小型實驗太陽연못에서 熱貯藏層의 두께에 關한 實驗的硏究

박이동(Pak Ee Tong),서지원(Seo Ji Weon) 한국태양에너지학회 1987 한국태양에너지학회 논문집 Vol.7 No.2

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

비선형이론에 의한 Supercavitation 익렬의 유동해석

박이동(Pak Ee-Tong),황윤(Hwang Yoon) 한국태양에너지학회 1997 한국태양에너지학회 논문집 Vol.17 No.1

비선형이론에 의한 Supercavitation 익렬의 유동해석

박이동,황윤,Pak, Ee-Tong,Hwang, Yoon 한국태양에너지학회 1997 한국태양에너지학회 논문집 Vol.17 No.2

In this study comparison of experiment results with the computed results of linear theory and nonlinear theory using singularity method was obtainable. Specially singularity points like sources and vortexes on hydrofoil and freestreamline were distributed to analyze two dimensional flow field of supercavitating cascade using nonlinear theory, and governing equations of flow field were derived and hydraulic characteristics of cascade were calculated by numerical analysis of the governing equations. The results compared linear theory and nonlinear theory with the experiment results of the study are as follows: The tolerances of nonlinear theory were larger than those of linear theory in case of ${\alpha}<10^{\circ}$. Moreover the computational range of attack angles could be expanded from ${\alpha}=10^{\circ}$ to ${\alpha}=25^{\circ}$, the flow field of supercavitating cascade could be analyzed in the condition which the wake thickness and the length of cavity are a variable. The shapes of cavity were changed sensitively according to various variable such as attack angles, pitches and wake thickness, and the pressure distribution of hydrofoil surface was identical almost disregarding wake thickness but changed largely according to attack angle and the length of cavity. Lift coefficient and drag coefficient were reduced according to increasing of wake thickness but the influences of wake thickness were very little in the situation of small pitch and long cavity.

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.

주거용 태양열 성층축열시스템의 시뮬레이션

박이동(Pak Ee-Tong),유호선(Yoo Hoseon) 한국태양에너지학회 1991 한국태양에너지학회 논문집 Vol.11 No.3

본 연구의 목적은 주거용 태양열 온수이용에 있어서 성층저장의 잠점을 평가하고 최적의 설계변수를 제시하되 실험이 아닌 시뮬레이션을 통한다는 것이다. 그 결과는 다음과 같으며 실험의 결과들과 잘 일치함을 보였다.<br/> 1. 탱크의 성층분할이 증가함에 따라서 태양부하율이 증가함을 보여 주었고 본 연구에서는 평균 10% 정도 증가함을 나타내었다.<br/> 2. 저장탱크의 높이 대 지름의 비가 3정도일 때가 태양부하율이 최대가 되었으며 그이상이 되면 감소하는 경향을 나타내었다.<br/> 3. 집열기로 부터 저장탱크로 유입되는 온수의 유동율이 증가할 수록 완전혼합저장에서는 태양부하율이 증가하지만 성층저장에서는 유입율이 감소하는것이 태양부하율을 증가시키는 결과가 되었다.<br/> 4. 이와같은 결과로 성층축열시스템 전체적으로는 약 17%의 성능 향상을 기대할 수 있다. The benefits of thermal stratification in sensible heat storage systems has been considered and studying by several investigators. In this paper, the basic data which is hard to obtain normally through the experiment 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 computer simulation, following results were obtained.<br/> 1. The solar load fraction increases with increasing the number of tank segments. In these simulation, the magnitude of the improvement was about 10%.<br/> 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%.<br/> 3. Increasing the collector flow rate slightly improved the performance of the mixed storage system(Node=l). But, 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.

