액상을 수직 상승하는 기포의 열전달 특성에 관한 실험적 연구

오율권,서동표,양호동 朝鮮大學校 機械技術硏究所 2004 機械技術硏究 Vol.7 No.2

In the present study, the gas injection system based on air-water model was designed to investigate the heat transfer characteristics of bubbles injected into a ladle. To analysis heat transfer characteristics rising bubbles, bubble temperature was experimentally measured in a gas-liquid flow region. Bubble temperature was obtained by a thermal infrared camera. Since bubble temperature is different from liquid temperature in a ladle, heat transfer occurs between gas and liquid phases. Actually, bubble temperature reaches liquid temperature in a short time after injection.

기체 주입 Ladle내에서 유동특성에 관한 연구

오율권,서동표 조선대학교 에너지.자원신기술연구소 2003 에너지·자원신기술연구소 논문지 Vol.25 No.1

In the air-water model, the characteristics of flow parameters were experimentally investigated. When gas was injected into the liquid bath, several flow patterns were observed bubble-liquid plumb, the spout flow that occurred at the free surface, liquid circulation flow by bubble's behavior, etc. In the pure liquid region, the large and small several vortices were formed and irregularly circulated. These irregular repetition and circulation play a important role of mixing in the bath. The vortices were developed in the upper and the side wall regions and the movement of flow in the low region was very small. It is known as "dead zone". The bubble rise velocity in the bottom region was relatively lower than in the upper region because the energy generated by bubbles' behavior in the near nozzle region was almost converted into kinetic energy. But bubble rise velocity increases with the increasing the axial distance since kinetic energy of bubbles is added to buoyancy force.

Air-Water 모델에서 기포특성에 관한 실험적 연구

오율권,서동표 한국산업안전학회 2003 한국안전학회지 Vol.18 No.1

The structural development of air-water bubble plumes has been measured under different condition on air flow rate in a cylindrical bath. The time-averaged structure of plumes has been measured with an oscilloscope and an electro-conductivity probe. The temperature of bubbles was also obtained by a thermal-infrared camera. Gas volume fraction and bubble frequency were high since bubbles concentrated on the nozzle. In general, their axial and radial values tended to decrease with increasing distance. Bubble temperature reached water temperature within a short time. The present study showed that thermal equilibrium between bubbles and water was completed before bubbles flow became stable.

異質材의 切削抵抗에 關한 硏究

吳栗權,沈在基 조선대학교 동력자원연구소 1983 動力資源硏究所誌 Vol.5 No.1

This paper dealt with the experiment of the Back Rake Angle on the cutting resistance of different material. The obtained result are as follows ; (1) When the back rake angle is increased, the magnitude of the three component of cutting force-the one of vertical component, of radial component and of axial component are gradually decreased. And in view of %for each component of the cutting force, the% of v.c is increased, the%of r.c is decrased and the% a.c is changed a little. (2) When the feed is increased, the magnitude of three component, the% of vertical and a.c are increased but the% of r.c is increased. (3) Three component of cutting force by the amount of feed, in the case of test material B, increased averagely 28.8% on the v.c, 84.1% on the r.c and 96.1% on the a.c when feed revealed 0.2mm/rev rather than 0.1mm/rev. (4) The proportion of three component of cutting force in the case of 0.1mm/rev feed on the v.c, r.c and a.c respectively reveals 55.8% 35.6% 8.6% in the base metal zone 56% 35.3% 8.6% in the heat affected zone and 55.8%, 35.7^, 8.4% in the weld zone according to the test material B. (5) The cutting force of different material are decreased in squence of bond zone, weld zone, base metal smaller than that of base metal zone then 1 think, this phenomenon is occurre because the heat affected zone has the properties of free-cutting steel.

환기시스템의 효율 향상을 위한 후드 내 유해물질 포착속도 개선에 관한 연구

오율권,김영선,박경수 朝鮮大學校 機械技術硏究所 2007 機械技術硏究 Vol.10 No.1

Most of the hood maximize on capture velocity concentrate in inhalation capacity of harmful materials on hood of center. But, decrease generally ventilation system efficiency because, the edge of hood decrease capture velocity of harmful materials. So, development on the gas-guidance-device for increase of capture velocity of harmful materials in hood increase generally ventilation system efficiency. In this study, flow in hood doing visibility after numerical analysis using the Phoenics 3.1 on commercial code of heat and fluid using finite volume method. And, boundary conditions establish the same condition as work space that it is temperature is 20 degrees, pressure in 1 atm, velocity in duct is 6.85m/s, diameter is 400mm. Also, gas-guidance-device draw optimum shape as a result comparison and analysis as being numerical analysis of variety shape. As the result of study, compare hood have gas-guidance-device with hood have no gas-guidance-device identify increase on harmful materials capture velocity. Also, gas-guidance-device identify best inhalation efficiency in hood when it is 125mm wide and a ratio of 4 to 6 on side. So, safety of worker and work environment improvement expect helped as a result remove effective on harmful materials in work space and cut down on expenses of occurrence when the inhalation volume again design for efficiency improvement of ventilation system.

