Rapporto Tecnico sul comportamento di miscele bifase in generatori di vapore a tubi elicoidali con diverse geometrie ed in soluzioni alternative

This document presents the research activities carried out by Politecnico di Milano on the subject of single and two-phase flow behaviour in helical coil tubes for innovative steam generators. The R&D activities refer both to experimental campaigns, carried out at SIET labs, and modelling. In Part 1, single phase and two-phase flow are investigated, for pressure drops measurement and density waves and Ledinegg instabilities. The activity is a follow-up of the previous year investigation, where only few experimental points/operating conditions were analysed. The content of the research has been published as a scientific paper presented at ICAPP international conference. In Part Il, a CFD model is described, developed and validated versus experimental data obtained from the facility at SIET. The model will be used to simulate different geometries and boundary conditions for the helical coil tubes. Even in this case, the work has been published as a scientific paper presented at ICONE20 international conference. Part III is specifically devoted to the description of the superposition of DWO type instability with Ledinegg type instability. This activity was required as a result of the experimental investigation at low pressure, where Ledinegg instability conditions occurred, thus a further investigation has been carried out. In the Appendix, the main data of the experimental campaigns carried out during the year are reported.