• Proceedings of the Korean Nuclear Society Conference
• /
• 1998.05a
• /
• pp.369-373
• /
• 1998

증기발생기에서 부식에 의한 전열관 손상은 전열관과 관판사이의 틈새에서 대부분 발생되고 이 틈새에서의 수질환경에 좌우된다. 틈새에서는 과열도가 높아 미량의 불순물이 농축되면서 틈새수화학 (crevice chemistry)은 증기발생기 내부수 수화학과는 달라진다. 전열관 손상을 억제하기 위해서는 틈새수질을 적절히 제어하여야 하는데 이는 틈새수화학을 정확히 분석평가할 수 있는 기술을 기반으로 하여야 한다. .기존의 틈새수질을 계산하는 방법으로는 증기발생기 내부수에 비해 틈새에서 화학종들이 얼마나 농축되는지를 가정하는 농축도 (concentration factor) 방법이 있으나 가정에 의한 불확실성으로 인해 틈새수질을 정확히 해석할 수 없었다. 그러나 원전 증기발생기의 잠복불순물 방출시험 자료로부터 틈새수질을 보다 정확히 평가할 수 있는 새로운 개념의 몰비지수(molar ratio index) 방법이 최근 EPRI에서 제시되었고 EPRI 산하의 많은 발전소에서 적용중이다. 본 연구에서는 PWR 원전 증기발생기의 틈새수화학을 평가할 수 있는 기술을 개발하기 위해 잠복불순물 방출시험 자료로부터 틈새에서의 몰비지수를 계산할 수 있는 CRAP (CRevice-chemistry Analysis Program) 전산프로그램을 작성하였다 CRAP를 국내원전에 적용하여 증기발생기 및 그 틈새에서의 수화학을 평가하였다.

• Journal of the Korean Society for Precision Engineering
• /
• v.17 no.2
• /
• pp.51-57
• /
• 2000

An automotive wheel bearing is one of the most important components to guarantee the service life of a passenger car. The endurance lift of a bearing is affected by many parameters such as material properties, heat treatment, lubrication conditions, temperature, loading conditions, geometry, internal clearance and so on. Under the same geometry and loading conditions, the internal clearance is the most effective parameters on the endurance lift of a bearing. Generally, bearings have the longest lift with a little negative internal clearance. But it is very difficult to measure and modify the internal clearance after a wheel bearing is assembled. In this paper, we analyze the effect of an assembling procedure on the clearance of wheel bearings and suggest a method to determine optimal clearance for automotive wheel bearings by selecting initial bearing clearance.

• Journal of the Speleological Society of Korea
• /
• no.79
• /
• pp.31-39
• /
• 2007

대금굴은 3년여 동안 암석 틈새를 들춰내며 150m쯤 물길을 찾아 들어가, 다시 18m의 수직동굴로 하강하여 좁은 틈새를 비집고 70m를 들어가는 악전고투의 탐사 끝에 2003년 동굴을 발견했다. 이렇게 3년여 동안 발굴된 대금굴은 또다시 4년여 동안의 모노레일 설치와 동굴내부 관람로 및 조명설치 등의 공사를 거쳐 2097년 6월 5일 일반 공개를 하였다. 총 길이 610m 중 4분의 3정도는 동굴 입구로 향하는 산길이고 나머지는 동굴 안쪽 길이다. 승강장에서 동굴 내부 140m에 설치된 "대금역"까지는 약 7분이 걸린다. 운전석이 없고 자동으로 운행하기 때문에 앞뒤로 동굴 안팎이 잘 보인다. 동굴 내부에 열차를 타고 들어가는 건 분명 이색체험이다. 그러나 모노레일 내부에 울리는 비발디의 "사계"라든지 동굴 벽에 붙여 놓은, 네온 빛에 가까운 퍼런 빛깔의 조명이 조용한 동굴 감상에 역효과가 초래될 수도 있다.

