scholarly journals Mathematical modelling of the stability characteristics of a natural circulation loop

1995 ◽  
Vol 22 (9) ◽  
pp. 77-87 ◽  
Author(s):  
A.K. Nayak ◽  
P.K. Vijayan ◽  
D. Saha ◽  
V. Venkat Raj
Keyword(s):  
Mathematical Modelling ◽  
Natural Circulation ◽  
Circulation Loop ◽  
Natural Circulation Loop ◽  
The Stability

Stability Analysis of a Supercritical Water Natural Circulation Loop

2012 ◽  
Author(s):  
ZhongChun Li ◽  
JiYang Yu ◽  
XiaoMing Song
Keyword(s):  
Supercritical Water ◽  
Natural Circulation ◽  
Basic Research ◽  
Circulation Loop ◽  
Two Phase ◽  
Water Reactor ◽  
Natural Circulation Loop ◽  
The Stability ◽  
Engineering Physics ◽  
Supercritical Water Reactor

As a part of “supercritical water reactor basic research”, the stability of the natural circulation research plays an important role on the feasibility of supercritical water reactor and experiment research. In this paper, the stability of a supercritical water natural circulation loop built by Department of Engineering Physics, Tsinghua University was studied by numerical method. It was confirmed that the static or Ledinegg instability doesn’t occur in HACA system, and there are no instabilities existing when the inlet enthalpy is larger than critical enthalpy. Instability was observed by numerical way, which is similar to DWOs and PDOs in two phase natural circulation loop. The system parameters’ influence on the instability of supercritical natural circulation loop was studied.

Influence of bidirectional inclination on the stability of single-phase natural circulation loop

2019 ◽  
Author(s):  
Adarsh R. Nair ◽  
Rupesh Shanmughom ◽  
Raveesh Gopalakrishnan ◽  
Abhijith A. S. Nair
Keyword(s):  
Single Phase ◽  
Natural Circulation ◽  
Circulation Loop ◽  
Natural Circulation Loop ◽  
The Stability

Steady State and Dynamic Analyses of Supercritical CO2 Natural Circulation Loop

2006 ◽  
Author(s):  
Prashant Jain ◽  
Rizwan Uddin
Keyword(s):  
Steady State ◽  
Natural Circulation ◽  
Stability Boundary ◽  
Operating Conditions ◽  
Circulation Loop ◽  
Steady State Flow ◽  
Natural Circulation Loop ◽  
Dynamic Analyses ◽  
The Stability ◽  
Flow Power

Numerical studies have been carried out to investigate supercritical flow instabilities in a CO2 natural circulation loop. For the steady state and dynamic analyses of the loop under supercritical conditions, a single-channel, one-dimensional model is developed. In this model, equations for the conservation of mass, momentum and energy are discretized using an implicit finite difference scheme. A computer code called FIASCO (Flow Instability Analysis under SuperCritical Operating conditions) is developed in FORTRAN90 to simulate the dynamics of natural circulation loops with supercritical fluid. Results obtained for the stability boundary substantially deviate from the results reported by previous investigators, and thus contradict some of the reported findings. The disagreement in results is most likely due to the undesirable dissipative and dispersive effects produced from the large time steps used in previous studies, thereby leading to a larger stable region than those found using smaller time step. Results presented here suggest that the stability boundary of a natural circulation loop with supercritical fluid, is not confined to the near-peak region of the (steady state) flow-power curve. Additional and more extensive experimental data are needed to resolve the differences between results obtained here and those reported earlier. However, results obtained for the range of parameter values used in this investigation always predict the stability threshold to be in the positive slope region of the (steady state) flow-power curve. Parametric studies for different operating conditions reveal the similarity of stability characteristics under supercritical conditions with those in two-phase flows.

Nonlinear Analysis for a Two-Phase Natural Circulation Loop Under Low-Pressure

2010 ◽  
Author(s):  
Arrdaneh Kazem ◽  
Zaferanlouei Salman ◽  
Mohsen Farahi ◽  
Asad Allah Ahmadi
Keyword(s):  
Low Power ◽  
High Power ◽  
Parametric Study ◽  
Stability Region ◽  
Natural Circulation ◽  
Circulation Loop ◽  
Two Phase ◽  
Natural Circulation Loop ◽  
The Stability ◽  
Power Region

The purpose of this paper is to develop a nonlinear model to investigate the instabilities of a two-phase natural circulation loop under low-pressure condition. Inlet velocity oscillations and the corresponding trajectories are respectively presented in the time evolution planes and phase planes. We obtain a stability map to explore the instability regions of this natural circulation loop. The results show that the considered loop has two unstable regions, instability type-I in the low power region and instability type-II in the high power region. Then the parametric study is carried out to understand the relation between the parameters of system and two types of instability. The parametric study reveals that lengthening the riser has an unstable effect on system stability. Thus, lengthening the riser causes a reduction in the stability region in the both low power and high power levels. Also it can be observed that by increasing the form loss coefficient at the inlet of heated section or in the downcomer section, the stability region expands, however by increasing the form loss coefficient at the outlet of heated section or in the upper horizontal section, the stability region decreases consequently.

