Analytical and numerical investigation of the heat exchange effect on the dynamic behaviour of natural circulation with internally heated fluids

Pini, Alessandro; Cammi, Antonio; Luzzi, L.

doi:10.1016/j.ces.2016.01.014

Cited by 31 publications

(11 citation statements)

References 21 publications

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“…Pini et al [24], Nadella et al [25] and Cammi et al [26] carried out a detailed and extensive assessment of the 1-D numerical and semi-analytical models against experimental literature and observed good agreement between the 1-D model predictions and the experimental literature data. The thermal inertia introduced due to the piping material was also observed to influence the stability of NCL systems.…”

Section: Chaotic Oscillations and Stability Analysis Of Ncl Systemsmentioning

confidence: 93%

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: 93%

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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“…The trends of the average difference temperatures and the average fluid velocity show an opposite behaviour when the power input increases, according to the (1) and (2) equations. Moreover, it is clear the influence of the heat sink temperature: when it increases, the average difference temperature decreases for a fixed heat power dissipated at the heater [24][25][26][27].…”

Section: No Connected Loop #1mentioning

confidence: 99%

Experiments on parallel connected loops in single phase natural circulation: preliminary results

Marchitto¹,

Misale²

2018

MMEP

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Natural circulation is the most important heat removal mechanism for passive protection systems in a lot of industrial applications, such as nuclear power plants, solar energy systems, reboilers and cooling of electronic systems. The aim of the present work is to investigate the flow and heat transfer characteristics of parallel loops, connected in the lower heated sections, in single-phase natural circulation. The test facility was composed by 2 vertical circuits connected in parallel; each of them was rectangular in geometry, the aspect ratio (defined as the height to width ratio) was 1.63, with circular copper tube of 4 mm (I.D.). An upper cold heat exchanger provided the heat sink, while the heat source at the bottom was a power supply system. Several calibrated thermocouples (T-type) placed in the fluid along the vertical tubes allowed the evaluation of the hot and cold legs average fluid temperature differences. Tests were carried out imposing 3 different heat sink temperatures (10, 20, 30°C); for each of these temperatures the power supply at the lower heater was increased from 20 to 90 W. The fluid investigated was distillate water. The experimental results have been analysed in terms of thermal performance of the single or connected loops. Collected data have also been compared with Vijaiyan's correlation.

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“…Thus, it is important to be able to correctly describe the flow regime of natural circulation systems. In this context, a useful equipment is represented by a Natural Circulation Loop (NCL), i.e., a rectangular or a toroidal loop with a heat sink and a heat source where the fluid flow is driven by natural circulation as a function of friction and buoyancy forces [5,7,8]. The simplicity of these systems allows focusing on the physical and phenomenological basis of the buoyancy-driven circulation and represents an ideal validation benchmark for testing modelling capabilities.…”

Section: Introductionmentioning

confidence: 99%

“…1) is aimed at investigating the stability and the dynamics of natural circulation in presence of distributed heating, in particular to investigate the decay heat removal mechanisms for the Molten Salt Fast Reactor [6]. Previous studies on the stability of singlephase NCLs with both localized and distributed heat sources applying analytical and numerical methods [7,10], indicate, that natural circulation with internal heat generation is potentially more prone to the instability with respect to the case with localized heat sources. Thus it is of interest and practical importance to further investigate the stability of NCLs with distributed heating.…”

Section: Introductionmentioning

confidence: 99%

Modelling and CFD analysis of the DYNASTY loop facility

Nalbandyan

Cammi²,

Lorenzi³

et al. 2022

EPJ Nuclear Sci. Technol.

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In this paper, CFD assessment of the DYNASTY natural circulation loop, adopting a RANS turbulence modeling approach, is performed using the OpenFOAM open source toolbox. The DYNASTY facility is designed to investigate the stability and dynamics of heat-generating fluids, in particular molten salts, in a natural or forced circulation regime and as such, it is one-of-a-kind, large scale facility for studying the natural circulation in presence of distributed heating. In this work, a CFD model of the facility is set up and validated by comparing the model results to experimental data obtained during the initial testing campaign of the facility, with water as working fluid. In particular, the equilibrium state of the system is investigated in terms of the mass flow dynamic behaviour and the temperature difference across the cooler section of the loop. It is shown that the CFD simulations adopting the k − ω SST turbulence model best reflect the experimental results. The CFD results are also in agreement with a simplified 1D modeling as well as an analytical solution.

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Analytical and numerical investigation of the heat exchange effect on the dynamic behaviour of natural circulation with internally heated fluids

Cited by 31 publications

References 21 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

Experiments on parallel connected loops in single phase natural circulation: preliminary results

Modelling and CFD analysis of the DYNASTY loop facility

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