Numerical analysis of the flow behavior in a helically coiled once through steam generator

The once-through steam generator (OTSG) is an essential equipment with a key position in the primary side and the secondary side usually used in small modular reactors. It is valuable for designers of the OTSG to investigate the flow behavior in the primary side. A three-dimensional (3D) computational fluid dynamics (CFD) model is conducted in this paper to study the flow behaviors in the primary side of OTSG. The unstructured polyhedral meshes were used in this paper, and ANSYS FLUENT was the solving tool to solve the governing equations by using Realizable k − ɛ turbulence model with enhanced wall treatment. Through a series of cases, the velocity profiles and pressure drop through the primary side of the OTSG were calculated, and the influences of different inlet parameters and different structure designs on the coolant behaviors and flow distributions were studied. Ultimately some suggestions for improvements were proposed to achieve a more rational design with more uniform flow distributions and smaller pressure drops. It was found that the flow distribution in the primary side of an OTSG is a property of its structure, on which inlet conditions have little effect. The position of inlet nozzle has a significant impact on the flow distribution.