Research and applications of drag reduction in thermal equipment: A review

Existing research on heat transfer enhancement in pipe flow shows that the improvement of thermal performance is generally accompanied by an increase in the pressure drop, which should be taken into consideration in the practical applications. To handle this dilemma, drag reduction (DR) technology is very promising and the related research has attracted more and more attentions. In this paper, different DR technologies are categorized and their development has been reviewed. The first part focuses on the studies conducted on additive DR while the second part focuses on surface modification DR. According to the different additives, the former is further divided into polymer and surfactant DR. The latter is divided into two categories, which are DR by introducing superhydrophobic surface and slippery surface. The development of the above technologies has been reviewed in detail, and their influences on heat transfer, related applications or future application potentials have been generalized.