Abstract
An investigation is carried out on the hydrodynamic instability in a system having two boiling channels. The basic equations for the circulation flow rates and driving heads are introduced from the laws of conservation of mass, energy and momentum. The stability of equilibrium in the hydrodynamic system and the modes of vibration are discussed. As the results, the following facts are found. (a) The system is always stable when the equilbrium of the hydrodynamic system lies in the range of positive inclination of the characteristic curve for each channel and (b) always unstable when the equilibrium in the range of negative inclination of the characteristic curve for each channel ; (c) When the equilibrium lies in the range of positive inclination for one channel and in that of negative inclination for the other channel, the system is either stable or unstable ; (d) There are two normal modes of vibration in the system with two boiling channels. The first is a mode in which each channel vibrates in the same phase and the second is a mode in which each channel vibrates in the opposite phase ; (e) In the case of (b) the second mode is always unstable and a throttle or a pump in the downcomer is not effective to cause positive damping to the second mode and (f) In the system with parallel channels there can be many equilibriums, so that non-uniform distributions of flow rates may occur.
