에너지이용효율

박이동 한국에너지학회 1997 한국에너지공학회 학술발표회 Vol.1997 No.-

多空質層內의 流體流動의 Diffusivity Equation의 誘導

朴伊東,吳炳旭 成均館大學校 1980 論文集 Vol.28 No.-

Science of underground water or oil reservoir is rather a global concept. One of the basic tool or elements are basic equation of flow in the underground. Flow through porous media has the viewpoint of using known or presumed knowledge of the reservoir material(media), the fluid (or fluids) present in the media, and the operating conditions of the system to descirbe mathematically the expected behavior of the reservoir system. The mathematical description could then be used to predict the behavior of the system. For effective production behavior, reservoir engineers are interested in all of these processes as they occur in porous media. In this study, as the first step derivation of diffusivity equation for slightly compressible fluid flow in the porous media was confined for linear horizontal flow system. Diffusivity equation (flow equation) was confined for linear horizontal flow system. Diffusivity equation (flow equation) was derived by combining three basic physical laws such as law of consercation of mass, darcy's law and equation of state which the fluid had to obey. As a result for derivation of diffusivity equation, ∂^2 p/∂x^2=øμc/k·∂p/∂t was obtained.

急傾斜 開水路上을 물이 流動할 때 粘性力과 重力의 效果

朴伊東 成均館大學校 科學技術硏究所 1985 論文集 Vol.36 No.2

Experiment results showed that film water flow(arount 0. 5mm of film thickness) on steep open channel (made of a normal glass with 160cm of the length) was affected by mainly gravity force rather than viscosity force. Characteristics of the gravity force affecting to the film water flow depended upon the flow rate of water, namely strong gravity force affected to the flow for a big flow rate than for a little flow rate. Very large deviation of the effect between a big and a little flow rate took place at entrance of the channel. Specialy, for the maximum flow rate(10 GPM) the most effect at the entrance decreased rapidly at early stage. Contrarily, for the minimum flow rate (0.25GPM) the effect at the entrance rather increased a little at early stage comparatively. Generally, the effects of gravity force kept almost constantly for all flow rate from mid point of the channel (about 80cm from the entrance of channel).

市場開放과 韓國經濟의 選擇

朴二東 건국대학교 사회과학대학 무역학과 1987 貿易硏究 Vol.5 No.-

실험 저장조내의 유입구 형상변화에 따른 열 저장효율에 관한 실험적 연구

박이동(Ee-Tong Pak),황성일(Sung-Il Hwang),최영일(Young-Il Choi) 한국태양에너지학회 1989 한국태양에너지학회 논문집 Vol.9 No.3

온수 추출특성에 관한 실험적 연구

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.

小型 Solar Pond 內에 鹽度變化에 따른 溫度와 密度樣相에 관한 實驗的 硏究

朴伊東,徐志源 成均館大學校 科學技術硏究所 1986 論文集 Vol.37 No.2

A salt-gradient solar pond is a body of saline water which performsas a collector of solar energy and long-term thermal storage system. Salt-gradient solar ponds usually consist of three direct zones: an upper convective zone, a nonconvective gradient zone and a bottom convective zone. The increased density in non-convective-layer, as a result of salt concentration, counterbalance the decrease in density due to thermal expansion caused by solar heating and thus prevents convective circulation. For this purpose, experimental apparatus was made, and temperature, density brine in test pond were measured by pycnometer that was moving vertically. The testing situations and states for data taken were as follows: The test pond is of 0.5m wide, 0.5m high, 1.0m long, 7.1cm of suction height of diffuser above the tank bottom, 1.8cm of discharge height of diffuser above the tank bottom, 0.3 cm of slot size of sunction diffuser, 1.0 cm of slot size of discharge diffuser, 47 cm of diffuser slot length, heating method of circulation of hot water(75℃) through hot water tank, the extraction method of circulation storage brine into a heat exchanger external to the pond. In small test solar pond, confirmed the typical three zone which showed up in real solar pond. The results obtained are as follows: 1. When the salt concentration was constant and flow rate of extration hot brine increased, the density and temperature of storage zone tended to decrease and the temperature of upper convective layer tended to decrease respectively. But the density of upper convective layer tended to increase slowly. 2. The content of salt resulted in the salinity variation had a great influence on typical three zone, then the temperature and density of each layer changed directly. 3. They, that is density and temperature profile, stability governing parameter (Richardson number, Froude number) and visual observation, made use of confirming the height of interface, but the absolute value of it accorded with one another perfectly, tended to be closely according to the high salinity. In this experiment the interface stability level was identitied at a level 18.7 cm or so above the test tank bottom. 4. Optimal operating condition in the test pond as follows: 10% of salt concentration, 0.05 ㎥/h of flow rate of extraction hot brine.

