Investigations on the dependence of the stability threshold on different operating procedures in a single-phase rectangular natural circulation loop

Elton, D.N.; Arunachala, U.C.; Vijayan, P.K.

doi:10.1016/j.ijheatmasstransfer.2020.120264

Cited by 16 publications

(2 citation statements)

References 53 publications

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“…They observed that the system remained stable in the considered power range as long as the system remained in the single phase flow at the reactor core. Elton et al [29] carried out an experimental study to determine the instability threshold of the NCL systems with larger diameters. They reported the influence of operating procedures (start-up from rest, power raising from stable steady state, etc.)…”

Section: Chaotic Oscillations and Stability Analysis Of Ncl Systemsmentioning

confidence: 99%

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

Dass,

Gedupudi

2020

Preprint

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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 nonperiodic 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.

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Section: Chaotic Oscillations and Stability Analysis Of Ncl Systemsmentioning

confidence: 99%

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

Dass,

Gedupudi

2020

Preprint

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“…In general, unstable flow dynamics of NCL can be classified as follows; (a) For the single-phase condition, only one unstable regime is prevalent; and (b) for the two-phase condition, two unstable regimes may exist. Although NCLs operating in two-phase and supercritical regions have been developed to cater to higher power ranges, single-phase natural circulation loops continue to be actively pursued by the researchers worldwide [14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Identification of Long-Term Behavior of Natural Circulation Loops: A Thresholdless Approach from an Initial Response

Bhattacharya

Saha

Mukhopadhyay

et al. 2021

Sci

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Natural circulation loop (NCL) systems are buoyancy-driven heat exchangers that are used in various industrial applications. The concept of passive heat exchange in NCL systems is attractive, because there is no need for an externally driven equipment (e.g., a pump) to maintain the fluid circulation. However, relying on buoyancy as the sole driving force may lead to several potential difficulties, one of which is generation of (possibly) time-varying nonlinearities in the dynamical system, where a difference in the time scales of heat transfer and fluid flow causes the flow to change from a steady-state regime to either an oscillatory regime or a flow-reversal regime, both of which are undesirable. In this paper, an algorithm is developed using tools of symbolic time-series analysis (e.g., probabilistic finite state automata (PFSA)) for the purpose of identifying selected regimes of operation in NCL systems using only data from the early transient operation, where the underlying principle is built upon the concept of pattern classification from measurements of fluid-flow dynamics. The proposed method is shown to be capable of identifying the current regime of operation from the initial time response under a given set of operational parameters. The efficacy of regime classification is demonstrated by testing on two datasets, generated from numerical simulation of a MATLAB SimuLink model that has previously been validated with experimental data. The results of the proposed PFSA-based classification are compared with those of a hidden Markov model (HMM) that serves as the baseline.

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Optimizing the geometry of tube-in-tube Thermosyphon heat transport device from instability Perspective: A computational study

Varun,

Arunachala,

Vijayan

2024

Applied Thermal Engineering

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Investigations on the dependence of the stability threshold on different operating procedures in a single-phase rectangular natural circulation loop

Cited by 16 publications

References 53 publications

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

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

Identification of Long-Term Behavior of Natural Circulation Loops: A Thresholdless Approach from an Initial Response

Optimizing the geometry of tube-in-tube Thermosyphon heat transport device from instability Perspective: A computational study

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