Interfacial Area Transport Equation for Vertical and Horizontal Bubbly Flows and its Application to the TRACE Code
Open Access
- Author:
- Talley, Justin D
- Graduate Program:
- Nuclear Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- March 21, 2012
- Committee Members:
- Seungjin Kim, Dissertation Advisor/Co-Advisor
Fan Bill B Cheung, Committee Member
John Harlan Mahaffy, Committee Member
Seong H Kim, Committee Member
John R Buchanan Jr, Special Member - Keywords:
- horizontal two-phase flow
interfacial area transport equation
four-sensor conductivity probe
TRACE - Abstract:
- Conventional thermal-hydraulic nuclear reactor system analysis codes utilize a two-field, two-fluid formulation to model two-phase flows. To close this model, static flow regime transition criteria and algebraic relations are utilized to estimate the interfacial area concentration (ai). However, to better reflect the continuous evolution of two-phase flow, an interfacial area transport equation (IATE) can provide a dynamic estimation of ai through mechanistic models for bubble coalescence and disintegration. While a significant amount of work has been performed in this area for vertical flows, less has been performed in horizontal flows. Therefore, the current work seeks to establish a one-dimensional, one-group, adiabatic IATE for horizontal bubbly flows. An experimental database is acquired in a 3.81 cm pipe air-water facility with a total development length of 250 diameters. A four-sensor conductivity probe is employed to measure time-averaged two-phase flow parameters at a maximum of 17 radial positions along 8 lines for L/D = 44, 116, and 244. To develop the IATE for horizontal flow, the mechanistic models for vertical flow are revised by considering the separation distance between bubbles necessary for turbulence based interactions. Furthermore, parameters to account for the effect of the asymmetric phase distribution on bubble interactions are developed through a construction of the local profiles using area-averaged information. Based on these revisions, the IATE for horizontal bubbly flow is established and predicts the current data within ±5.5%. A study is also performed to implement and assess the IATE for vertical bubbly flows in the nuclear system analysis code TRACE. In total, 50 conditions with ID pipe sizes ranging from 2.54 to 20.32 cm in co-current upward and downward flows are employed. It is found that TRACE with the IATE capability (or TRACE-T1) predicts the ai data within ±13.0%, while the conventional TRACE underestimates the data on average by 43.6%. Therefore, TRACE-T1 demonstrates a significant improvement in predicting ai by accounting for bubble interactions.