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  • 1.
    Adamsson, Carl
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorteknologi.
    Dryout and Power Distribution Effects in Boiling Water Reactors2009Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Film flow measurements at several axial positions in round pipes with variousaxial power distributions are presented for conditions corresponding to normaloperation of a BWR. It is confirmed that the film flow rate approaches zero atthe onset of dryout. Selected phenomenological models of annular two-phaseflow are shown to reasonably reproduce the measurements. It is concluded thatmodels are in better agreement with measurements if terms corresponding topossible boiling induced entrainment are excluded.

    A method to perform film flow analysis in subchannels as a post-processto a standard two-field subchannel code is suggested. It is shown that thisapproach may yield accurate prediction of dryout power in rod bundles to alow computational cost and that the influence of the power distribution is wellpredicted by the model.

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    FULLTEXT01
  • 2.
    Adamsson, Carl
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorteknologi.
    Measurements of Film Flow Rate in Heated Tubes with Various Axial Power Distributions2006Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Measurements of film mass flow rate for annular, diabatic steam-water flow in tubes are presented. The measurements were carried out with four axial power distributions and at several axial positions at conditions typical for boiling water reactors, i.e. 7 MPa pressure and total mass flux in a range from 750 to 1750 kg/m2s. The results show that the influence of the axial power distribution on the dryout power corresponds to a consistent tendency in the film flow rate and that the film tends to zero when dryout is approached. Furthermore it is demonstrated that two selected phenomenological models of annular flow well predict the present data. A model for additional entrainment due to boiling is shown to degrade the predictions.

    Ladda ner fulltext (pdf)
    FULLTEXT01
  • 3.
    Adamsson, Carl
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorteknologi.
    Anglart, Henryk
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorteknologi.
    A reinterpretation of measurements in developing annular two-phase flow2011Ingår i: Nuclear Engineering and Design, ISSN 0029-5493, E-ISSN 1872-759X, Vol. 241, nr 11, s. 4562-4567Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Measurements of developing films in adiabatic high pressure steam-water flow in annular geometry have been reanalyzed and compared to a linearized film-flow model. The development rate of the outer film could be determined with good accuracy in four cases. In one case it was also possible to conclude that the inner film develops faster than the outer one. When compared to the linearized model, these observations show that the deposition rate has to be almost independent of the drop concentration at the investigated conditions. Furthermore, any significant deposition by direct impaction of drops can be excluded as it would couple the development of the two films. These conclusions are quite general and do not depend on the use of any particular correlation for the deposition or entrainment rates. Finally, a rough estimate of the deposition rate was possible, confirming that deposition rates are considerably lower at high pressure steam-water flows than in air-water flows.

  • 4.
    Adamsson, Carl
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorteknologi.
    Anglart, Henryk
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorteknologi.
    An investigation of cross-section geometry effects on the deposition rate in annular two-phase flows with a Lagrangian model2007Ingår i: Proceedings - 12th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH-12, 2007Konferensbidrag (Refereegranskat)
    Abstract [en]

    The motion of liquid drops in annular two-phase flow in pipes, annuli and subchannels has been investigated with a model based on Lagrangian particle tracking. The results confirm that large drops may deposit by direct impaction. It is also demonstrated that the deposition rate does not differ significantly between pipes and subchannels except for very large drops, which deposit slower in subchannels. Furthermore the Saffman lift force is shown to have a large impact on the results but it is questionable of the standard formulation is applicable to the drops considered here. Finally it is concluded that accurate modeling of high pressure steam-water flows requires a model for drop-drop collisions.

  • 5.
    Adamsson, Carl
    et al.
    KTH, Tidigare Institutioner, Fysik.
    Anglart, Henryk
    KTH, Tidigare Institutioner, Fysik.
    Dryout predictions in bwr fuel assemblies with spacers2004Ingår i: Proceedings of the Sixth International Conference on Nuclear Thermal-Hydraulics, Operation and Safety, 2004Konferensbidrag (Refereegranskat)
    Abstract [en]

    A new spacer model has been implemented into the subchannel code Mona-3 and validated against dryout experiments in various rod bundles with different number of spacers and different spacer designs. The spacer-induced deposition enhancement is captured by proper modeling of the turbulence intensity downstream of a spacer.

