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박이동,장영근 成均館大學校 科學技術硏究所 1995 論文集 Vol.46 No.1
A lot of research on energy storage process has been performed but few extraction process has been studied. In this study, extraction process of hot water stored in a hot water storage tank was analyzed according to dynamic and geometric parameters dominating the hot water withdrawal process. For this study, the experiments of hot water extraction were carried out by changing withdrawal rates of hot water ranged from 4LPM to 8LPM (Q=4, 6, 8LPM) and by changing temperature differences between hot water initially stored in a storage tank and cold water inflowed to a storage tank ranged from 10℃ to 30℃ (△T=10, 20, 30℃). And also, single round port, perforated distributor (Aspect Ratio=2) and modified distributor (Aspect Ratio=2. 5) were used as a inlet and outlet shapes. The purpose of this investigation was to experimentally determine what outlet conditions are favorable to enhance hot water extraction efficiency during the hot water withdrawal process. As a results, during the hot water extraction, as the extraction rate of hot water decreased, at the same time the temperature difference between cold water inflowed to the storage tank and hot water initially stored in the storage tank increased and modified distributor I(MDI) was used outlet shape, thermocline appeared at the lower region of the storage tank, extraction efficiency of hot water increased.
Insulated Raft가 장기온수저장에 미치는 영향
박이동,조운,Pak, Ee-Tong,Cho, Woon 한국태양에너지학회 1997 한국태양에너지학회 논문집 Vol.17 No.2
Thermal energy storage system used a storage tank is a reasonable method to solve energy problem. In thermal energy storage system, energy collected from many types of heat source is stored in a storage tank and then supply to load at the time is in demand. In this study, flow characteristics and storage efficiency were analysed by using a insulated raft in longterm hot water storage system. From the experiment it is found that insulated raft has a important role in longterm hot water storage system and storage efficiency can be obtained to 96% using inletport type and insulated raft together.
LDV를 이용한 저속 원심회전차내 유동 속도 측정에 관한 연구
박이동,권양구 成均館大學校 科學技術硏究所 1993 論文集 Vol.44 No.2
To understand the flow phenomena within a channel of impeller and estimate the performance of compressor or pump, the flow velocity was measured by LDV with the advantages of non-intrusion in a flow field. The object of this study is to present a measuring method of flow velocity by LDV and to improve the measuring techniques. In order to estimate the characteristics of flow field within a channel, the flow velocity has been measured with respect to variation of blade angle of exit and to increase the S/N ratio of LDV, the half angle of lens has been increased and the hub wall coated with the soot to absorb the diffused reflection light. For the blade angles of exit, flow losses and deviation angle were small at 54° and large at 122°, and energy transfer coefficient had a good performance at 90°.
박이동,황성일 成均館大學校 科學技術硏究所 1992 論文集 Vol.43 No.1
The enhancement of the thermal stratification in sensible heat storage tank is important since it can significantly improve thermal storage efficiency and total system efficiency. In order to decide the optimum conditions, the experiments were carried out during turnover time for flow rate ranging from 1.6 LPM to 6.4 LPM and reference temperature difference(temperature difference between the inflow water into the tank and the water which is initially in the tank) of 5 ℃ to 30℃. And also, one inlet port type and another three stratification enhancement devices were used as inlet geometries. As a results, when the flow rate was lower, the reference temperature difference was larger, more stable thermal stratification was obtained and thermal storage efficiency was more improved. And at the same operating condition, generally using stratification enhancement devices was better than using inlet port to form stable thermal stratification and to improve thermal storage efficiency. Especially, it was possible to get thermal storage efficiency of 94% with using the perforated distributor type as Richardson number was 5.0, which was higher than thermal storage efficiency of 66% with using inlet port type as Richardson number was 0.08.
공기를 자동 유체로 하는 열다이오드의 열성능에 관한 실험적 연구
박이동,김철주,황영규,장영근,황인주 한국태양에너지학회 1996 한국태양에너지학회 학술대회논문집 Vol.- No.-
열다이오드란 유체의 밀도차에 기인한 대류에 의하여 일방향성 열전달이 주로 일어나며 역방향의 열전달은 미미하도록 고안된 장치이다. 본연구에서는 실용적인 측면에서 좌우에 수직 평판을 가진 평행사변형 형상이 열다이오드에 적절하므로 유체 흐름이 정체된 영역을 개선한 기하학적 형상과 내부 안내판을 가진 열다이오드를 제작하였다.<br/> 공급된 열속에 따른 Gr는 9.27×10^9~1.18×10^(10) 사이에 존재하였고 전체 실험과정에 있어서 Gr 값은 ±3% 이내로 유지되었다. Gr의 증가에 따라 Nu값은 거의 선형적으로 증가하는 경향을 보였으나 guide vane의 유무와 유동통로의 깊이(channel depth)에 따라서는 민감한 경향을 보였다.
박이동,김철주,황영규,장영근,이도영 한국태양에너지학회 1996 한국태양에너지학회 학술대회논문집 Vol.- No.-
실내로 유입되는 온기와 실내공기사이의 온도차 및 유입속도에 따라 발생되는 부력의 영향 및 실내로 유입된 온기의 균일분포특성에 관한 연구는 시스템의 성능향상에 크게 기여할 수 있다. 따라서 본 연구에서는 실제크기의 모형room에서 동적 조건인 기준온도차를 10℃, 20℃, 30℃로 유입속도를 0.5㎧, 1㎧, 2㎧, 3㎧로 변화시켰고, 기하학적조건으로 아네모스형과 베인형을 사용하여 열유동특성을 해석하였다. 실험결과 혼합도의 정의로부터 임계속도(1.2~1.6㎧)전 후로 기하학적영향에 대하여서 혼합과의 관계를 파악할 수 있었다. 그리고 축열효율과의 관계는 속도가 크고 기준온도차가 작을수록 부력의 영향을 적게 받아서 아네모스형, 베인형 모두 높은 축열효율을 나타냈다. 그리고 속도가 클 때는 베인형이 전반적으로 우수한 축열효율을 보였으나 속도가 낮으면 온기의 상부정체의 영향이 뚜렷하게 나타났다. 유입속도에 의한 영향이 기준온도차에 의한 영향보다 지배적인 경향을 보였다.