Analysis of Velocity Distributions Across a Model Helical Coil Steam Generator

A model helical coil steam generator test section was designed and constructed to visualize the flow between two adjacent tube bundles—inner and outer bundle—that coil in opposite directions to one another. This study focuses on visualizing and characterizing fluid properties on the shell side of the unique tube-and-shell heat exchanger design. Flow within the shell side is characterized by recirculation regions below the tubes, or wake regions, and streamlined flow between tube bundles. The matched refractive index particle image velocimetry (PIV) experimental technique was used to experimentally capture the flow between the adjacent tube bundles. Images for PIV analysis were taken at three cross-sectional planes of the test section at 10 000 frames per second of an area approximately 24.54  23.20 mm. Average vertical and transverse velocity components were analyzed at a distance of r/r_r = 1.1 about the tube centers at a specific rod height to observe flow separation and flow characteristics between the tube bundles. Measurements showed the magnitude of the normalized vertical velocity increased through the planes as the flow followed the helical pitch of the tube bundles. The flow was also observed to experience significant flow separation from recirculating eddies and vortex shedding across the rods.