Effect of various structures on the shell-side flow over coil tube bundles

Abstract

In response to the increasing number of applications and safety considerations for coil tube bundles, an investigation on the influence of structural parameters (the pitch diameter ratio between adjacent tube layers, a, the pitch diameter ratio in the same layer, b, and the helix angle, α) on the flow in the shell side over simplified three-layer bundles was carried out using detached-eddy simulation (DES), which was verified by previous studies. In this study, the local flow structures were discussed by observing a zoomed-in view of the gaps, which revealed that irregularly distributed vortices appeared. The spiral wound structure made the flow structures asymmetric and increased the lateral velocity between tubes of the same layer. By applying power spectral density (PSD) and continuous wavelet transform (CWT) functions, the time–frequency data of velocity fluctuations were analyzed to obtain the flow and evolution of coherent structures over time, revealing vortex shedding frequency bands and Strouhal numbers (St). In addition, multimodal Gaussian distribution approximations (MGDA) were employed to indicate that the shell-side flow was composed of multiple flow modes.