Two phase flow stability analysis of multiple horizontal uniformaly heated channel

Abstract

Two-phase flow in multiple horizontal heated channels has wide applications in heat exchangers, solar heating systems, nuclear systems etc. The theoretical study of the two-phase flow instability analysis for parallel channel was carried by Zhang et al. [1]. This was done for vertical channels and they used nodal method to analyze stability of the system. Similar analysis was done by Lee et al. [2, 3] and Nayak and Vijayan [10], for multiple, vertical boiling channels with forced flows. Following the Zhang et al. [1] and Lee et al. [2, 3], the stability analysis of multiple horizontal channels with uniform heat flux has been carried out. The system is mathematically represented by non-linear PDEs using mass, momentum and energy equations in single as well as two-phase regions. Coupling equation is being used under the assumption that pressure drop in each channel is same and the total mass flow rate is equal to sum of individual mass flow rates. The homogeneous equilibrium model is assumed to be valid in the two phase region. Stability boundary is obtained in terms of phase change number (Npch) and Sub-cooling Number (Nsb) and is validated by comparing it with result obtained by MatCont using the same parametric values. Numerical simulation of the time-dependent, nonlinear ODEs are carried out for selected points in the operating parameter space to obtain the actual damped and growing oscillations in terms of the channel inlet velocity which verifies the stability behavior across the stability map.