상변화 물질을 이용한 빙축열조에서 축열, 방열 특성에 관한 실험적 연구

박이동(Pak Ee-Tong),유석재(Seok-Jae You) 한국태양에너지학회 1996 한국태양에너지학회 논문집 Vol.16 No.1

빙축열 시스템의 축열ㆍ방열 과정 동안의 열유동 특성을 해석하기 위해서 유입구 형상을 perforated distributor(이후 perforator)와 simple distributor(이후 distributor)로, brine의 유입 방향을 up-ward, down-ward로 변화 시켜 성층, 빙충진율, 효율 등을 실험적으로, 연구 분석하였다.<br/> 축열시 동일한 유량, 온도, 시간 동안은 perforater up-ward를 사용하면 distributor를 사용했을 때 보다 IPF가 최대 40% 높아져 축열 효율이 13%~35% 향상되었고, 방열시는 동일한 조건하에서 distributor down-ward를 사용했을 때 방열 효율이 5%~29% 향상되었다. 그러므로 빙축열 시스템의 운영에서 축열 과정에는 perforater up-ward의 유동을 방열 과정에서는 distributor down-ward의 유동 형태를 취하는 것이 전체적인 효율 향상을 가져올 수 있음을 알았다. This paper deals with the characteristics of charging and discharging including temperature profiles, thermal stratification, ice packing factor, and efficiencies of charging and discharging due to the brine flow direction in the rectangular storage tank with the ice ball of 103㎜Φ. Ranges of the parameters were defined for flow direction and inlet geometry such as distributor and perforater type, keeping flow rate constantly and temperature difference between temperature of inlet brine and temperature of initially stored normal brine.<br/> Distributor is better restrained for the mixing inlet brine with inner initial normal brine. The case of thermal stratification using distributor is shown to be superior to perforater by 1% at charging and 2% at discharging in the same condition and the up-ward brine flow direction is superior to down-ward direction by 9%. But the case of ice packing factor using perforater is superior to distributor by 5% at one turn over time(τ=1), 40% at twice turn over time(τ=2). Charging efficiency is highest in up-ward direction with perforater and discharging efficiency is highest in down-ward direction with distributor. Therefore, higher thermal storage effect is obtainable by increase of ice packing factor in up-ward direction with perforater and higher thermal release effect is obtainable by reducing duration of heat transfer in down-ward diraction with distributor.

Experimental Study on the Effective Use of Thermally Stratified Hot Water Storage System

박이동,Pak, Ee-Tong 한국태양에너지학회 1993 한국태양에너지학회 논문집 Vol.13 No.2

The benefits of thermal stratification in sensible heat storage were investigated for residential solar applications. The effect of increased thermal useful efficiency of hot water stored in an actual storage tank due to stratification has been discussed and illustrated through experimental data and computer simulation, which were taken by changing dynamic and geometric parameters. When the flow rate was 8 liter/min and ${\Delta}T=40^{\circ}C$ was $40^{\circ}C$, the useful efficiency(${\eta}_u$) was about 90% in case of using a distributor, but not using a distributor the useful efficiency(${\eta}_u$) was about 82%. So these kinds of distributor would be recommendable for a hot water storage system and residential solar energy application to increase useful efficiency(${\eta}_u$). In the case of the uniform circular distributor, when the flow rate was 8 liter/min partial mixing was decreased and a stable stratification was obtained. Furthermore, if the distrbutor was manufactured so that the flow is to be the same from all perforations in order to enhance stratification, it might be predicted that further stable stratification and higher useful efficiency(${\eta}_u$) are obtainable. 현열저장에서 열성층의 이점을 태양열 주택에 적용해보았다. 성층으로 인하여 에너지 입력의 열이용 효율이 증가되는 효과가 논의되었고, 실험과 시뮤레이션을 통하여 설명되었다. 성층을 촉진시키기 위하여 Distributor를 사용하였으며, 본 실험에서 Q=8 liter/min, ${\Delta}T=40^{\circ}C$일 때, 최대 90%의 열이용 효율을 얻을 수 있었다. 한편 성층을 촉진시키기 위하여 Distributor의 적은 구멍에서 나오는 유동(속도와 압력)이 같게 제작할 수만 있다면 그 이상의 열이용효율도 얻을 수 있음이 입증되었다.

원심형 회전차 내부 난류유동에 대한 수치해석적 연구

박이동(Ee-Tong Pak),윤상건(Sang-Geun Yoon) 한국태양에너지학회 1996 한국태양에너지학회 논문집 Vol.16 No.4

원심형 회전차 내부유동을 예측하기 위하여 일반곡선좌표계를 사용한 유한체적법을 이용하여 완전 타원형 Navier-Stokes방정식을 수치적으로 계산하였다. 난류모델로는 표준k-ε모델을 사용하였으며, 그 결과 합리적인 압력분포를 예측하였다. For prediction of flow pattern in centrifugal impeller a finite volume method based on a generalized nonorthogonal coordinate system is introduced to solve fully elliptic Navier-Stokes equation, and a standard k-ε model is applied to simulate the turbulent flow. The result of this study shows reasonable pressure distribution within the impeller passage. But result of the pressure side near the shroud is higher than experimental data.

태양열 온수 저장조의 성층 온수 추출에 관한 연구

박이동(Ee Tong Pak),정운철(Un Chul Jeong),성상우(Sang Woo Sung) 한국태양에너지학회 1991 한국태양에너지학회 논문집 Vol.11 No.2