A full size section from a helical coil steam generator with five concentric coils with a helix-to-rod diameter ratio of 127 was constructed to study shell side fluid flow. The geometry has a constant transverse pitch ratio (a = 2.96), but changing lateral pitch ratio (b = 0.6-0.9) across the image planes of interest. Particle Image Velocimetry (PIV) with an index of refractive matching fluid technique was used to capture images of the flow behavior at these planes of interest. Experiments focused on visualizing cross-flow at the entrance and center regions of the test section at each plane of interest at Re = 8500. Analysis was conducted to study average vertical and transverse velocity components, vorticity and streamline fields for the shell side flow. Averaged results showed characteristic flow structures common of staggered cross-flow behavior within tube and shell heat exchangers. Select linear heights based on rod geometry show a consistent average velocity pattern across all three planes of interest regardless of lateral pitch ratio. Average velocity components do not suggest a correlation with lateral pitch ratio as previous studies with constant lateral pitch ratio designs have shown. The constantly changing geometry of this particular helical coil steam generator design affects the development and dependence of vortex formation and motion. Published by Elsevier Ltd.