Abstract: The heat exchanger with large-and-small-hole segmental baffles can reduce the flow dead zone and the pressure drop，which behind the baffle，but the heat transfer enhancement effect on the shell side is not obvious. The longitudinal vortex generator can make the fluid produce strong disturbance，which can enhance the heat transfer and reduce the flow loss. Given this situation，the heat exchanger structure of large-and-small-hole segmental baffles coupled with longitudinal vortex generators is proposed， and the longitudinal vortex generators are called small fins. The model of the heat exchanger with small fins and large-and-small-hole segmental baffles was built and the structure was numerically simulated by ANSYS-Fluent software. The thermal-hydraulic performance of three kinds of small fins with different structures was compared and analyzed. The results show that when the small fins are arranged in alignment with the rectangular wing array，the thermal performance of the heat exchanger is the highest，compared with the segmental baffle heat exchanger with large-and-small-hole. The comprehensive performance of the large-and-small-hole segmental baffle heat exchanger without small fins is the highest.

Key words: large-and-small-hole segmental baffle, small fin, heat transfer enhancement