On spatial approximations for liquid enthalpy and two-phase quality during density-wave oscillations
In the analysis of two-phase flow stability, reasonablyrealistic models that explicitly retain the space and time dependence of the conservation equations, lead to sets of equations that are difficult, if not impossible, to analyze. A one-dimensional problem can be formulated mathematically by integrating the momentum equations along the axial direction in the single- and two-phase regions and imposing appropriate pressure boundary conditions. Although, for the case of homogeneous equilibrium models and drift flux models this formulation can be carried out exactly, the set of partial differential equations (PDEs) is reduced to a set of nonlinear integrodifferential equations. To reduce the set of PDEs to a set of nonlinear ordinary differential equations (ODEs), simplifying assumptions are necessary. Various assumptions have been suggested and used to simplify the set of governing equations. In one simplifying approach, the spatial component in the space- and time-dependent variables is explicitly specified. Clausse and Lahey developed a simple model for the boiling flow problem by assuming a time-dependent but piecewise linear single-phase enthalpy profile in the axial direction and a time-dependent, spatially linear mixture-enthalpy profile in the two-phase region. To assess the extent of error introduced in the stability boundaries by such approximations, we have studied the effects of various approximations in the spatial variation of single-phase enthalpy and two-phase quality. We report the effects of these approximations on stability boundary in an operating parameter plane and compare the results with the exact solution of the mathematical model.
- OSTI ID:
- 89324
- Report Number(s):
- CONF-941102-; ISSN 0003-018X; TRN: 95:004215-0401
- Journal Information:
- Transactions of the American Nuclear Society, Vol. 71; Conference: Winter meeting of the American Nuclear Society (ANS), Washington, DC (United States), 13-18 Nov 1994; Other Information: PBD: 1994
- Country of Publication:
- United States
- Language:
- English
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