• 상하수도학회지
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• 제25권1호
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• pp.41-49
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• 2011

The diffuser which is conventionally adapted to MBR, has problem that decreasing the cleaning effect of membrane module by inflexible air supply due to the occlusion of sludge from diffuser hole. To solve this problem, diffuser structure of submerged module should be improved to discharge sludge which is flow into the diffuser for prevent occlusion in the diffuser. In this study, the structure of the diffuser was reformed to open lower part for preclusion the blocking. And the outlet diameter of the diffuser was drawn through the condition for the depth of water and air rate, to prevent air-leak condition of improved diffuser. Moreover, application is evaluated by comparing test with occlusion effect of the conventional and improved diffuser. From the results, air-water boundary changes are steady with changes of water depth and it shows linear relation about air rate. By using this linear numerical formula, the height of diffuser's outlet can be decided. Also, it displays that it can prevent the occlusion effect during the comparing test. Hereafter, if this diffuser is applied to practical MBR process, the occlusion problem of diffuser will be disappeared.

• 유기물자원화
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• 제19권1호
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• pp.93-101
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• 2011

본 연구는 소각 시스템에 적용되는 반건식 반응기의 모델링 연구를 수행 하였다. 전산유체역학(CFD)을 이용하여 반건식 반응기에서 속도분포 온도분포를 조사하여 반응기의 최적 운전 조건을 조사하였다. 본 모델에 사용된 반응기의 직경은 3 m 이며 높이는 9 m 이다. 반응기로 유입되는 연소가스의 양은 $6,125Nm^3/hr$ 이며 반응기 유입 가스의 온도는 493K 이다. 반응기에 유입되는 소석회 양은 151 kg/hr 이다. 반응기의 입구 형상이 변하면 반응기 내의 온도가 변하며 반응기 내의 가스속도는 0.48 m/sec 에서 1.17m/sec 였으며, 반응기 출구의 가스속도는 6.9에서 7.42m/sec 였다. 모델링 결과에 의하면 반응기 내의 평균 가스 속도와 출구에서의 평균가스 속도는 각각 0.489 m/sec와 7.424 m/sec 였으며, 반응기 출구 온도는 448 K 였다.

• 한국해안·해양공학회논문집
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• 제20권5호
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• pp.452-460
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• 2008

발전소의 냉각수 방류과정에서 대량으로 발생하는 거품의 제거를 위하여 지금까지 소포제와 확산방지 막에 의존해왔지만 유지보수나 비용 등의 문제로 안정적인 구조물에 의한 거품발생 방지 방안 마련이 요구되어왔다. 따라서 본 연구에서는 거품저감 구조물 설계 기술을 확보하기 위하여 공기연행 해석이 가능한 난류 수치 모형을 적용해 보았다. 방류수의 낙하양상에 따라 공기연행률의 차이가 있고 차단벽의 잠김 깊이와 통과 유속에 따라 연행공기의 유출률이 달라지므로 각 Case에 대한 비교를 통해 적정 단면을 설계할 필요가 있다. 본 연구에서는 단면 형상에 따른 공기 연행률과 유출률을 비교하여 거품의 발생 및 유출이 최소가 되는 단면을 찾았으며, 설계 기준은 현장 여건 특히, 바닥 수심고와 월류양상 등에 따라 달라질 수 있으나 수중 방류구 통과 유속은 1 m/s이내가 되도록 하고 차단벽의 잠김 깊이는 최소한 수중 방류구 단면의 수직고 이상은 되어야 함을 알 수 있었다.

• 태양에너지
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• 제5권2호
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• pp.11-19
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• 1985

In this paper, the interface stability not to occur mixing and entrainment between the adjacent layers has been studied in the case of the selective withdrawal of a stratum and the injection in stratified fluid formed by the density difference in a small solar pond. There are stability parameter, Richardson number, Rayleigh number and Froude number as the parameters governing stability in order to measure the interface stability on the stratified fluid. The model which could measure the interface stability on the stratified fluid was the small solar pond composed by 1 meters wide, 2 meters high, and 5 meters long. In order to measure the interface stability on the stratified fluid at the inlet port, the middle section and the outlet port, Richardson number, Rayleigh number, and Froude number involved in the parameters governing the stability were calculated by means of the data resulted from the test of the study on hydrodynamic stability between the convective and nonconvective layers in that solar pond. Richardson number written by the ratio of inertia force to buoyancy force can be used in order to measure the stability on the stratified fluid related to the buoyancy force generated from the injection of fluid. Rayleigh number written by the product of Grashof number by Prandtl number can be used in order to measure the stability of the fluid related to the heat flux and diffusivity of viscosity. Froude number written by the ratio of gravity force to inertia force can be used in order to measure the stability of the nonhomogeneous fluid related to the density difference. As the result of calculating the parameters governing stability, the interface stability on the stratified fluid couldn't be identified below the 70cm height from the bottom of the solar pond, but it could be identified above the 70cm height from it at the inlet port, the middle section and the outlet port. When compared with such the three parameters as Richardson number, Rayleigh number, Froude number, the calculated result was in accord with them at inlet port, the middle section and the outlet port. Henceforth, it is learned that even though any of the three parameters is used for the purpose of measuring the interface stability on the stratified fluid, the result will be the same with them. It is concluded that all the use of Richardson number, Rayleigh number, and Froude number, is desirable and infallible to measure the interface stability on the stratified fluid in the case of considering the exist of the fluid flow and the heat flux like the model of the solar pond.

