Adopting enhanced tube is an effective way to enhance the performance of a shell-and-tube heat exchanger. In this paper, a drop-shaped tube with streamlined cross-section was used to enhance heat transfer of the torsional flow heat exchanger. The characteristics of the fluid flow and heat transfer in torsional flow heat exchanger with drop-shaped tube were studied numerically, considering three kinds of axis ratios (a/b=1.5, 1.8, 2) of the tube. The reliability of numerical results was verified through experimental results. The results indicate that the wake size of the streamlined drop-shaped tube is smaller than that of the conventional smooth tube, and the drop-shaped tube reduces the flow dead zone in torsional flow heat exchanger. As the axis ratio of a/b increases, the shell side Nusselt number and comprehensive performance increase, due to enhancement of the turbulence kinetic energy of the transition section. When the axis ratio is 2, the Nusselt number is increased by 12.44-18.99%, and the comprehensiveness is increased by 13.27-19.2%, compared with the torsional flow heat exchanger with the smooth tube. The quantitative analysis of the velocity indicates that the relative magnitude and proportion of transverse velocity components of fluid are important factors affecting the thermal-hydraulic performance of torsional flow heat exchanger.

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Shell and tube heat exchanger is an important part of industrial heating and cooling system. Because of the harsh operating conditions, and its complex fin and baffle structure with numerous holes, it is a great challenge for engineers to design and evaluate the baffle structure on the premise of ensuring the comprehensive performance. This paper aims to provide a method to optimize the baffle structure of torsional flow heat exchanger by comprehensively considering thermal, hydraulic and mechanical properties. Based on fluid-structure interaction method, response surface methodology was applied to improve the structure configurations of torsional flow heat exchanger. The results show that the effects of various input parameters on objectives are related to each other, and the baffle width and inclination angle have a more obvious impact on heat exchanger. The tradeoff analysis is carried out for the optimization objectives, the candidate points obtained by optimization reveal that the fluid comprehensive performance of the optimal structure is increased by 10.99%, and the maximum equivalent stress is reduced by 8.74%. The research results offer theoretical guidance for the equipment maintenance and structural design of torsional flow heat exchanger.

Based on the enhanced heat transfer technology of the torsional flow heat exchanger (TFHE), the characteristics of fluid flow and heat transfer in the TFHE with twisted oval tube (TOT) were analyzed by combining numerical simulation and theoretical analysis. The field synergy principle was used to evaluate thermal convection on both tube and shell sides. The influences of the TOT on the heat transfer enhancement and flow resistance performance of the TFHE were discussed. The results show that contrasted with smooth tube, on the tube side, the convective heat transfer coefficient of the TOT is increased by 25.17–38.28%, and the comprehensive performance is increased by 18.56–24.21%. On the shell side, the convective heat transfer coefficient is increased by 117.99–126.53%, and the comprehensive performance is increased by 40.82–48.28%. The study provides a reference for the development of shell-and-tube heat exchangers.

By using the residence time distribution method (RTD), the fluid retention zones in the shell and tube heat exchanger with segmental baffle (STHX-SB) and the heat exchanger with helical baffle (STHX-HB) are compared and discussed. The flow pattern and fluid retention zone of the similar double helical flow heat exchanger (STHX-SDH) were analyzed by using the same method. The result shows the spiral flow can reduce the fluid retention zone. The flow pattern in the STHX-SDH likes a double helical shape and leads to a very small fluid retention zone. According to the simulation results, the location of the fluid retention zone of STHX-SDH is determined. The verification line method and the zone assessment method were adopted, to discuss the flow velocity of each point on the verification line and the average flow velocities of the selected zones. The change laws of the flow velocities on the verification lines and the average flow velocities of the selected zones at different Reynolds numbers were compared. The result reveals the distribution of the fluid retention zone of the STHX-SDH and the sensitivity of each fluid retention zone to the Reynolds number. By optimization of the angle of the baffle, the volume fraction of the fluid retention zone is reduced to 1.61%, and the heat transfer performance is improved by 13.23%. It is verified that reducing the fluid retention zone can effectively enhance the heat transfer performance. This research method provides a theoretical basis for reducing the fluid retention zone of the heat exchanger and enhancing heat transfer performance.