FEM을 이용한 자동차 타이어용 알류미늄 합금 금형의 열변형 특성에 관한 연구

오율권,서동표,양호동,박근욱,김용범 朝鮮大學校 機械技術硏究所 2006 機械技術硏究 Vol.9 No.1

대부분의 타이어 제조를 위한 금형생산 공정은 실험적인 결과에 바탕을 두어 거의 경험치에 의존하고 있다. 이러한 방법은 금형제품을 생산하는데 있어 비효율적이고 비경제적인 측면이 많다. 따라서, 정밀도를 향상시키고 품질이 좋은 타이어를 제조하기 위해 금형의 제조공정은 재평가가 이루어져야 한다. 본 연구에서는 자동차 타이어용 알루미늄 합금 금형의열변형 및 특성을 조사하기 위해 유한요소법을 이용하여 수치해석적으로 연구를 수행하고자 하였다. 알루미늄 합금의 금형의 열변형 및 특성에 관해 조사하기 위해, 알루미늄 합금 금형 내부에서 발생되는 온도분포, 수축량, 응력 그리고 변형량을 수치해석적으로 계산하는연구를 수행하였다. 뿐만 아니라, 정밀도를 향상시키고 좋은 품질의 금형을 얻기 위해, 알루미늄 합금과 연강의 수치해석 결과를 비교하였다. 결국, 수치해석을 통해 얻은 결과들은향후 효과적이고 최상의 금형 제품을 제작하는데 도움을 줄 수 있으리라 본다. Most the mold product process is based on a experimental results and is almost dependent on experiments for tire manufacturing. This method produced the mold product is not only the ineffectiveness but also the bad economy. So, the product process of metal mold should be revaluated to produce the improved precision and good quality of tires. In this study, numerical analysis applied a finite element method (FEM) was used to predict the thermal strain characteristics of Aluminum (AI) alloy mold for automobile tire. To investigate the thermal strain and characteristics of Al alloy mold, it was performed that the temperature distribution. the contraction rates, the stress and the strain occurred on the inside of Al alloy mold was calculated by numerical works. Moreover, numerical analysis results of Al alloy mold were compared with those of mild steel mold in order to obtain the improved precision and good quality of mold. So, the numerical results of this study will be presented to help to make the effective and the best mold products.

작동유체의 등온 가열 상태에서 펌프의 이상유동 특성에 관한 실험적 연구

오율권,유영태,이용헌,서동표 조선대학교 생산기술연구소 1996 生産技術硏究 Vol.18 No.1

This study is to examine the effects of entrained air on the pump performance in a centrifugal pump. Using a 1/10 scale model pump. which is designed and manufactured to simulate two phase flow performance of the reactor coolant pumps of Y.G.N #3 and 4. a set of experiments was executed with water and air mixtures at heated state of 50℃ and at atmospheric pressure. A head loss coefficient. which is defined as a nondimensional ratio of the difference of theoretical and actual pump head coefficient in a single phase. ◁화학식 삽입▷ (원문을 참조하세요) was determined as a function of void fracrtion, α , and flow coefficient, Φ. The calibrated mass flow rates of air and water were used to calculate void fraction using the void meter of the conductivity probe type. compensate the defect of drift flux model and calculate the void fraction. In particular. the flows were stoped when the void fraction was about 0.13.

고도로 과열된 액체분사의 분해의 메카니즘에 관한 연구

오율권,정낙규 조선대학교 동력자원연구소 1988 動力資源硏究所誌 Vol.10 No.2

Delay time and jet divergence angle measured were studied for slashing jets at high degrees of superheat. n-pentane, n-hexane, and ethanol were injected into nitrogen at two injection pressures and for three nozzle diameters. Proposed hypothesis for the delay time based on homogeneous nucleation are not confirmed by our experimental data. The assumption that the spray angle is related to the heat-transfer-controlled bubble growth appears to be supported by our data but important details concerning the number of bubbles in the jet and the state of the vapor in the bubble at breakup have not yet been properly explained. Both delay time and jet divergence angle are found to be sensitive to the degree of superheat and liquid properties, influenced by the liquid pressure and insensitive to jet diameter.

Air-Water 모델에서 액상의 유동특성에 관한 연구

오율권,서동표,박설현 한국안전학회 2004 한국안전학회지 Vol.19 No.1

In the present study, the gas injection system based on air-water model was designed to investigate the flov< characteristics of liquid phase. A PIV system was applied to analyze the flow pattern in a ladle which gas started to rise upward from the bottom. Gas flow is one of most important factors which could feature a flow pattern in a gas injection system. As the gas injected into the liquid, the kinetic energy of bubble transfer to liquid phase and a strong circulation flow develops in the liquid phase. Such a flow in the liquid develops vortex and improve the mixing process. Due to the centrifugal force, circulation flow was well developed near both wall sides and upper region respectively. Increasing gas flow was helpful to remove dead zone but, weak flow zone still exists in spite of the increasement of gas flow rate.

배관내 자유수면에서 와류현상에 대한 연구

오율권,장완호,이종원,김상녕 대한기계학회 1992 대한기계학회논문집 Vol.16 No.11

In order to prevent the decay heat removal system from failure due to air entrainment or free surface vortex in the piping system, a set of simulating experiments for the midloop operation of nuclear power plant was performed. Through these experiments, a relation between the dimensionless numbers, such as submergence H/d, froude number, reynolds number, was found. However, the effect of reynolds number was negligible for the operation conditions of Nuclear power plant. It was also found that the perturbation of the system by the disturbance such as pump start, valve operation, etc., has a strong effect on the free surface vortex. Furthermore, from a view point of reactor safery, a modified inlet device of reducer type is strongly recommendable for the prevention of air entrainment. 본 연구에서는 국내 원자력 발전소중 영광 3,4호기의 설계자료를 토대로 1/6 크기로 축소한 모델실험을 통해서 공기흡입이 발생하는 임계수위를 결정하는 상관식을 개발하였으며 또한 공기흡입구를 reducer type으로 개선함으로써 공기흡입을 방지할 수 있음을 밝혔다.