서지주요정보
2상 자연순환 회로내에서의 유동 불안정에 관한 연구 = A study on the flow instabilities in two-phase natural circulation loops
서명 / 저자 2상 자연순환 회로내에서의 유동 불안정에 관한 연구 = A study on the flow instabilities in two-phase natural circulation loops / 이동원.
발행사항 [대전 : 한국과학기술원, 1993].
Online Access 원문보기 원문인쇄

소장정보

등록번호

8003323

소장위치/청구기호

학술문화관(문화관) 보존서고

DME 93018

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리뷰정보

초록정보

The two-phase natural circulation is induced by the density difference between the vapor and the liquid phase. The concept of the two-phase natural circulation is often adopted in designs of thermosyphon reboiler, solar collector and various cooling systems. In a two-phase natural circulation mode, various types of flow instabilities occur depending on the system geometry, fluid properties and the operating conditions, and often lead to abnormal behaviors such as limit cycle oscillations or premature burnout. That is, the self-sustained flow oscillations may cause mechanical vibrations of compenents, and affect the local heat transfer characteristics which can induce a boiling crisis. In the present study, the time-averaged behavior and the density wave instability were predicted numerically for the three loop types;open loop, closed loop and semi-closed loop. The system pressure is constant in the open and the semi-closed loops, but it varies with the heat flux in the closed loop. The time-averaged equation was obtained by using the one-dimensional two-phase homogeneous equilibrium model, and the characteristic equation was derived by using the perturbation technique with linearizations. Heat flux, condenser liquid level(for the open loop), condenser and heater section lengths, loop height and the flow restrictions in the liquid-and two-phase regions were taken as parameters to examine the flow behavior. Effect of the inlet subcooling was also considered in the open and the semi-closed loops. Stability criteria for the excursive and the density wave instabilities were obtained along with the variation of the steady liquid velocity with the heat flux for each loop. For the open and semi-closed loops, excursive instability and density wave instability boundaries were shown on the instability map in the plane of $N_{\mbox{pch}}(Fr)^{1/2}{\mbox{vs}}N_{\mbox{sub}}$. It was found that examination of the density wave instability conditions is sufficient for the two-phase flow stability analysis. Both the stable region and the excursive instability region shift to the higher heat flux range with the higher condenser liquid level. The increase of the loop height results in a larger unstable region, and the stable region extends to the higher inlet subcooling range with the longer heater section. The system is stabilized with the increase of the liquid-phase restriction and/or with the decrease of the two-phase restriction. In the closed loop, the dynamic instability boundary shows a convex shape in the plane of the heat flux vs. the condenser coolant temperature ($q_h$ vs $T_c$). the excursive instability dose not occur because the fluid inventory(charging level) remains constant in this loop. Flow becomes unstable as the charging level decreases. When the lengths and the vertical locations of the condenser and the heater sections are fixed, the system becomes unstable with the longer riser section. The systems is destabilized with the longer heater and condenser sections for the fixed heating rate. As for the open loop or the semi-closed loop, the systems is stabilized with the increase of the liquid-phase restriction or with the decrease of the two-phase restriction.

서지기타정보

서지기타정보
청구기호 {DME 93018
형태사항 xiiii, 136 p. : 삽화 ; 26 cm
언어 한국어
일반주기 부록 수록
저자명의 영문표기 : Dong-Won Lee
지도교수의 한글표기 : 이상용
지도교수의 영문표기 : Sang-Yong Lee
학위논문 학위논문(박사) - 한국과학기술원 : 기계공학과,
서지주기 참고문헌 : p. 121-130
주제 Stability.
Two-phase flow.
Limit cycles.
Density wave theory.
Heat --Transmissions.
안정성. --과학기술용어시소러스
밀도류. --과학기술용어시소러스
순환류. --과학기술용어시소러스
상류. --과학기술용어시소러스
비선형성. --과학기술용어시소러스
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