Computational Analysis of Static Flow Instabilities in Supercritical Natural Circulation Loop

Abstract

The present paper is to study and explore the possibility of static instability, Ledinegg flow excursion, in a rectangular supercritical natural circulation loop (RSCNCL). Due to drastic change of thermo-physical properties of fluid near the pseudo-critical point, various static and dynamic instabilities might occur in the loop. The instability may be either Ledinegg excursion or density wave oscillations (DWOs). Many previous researchers have analyzed dynamic instability, DWO, in SCNCL, whereas the Ledinegg excursive instability is not studied in depth. In the present research work, a mathematical model will be implemented to predict the Ledinegg instability in SCNCL. The numerical investigation is successful to find whether there would be any Ledinegg instability in the case of SCNCL or not. KeywordsLedinegg excursive instability • Supercritical water reactor • Rectangular natural circulation loop Nomenclature A Cross sectional area (m 2 ) D Hydraulic diameter (m) f Friction factor G Mass flux density (kg/m 2 ) H Loop height (m) h Specific enthalpy K Loss coefficient L Length of the section (m)

Mathematical modeling and numerical investigation of density wave instability of supercritical natural circulation loop

“…The eigenvalues of A are found to be real and distinct, and the equation ( 8) identified as a hyperbolic in nature. Further, the equation ( 8) is modified in a characteristic form which is given in equation (9).…”

“…It is produced clean and economical energy compared to the current water reactor. SCWRs will experience drastic change in the density along the core, therefore there is lot of chances to occur instability in the SCWRs, which is similar to the BWRs insatiability namely static, Ledinegg, dynamic, density wave oscillation and pressure wave oscillation instability etc [6][7][8][9][10][11][12]. These instabilities are not desirable in the reactor because failure of control and damage to the wall of the reactor.…”

A Study on the Effect of Geometry and Operating Variables on Density Wave Oscillation in a Supercritical Natural Circulation Loop

“…Due to the unique thermophysical properties of SCW, it is used as a working fluid in a nuclear reactor [7,8]. For example, the thermal efficiency of the SCW used in nuclear power plants (SCWRs) is close to 44-45%, which is higher than the thermal efficiency of 30-32% of the boiling water reactor (BWR) [9][10][11][12][13][14]. In the SCWRs, the size of the turbine is compact due to high steam enthalpy and specific heat capacity, which reduces the capital cost of the load [15].…”