Instability of single-phase natural circulation under double loop system

The natural circulation in a single loop system has been studied by many researchers. In a multiple loop system, the instability of natural circulation is more complicated because of the interaction between the loops. In this study, the effects of the multiple loops on the natural circulation instability were investigated numerically. The double loop system with one heating tube and two cooling tubes were evaluated. The one-dimensional energy and momentum equations were solved using the Finite Difference Method. The Bow regimes of the instability were evaluated with variations in the heat Bur and the initial velocity condition. In a double loop system, the observed flow was classified into five regimes, namely, steady, transient-CS, transient-CS;CL, transient-CL and complex chaotic regimes, which were more complicated than those observed in single loop system. The flow regimes were qualitatively explained by the stability of the attractor in the phase spate. The complexity of thr regime was caused by the coexistence of two attractors. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.