Boiling instabilities in helical coil steam generatorChowdhury, Debasish (Avtor) Vihavainen, Juhani (Mentor) Tiselj, Iztok (Komentor) nuclear engineeringhelical coilsteam generatorsmall modular reactorsinstabilitiesHelically coiled steam generator is an essential part of current generation small modular reactors like NuScale due to its compactness and high heat transfer area. Instabilities due to boiling water inside helically coiled tubes is an important research question due to its im-portance for the steady-state operation of the plant. This study presents an experimental in-vestigation of two-phase boiling instabilities inside helically coiled tubes. Five experiments were carried out with different thermal power, and mass flow rates to understand flow be-haviour under different system conditions. It is found that thermal oscillation inside the tube increases with the power step and tube length while decreasing with the mass flow rate. The thermal oscillation period also increases with a higher power step. A semi-empirical corre-lation based on experimental data is developed. The overall heat transfer coefficient is cal-culated theoretically using the Chen correlation and later compared with the experimental value. Both experimental and theoretical value of the heat transfer coefficient agrees well.[D. Chowdhury]20222023-03-03 12:56:26Magistrsko delo/naloga144625UDK: 621.039.5COBISS_ID: 143949315sl