Abstract: According to the physical mechanism of the field synergy that controls the turbulent fluid heat transfer in the converging-diverging tube, an enhanced heat transfer structure is proposed here, that is to extend the converging section length as far as possible while retaining the optimal rib height and pitch and the tube diameter obtained by Мигай.A numerical study has been carried out to investigate the heat and flow characteristics of the converging-and-diverging tube with different converging length ratio.The results of numerical study indicate that increasing the converging length ratio can augment the synergy effect of the velocity and heat flux vector fields.Additionally, different types of way how to joint the converging section with diverging one are compared and the jointed convexly way is found to be the best among them.Therefore a developed geometry configuration is presented in the paper.A 4.67%—8.34% increase of Nusselt number is observed and a 7.87%—15.22% increase of friction factor is detected for the developed configuration (Re=1.5×10⁴—5×10⁴).Finally, Webb’s comparison method is adopted to evaluate the combined performance of the developed tube.The performance evaluation factor of the developed tube is η=1.008—1.06 against the Reynolds number in the range of 1.5×10⁴—5×10⁴ as compared with the optimal configuration proposed by Мигай, whose converging length is twice the diverging length.