Stability analysis of a single-phase rectangular Coupled Natural Circulation Loop system employing a Fourier series based 1-D model

TL;DR

This paper presents a Fourier series based 1-D model for analyzing the stability of a single-phase rectangular Coupled Natural Circulation Loop system, validated against CFD simulations, and explores how system parameters influence stability.

Contribution

It introduces a novel Fourier series based 1-D stability analysis method for CNCL systems and compares it with CFD results to validate its accuracy.

Findings

Fourier number and flow resistance coefficient increase stability domain.

Non-linear terms have minimal impact on stability boundaries.

Multiple steady states are identified and their stability maps are presented.

Abstract

A linear stability analysis of a single-phase Coupled Natural Circulation Loop (CNCL) is carried out using a Fourier series based 1-D model. A 3-D CFD study is undertaken to assess the ability of the 1-D model to capture the non-periodic oscillatory behaviour exhibited by the CNCL system. After the model verification, the stability maps of the system are obtained from the eigenvalues of the steady-state. The CNCL has multiple steady states and the stability maps of consistently observed steady states are presented. A thorough parametric study is conducted to observe the influence of non-dimensional numbers on the CNCL system. Increase in the Fourier number and flow resistance coefficient lead to an increase in the domain of stability. A comparison of the linear stability map with the empirical stability map indicates that the non-linear terms do not significantly affect the stability boundary.