열성층수(熱成層水) 사이의 중간경계면 부근의 유동과 응력

박이동,황성일 成均館大學校 科學技術硏究所 1988 論文集 Vol.39 No.1

Stress near interface between thermal stratified water was investigated, changing the temperature difference between the mean temperature of the water in the test tank (1 m wide, 1m high, 2.1m long) and the temperature of the inflow water into the tank, flow rate of circulating water and height of the sink diffuser in the test tank. The objective of this investigation was to observe the mean stress near an interface by measuring the velocities and the temperature difference. Following results were obtained through the experiments. (1) When the flow rate was constant and the difference (T_∞-T_i) between the mean temperature of the fluid in the test tank and the temperature of the inflow water increased by 5. 6,9. 5, 13.5(℃), the mean stress near an interface increased gradually in accordance with the increment of ΔT = T_∞-T_i (2) When ΔT = T_∞-T_i was constant and flow rate increased by 4.0, 4.8, 6.4, 8.0(LPM), the mean stress near an interface increased gradually in accordance with the increment of the flow rate. (3) When the height of the sink diffuser was 25cm from tank bottom in comparison with 50cm, the mean stress near an interface increased.

兩面이 볼록한 物體周邊에 形成된 非壓縮性 層流 境界層內의 剝離現象에 관한 數値解析的 硏究

朴伊東,鄭雲哲 成均館大學校 1982 論文集 Vol.32 No.-

The object of this study was to find the separation point through Numerical Method, which happened at lower surface in a two dimensional incompressible laminar boundary layer formed around symmetrical biconvex body at angle of attack. It was assumed that a half thickness of biconvex body was unit length. A chord length was varied 20, 60, 100, 200, 400, and an angle of attack was varied from 0 degree to 45 degree. In order to obtain solutions finding the separation point, Momentum equation, continuity equation and Bernoulli's equation were combined and the corditton of separation was found. Equation of Velocity distribution around biconvex body given by Van Dyke was substituted to this condition and solution on each variables were obtained. The result was that seperation point happened at the more back of model as chord length and angle of attack were more increasing.

열성층 형성 촉진이 열저장에 미치는 영향

박이동,황성일,박상혁 成均館大學校 科學技術硏究所 1990 論文集 Vol.41 No.2

This paper deals with experimental research to increase thermal storage efficiency of hot water stored in a actual storage tank for solar application. the effect of increased energy input rate due to stratification has been discussed and illustrated through experimental data, which was taken by changing dynamic and geometric parameters. Ranges of the parameters were defined for flow rate, the ratio of diameter to height of the tank and inlet-exit water temperature difference. During the heat storage, when the flow was lower, the temperature difference was larger and the ratio of diameter to height of the tank was higher, the momentum exchange decreased. As for this experiment, when the flow rate was 8liter/min, the temperature difference was 30℃ and the ratio of diameter to height of the tank was 3, the momentum exchange was minimized resulting in a good thermocline and a stable stratification. In the case of using inlet ports, if the modified Richardson number was less than 0.004, full mixing occured and so unstable stratification occured, which mean that this could not be recommended as storage through thermal stratification. Using a distributor was better than using inlet ports to form a sharp thermocline and to enhance the stratification. It was possible to get storage efficiency of 95% by using the distributor, which was higher than a storage efficiency of 85% obtained by using inlet ports in same operation condition. Furthermore, if the distributor was manufactured so that the main pipe decreases in diameter toward the dead end to maintain constant static pressure, it might be predicted that further stable stratification and higher storage efficiency are obtainable(more than 95%).