The effect of swallow-shaped bionic ribs on the thermal-hydraulic performance of heat exchanger tubes

Abstract

This paper combines the bionic structure and multi-vortex longitudinal swirl to enhance the heat transfer in the heat exchanger tube while reducing the increase in flow resistance. The design of the enhanced tube with swallow-shaped bionic ribs is inspired by the aerodynamic profile of the swallow flight process to improve the comprehensive performance. The SST k-ω model is selected for numerical simulation. The study of the effect of TCR (triangular concave rib) bionic rib and TVR (triangular convex rib) bionic rib on the flow field characteristics and thermal–hydraulic performance, and the analysis of the effect of pitch ratio (P*) on the thermal–hydraulic performance of TCR tube. The results show that both types of bionic ribs promote the formation and development of multi-vortex longitudinal swirl and transverse swirl in the tube, strengthening the mixing of hot and cold fluids in the tube, improving the synergy of velocity and temperature fields, and making the temperature distribution in the tube more uniform. When P* = 0.75, Nusselt number of the TCR and TVR enhanced tubes is increased by 52.3 %–65.8 % and 43.3 %–57.9 %, respectively, and friction factor is increased by 92.7 %–202.3 % and 78.7 %–263.9 %, respectively, over the smooth tubes. The effect of P* on the thermal–hydraulic performance of the TCR tube is studied, and the PEC value increases as P* decreases. Compared to smooth tubes, TCR enhanced tubes have improved Nusselt number by 26.4 %–95.6 %, friction factor by 50.4 %-345.8 %, and PEC can reach 1.335 when the pitch ratio P* = 0.5. Consequently, the enhanced tube obtains the good comprehensive performance.