Theoretical and numerical study on new evaluation criteria for longitudinal vortex enhanced heat transfer

The enhancement of heat transfer caused by longitudinal vortex phenomena has been a widely studied topic for a significant period in fluid mechanics and heat transfer. However, despite extensive efforts, the current understanding of longitudinal vortex flow and the involved physical mechanisms leading to enhanced heat transfer remains qualitative in nature. To unveil the physical mechanisms underlying the enhancement of convective heat transfer by longitudinal vortices, further quantitative research and in-depth discussions are necessary. By performing detailed derivations and proofs of the equations, this study aims to further understand the relationship between local vortex variations and heat transfer performance. The results indicate that the presence of longitudinal vortices alters the gradient of the convective term and ultimately leads to enhanced heat transfer performance. Based on the derived results, corresponding metrics have been proposed to quantitatively analyze the degree of heat transfer enhancement due to longitudinal vortices. This proposed quantitative analysis metric has been applied to evaluate the heat transfer performance of a cross-wavy primary surface heat exchanger, validating the reliability of the metrics. The research content and conclusions provide valuable insights for both theoretical investigations and practical engineering applications in the field of enhanced heat transfer.