Validity of homogeneous flow model for instability analysis

Abstract

The main objective of this paper is to present the validity of using a homogeneous flow model which predicts density-wave oscillation of water in a natural-circulation boiling-fluid channel. The seven different homogeneous flow models presented here are all based on linearized approximation, and the transient responses of the pressure drop as to the inlet flow rate are calculated by the Laplace transformation technique. The major differences between these seven models are in their heat capacities in the subcooling region and in their frictional coefficients. The test results using the analytical models are then compared with the data obtained from two different apparatuses: one apparatus is for the data in the region up to 2.94 MPa of pressure, and a second larger apparatus in the region up to 11.8 MPa of pressure. Furthermore, they are evaluated with some other authors' work to make the generalization. The model which best predicts the onset of oscillation is finally selected by carefully comparing the results of these comparisons.