This article deals with the experimental investigation of t hermal performance of detached circular r ing turbulators in
turbulent flow regime. T he experiments were conducted by f our diff erent circular r ings. Two diff erent pitch ratios ( 1 and 2)
and two different distances (1 mm and 2 mm) at which t he circular rings were detached from the t ube wall were considered in
the experiments. Uniform heat flux was applied to the external surface of the tube and Reynolds number w as varied from 4350
to 24,920. The tube with circular ring turbulators introduced both higher heat transfer and higher pressure drop than the
smooth tube, depending on pitch ratio and distance. According to the experimental results, the Nusselt number and friction
factor increased w ith decreasing of pitch ratio and distance. Therefore, the circular r ing t urbulator w ith a pitch ratio of 1
and distance of 1 mm offered the highest heat transfer rate accompanied by the highest pressure drop. The highest thermal
performance efficiency of 26% was also achieved for t his case at a Reynolds number of 4421. Evidently, t he experimental
results revealed t hat the best operating regime of all circular ring turbulators w as found at low R eynolds number, leading to
a more compact heat exchanger