Experimental investigation of the isothermal flow field across slant 5-tube bundles in helically coiled steam generator geometry using PIV

Next generation nuclear power plant designs have been considering Helically Coiled Steam Generators (HCSGs) because of its compactness and capability to absorb thermal expansion. During the design phase, Computational Fluid Dynamics (CFD) has been becoming a powerful tool and being applied to HCSG to predict important engineering parameters including pressure drop and flow induced vibrations. However, the complex geometry of the HCSG requires experimental data to validate the simulation results generated by the highly turbulent flow. In this study, an experimental test facility was constructed with five-rod bundles that coils against adjacent rod to produce high-resolution flow field data in space and time. A Particle Image Velocimetry (PIV) visualized the flow field between adjacent rods in three regions at approximately Re 3600 with up to 5000 frames per second (5 kHz). The flow interaction between the rods and the vortical structure were observed from side view of the flow channel. The slant rod bundle created different flow bifurcation patterns. In a small flow channel between adjacent rods at top and bottom, there exist two opposite directional horizontal flows changing magnitude in time. However, once the pattern was formed, it did not change the pattern but only the magnitude during the current test. The current study more focused on the local flow measurement for a short time period. In further works, relatively large areas within the test section need to be monitored for a longer period to investigate whether the bifurcation pattern changes or not.