Vibration-Enhanced Heat Transfer of Helical Tube with Different Number of Tubes

Abstract

Based on a two-way fluid/solid coupling model, the heat transfer enhancement mechanism of a helical elastic coiled tube (HECT) by fluid-induced vibration (FIV) was numerically studied. The field synergy principle was used to compare and analyze the shell-side convective heat transfer of the HECT. The field synergy angle, Nusselt number, and comprehensive enhanced heat transfer performance were quantitatively studied from the overall and local perspectives. The influences of the Reynolds number and the number of tubes on heat transfer performance and vibration-enhanced heat transfer performance were analyzed. Numerical results show that the field synergy level and the oscillation relative velocity near the tube are two important factors for fluid-induced tube vibration to enhance heat transfer. The average Nusselt number of coiled tubes decreases when the number of tubes increases and increases when the Reynolds number increases. The comprehensive heat transfer enhancement capability of the heat exchanger with different numbers of tubes of 2, 4, and 8 gradually decreases as the number of tubes increases, and the average performance evaluation criteria of the heat exchanger are 1.043, 1.023, and 1.004, respectively, for the three typical cases. The tubes on the upper and lower sides have a better heat transfer enhancement effect by the FIV.