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Research Papers: Nuclear Power

Linear and Nonlinear Stability Analysis of a Supercritical Natural Circulation Loop

[+] Author and Article Information
Manish Sharma

Reactor Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, Indiamanishs@barc.gov.in

P. K. Vijayan

Reactor Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, Indiavijayanp@barc.gov.in

D. S. Pilkhwal

Reactor Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, Indiapilkhwal@barc.gov.in

D. Saha

Reactor Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, Indiadsaha@barc.gov.in

R. K. Sinha

Reactor Design and Development Group, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, Indiarksinha@barc.gov.in

J. Eng. Gas Turbines Power 132(10), 102904 (Jun 30, 2010) (9 pages) doi:10.1115/1.4000342 History: Received July 21, 2009; Revised September 02, 2009; Published June 30, 2010; Online June 30, 2010

Supercritical water (SCW) 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 cooled 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 (SCWNCL). The conservation equations of mass, momentum, and energy have been linearized 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 SCWNCL. A separate computer code, NOLSTA, has been developed, which investigates stability characteristics of supercritical natural circulation loop using nonlinear 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 nonlinear 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.

Copyright © 2010 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Simplified Loop geometry considered for analysis

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Figure 2

(ac) Comparison of supercritical water properties as predicted by IAPS formulations with NIST database

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Figure 3

Polynomial for specific volume of supercritical water at 25 MPa

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Figure 4

(a) Loop geometry considered in Chatoorgoon (1) and (b) steady-state natural circulation flow rate for Chatoorgoon’s loop at 25 MPa and 350°C heater inlet temp

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Figure 5

Nyquist plots for the Chatoorgoon’s loop at 25 MPa and heater inlet temperature of 350°C

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Figure 6

Steady-state characteristics for different diameter loops at 25 MPa and heater inlet temperature of 370°C

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Figure 7

Effect of loop pressure on steady-state mass flow rate at heater inlet temperature of 370°C

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Figure 8

Effect of heater inlet temperature on steady-state mass flow rate at 25 MPa

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Figure 9

Variation in volumetric expansion coefficient with temperature for water

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Figure 10

(a) and (b) Effect of loop diameter on stability behavior of SCWNCL

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Figure 11

(a) and (b) Effect of loop pressure on stability behavior of SCWNCL

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Figure 12

Steady-state results comparison for 14 mm 1D loop by SUCLIN and NOLSTA

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Figure 13

Typical stable, unstable, and neutrally stable operating conditions for 14 mm 1D loop

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Figure 14

(a) and (b) Effect of no of control volumes on stable and unstable operating condition

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Figure 15

(a) and (b) Stability maps comparison for SUCLIN and NOLSTA for 14 mm 1D loop

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Figure 16

(a) and (b) Stability maps comparison for SUCLIN and NOLSTA for 28 mm 1D loop

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Figure 17

(a) and (b) Lower threshold of stability predicted by SUCLIN and NOLSTA for 14 mm and 28 mm 1D loop shown in detail

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