1차원 난류유동장내에서 축회전하는 구면두부Fin의 후류에 의한 열전달 특성의 연구

김양수 영남이공대학 1998 論文集 Vol.27 No.-

This study was carried out to investigate the heat transfer characteristics by wake effect for the axial rotating fin of spherical surface in one dimensional turbulent flow. The results by mass transfer experiment using naphthalene sublimation technique and the measurement of pressure distribution at the front and back of the fin. 1. The rotating fin has comparatively high value than the fixed one(comparison of Fig. 7 and Fig. 4. 5 and 6). According to the increase of Reynolds number, the mean Nusselt number increased. However they are not proportion to the change of relative length. In the case of the fixed fin, the relative length(UD) has shown its maximum value around 0.5. On the contrary the rotating fin, the tendency has varied from the difference of circular velocity as shown in Fig. 4. 5 and 6. 2. The correlating formula has obtained like table 1, 2 and 3 owing to the variance of L/D and Reynolds number at the rotating spherical type fin.

A Method for Testing Surface Deforms of Large Convex Mirrors

KIM Yaung-Soo 한국우주과학회 2004 한국우주과학회보 Vol.13 No.2

Hydraulics of KSTAR Central Solenoid Model Coil 2nd Campaign

Soo Hwan Park,Han, W.S.,Moon, K.M.,Park, W.W.,Kim, J.S.,Yonekawa, H.,Yong Chu,Hyun Jung Lee,Cho, K.W.,Park, K.R.,Kim, W.C.,Yaung-Soo Kim,Oh, Y.K.,Bak, J.S. IEEE 2009 IEEE transactions on applied superconductivity Vol.19 No.3

<P>KSTAR (Korea Superconducting Tokamak Advanced Research) superconducting magnet consists of a CICC (Cable-In-Conduit Conductor) and is cooled down less than 5 K using supercritical helium. The length of CICC is 610 m for TF coil and maximum about 2,500 m for PF coil respectively, especially the cooling channel is about maximum 300 m in PF coil because of continuous winding scheme. There are many cooling channels in KSTAR coils especially 84 channels in TF magnet system and 100 channels in PF magnet system. Flow imbalance affects cool down of magnet and leads to a difficulty of flow control. The pressure drop between CICC terminals has a close relationship with CICC hydraulic characteristic, helium refrigerator's performance and efficiency. The friction factor which is a representative parameter can be obtained under cryogenic operation condition. We attempt to find out the friction factor of KSTAR CS and PF CICC according to the test result of KSTAR CSMC (Central Solenoid Model Coil) 2nd campaign and compare the results with previous tests. The hydraulic characteristics of KSTAR superconducting magnet system like mass flow distribution, friction factor in conductor, pressure drop and etc during CSMC test and initial commissioning of KSTAR are presented. We can confirm the KSTAR CICC's unique hydraulic behavior in states of cool down and current charging period. Also, we expect that measured data will help to operate KSTAR and be a reference for thermo-hydraulic simulation.</P>

圓錐形 物體에 對한 强制對流 熱傳達 特性에 瓘한 實驗的 硏究

金良洙 영남이공대학 1987 論文集 Vol.16 No.-

Small wind tunnel experiments were performed to determine the average heat transfer coefficients and pressure coefficients for a truncated cone facing a uniform oncoming flow. The experiments covered the range of Reynolds numbers Re from 3X10³ to 40X10³and cone angles θ 6˚, 16˚, 30˚. These were important paramcte-ts. Mass transfer measurements by using the naphthalene sublimation technique were carried ont to obtain the average Nusselt numbers through the heat-mass transfer analogy, It was showed that average Nusselt number almost increased linearly with Reynolds number and each cone angle. and the correlations between the Re and Nu number were made in fully developed turbulent flow. Furthermore, it was found that the smaller the cone angle, the larger the Nusselt number. I thought it was influence of the flow characteristics is vortex flow, stagnation flow, etc.. Surface pressere coefficients of the downstream were decreased qualtatively by the Reynold number increased.

수평으로 놓인 평면두부 원통 Fin의 후류효과에 의한 열전달 특성의 실험적연구

김양수,이상배 영남이공대학 1992 論文集 Vol.21 No.-

In order to investigate and forced convection heat transfer characteristics for wake effects on back surface of colum fin equipped in small wind tunnel, mass transfer experiment applied naphthalene sublimation techique and measured results of pressure distribution of test piece of front and rear are considered. Mean Nusselt number is increased with the increasing of Reynolds number, Nusselt decreased with increasing of relativity length. When relativity length is 0.25, Mean Nu number is maximum value in the relativity length 0.125, 0.25, 0.5, 1.0, 2.0. But Nu Mumber showes the decreasing when Nu Number is 0.125. When Re Number is more than 20000, Pressure coefficient not changed mostly, when it is less than 20000, Pressure coefficient increased suddenly. And Pressure coefficient is minimal value when relativity length 0.25. In each relativity length, the relation formula and the change of mean Nusselt number on the back surface of hemispher fin in proporation to the changr of Reynolds number is described in table. 1.

