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A moving boundary analysis for start-up performance of a nuclear steam generator / S. Paruya in Transactions of the ASME . Journal of fluids engineering, Vol. 130 N° 5 (Mai 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 5 (Mai 2008) . - 11 p. Titre : A moving boundary analysis for start-up performance of a nuclear steam generator Type de document : texte imprimé Auteurs : S. Paruya, Auteur ; P. Bhattacharya, Auteur Année de publication : 2009 Article en page(s) : 11 p. Note générale : Fluids engineering Langues : Anglais (eng) Mots-clés : Pressure;  flow  (dynamics);  channels  (hydraulic  engineering);  boiling;  equations;  steam;  water;  nuclear  reactor  steam  generators;  temperature;  computation;  density;  porosity Résumé : 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. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...] [article] A moving boundary analysis for start-up performance of a nuclear steam generator [texte imprimé] / S. Paruya, Auteur ; P. Bhattacharya, Auteur . - 2009 . - 11 p. Fluids engineering Langues : Anglais (eng) in Transactions of the ASME . Journal of fluids engineering > Vol. 130 N° 5 (Mai 2008) . - 11 p. Mots-clés : Pressure;  flow  (dynamics);  channels  (hydraulic  engineering);  boiling;  equations;  steam;  water;  nuclear  reactor  steam  generators;  temperature;  computation;  density;  porosity Résumé : 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. En ligne : http://fluidsengineering.asmedigitalcollection.asme.org/issue.aspx?journalid=122 [...]

Validations of thermohydraulic models for geysering in a natural circulation loop using an impedance needle probe / S. Paruya in Industrial & engineering chemistry research, Vol. 48 N°4 (Février 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N°4 (Février 2009) . - p. 2020–2033 Titre : Validations of thermohydraulic models for geysering in a natural circulation loop using an impedance needle probe Type de document : texte imprimé Auteurs : S. Paruya, Auteur ; Saha, A. K., Auteur ; P. Bhattacharya, Auteur Année de publication : 2009 Article en page(s) : p. 2020–2033 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Thermohydraulic  models  Geysering  instability  Short-tube  natural  circulation  evaporator  Impedance  void-needle  probe Résumé : This paper describes the validations of thermohydraulic models that predict the geysering instability observed at the riser section of a short-tube natural circulation evaporator (STNCE) at low heat flux and low pressure. The validations have been made by measuring the void fraction in the steam−water system at the riser section of a STNCE with the help of an impedance void-needle probe. The calibration of the probe shows that in the range of low void fractions the probe indicates lower values while in the range of high void fractions it indicates higher values compared to those measured by the manometer. Measured data of void fraction have been analyzed by thermohydraulic models. Both measured data and simulated data of temporal variation of void fractions during geysering have been observed to be periodic pulses of high amplitudes. Effects of riser height and loop resistance on the geysering frequency have been demonstrated in detail. The paper also discusses both the measurement uncertainties and the model uncertainties. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8005462 [article] Validations of thermohydraulic models for geysering in a natural circulation loop using an impedance needle probe [texte imprimé] / S. Paruya, Auteur ; Saha, A. K., Auteur ; P. Bhattacharya, Auteur . - 2009 . - p. 2020–2033. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N°4 (Février 2009) . - p. 2020–2033 Mots-clés : Thermohydraulic  models  Geysering  instability  Short-tube  natural  circulation  evaporator  Impedance  void-needle  probe Résumé : This paper describes the validations of thermohydraulic models that predict the geysering instability observed at the riser section of a short-tube natural circulation evaporator (STNCE) at low heat flux and low pressure. The validations have been made by measuring the void fraction in the steam−water system at the riser section of a STNCE with the help of an impedance void-needle probe. The calibration of the probe shows that in the range of low void fractions the probe indicates lower values while in the range of high void fractions it indicates higher values compared to those measured by the manometer. Measured data of void fraction have been analyzed by thermohydraulic models. Both measured data and simulated data of temporal variation of void fractions during geysering have been observed to be periodic pulses of high amplitudes. Effects of riser height and loop resistance on the geysering frequency have been demonstrated in detail. The paper also discusses both the measurement uncertainties and the model uncertainties. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8005462