Research Papers: Multiphase Flows

A Moving Boundary Analysis for Start-Up Performance of a Nuclear Steam Generator

[+] Author and Article Information
S. Paruya

Department of Chemical Engineering, Haldia Institute of Technology, Haldia 721 657, Indiaswapanparuya@rediffmail.com

P. Bhattacharya

Department of Chemical Engineering, Jadavpur University, Kolkata 700 032, Indiapinaki̱che@yahoo.com

J. Fluids Eng 130(5), 051303 (May 05, 2008) (11 pages) doi:10.1115/1.2911684 History: Received March 08, 2007; Revised November 30, 2007; Published May 05, 2008

Thermohydraulic phenomena of a steam-water natural-circulation (SWNC) system are very complicated, particularly, during its start-up and shutdown. Its performance strongly depends on the circulation inside it. Accurate quantification of the flow, void fraction, two-phase level, boiling boundary, etc., is difficult at both steady state and transient states like load variation, start-up, and shutdown. Attempts have been made to develop a high-fidelity thermohydraulic model (five-equation scheme) that caters to nonhomogeneous and thermal nonequilibrium flow to derive the dynamic effect of heating rate on the performance of the SWNC loop of steam generator of an Indian nuclear reactor during steaming-up period. The proposed work also attempts to predict boiling height, flow reversal, and density-wave oscillation (DWO). The boiling channel of the SWNC loop is modeled based on the moving boundary analysis using finite volume method. In this moving boundary problem, both control volumes of single-phase zone and two-phase zone change with time. Numerical results have been presented in this paper. The results indicate that both circulation flow variation and two-phase level variation in steam drum have strong dependency on void fraction in the boiling channel. Flow-reversal phenomenon is identified during the initial stage of boiling. Two-phase swelling and collapse that occur during the start-up are predicted. Above a critical heating rate, DWO has been observed. All these phenomena have been explained.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

Schematic of the SWNC loop

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Figure 3

Nodalization of the SWNC loop

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Figure 4

Computational cells in the single-phase zone

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Figure 5

Steam drum (steam-water separator)

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Figure 6

Schematic of steam-water separator

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Figure 7

Schematic diagram of the nuclear steam generator loop

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Figure 8

Variation of the steam drum pressure

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Figure 9

Variation of the steam drum level

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Figure 10

Variation of the net steam generation rate

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Figure 11

Variation of void fraction in riser

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Figure 12

Variation of boiling height

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Figure 13

Variation of circulation flow rate in the SWNC loop

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Figure 14

Channel inlet mass flow rate at 3atm, 6kW, and 60°C inlet subcooling (7)

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Figure 15

Channel inlet mass flow rate at 5atm, 6kW, and 60°C inlet subcooling (7)

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Figure 16

DWO in RI at 50% steady-power level



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