Flow reversal prediction of a single-phase square natural circulation loop using symbolic time series analysis

Saha, Ritabrata; Ghosh, Koushik; Mukhopadhyay, Achintya; Sen, Swarnendu

doi:10.1007/s12046-020-01466-3

Cited by 4 publications

(5 citation statements)

References 24 publications

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“…The governing equations (e.g., conservation of mass, momentum, and energy) for the loop fluid flow, and coolant and wall temperatures are solved numerically. These equations, which are similar to those in earlier publications [18][19][20], are only briefly explained here. For example, the continuity, momentum, and energy equations are represented by Equations (1)-(3), respectively.…”

mentioning

confidence: 68%

“…The numerical model used in this paper was compared and validated with the experimental and numerical results in the previous publications [18][19][20]; therefore, a validation study is not repeated here for compactness of the paper.…”

Section: Conservation Of Energy (Heat Exchanger Tube Wall)mentioning

confidence: 99%

“…A numerical model of a single-phase NCL loop, which was already validated with experimental data [18][19][20], has been used to generate the time-series response in the work reported in the current paper. For different inputs of heater power under different (physically relevant) initial conditions, the simulated NCL system is observed to stabilize to a steady-state regime of operation within the 7200 s (2 h) mark.…”

Section: Introductionmentioning

confidence: 99%

“…An annular-type cooler, with a length of 600 mm, is placed with a 100 mm offset on the upper horizontal arm of the loop to cool the loop fluid; this offset is necessary to start the simulation. Although detailed descriptions of the loop geometry, model construction and validation, and grid and time independence studies are reported in previous publications [18][19][20], a concise description of the model equations is provided in this section for completeness of the paper and ease of readability. The nomenclature of the terms used in the development of equations is provided at the end of the paper.…”

mentioning

confidence: 99%

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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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mentioning

confidence: 68%

Section: Conservation Of Energy (Heat Exchanger Tube Wall)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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

Bhattacharya

Saha

Mukhopadhyay

et al. 2021

Sci

Self Cite

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“…Lu and Rizwan-uddin [32] carried out an extensive stability analysis of natural circulation in lead cooled fast reactor accounting for both the thermal-hydaulics and neutronics using a 1-D model. Saha et al [33] conducted the symbolic time series analysis to predict the flow reversal in NCL systems employing a 1-D NCL model accounting for the wall effects. The symbolic state histograms are utilised to identify how far the system is from the chaotic regime.…”

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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Stability analysis of a single phase rectangular coupled natural circulation loop system employing a Fourier series based 1-D model

Dass

Gedupudi

2022

Chemical Engineering Science

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Flow reversal prediction of a single-phase square natural circulation loop using symbolic time series analysis

Cited by 4 publications

References 24 publications

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

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

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

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