Heat transfer in a water flow in tubes with ribbed twisted tape inserts

The results of an experimental study of heat transfer in a water flow in a channel with a twisted tape insert with discrete ribs installed at an angle to the tape axis are presented. The experiments were performed in a straight smooth tube with an inner diameter of $10$ mm. The tape inserts had a twist ratio of $2.5$, $3$, or $4$ with a $180^{\circ}$ rotation; the rib height ranged from $0.5$ to $1.5$ mm, the rib pitch was from $40$ to $120$ mm, and the rib angle was from $40$ to $50^{\circ}$ to the tape axis. The results of experiments in the mentioned range of geometries suggest that the ribbed tape inserts increase heat transfer by a maximum of $40\%$ as compared with that in tubes with a twisted tape without ribs. The generalized correlation is given for the prediction of heat transfer in a Reynolds number range $\rm Re = 10^4$–$2 \times 10^5$.