Thermal-Hydraulic Characteristics of Twisted Elliptical Tube Bundle in Staggered Arrangement

Based on experimental data, numerical simulations by turbulent air flowing across staggered tube bundle composed of twisted elliptical tube (TET) with constant tube wall temperature are conducted in present study. Parametric study on the thermal-hydraulic characteristics of air crossflow in TET bundles is investigated with physical parameters and Reynolds number (Re). The results show that spiral channels created by spiral deformation of TETs have a diversion effect on the air flow, which changes the flow direction of the air near the tube wall. The air in the near wall region is a three-dimensional flow, consisting of a flow perpendicular to the normal direction of the elliptical cross section and a spiral flow along the helicoid on the downstream side and the upstream side. And the interaction of the spiral channels makes the two flows and their mixing more complicated. The excellent heat transfer performance of staggered TET bundles is confirmed by the comparison of the comprehensive heat transfer performance with that of circular tube bundles. The average Nusselt number (Nu) increases with the increase of the aspect ratio (A/B) and with the increase of Re while decreases as the twist pitch (S) increases. The average Euler number (Eu) increases as A/B increases, while it decreases as Re increases and as S increases. Due to the fact that the suitable correlations for staggered TET bundles are not reported, correlations for Nu and Eu obtained from experimental data and numerical results are presented in the multiple forms.

Automated summary

The study investigates the impact of spiral channels created by twisted elliptical tubes (TET) on air flow, showing that the spiral channels change the flow direction of air near the tube wall, resulting in a more complex airflow field. Staggered TET bundles exhibit excellent heat transfer performance, with the average Nusselt number increasing with the aspect ratio and Reynolds number.