Phenomenological extensions to APROS six-equation model. Non-condensable gas, supercritical pressure, improved CCFL and reduced numerical diffusion for scalar transport calculation: Dissertation

This thesis focuses on the development of the two-fluid model of the APROS simulation program. The system of constitutive equations and how equations are related to basic equations have been presented and discussed. The new non-condensable gas model, which was implemented to the two-fluid model, has been described in detail. The extension of the non-condensable gas model to the two-fluid system and the validation of the model have also been presented. The changes made to the six-equation model when the model has been applied to supercritical pressure calculation have been depicted. Finally, the author describes how the whole complicated system is verified and validated. Through the simulations, the applicability of the two-phase model for the analyses of real plant applications is substantiated and verified. In addition to this summary, the thesis consists of four publications. The first paper deals with how the CCFL (Counter Current Flow Limitation) correlations have been implemented to the code and how these correlations have been veri-fied. In the second paper, the non-condensable gas model and its implementation to the two-fluid model have been presented. The third paper describes how the sharp temperature distribution can be maintained in the liquid flow through the aid of simple higher order discretization. In the fourth paper, the modifications carried out to the two-fluid model when applied to the calculation of the super-critical pressure flow are described and discussed.