• Proceedings of the KSME Conference
• /
• 2004.11a
• /
• pp.1715-1720
• /
• 2004

This paper presents the characteristics of internal clearances for the interstage of blades and shaft gland seals on the steam turbine which are installed in tandem compound. Internal clearances was changed when the rotor turned in the cylindrical sleeve bearing due to the generation of oil film wedge. This presented concern is very useful to prevent the rubbing damage of seal edge between the fixed and moving parts in steam turbine due to the misalignment at the rotating and stationary parts. This method is applied for the unbalanced clearances distribution to the left and right sides in the turbine casing. A considerable amount of unbalanced clearances distribution trend is determined according to the rotating speed of rotor, size and type of proceeding bearing, oil viscosity, surface roughness of bearing and shaft, oil temperature, oil pressure and bearing load.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.35 no.3
• /
• pp.237-244
• /
• 2011

An experimental study was carried out to investigate the effect of the inclination angle on the nucleate pool boiling of saturated water at atmospheric pressure. We considered an annulus with a gap of 5 mm and a bottom opening. The inner tube of the annulus was heated, and the outer diameter and the length of the tube were 25.4 mm and 500 mm, respectively. The inclination angle was varied from horizontal to vertical. The results were compared to those for an annulus with a larger gap and a single tube. In the small-gap annulus, the effect of the inclination angle on the heat transfer was not significant. However, an early onset of the critical heat flux was observed at 80 kW/$m^2$ when the annulus was horizontal. Liquid agitation and bubble coalescence were considered to be the major heat-transfer mechanisms.

• Journal of the Korean Society for Precision Engineering
• /
• v.26 no.5
• /
• pp.135-141
• /
• 2009

The bearing clearance is influenced by shrink fit and thermal expansion during operation. The designer must take into account the reduction of clearance after installation to the interference fits, and thermal expansion must be considered. The purpose of this study is to grasp the internal clearance variation and behavior of a bearing which is a deep connected with fatigue life of bearing and performance of spindle through FEM(Finite Element Method). Finite element analysis is performed by using commercial code ANSYS according to variation of thermal condition and rotational speeds. This paper presents correct negative internal clearance according to temperature during operation. Furthermore, interrelation between thermal expansion and contraction are presented to maintain adequate contact force for three type of spindle system (HSK-A60, HSK-40E, HSK-32E). The influence of the centrifugal force and Internal clearance variation of bearing is studied to operating rotational speed.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
• /
• 2011.04a
• /
• pp.357-360
• /
• 2011

고층 건축물에 주로 사용되는 커튼월의 경우 구조체와의 접합으로 인해 층간 틈새가 발생하게 되고 이는 화재 시 틈새를 통해 화염이나 연기 등의 확산 경로가 될 수 있다. 본 연구에서는 커튼월 시스템에 적용되는 선형조인트 내화충전시스템의 개발을 위해 경제적이고 시공이 간편한 박스형 시스템을 도입하고 내부에 다양한 변경하여 내화성능을 평가하였으며, 그 결과 케이싱 내부의 단열재 20mm두께의 내화 뿜칠재와 석고보드를 케이싱 안쪽에 박스 형태로 구성한 시스템이 가장 안정적이고 온도상승도 작은 것으로 나타났다.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.46 no.12
• /
• pp.994-1003
• /
• 2018

The clamping characteristics of segmented nuts in pyrotechnic separation nut are investigated using finite element analysis. When the segmented nuts are used to clamp objects, a constraint cylinder is necessary to prevent the segmented nuts from spreading out to the radial direction. During the manufacturing process, a clearance is usually introduced between the outer diameter of the segmented nuts and the inner diameter of the constraint cylinder. Therefore to find out the effect of the clearance, proper finite element modeling method is suggested to describe the clamping procedure appropriately. In addition, finite element analysis with the clearance of 0.00, 0.03, 0.06, and 0.10 mm are performed. From the analysis results, the clamping characteristics of segmented nuts are investigated according to the clearance, and several factors which should be considered to design a reliable pyrotechnic separation nut are figured out.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.36 no.8
• /
• pp.775-782
• /
• 2012

To investigate pool boiling heat transfer in a vertical annulus with closed bottoms, the length of an outer tube was varied between 0.3 and 0.6 m. For the test, a heated tube of 0.2-m length and 19.1-mm diameter and water at atmospheric pressure were used. To elucidate the effects of the outer tube length on heat transfer, the results for the annulus were compared with data for a single unrestricted tube. The increase in the outer tube length resulted in an increase or decrease in heat transfer depending on the gap size. This tendency is mainly attributed to the difference in the intensity of liquid agitation.

• Solar Energy
• /
• v.18 no.2
• /
• pp.115-121
• /
• 1998

In this study a channel cavity flow was performed. The channel has small size in the upper cavity region. At the gap is supplied by driven flow for Reynolds number. The experimental study was carried out in a channel cavity with square heat surface by visualization equipment with Mach-Zehnder interferometer and laser apparatus. Heat source was uniform heat flux($0.4W/cm^2,\;0.8W/cm^2,\;1.2W/cm^2$). When the bottom wall is heated, the tendency of natural convection flows are vigorous increasing heat flux.