Numerical Simulation of Turbulent Cross Flow Over Helical Tube Bundles With Supporting Structures

Abstract Helical tube bundles are usually used for the steam generator of high temperature gas-cooled reactor pebble-bed module (HTR-PM). The helical tube bundle is composed of several layers of helically coiled tubes, which are fixed by the supporting structures for preventing flow induced vibration. In the helical tube bundle, there are ideal flow paths separated by different layers of helical tubes. The blocking area ratio (the ratio of tube area to total area) of each flow path is different due to the helical diameter of each layer tubes, which may result in non-uniform flow. The presence of supporting structures will also affect the blocking area ratio, which may further increase the flow non-uniformity. The cross flow over helical tube bundles is complicated and difficult to predict. In the current investigation, RANS with SST k-ω model is used to simulate cross flow over a helical tube bundle with supporting structures. The influence of the supporting structure on the flow uniformity is investigated. The computational domain consists of 5 layers and 5 rows of helically coiled tubes. The influence of the helix angle is neglected. Due to the symmetry of the structure, only 1/3 part in the circumferential direction of the helical tube bundle is simulated. The velocity at the gap region between different layers of tubes is 19.74 m/s, corresponding to a Reynolds number of 28, 745. The simulation results are averaged over a long time and full length in the circumferential direction. Time-averaged distributions of velocity and pressure coefficient at different positions are obtained and compared. Multiple symmetrical secondary flows form in the z-normal plane and the secondary flows near the supporting structures are small. The averaged streamwise velocities in different flow paths are non-uniform. The flow oblique direction is investigated at different positions. In the region near the supporting structures, the flow direction is almost along the streamwise direction.