• 한국농공학회지
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• 제6권2호
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• pp.816-825
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• 1964

1. Outline: The flow of the siphon spillway is very intricate and affected by vacuous condition. It is an intresting problem to make vacuum rapidly in_siphon, i.e, to provoke the perfect siphonaoge with the lowest water-level of overflow. The hydraulic experiments of siphon spillway have practiced at the Masan Lake, Haenam, the province of Junnam and gained rational and economical results which cannot be odtained by calculation. 2. Experiment: The model scale was a half of that of the prototype. 3. Results and discussion: In the experiments of 14 runs, washing, overflow water level, outlet, water level of cushion, phenomenon of water flying and water pressure of every part, etc. were studied. a) The relation of overflow water-level at siphon inlet and deflector When the elevation of the deflector is 10. 65m and the form of deflector O.4m long is the hypotenuse of an $45^{\circ}$ isosceles triangle, the over flow water-level is the minimum, i. e. the siphonage was excellent. There is no effect by the rising of overflow water-Ievel between 11.95m to 1O.65m of deflector elevation (in the first plan, it is 11.05m). But the overflow water-level rises remarkably in the outside region of the above limits. b) The relation of overflow water-level, the length of cushion and standard height of the base. The reduction of the length of cushion brings the rising of overflow waterlevel, and the rising of the standard height of the base brings the rising of overflow water level. For the long cushion length and low standard height of the base, it cannot be expeted to have the falling of overflow water-level. The most satisfactory data were obtained at 5.20m of the base standard height and 6.1m of the length of cushion. The first vah,le planned was 5.70 m and 4.30m.

• 대한설비공학회지:설비저널
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• 제17권6호
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• pp.708-716
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• 1988

Local heat transfer coefficients were measured on semi-cylinders on which a circular water jet impinged in crossflow. The ratio of the semi-cylinder's diameter and the nozzle outlet diameter were varied parametrically, as were the Reynolds number and the supplementary water heights. The measurements showed that the circumferential distribution of the heat transfer coefficient peaked at the stagnation point. For a fixed supplementary water height, the peak heat transfer coefficient was not depend on the curvature of test specimen(d/D). Optimum height of supplementary water which brought about the augmentation of heat transfer at the stagnation point was S/D=1. The Nusselt number decreased as the circumferential distance or angle increased. The circumferential distribution of dimensionless heat transfer (Nu/Nus) was independent of d/D ($d/D{\geq}8.33$), but for the d/D<8.33, it was depended on d/D. At a fixed angle of specimen, dimensionless heat transfer (Nu/Nus) decreased as the ratio d/D increased. The extent of the decrease between d/D=6.67 and 8.33 was markedly greater than that between d/D=8.33 and 10, or d/D=10 and 11.67.

• International Journal of Fluid Machinery and Systems
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• 제2권2호
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• pp.127-135
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• 2009

A conventional centrifugal pump causes a drastic deterioration of air-water two-phase flow performances even at an air-water two-phase flow condition of inlet void fraction less than 10% in the range of relatively low water flow rate. Then we have developed a two-phase flow centrifugal pump which consists of a tandem arrangement of double rotating cascades and blades of outer cascade have higher outlet angle more than $90^{\circ}$. In design of the two-phase flow pump for various sized and operating conditions, similarity relations of geometric dimensions to hydraulic performances is very useful. The similarity relations of rotational speed, impeller diameter and blade height are investigated for the developed impeller in the present paper. As the results, the similarity law of rotational speed and impeller diameter is clarified experimentally even in two-phase flow condition. In addition, influences of blade height on air-water two-phase flow performances indicate a little difference from the similarity relations.

• 한국태양에너지학회 논문집
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• 제27권4호
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• pp.43-49
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• 2007

This study is conducted to improve the efficiency of a thermal storage tank. The thermal storage tank was designed to store heat energy that obtained from the solar or the others heat sources. However, it has difficulties in storing heat with nonuniform temperature through the entire tank with respect to the vertical direction, This study is focused on the thermal stratification to improve thermal comfort for the resident in house. To enhance temperature stratification of the tank, a distributor was designed and installed in the middle of the storage tank vertically. The vertically designed distributor could supply the return water with stratified temperature in the storage tank with respect to the height. The water velocity from the distributor hole is the same with the other outlet in the distributor. However, gravity effect on the flow in the storage tank is much higher than that of the velocity effect due to that Froude Number is less than 1. During the heat charging process in the storage tank, temperature maintained with little difference with respect to the height. However the charging process takes long time to get a effective temperature for the heating or hot water supply because of all of water in the storage tank needs to be heated.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.271-274
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• 2009

This paper deals with an evaluation of the product quality according to intermesh of the roller straightening process of a steel cord. To perform the experiments, a single-layered steel cord with three wires is selected as a target. Intermeshes at inlet and outlet of the roller straightening device are selected as a respective design parameter. According to two intermeshes of the roller straightening device, a design table is generated and experiments were performed. Three assessment items of the product quality, such as the residual torsion, the arc-height and the pre-forming ratio, are measured in each experimental case for the quantitative evaluation of a steel cord. Based on the measured data, the sensitivity of two intermeshes was analyzed and the prediction equation for the product quality of a steel cord was also constructed from the regression analysis.

• 한국터널지하공간학회 논문집
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• 제5권4호
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• pp.389-400
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• 2003

본 연구는 지하철방재대책의 일환으로 터널구간에 설치된 환기기의 제연절환 운전모드 및 승강장 선로부 환기장치를 포함한 6종류의 제연운전모드를 대상으로 승강장에 정차된 열차화재 시나리오에 따라 3차원 실시간 화재 시뮬레이션을 수행하여 제연방식별 열 및 연기전파특성을 규명함으로서, 승강장에서 열차 화재 발생시, 승객이 안전하게 최적 대피가 가능한 환기기의 제연절환 조합운전의 도출을 목표로 한다.