Stability Behavior of Single-Phase Natural Circulation Loop

2003 ◽  
Author(s):  
Seyed Khalil Moussavian ◽  
Mario Misale ◽  
Francesco D’Auria ◽  
Mahmoud Salehi
Keyword(s):  
Natural Circulation ◽  
The Body ◽  
Linear Stability Theory ◽  
Circulation Loop ◽  
Conservation Equations ◽  
Cold Zone ◽  
Natural Circulation Loop ◽  
The Stability ◽  
The One ◽  
The University

The circulating fluid in natural circulation loops would absorb heat from the hot zone (source) and will transport it to the cold zone (sink) without using of any mechanical pumps or other devices. The fluid density differences in hot and cold zones would lead buoyancy force which is introduced as the body force for the loop. By introducing the one-dimensional conservation equations; mass, momentum and energy in the loop and applying the perturbation method, or linear stability theory, would help us to study the stability of the rectangular natural circulation loop. The conservation equations in transient form were solved using the finite difference method. The results obtained from the linear and nonlinear stability studies would be compared with the experimental data of DITEC loop (LOOP#1) obtained at the University of Genova and with other suitable data in the literature.

Study of Flow Instabilities in a Natural Circulation Boiling System

2010 ◽  
Author(s):  
Arrdaneh Kazem ◽  
Ahmadi Asad allah ◽  
Mohsen Farahi ◽  
Zaferanlouei Salman
Keyword(s):  
Low Power ◽  
High Power ◽  
Parametric Study ◽  
Stability Region ◽  
Natural Circulation ◽  
Loss Coefficient ◽  
Circulation Loop ◽  
Natural Circulation Loop ◽  
The Stability ◽  
Power Region

The purpose of this paper is to develop a nonlinear model to investigate the instabilities of a two-phase natural circulation loop. We obtain a stability map to explore the unstable regions of this natural circulation loop. The results show that the considered loop has two unstable regions, instability type-I in the low power region and instability type-II in the high power region. Then the parametric study is carried out to understand the relation between the parameters of system and two types of instability. The parametric study reveals that lengthening the riser has an unstable effect on system stability. Thus, lengthening the riser causes a reduction in the stability region in the both low power and high power levels. Also it can be observed that by increasing the form loss coefficient at the inlet of heated section or in the downcomer section, the stability region expands, however by increasing the form loss coefficient at the outlet of heated section or in the upper horizontal section, the stability region decreases consequently.

Linear and Non-Linear Stability Analysis of a Supercritical Natural Circulation Loop

2009 ◽  
Author(s):  
Manish Sharma ◽  
P. K. Vijayan ◽  
D. S. Pilkhwal ◽  
D. Saha ◽  
R. K. Sinha
Keyword(s):  
Stability Analysis ◽  
Supercritical Water ◽  
Natural Circulation ◽  
Computer Code ◽  
Linear Analysis ◽  
Circulation Loop ◽  
Stability Behavior ◽  
Natural Circulation Loop ◽  
Non Linear ◽  
The Stability

Supercritical water has excellent heat transfer characteristics as a coolant for nuclear reactors. Besides it results in high thermal efficiency of the plant. However, the flow can experience instabilities in supercritical water reactors, as the density change is very large for the supercritical fluids. A computer code SUCLIN has been developed employing supercritical water properties to carry out the steady state and linear stability analysis of a SCW natural circulation loop. The conservation equations of mass, momentum and energy have been linearised by imposing small perturbation in flow rate, enthalpy, pressure and specific volume. The equations have been solved analytically to generate the characteristic equation. The roots of the equation determine the stability of the system. The code has been benchmarked against published results. Then the code has been extensively used for studying the effect of diameter, heater inlet temperature and pressure on steady state and stability behavior of a Supercritical Water Natural Circulation Loop (SCWNCL). A separate computer code NOLSTA has been developed which investigates stability characteristics of supercritical natural circulation loop using non-linear analysis. The conservation equations of mass, momentum and energy in transient form were solved numerically using finite volume method. The stable, unstable and neutrally stable points were identified by examining the amplitude of flow and temperature oscillations with time for a given set of operating conditions. The stability behavior of loop, predicted using non-linear analysis has been compared with that obtained from linear analysis. The results show that the stability maps obtained by the two methods agree qualitatively. The present paper describes the linear and nonlinear stability analysis models and the results obtained in detail.

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