydrogen bonding and create host lattice cavities that can enclose many kinds of guest(gas) molecules. There are abundant resources of methane(gas) hydrate in the earth and distributed widely at offshore and permafrost. The natural gas(or methane) hydrate exists in nature at low temperature above the normal freezing point of water and high pressure greater than relatively 30bars. In the present investigation, extensive experimentations have been carried for these characteristics using a semibatch stirred tank reactor. The temperatures considered in the experiments were in the range of 274.6i 289.5K under to find out equilibrium points 2.90i 15.14MPa. Initially, the experiments have been carried out by increasing temperatures of the cell at fixed pressures. Then, experiments for the influence of gas consumption under various degrees of subcooling and stirring rates has been investigated to determine kinetic characteristics of the hydrates. The results of present investigation show that the gas consumption rates were closely related to operational pressure, temperature, degrees of subcooling and stirring rates.
Thermal Analysis of Passive Solar Schoolroom Designs
Chun,Won-Gee 濟州大學校 工科大學 産業技術硏究所 1998 尖端技術硏究所論文集 Vol.9 No.2
This paper studies thermal Performances of three types of schoolroom configurations designed to maximize the use of solar energy. Each design contains certain distinctive characteristics in trapping and utilization of solar energy. To carry out the thermal analysis here numerical simulations as well as on-the-site measurements are peformed for a certain period of time (unsteady state). The results are then extended to predict the long term average thermal performance of each configuration during a typical wintry season. Suggestions are further made to improve its overall environmental conditions when designing a schoolroom with passive solar concepts.
Image Capturing of Dispersed Phases in DCHXs by Electric Tomography
Chun, Won-Gee,Kim, Min-Chan,Lee, Heon-Ju,Kang, Yong-Heack,Kwon, Hyok-Bo The Korean Solar Energy Society 2001 한국태양에너지학회 논문집 Vol.21 No.2
This paper introduces the physical phenomena involved in Direct Contact Heat Exchangers (DCHXs) and also investigates the possibility of applying of EIT(Electrical Impedance Tomography) technique for capturing the images of dispersed phases as they stream through a stagnant body of water. A number of cases are studied where two dimensional cross-sectional static images are given for fictitious and actual masses present in a column of water(saline solution). In most direct contact liquid-liquid heat exchangers, oil or hydrocarbon with a density different(lighter or heavier) from water is normally used as dispersed working fluid. The main difficulty that arises with this arrangement lies in the elucidation of complicated flow field where the dispersed phase fluid tends to change its shape and size constantly during its journey through the other phase(water). This paper presents a number of results with different types of dispersed phases that are immiscible with water. The EIT technique has been employed in this context to test its applicability in capturing the dynamic images of dispersed phases. It shows static images of dispersed phases where dynamic images could be obtained by simply extending the algorithms and strategies employed in the present analysis.
Chun, Won Gee,Kim, Min Chan,Kim, Sin 한국화학공학회 2001 Korean Journal of Chemical Engineering Vol.18 No.1
A numerical scheme based on the enthalpy method is applied to one-dimensional Stefan problems. The discretization equation is derived based on the finite control volume method. To improve the convergence rate, a simple and cost-effective single-point predictor-connector algorithm is proposed. Usefulness of the present approach is discussed by means of various solidification problems.
천원기(Chun Won-gee),임상훈(Lim Sang-Hoon),전명석(Jeon Myung-Seok),윤종호(Yoon Jong-Ho) 한국태양에너지학회 1992 한국태양에너지학회 논문집 Vol.12 No.1
본 연구에서는 f-chart method를 이용하여 대전지방에서 공기식 시스템을 적용하였을 경우의 난방효과에 대한 성능 분석을 수행하였다. 공기의 유량, 집열판 덮개의 수, 페블베드의 축열 용량 그리고 집열판의 코팅 등에 따른 공기식 시스템의 난방 효과를 분석하였으며 아울러 액체식 시스템을 이용한 난방 시스템과도 동일 조건하에서 그 성능을 비교 분석하였다. The present study has carried out thermal performance evaluation of air systems for space heating in Daejeon by the f-chart method. The various effects with the .change in air flow rate, number of glazings, storage capacity of pebble bed, and coating materials of absorber plate are analyzed with regard to the effectiveness of air systems for space heating. A comparison is also made with liquid systems under the same operating conditions.
루프형 양방향 열 다이오드 시스템의 열 성능에 관한 실험적 연구
천워기(Won Gee Chun),김신(Sin Kim) 한국태양에너지학회 1998 한국태양에너지학회 논문집 Vol.18 No.2
일반적으로 열 다이오드(thermo-diode)란 임의의 한 방향으로만 열 전달이 가능하도록 설계된 열 전달 기구이나, 열 흐름이 원하는 방향으로 이루어지는 양방향 열 다이오드를 사용한다면 겨울철 난방과 여름철 냉방부하 감소에 모두 효과적으로 적용될 수 있다. 본 연구에서는 루프형 양방향 열 다이오드를 응용한 태양열 이용 시스템을 설계·제작하였으며, test call을 이용한 옥외 실험을 수행하여 실용 가능성을 확인하였다. In general, the thermo-diode is a device designed to allow heat to be transferred only in one direction. However, the bidirectional thermo-diode devised to change the heat flow in the desired direction can be used for the reduction of the heating load in winter as well as the cooling load in summer. In this study, a solar heating system using loop-type bidirectional thermo-diodes is designed and set up, also it is successfully applied to an outdoor test cell for the verification of its usefulness.
저온 활용 시스템의 효율 제고를 위한 마찰 저항 감소 연구
천원기(Won Gee Chun),김철암(Chul Am Kim),성준희(Jun Hee Sung),최형진(Hyoung Jin Choi),김종보(Chong Bo Kim),김형택(Hyung Taek Kim) 한국태양에너지학회 1997 한국태양에너지학회 논문집 Vol.17 No.4
본 연구에서는 회전원판 장치를 사용하여 난류 유동장에서의 고분자에 의해 유도되는 마찰저항 감소효과에 대하여 조사하였다. 해양온도차 발전에서 해수를 이동시키는 유동장은 난류상태로 이러한 난류계에 대하여 마찰저항 감소는 충분한 적용가치가 있다. 네가지의 분자량이 다른 PEO를 마찰저항 첨가제로, 실험실에서 제조한 인공해수를 용매로 사용하여 고분자의 분자량, 고분자의 농도와 원판의 회전속도와 같이 마찰저항 감소효과에 영향을 줄 수 있는 여러 인자들에 대해서 살펴보았다.<br/> 마찰저항 감소의 농도의존성은 Virk의 Universal correlation를 따르는 것을 확인하였다. 해수에서도 PEO와 용매간의 Universal 곡선이 증류수를 용매로 하였을 때와 동일함을 확인하였다. Drag reduction produced by the dilute solution of polymer under turbulent flow in a rotating disk apparatus (RDA) was investigated in this study for the purpose of potential application to the Ocean Thermal Energy Conversion (OTEC) system, Four different molecular weights of poly(ethylene oxide) (PEO) were used as drag reducing additives, and synthetic seawater was adopted as a solvent. Experiments were undertaken to observe the dependence of drag reduction on various factors such as polymer molecular weight, polymer concentration and the rotating speed of the disk. The concentration dependence on the drag reduction of this polymer system was shown to obey an empirical drag reduction equation of the Virk's universal correlation.