    The Mona-3 code with the new spacer model captures spacer effects in a correct manner. Both the effect of the number of spacers and the effect of the spacer design are predicted correctly. In particular, the critical power difference between 24-rod bundles with 6 and with 7 spacers is measured to be larger than the difference between 25-rod bundles with 6 and with 7 spacers. This experimental finding is well captured with the Mona-3 code with the present spacer model.

  • 6.
    Adamsson, Carl
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorteknologi.
    Anglart, Henryk
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorteknologi.
    Eperimental Investigation of the Liquid Film for Annular Flow in a Tube with Various Axial Power Distributions2005Ingår i: NURETH 11, Avignon, France, October 2–6, 2005, 2005Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper was published when the measurements with non-uniform powerdistribution were still ongoing. Therefore only the measurements with uniformand top-peaked power profiles were included. The paper compares the measured data with deposition and entrainmentmodels by Hewitt & Govan (1990) and Okawa et al. (2003). These models are also discussed in Sections 4.2.1 and 4.2.2. The issue of a correct boundarycondition at the onset of annular flow was avoided by starting the integrationof the film flow model from the most upstream measurement point. In this way the net mass exchange rate (deposition less entrainment) could be studied without any initial bias from the boundary condition.The entrainment correlation proposed by Okawa et al. (2003) included a heat flux dependent term to account for boiling entrainment (Section 4.2.2). Paper 2 concludes that the model agrees better with measurements if this term is omitted. The result suggests that boiling entrainment may not be an important effect at the investigated conditions.

  • 7.
    Adamsson, Carl
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorteknologi.
    Anglart, Henryk
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorteknologi.
    Film flow measurements for high-pressure diabatic annular flow in tubes with various axial power distributions2006Ingår i: Nuclear Engineering and Design, ISSN 0029-5493, E-ISSN 1872-759X, Vol. 236, nr 23, s. 2485-2493Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Measurements of film flow rates in diabatic annular flow in tubes with various axial power distributions were carried out in the high-pressure two-phase flow loop at the Royal Institute of Technology (KTH), Sweden. The measurements were performed at conditions typical for boiling water reactors, i.e. 7 MPa pressure and total mass flux in a range from 750 to 1750 kg/m(2)s. Four different axial power distributions were used and the film mass flow was measured at 7 axial locations for each set of boundary conditions. The results show that the outlet peaked distribution gives less film than the inlet peaked one. This result is consistent with well known trends from measurements of dryout power. The measurements also show that the film flow at the onset of dryout is very small at investigated conditions in agreement with earlier studies. Finally it is shown that the present data is well predicted by two selected phenomenological models of annular flow.

  • 8.
    Adamsson, Carl
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorteknologi.
    Anglart, Henryk
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorteknologi.
    Influence of Axial Power Distribution on Dryout: Film-Flow Models and Experiments2010Ingår i: Nuclear Engineering and Design, ISSN 0029-5493, E-ISSN 1872-759X, Vol. 240, nr 6, s. 1495-1505Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of axial power distributions on dryout occurrence in nuclear fuel assemblies has been studied extensively for several decades. Even though it is well known that axial power shapes which may significantly vary in nuclear reactors during their operation significantly change the dryout power level, this particular influence is rather difficult to capture with current correlations. In this paper it is shown that this influence can be captured using a phenomenological liquid film model coupled to a standard sub-channel code. The model has been applied to various geometries, including a round pipe, as well as 5 x 5 and 8 x 8 fuel rod assemblies, and highly accurate predictions have been obtained.

  • 9.
    Adamsson, Carl
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorteknologi.
    Henryk, Anglart
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorteknologi.
    Measurements of the Liquid Film Flow Rate in High Pressure Annular Flow with Various Axial Power Distributions2005Ingår i: HEAT 2005, Gdansk, Poland, June 26–30, 2005, 2005Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents film flow measurement technique and the results with uniform power distribution. Based on these measurements it is possible to estimate the critical film thickness. The measured film thickness was plotted versus steam quality and slightlyextrapolated up to the measured critical steam quality. The conclusions werein line with Hewitt et al. (1965), i.e. that the critical film thickness is insignificantly small. This does not contradict e.g. Ueda & Isayama (1981) since the conditions were not the same, but for the flow conditions and heat fluxes that are typical for BWR operation it was concluded that the critical film thickness is, for practical purposes, zero.

