Helical coil thermal hydraulic model

A model has been developed in Matlab environment for the thermal hydraulic analysis of helical coil and shell steam generators. The model considers the internal flow inside one helix and its associated control volume of water on the external side, both characterized by their inlet thermodynamic conditions and the characteristic geometry data. The model evaluates the behaviour of the thermal-hydraulic parameters of the two fluids, such as temperature, pressure, heat transfer coefficients, flow quality, void fraction and heat flux. The evaluation of the heat transfer coefficients as well as the pressure drops has been performed by means of the most validated literature correlations. The model has been applied to one of the steam generators of the IRIS modular reactor and a comparison has been performed with the RELAP5/Mod.3.3 code applied to an inclined straight pipe that has the same length and the same elevation change between inlet and outlet of the real helix. The predictions of the developed model and RELAP5/Mod.3.3 code are in fairly good agreement before the dryout region, while the dryout front inside the helical pipes is predicted at a lower distance from inlet by the model

Thermal hydraulic comparison of helical coil and bayonet tube steam generators for Small Modular Reactors

In the present paper a comparative analysis of the thermalhydraulic performance of helical coil and bayonet tube steam generators (SG) is presented. The tool chosen for the analysis is RELAP5-3D/4.0.3. The reference conditions are the ones of the primary and secondary fluids of the SMART Small Modular Reactor. The analysis has been carried out by considering different operating conditions. First, the performance of the SGs in nominal conditions has been compared; subsequently, assuming a power load control at constant average primary temperature, the thermal hydraulic response of the components at different operating conditions has been studied and the helical coil SG results to be the most compact configuration. It’s behavior is characterized by higher frictional pressure losses and lower inner heat transfer coefficient if compared with the bayonet tube SG. To analyze the performance of the components out of the nominal condition a region of the map of operation is studied by varying the inlet temperatures of the fluids. A common behavior is found in the considered region. Differences of approximately 12% for the outlet temperatures and 6% for the power have been found