THREE REGION REDUCE ORDER MODEL FOR STABILITY ANALYSIS OF THE SUPERCRITICAL FLUID IN HEATED CHANNEL
This paper captures the phenomena of density wave oscillation instability of supercritical water (SCW) flowing as a working fluid in a single heated channel. In the heated channel, the SC fluid density shows dramatic downfall near the pseudo-critical temperature based on which it has been divided into three zones viz. heavy fluid phase, mixture fluid phase and supercritical fluid phase. These zones are mathematically presented by the conservation equations which are in the form of partial differential equations (PDEs). The reduced order model (ROM) is developed by using weighted residual method on these PDEs. The corresponding time dependent non-linear ordinary differential equations (ODEs) are obtained under appropriate assumptions and approximations for each zone. These ODEs are used to capture the stability boundary (SB) in terms of trans-pseudo-critical phase change number (Ntpc), pseudo-subcooling number (Nspc) by applying constant external pressure drop (ΔPext) condition across the channel. The results have been verified by numerical simulation and the dependence of the parametric values on the system is also presented.