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Hun Sik Han(한훈식),Han-Ok Kang(강한옥),Juhyeon Yoon(윤주현),Young In Kim(김영인),Youngmin Bae(배영민),Sang Ji Kim(김상지) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11
A numerical study is conducted for the secondary side screw-type tube inlet orifice design of a once-through steam generator. Various tube plugging conditions and power levels are considered, and the secondary coolant inlet temperature is adjusted to maintain a constant thermal power. Comprehensive numerical solutions are acquired to evaluate the minimum orifice length under various operating conditions, and the required minimum orifice length to suppress the flow oscillation below the allowable level is evaluated. The results obtained show that the lowest power level results in the highest minimum orifice length and non-plugging condition provides a limiting case for the orifice length criterion.
Jae-Kwang Seo(서재광),Han-Ok Kang(강한옥),Juhyeon Yoon(윤주현),Sung-Qunn Zee(지성균) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.11
A once-through steam generator (OTSG) with a modular feedwater line (MFL) is located inside a reactor vessel. A sufficient heating of the feedwater in the MFL can cause an aperiodic instability especially at low flow and low pressure conditions. Aperiodic instability is an instability related to the change of a flow direction in individual steam generating U-shaped channels operating at given pressure difference. The nature of an aperiodic instability is close to a Ledinegg instability related to the presence of multiple flows at the full hydraulic curve of a U-shaped channel. In this paper, the conditions for a reverse flow at the OTSG with a tube-in-tube MFL are studied. From the results of the studies, it is revealed that the change of a flow direction in the MFL is due to the boiling of the feedwater in the downcomer branch of the U-shaped pipe and that multiple flows start in the area of the extreams corresponding to the minimum pressure difference of the hydraulic curves.