Numerical study on convective heat transfer and flow characteristics in twisted tri-lobed tubes

Abstract

ABSTRACT The convective heat transfer and flow resistance properties of water flowing through a twisted trilobed tube (TTT) with Reynolds numbers that ranged from 10,000 to 40,000 were examined in this work. Specifically, we examined how the tip circle radius (r), straight length (l), transition radius (R), and twist pitch (S) influenced the heat transfer and flow resistance in the tube. Our results showed that the TTT had an average Nusselt number (Nu) that was 30% higher than that of a plain tube, while the friction coefficient (f) increased by 39%. We also presented temperature and velocity field distributions and explained the enhanced heat transfer process using the field synergy principle. Furthermore, we found that a larger tip circle radius (r) and straight length (l), as well as a smaller transition radius (R) and twist pitch (S), led to better overall heat transfer performance of the TTT. Among the different cases evaluated, Case 7 had the highest overall heat transfer performance with a PEC of 1.37. The unusual structure of the TTT caused a rotating motion, which resulted in secondary and spiral flows that increased the synergy through the velocity and temperature fields. Finally, our research found a correlation with the Nusselt number (Nu) as well as the friction coefficient (f).