Unstable behavior of single-phase natural circulation under closed loop with connecting tube.

The single-phase natural circulation in a single loop system had been studied by many researchers. In a multiple loop system, the characteristics of natural circulation was more complicated because of the interaction between the loops. In this study, the effects of the multiple loop on the natural circulation instability were investigated experimentally. As the simple multiple loop system, the troidal loop with insulated connecting tube between both sides (θ-loop) was evaluated. The variation of flow regime in θ-loop was almost the same with that in single loop. However the chaotic condition in inclined θ-loop was narrower than that of inclined single loop. The flow and the pressure transfer in the connecting tube played an important role in the chaotic condition in θ-loop.