Experimental shell-side surface pressure measurements on tubes within a model helical coil heat exchanger

The tube and shell Helical Coil Heat Exchanger (HCHX) geometry, also known in multiple industries as the Coil wound (CWHE), and Spiral-wound heat exchanger (SWHE), has recently been under greater investigation due to the interest in cryogenic, solar, and nuclear industry applications. Helical Coil Steam Generators (HCSGs) have adjacent tube bundles that coil in opposite directions at different helical pitches. While this design is known to increase heat transfer and provide a higher volumetric efficiency, few studies look at the changes the coiling arrangement has on forces acting on the tube. This study investigates the pressure on the surface of the tubes in this complex type of cross-section arrangement as compared to standard tube bundle arrangements. Experiments were conducted at Reynolds Numbers 8500 and 11,700 based on tube diameter and free-stream velocity. Pressure Sensitive Paint (PSP) was used on the shell-side surface of the tubes along with dynamic pressure sensors to visualize tube surface pressure and measure pressure fluctuations. Instantaneous pressure analysis using PSP and dynamic pressure transducers showed agreement with peaks of transient pressure fluctuations at approximately 9.8, 19.7 and 27.5 Hz. Previous studies have grouped tube surface pressure based on geometric parameters such as lateral pitch ratio, while the analysis of the pressure fields from this geometry showed pressure profiles unique to individual planes regardless of equivalent lateral pitch ratio.