A status review on DNB prediction using CASL baseline boiling model and possible suggestions regarding wall boiling closures

Technical Report · Tue Aug 28 04:00:00 EDT 2018

DOI:https://doi.org/10.2172/1467376· OSTI ID:1467376

Kim, Seung Jun ^[1]

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1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

The main goal of FY18 THM’s focus task is to evaluate where the current CASL boiling model stands for DNB predictive performance, to identify which components should be improved or calibrated to enhance DNB performance. Over the past three year’s validation tests, Gen1A boiling model has presented an under-predictive behavior for DNB at the high pressure of interest for PWR application. With this in mind, this year’s task is to focus on 1) best practice guidelines on DNB detection criteria, 2) interfacial momentum transfer closure tests, and 3) wall boiling closure sensitivity on DNB. Best practice guidelines on DNB detection criteria are demonstrated by the following three monitoring variables: 1) max wall temperature, 2) K-value and 3) energy balance. Interfacial momentum transfer closure govern the bubble distribution, especially in lateral direction, as well as bubble mean diameter. A clear correlation between interfacial momentum closure and DNB prediction is not observed in the current tests. However, void distributions are changed with different interfacial momentum closure tests which requires further validation with corresponding experimental measurement. From a variety of wall boiling closure tests, bubble departure diameter seems the most sensitive for DNB performance while fulfilling numerical robustness in DNB simulation. Tolubinski’s bubble departure diameter model was calibrated to see if any improvement is observed in DNB performance. Notable DNB improvement was observed as the bubble departure diameter is reduced. However, reduced bubble departure diameter by calibrated Tolubinski’s model seemed to lead to relatively high wall superheat temperature prediction which requires further validation with associated experimental measurement It should be noted that lack of experimental measurement close to DNB condition hampers this boiling closure sensitivity study significantly. This situation directly reflects some of limitations of the CASL boiling model development. With this in mind, the implementation of improved boiling closure on 5x5 NMVG and MVG tests will be pursued in FY19, the associated DNB best practice guidelines and possible limitations will be addressed for industry DNB application.

• Research Organization: Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE Office of Nuclear Energy (NE)
• DOE Contract Number: AC52-06NA25396
• OSTI ID: 1467376
• Report Number(s): LA-UR--18-28198
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
Multiphase CFD
Boiling Crisis
DNB
CASL