Turbulent flow thermal characteristics in a pipe with ring insert: An experimental and numerical study

Abstract

Using obstacles inside the tube to improve thermal performance is one of the appropriate and new methods. In most research, stationary inserts have been used, and few studies examined the effect of rotating inserts. In the present work, experimental and numerical study for investigated influence of the obstacle rotational with 10 to 3000 rpm inside the pipe is done. To flow excitation, ring obstacles of complete and 90 ° are placed inside the pipe. Comparison of ring-90 deg with rotating and the complete stationary ring shows an increase of 1.37–1.803 times the coefficient of thermal performance at Re=6000 with the same excitation of the pipe surface. Experimental results showed that ring insert inside the tube at the range of rotating speed 300 to 600 rpm, the coefficient of thermal performance and the Nusselt number compared to the smooth pipe is changed in the range 0.88–2.1 and 2.6–4, respectively. The study demonstrated that using rings with lower angle ratios in rotation mode is an optimal choice and economical and, due to the uniformity of heat flux at the tube surface, better thermal performance than a complete stationary obstacle.