Implementation and Assessment of the Interfacial Area Transport Equation in the System Analysis Code TRACE
Open Access
- Author:
- Worosz, Theodore Stanley
- Graduate Program:
- Nuclear Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- None
- Committee Members:
- Seungjin Kim, Thesis Advisor/Co-Advisor
- Keywords:
- two-phase flow
interfacial area concentration
interfacial area transport equation
system analysis code - Abstract:
- The interfacial area concentration, a_i, is an important geometric parameter in two-phase flow, as it describes the amount of surface area between the two phases per unit mixture volume. Conventionally, a_i has been specified through algebraic flow regime-based correlations. However, this approach cannot capture the dynamic evolution of the interfacial structure. Alternatively, a_i, can be specified through a transport equation that provides a dynamic prediction of the interfacial area concentration through mechanistic models for bubble coalescence and breakup. Therefore, the focus of the present study is on the implementation and assessment of the interfacial area transport equation (IATE) into the nuclear reactor system analysis code TRACE. Available TRACE frameworks are reviewed focusing on the constitutive relations for the interfacial area concentration. The pilot code TRACE-T1, which employs the one-group IATE applicable to dispersed bubbly flow, is assessed against experimental databases for vertical co-current upward and downward air-water two-phase flows obtained in round pipes ranging in diameters from 2.54 cm to 20.32 cm. Predictions of experimental pressure, void fraction, bubble velocity, and interfacial area concentration are generated with TRACE-T1 and TRACE-NT (a non-transport version of the code) for comparison. TRACE-T1 allows for non-linear development of a_i and demonstrates significant improvement over the non-transport approach. The TRACE-T1 code is extended to include a two-group IATE model, applicable to bubbly, slug, and churn-turbulent flows in moderate diameter pipes, to establish the pilot code TRACE-T2. An overview of the selected IATE model and the details of its implementation are provided. Furthermore, the feasibility of two-group interfacial area transport in TRACE-T2 is demonstrated through predictions of two-group experimental data. Lastly, recommendations for future code development and improvements to the interfacial area transport approach are made.