에너지이용효율

박이동 한국에너지학회 1997 한국에너지공학회 학술발표회 Vol.1997 No.-

현열 축열조 내의 열 성층 특성 해석

박이동,황성일 成均館大學校 科學技術硏究所 1992 論文集 Vol.43 No.1

The effects of several dynamic and geometric factors on thermal stratification have been investigated through experiments and simulations in sensible heat storage tank by many investigators. The improvement of thermal stratification which obtains higher thermal storage efficiency might be predicted through enhancing a thin thermocline thickness. The major objectives of the study were to decide the optimum design conditions of the sensible heat storage tank according to variations of the dynamic, geometric factors by measuring temperature for the vertical temperature profiles and characteristics of outlet temperature of the tank. In order to decide the optimum conditions, the experiments were carried out during turnover time for flow rates from 1.6LPM to 6.4LPM 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, inlet shape was used by inlet port type and five stratification enhancement devices. It was possible to get higher storage efficiency and further stable thermal stratification by using the perforated distributor than using inlet port, slotted distributor, radial diffuser, impingement and sprayer in same operation condition.

노통 연관식 폐열 보일러의 최적 설계

박이동,이관종,장영근 成均館大學校 科學技術硏究所 1995 論文集 Vol.46 No.2

This study is to obtain optimized design parameters of waste heat boiler with fire and smoke tube which are widely used to provide process and building heat. The optimum parameters obtained in this study can be used as a guideline for actual. boiler design of this type. The design optimization considered here is to find the most economical dimensions of the boiler considered which results in a minimum cost in producing a unit amount of steam per given period of operation. For this purpose, the first we have to determine what are the main parameters of affecting the total cost of producing a unit amount of steam which is comprised of manufacturing cost of the boiler, operating cost of the fan, etc. For the selected design parameters, we will have to decide the conditions of each parameter which will result in the minimum total cost. For the waste heat boiler with fire and smoke tube under consideration, the major parameters of affecting the total cost are considered to the diameter of the smoke tube and the gas velocity among others. The two parameters selected here are considered for finding the optimum size of the boiler by minimizing the total cost which is a function of the manufacturing cost, purchasing cost of the fan, and the operation cost of the system. Through computer simulation, the optimum conditions of these two parameters are obtained for different boiler capacities and different periods of operation.

태양열 온수의 효과적 이용에 관한 시뮬레이션

박이동,정운철,임종오 成均館大學校 科學技術硏究所 1992 論文集 Vol.42 No.2

The benefits of thermal stratification in sensible heat storage systems have been considered and studying by several investigators. In this paper, the basic data which is hard to obtain normally through experiments were obtainable through the computer simulation. The major objectives of the study were to assess the benefits of stratified storage in residential solar water heating application and to suggest the optimum design parameters. From the above computer simulation, following results were obtained. 1) The solar load fraction increases with increasing the number of tank segments. In these simulation, the magnitude of the improvement was about 10%. 2) The solar load fraction increases when the ratio of diameter to height of the tank(H/D) increases to 3, but H/D exceed 3 then, the solar load fraction decreases. In these simulation, the magnitude of the improvement was about 3 %. 3) Increasing the collector flow rate slightly improved the performance of the mixed storage system (Node = 1). Also, for the stratified storage system(Node = N), the solar load fraction increases with decreasing flow rate until the point is reached at which the collector outlet temperature reaches the boiloff limit of 100℃ over some portion of the simulation period.

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°.

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.

熱 PIPE用 蓄熱槽內의 流動特性과 蓄熱效率에 관한 實驗的 硏究

박이동,서병택 成均館大學校 科學技術硏究所 1995 論文集 Vol.46 No.1

In thermal energy storage system, for the improvement of energy storage from collector to storage tank, study on flow characterisitics and heat storage effeiciency is necessary. In this study, temperature distribution in the storage tank and heat storage efficiency were analyzed due to dynamic conditions in case of heat storage process only, and the case of heat storage extraction process simultaneously. For this study, the experiments were carried out changing inflow rates ranging from 1LPM, 2LPM and 4LPM, and the arnount of heat supplied ranging of from 80W and 100W. Obtained results are as follows: [Heat storage process] 1. As the heat supplied from heat pipe increased, the average temperature of initial storage water increased and the thermal storage efficiency was constant. 2. When the heat was supplied from heat pipe, initial storage water heated entrained the surrounding water and rised to the top of storage tank and mixed with the water existed on the top of storage tank. In case of the heat supplied from heat pipe was 100W and 80W, the time initial water heated located at bottom of storage tank, reached at the free surface of storage tank was 20 seconds and 60 seconds respectively. [Heat storage and extraction process] 1. When the inflow rate was 1LPM and the heat supplied was 100W, thermocline was established and hence the initial storage water heated could be extracted as a hot water. 2. When the flow rate was rather 4LPM than 1LPM and the heat supplied was rather 80W than 100W, the temperature distribution had a steep gradient. It meant. a rather good stratification was developed. 3. When the heat was 80W, the temperature distribution under the thermocline region was showed higher than 100W for the reason of small buoyancy effect.

一定幅 急傾斜 開水路上을 流動하는 물의 깊이 變化에 관한 實驗的 硏究

박이동 대한기계학회 1986 대한기계학회논문집 Vol.10 No.1

본 연구에서는 폭이 일정한 급경사 개수노상(0.15mW*1.6mL)을 상온의 물이 유동할 때 유동율과 수로 급경사에 따른 명입치에서의 유동깊이 변화를 실측을 통하여 밝히고 이념치와 비교하였다. A study on film water flow on steep open channel has been seldom found up to date. Therefore, this paper dealed with the depth variation of film thickness of water (city supply normal water) flowing on steep open channel. For this purpose, Experimental apparatus (made of a normal glass with 160cm of length and 15cm of width) was made and the depths of the water flowing on the channel were measured experimentally, changing the channel slope angle from 30 to 80 degree (5 steps) and the flow rate from 0.25 to 10CPM (11 steps). The results obtained, some characteristics of the film flow on the channel are as follows. (1) When thin film water flowed on steep open channel, the depths of flow tended to increase after decreasing and was kept nearly constant in its downstream in case of laminar and transitional flow region. The turining point of the depths of flow from decrease to increase tended to move downward with the increase of Reynolds number. In turbulent flow region, the depths of flow showed reapid decrease in its upper stream, gradual decrease in its midstream and were kept nearly constant in its downstream. (2) While the differences between the depths of flow along the channel slope got small in its upper stream and got large in its downstream in case of laminar flow region, they got very large in its upper stream and were kept nearly constant in its downstream in case of transitional and turbulent flow region. And the move flow rate increases, the more the differences between the depths of flow along the channel slope got large in its upper stream.

집광식 난방 시스템

박이동,장영근,최우석,이종철 한국태양에너지학회 1998 한국태양에너지학회 학술대회논문집 Vol.- No.-

실내유입온기의 열유동특성과 고효율 축열에 관한 연구

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.