Conference Proceedings Paper
A PRELIMINARY THREE DIMENSIONAL CFD MODEL OF THE APR1400 STEAM GENERATOR USING ANSYS
11th International Conference on CANDU® Maintenance and Nuclear Components - 2017 Oct. 01-04
K. Zabrzycki (KEPCO International Nuclear Graduate School)
A. Diab (KEPCO International Nuclear Graduate School)
Understanding complex flow within a nuclear Steam Generator (SG) requires advanced thermal-hydraulic analyses given the localized flow characteristics and associated two-phase flow phenomena. Such phenomena are usually studied using dedicated SG thermal-hydraulic pseudo multi-dimensional tools or by using generic system tools (e.g., lumped one- dimensional codes). However, dedicated codes such as ATHOS3 or CUPID, require significant and complex model preparation primarily due to the complex geometry of the SG internal structures. On the other hand, lumped one-dimensional tools, such as RELAP5®/MELCOR/CATHARE are incapable of capturing the localized 3D flow characteristics associated with SGs. As such, application of Computational Fluid Dynamics (CFD) tools could be used to model the complex three-dimensional flow patterns relevant to SGs with good fidelity. However, modeling of two-phase flow phenomena, particularly those related to phase change (i.e. boiling and condensation), remains a challenge for the available CFD tools. Thus models using these tools need to be complimented via the user defined function capability. This study focuses on the development of a CFD model for APR1400 SG, suitable for modeling steady state conditions. ANSYS Fluent is selected as the computational engine. This research is divided into three main stages of which the first is detailed here. Stage 1 is focused on the primary (tube) side representing the flow field by a porous medium with equivalent pressure drop. The secondary (shell) side is modeled as a heat sink. This is to be followed by Stage 2 modeling of the secondary side. This stage involves preparation of a User Defined File (UDF) that describes in detail the attendant physical models appropriate for the specific system conditions. The Stage 3 model would then integrate the primary and secondary sides into a single model. ANSYS® Fluent results using the Stage 3 model would be benchmarked to available APR1400 steam generator data as reported in the Standard Safety Analysis Report (SSAR). The Stage 3 tool may then be used to analyze complex three-dimensional flow phenomena. For example: Fluid-Structure Interaction (FSI), tube fouling, and system response under (slow) reactor transients or accident conditions would be amenable to analysis using the ANSYS Fluent Stage 3 model as a foundation.
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