Particle image velocimetrymeasurements between two layers of a model helical coil steam generator

Current and prospective nuclear power plant designs depend on the ability of steam generators to increase their efficiency. Various configurations of tube and shell heat exchangers have been studied to minimize geometry and maximize the heat transfer across the tube bundles. The Helical Coil Steam Generator, HCSG, has been regarded as having increased heat transfer within a smaller design due primarily to its complex configuration. Heat transfer between the multiple layers of coils relies on their location and fluidic properties. A simplified HCSG model was constructed to study the flow on the shell side with half-rod facing bundles that coil against one another, as characteristic of most recent proposed HCSG designs. The closed loop test facility monitored the acrylic test section’s inlet conditions such as temperature, velocity and pressure. To resolve optical distortions, experiments used para-cymene to match the refractive index of the test section. Three equally spaced regions of interest at ¼, ½ and ¾ length of the model each have unique traverse rod pitch ratios. Experiments focused to capture the flow fields at each section between the adjacent coils with particle image velocimetry windows of approx. 23.5 by 22.2 mm at 10,000 fps with a Reynolds number of 9,000. PIV analysis demonstrated average velocity in the stream-wise and traverse directions as well as streamline profiles across the three sections. These regions demonstrate the complex flow structures and interactions between local adjacent rods that the changing geometry of the helical coil steam generator produces throughout its configuration. It is visible that the constant changing traverse pitch affects the flow development on the outside of tube bundles. Future studies will look to quantitatively characterize these differences between in-line, staggered, and constantly changing tube bundles by the stream-wise and traverse pitch ratios.