HEAT TRANSFER ENHANCEMENT FOR CIRCULAR CYLINDERS UNDERGOING FLOW-INDUCED VIBRATIONS: EFFECT OF SPACING RATIO AND STAGGER ANGLE

Effective heat transfer is of utmost importance in the design and operation of industrial components, such as heat exchanger tube bundles, as it directly dictates their efficiency and durability. These components often encounter flow-induced vibrations, which subsequently influence the heat transfer characteristics. This study focuses on investigating heat transfer and flow-induced vibrations in two circular cylinders. The Reynolds number (Re) is set at 100, and the reduced velocity (Ur) is increased from 2 to 14. The cylinders' dimensionless spacing (L/D), arranged in tandem, is changed from 1.5 to 6, and the stagger angle (alpha) between the cylinders is varied from tandem (0 degrees) to staggered ( 45 degrees) and side-by-side arrangement (90 degrees). The lift (C-L) and drag (C-D) coefficients, streamwise and transverse vibrational amplitudes (Ax/D and Ay/D), average Nusselt number (Nu(avg)), Strouhal number (St), vortex shedding patterns, and temperature distribution are analyzed. Results reveal that the lock-in occurs at Ur = 8 for all arrangements. The results demonstrate that the Nu(avg) for the downstream cylinder is consistently lower than the upstream cylinder in the tandem arrangement due to the upstream cylinder providing a shielding effect. Rising L/D to 6 from 1.5 increases the Nu(avg) by 8.6% and 9.8% for downstream and upstream cylinders, respectively. As the L/D increases, the Nu(avg) for both cylinders increases, implying a reduction in the effect of each cylinder on the other. However, in the staggered and side-by-side arrangement, the Nu(avg) for both cylinders are similar, indicating that the cylinders have little to no influence on each other. The highest Nu(avg) is observed at the lock-in condition for all L/D and alpha values. The temperature contours mirror the vorticity contours, suggesting that vortex shedding has a positive effect on heat transfer.