1차원 난류유동장내에서 축회전하는 원추형 Fin의 후류 효과에 의한 열전달 특성의 연구

김양수 영남이공대학 1996 論文集 Vol.25 No.-

Heat transfer chacteristics by wake effect on the back surface of rotating fin of truncated cone type were investigated in a small wind tunnel. Naphthalene sublimate technique was applied to mass transfer experiment. And the pressure distributions of the front and rear fm were measured. The fin angles,θ used for the experiment were 30°, 60°. 90° , 120° , and 150° . The Reynolds number were varied from 8,000 to 45,000 and circular velocities were 03, 0.6 and 1.2 m/s. The Nusselt number of the rotating fm has greater in tendency than that of fixed fin. And the maximum value was in the cone angle 60° of both of fixed and rotating fin. The experiments has shown that them is a correlation between Nusselt and Reynolds numder. (Table. 1, 2, 3)

回轉하고 있는 圓錐形 物體 周圍에 對한 强制對流 熱傳達特性에 瓘한 實驗的 硏究

金良洙 영남이공대학 1987 論文集 Vol.16 No.-

Mass Transfer measurements via the naphthalene sublimation technique have been performed to determine the heat(mass) transfer coefficient for the rotation truncated cone which situated on the center of the tube. Experiments were performed with variations of the angle θ 6˚, 16˚, 30˚, and Reynolds No. 3X10³ 9X10³ From the experiments, it was showed that there was a correlation between Nusselt No. and Reynolds No. of the induced flow and Reynolds No. of the peripheral flow. If the Reynolds No. of the peripheral flow was smaller than the Reynolds No. of the induced flow, the heat transfer coefficient was mainly dependent with the Reynolds No. of the induced flow. When larger, the coefficient was dependent with the Reynolds No. of the peripheral flow. On the other hand, when the Reynolds No. of the induced flow was Iarger than the Re. No. of the peripheral flow, the larger the cone angle, linearly the smaller the Nusselt No. But alternative case, Nusselt No. was inclined to decrease abruptly from 6˚ to 16˚ and to increase from 16˚ to 30˚ because of flow characteristics.

원추형 Fin후면의 후류에 의한 열전달 특정에 관한 실험적 연구

김양수 영남이공대학 1989 論文集 Vol.18 No.-

In order to investigate heat transfer characteristics for wake effects on back surface of turncated cone type equipped in small wind tunnel. mass transfer experiment applied naphthalene sublimation technique and measured results of pressure distribution of test piece of front and rear are considered. Mean Nusselt number is increased with the increasing of Reynolds number. Heat transfer in proportion to the charge of cone angle showl maximun value with the Reynolds number. When cone angle is lass than 60˚ the amount of heat transfer is influenced by the charage of Reynolds number and cone angle. But, it is more than 90˚ it is primarily increased with the increasing of Reynolds number. (Fig. 4). Pressure coefficient shows the repeating cycle of increase and decrease with the increasing and change of Reynolds number and cone angle each other. (Fig. 6). In each cone angle, the relation formula and the change of mean Nusselt number on the back surface of turncated cone type fin in proportion to the change of Reynolds number is described in table 1.

반구두부를 갖는 Fin 후면피 후류에 의한 열전달 특성의 실험적 연구

김양수,김우섭 영남이공대학 1991 論文集 Vol.20 No.-

In order to investigate and forced convection heat transfer characteristics for wake effects on back surface of hemispher fin equipped in small wind tunnel, mass transfer experiment applied naphthalene sublimation technique and measured results of pressure distribution of test piece of front and rear are considered. Mean Nusselt number is increased with the increasing of Reynolds number. Neat transfer in proportion to the charge of hemispher fin shows maximum value with the Reynolds number. When relativity length is less than 0.5, the amount of heat transfer is influenced by the charago of Reynolds number and relativity length. But, it is more than 0.5, it is primarily decreased with the increasing of Reynolds number.(Fig.4) Pressure coefficient shows the repeating cycle of increase and decrease with the increasing and changeof Reynolds number and less then relativity length 0.5.(Fig.6) In each relativity length, the relation formula and the change of mean Nussclt number on the back surface of hemispher fin in melioration to the change of Reynolds number is described in table. I.

Practical study of optimizing the cool-down scenario for the KSTAR helium refrigeration system

Park, Dong-Seong,Moon, Kyung-Mo,Kim, Nam-Won,Song, Nak-Hyung,Joo, Jae-Joon,Kwag, Sang-Woo,Lee, Young-Ju,Chang, Yong-Bok,Lee, Chul-Hee,Ahn, Hee-Jae,Kim, Yaung-Soo Elsevier 2017 Fusion engineering and design Vol.123 No.-

<P><B>Abstract</B></P> <P>The cooling of superconducting (SC) magnet system for fusion device is the first procedure of the experiment. The Korea Superconducting Tokamak Advanced Research (KSTAR) device is fully SC tokamak that is made of NbTi and Nb<SUB>3</SUB>Sn. The KSTAR SC magnets are composed of 16 Toroidal Field (TF) coils and 14 Poloidal Field (PF) coils with 300 tons of cold mass. A Helium Refrigeration System (HRS) with 9kW@4.5K was installed and has been operated since 2008 to cool the SC magnets and keep all magnets at appropriate temperature conditions. This paper describes and analyzes the operational result of HRS during the KSTAR cool-down in 2008 and 2013. According to the cool-down analysis, the larger cryogenic helium flow from HRS made more efficient cooling of SC magnets. Furthermore, the study of cool-down optimization based on practical approach is presented and the build-up of control logic by using of cool-down optimization is also discussed.</P>