Abstract
Turbulent flow characteristics and heat transfer performance of heat exchanger tube fitted with annulus circular-rings (A-CRs) are experimentally studied. The d/D_o = 0.1, 0.15 and 0.2 were inserted into a round tube at constant space length ratio (s/D_o) of 1.0. For optimization, the A-CRs at different annulus diameter ratios of d/D_o = 0.1, 0.15 and 0.2 were comparatively tested. The experimental data of the tube with A-CRs are compared with those of the tube with a typical circular-rings (CRs) and also the plain tube. The results show that using the A-CRs with d/D_o = 0.1, 0.15 and 0.2 improves heat transfer rates by around 210%, 244% and 303%, respectively over that of the plain tube. The enhanced heat transfer rates are respectively accompanied with the increased friction factors of around 28, 47 and 90 times of the plain tube. Both friction factor and heat transfer caused by the A-CRs are considerably higher than those caused by the CRs. However, the tubes with A-CRs yield lower thermal performance factors than the one with CRs. In order to understand the heat transfer enhancement mechanism of the heat exchanger tube fitted with A-CR, the numerical results of streamlines and fluid temperature distributions are also reported.
