Experimental of turbulent flow heat transfer of dimple vortex generators with rounded edge

An experimental study of the local heat transfer performance and flow friction characteristics in a channel with spherical dimples with rounded edge is conducted using a transient liquid crystal (TLC) thermography technique. Two different rounding schemes for the dimple edge are investigated: the front edge rounding, and the whole edge rounding. The ratio of the dimple print diameter to the duct height is 1.0, the ratio of the dimple depth to diameter is 0.2, and the Reynolds number ranges from 10 000 to 60 000. As is shown in the experiment, the Nussult number of the channel with conventional dimples is about 62.0% higher than that of the smooth channel, with the friction factor being about 73.0% higher than that of the latter. Compared with the conventional dimples, the Nussult number of the dimples with the whole edge rounded is about 3.6% higher, with the friction factor being about 4.6% lower; the Nussult number of the dimples with the front edge rounding is about 11.0% higher, with the friction factor being about 5.2% higher. It is still found that the existence of dimple edge rounding can improve the heat transfer uniformity on the surface of the dimples. The overall thermal performance of the dimples with the front edge rounding is the best, which is about 9.6% higher than that of the normal dimples; while the dimples with the whole edge rounding is about 4.4% higher than that of the normal dimples.