Numerical study on hydrodynamics, mixing and heat transfer of highly viscous fluid in a novel shell-and-tube heat exchanger with X-type baffles

Heat transfer and mixing of highly viscous fluid in shell-and-tube heat exchangers are challenging. Computational fluid dynamics was applied to investigate the hydrodynamics, mixing, heat transfer and residence time distribution characteristics for highly viscous fluid in a shell-and-tube heat exchanger with X -type baffle (HEX), which is a novel baffle configuration proposed in this work. The influence of structural parameters, including the length-diameter ratio, the combination pattern of baffles and the crossbar number, was discussed. The results indicate that a smaller length-diameter ratio results in better dispersive and distribution mixing performance, and higher heat transfer coefficient, but leads to higher pressure drop. The increase of crossbar number will reduce the heat transfer coefficient and pressure drop, while improve the comprehensive performance. The analysis on the impact of structural parameters provides guidance for the design and optimization of HEX. For the evaluation of process intensification effect, HEX was considered for comparison with Sulzer mixer reactor (SMR), which has been proved to be an efficient heat exchanger for highly viscous fluid. The significant radial flow motion and effective splitting and remixing processes of fluid in HEX result in better distribution mixing performance. The heat transfer performance of HEX is equivalent to that of SMR when Re <0.03 and better than SMR when Re >0.03 at the cost of higher pressure drop. In addition, the residence time distribution of HEX is narrower than that of SMR, making it easier for the process control of highly viscous fluid.