抄録
This paper deals with the experimental results on the flow instability in boiling channel systems. The parameters considered in this study include; (1) heat input q (kcal/m3·sec), (2) subcooling ΔTsub(°C), (3) drag coefficient ζ (dimensionless).
The flow instability occurs in the transitional range from undeveloped slug flow to developed slug flow. There are two stable regions of flow: (a) the region of spherical bubble and undeveloped slug flow (the first stable; when subcooled time τsub is large); and (b) the region of developed slug flow (the second stable; when τsub is small). When ζ is increased, the unstable region widens, and the flow pattern changes from undeveloped slug flow (the first stable) to unstable flow. When ζ is further increased more, the flow pattern changes from unstable flow to developed slug flow (the second stable).
In the case of forced circulation, the unstable region is narrow and is displaced downward in the (ζ, τsub) plane.
The period of flow oscillations in the unstable region is increased when q is decreased. The same tendency of increasing period is observed in the case of increasing ΔTsub and decreasing ζ. When forced circulation is present, the period of flow oscillations is increased and the amplitude is decreased as compared with the case of natural circulation.
