Simulation of oscillatory flow phenomena in vertical condensing flows inside a tube

This paper presents the results of a simulation of unstable flow phenomena in vertical condensing flows. The horizontal condensing flow model was extended to include gravitational effects. The simulations revealed existence of limit-cycle type of oscillations of large amplitude, including possibilities of flow reversals, as were observed on horizontal flows. The simulations also revealed that the gravitational effects have an attenuating effect on the oscillatory behavior in downward flows, and an enhancing effect on the upward flows. Matlab/Simulink tools were used for the system simulations.