  • 10.
    Adamsson, Carl
    et al.
    Westinghouse Electric Sweden.
    Le Corre, J. M.
    Westinghouse Electric Sweden.
    Modeling and Validation of a Mechanistic Tool (MEFISTO) for the Prediction of Critical Power in BWR Fuel Assemblies2011Ingår i: Nuclear Engineering and Design, ISSN 0029-5493, E-ISSN 1872-759X, Vol. 241, nr 8, s. 2843-2858Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Westinghouse is currently developing the MEFISTO code with the main goal to achieve fast, robust, practical and reliable prediction of steady-state dryout Critical Power in Boiling Water Reactor (BWR) fuel bundle based on a mechanistic approach. A computationally efficient simulation scheme was used to achieve this goal, where the code resolves all relevant field (drop, steam and multi-film) mass balance equations, within the annular flow region, at the sub-channel level while relying on a fast and robust two-phase (liquid/steam) sub-channel solution to provide the cross-flow information. The MEFISTO code can hence provide highly detailed solution of the multi-film flow in BWR fuel bundle while enhancing flexibility and reducing the computer time by an order of magnitude as compared to a standard three-field sub-channel analysis approach. Models for the numerical computation of the one-dimensional field flowrate distributions in an open channel (e.g. a sub-channel), including the numerical treatment of field cross-flows, part-length rods, spacers grids and post-dryout conditions are presented in this paper. The MEFISTO code is then applied to dryout prediction in BWR fuel bundle using VIPRE-W as a fast and robust two-phase sub-channel driver code. The dryout power is numerically predicted by iterating on the bundle power so that the minimum film flowrate in the bundle reaches the dryout criteria. Predicted dryout powers (including trends with flow, pressure, inlet subcooling and power distribution) and predicted dryout locations (both axial and radial) are compared to experimental results, using the entire Westinghouse SVEA-96 Optima3 dryout database, and are shown to yield excellent results.

  • 11.
    Caraghiaur, Diana
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorteknologi.
    Adamsson, Carl
    Lab of Reactor Physics and System Behaviour (LRS), 5232 Villigen, Paul Scherrer Institute, Switzerland .
    Anglart, Henryk
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorteknologi.
    Deposition of Inertial Drops in Eulerian Formulation2013Ingår i: Proceedings of NURETH-15, 2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    The drop deposition increase due to flow obstacles is presently quantified by empirical coefficients. To avoid the empiricism, a new deposition model is proposed with the capability to predict the obstacle effect. By the proposed method the deposition is calculated from the local concentration of drops and the normal-to-wall fluctuating velocity. The model shows promising results in predicting the obstacle effect.

  • 12.
    Krejci, Marko
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorteknologi.
    Adamsson, Carl
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorteknologi.
    Anglart, Henryk
    KTH, Skolan för teknikvetenskap (SCI), Fysik, Reaktorteknologi.
    Development of a model for prediction of annular flow and dryout in BWR fuel assemblies with spacers2005Ingår i: Proceedings of the Eleventh International Topical Meeting on Nuclear Reactor Thermal-Hydraulics, 2005Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper deals with development of a phenomenological annular flow and dryout model for BWR fuel assemblies. The model is based on a solution of conservation equations for mass, momentum and energy for each subchannel in the bundle. Proper closure relations are included to model the inter-subchannel mass, momentum and energy transfer. A fullNewtoniteration scheme is used to solve the algebraic set of finite difference equations. The convergence of the scheme is very robust and it typically takes 5 iterations to find the solution. After finding the flow and enthalpy distribution between all subchannels in a bundle, a newly developed algorithm is applied to calculate the liquid film distribution on channel walls. The algorithm predicts the liquid film flow rate taking into account the local values of the entrainment, deposition and evaporation rates. The spacer influence is taken into account through proper model of intensified deposition rate downstream of spacer locations. The model has been applied for prediction of flow and phase distributions in various fuel assemblies and the results of calculations have been compared to measurements. Good agreement between predictions and measurements has been obtained. The model is also applicable to prediction of dryout occurrence in fuel assemblies, where proper predictions of various effects, e.g. influence of axial power distribution on dryout power, have been obtained.

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