Surface Pressure Measurements in a Model Helical Coil Steam Generator Using Pressure Sensitive Paint

Helical coil steam generators (HCSGs) are tube and shell heat exchangers under investigation due to their future in nuclear power applications. A model of an HCSG with a transverse pitch ratio of 2.98 and changing lateral pitch ratio was created to study the pressure on the surface of the tubes under low Reynolds number flow. Pressure-sensitive paint was applied to rods of an outer bundle of the test section, and instantaneous and average pressure fields were analyzed for Reynolds numbers 4000 and 6000. A comparative study showed that the pressures along the rods had nonlinear behavior. Previous studies suggested a relationship between tube bundle characteristics and the lateral pitch ratio in heat exchanger designs. Since the transverse pitch ratio is constant, the lateral pitch ratio defines the tube bundle cross section as either staggered or inline depending on the cross-section location. Averaged pressure distributions were compared to lateral pitch ratios at respective locations. The pressure distributions along the staggered cross-section portion of the test section were found to exhibit a linear behavior across the heat exchanger body. While this study focuses on average surface pressure measurements, the differences between the same lateral pitch ratio and surface pressure show disagreement with previous studies focused on constant cross-section tube bundles. Flow phenomena within tube bundles, such as vortex shedding, are suspected to be the cause of this discrepancy but a transient analysis is necessary to determine its source.