Convection and radiation heat transfer in a tube with core rod insert at high temperature

Abstract

Heat transfer and friction factor characteristics in a circular tube fitted with core rod at high temperature have been investigated experimentally. In the experiments, ambient air with Reynolds numbers in a range of 9,000–26,000 is passed through a circular tube with uniform wall temperature and convection and radiation heat transfer phenomena are studied. Experiments have been performed on the tube with core rod insert considering four values of uniform wall temperature. For each wall temperature considered, convection and radiation heat transfer coefficients have been determined. The experimental results show that at uniform wall temperature of 373, 473, 553 and 633 K the average share of the radiation heat transfer coefficient to the total heat transfer coefficient is 10.7, 14.6, 20.5 and 22.3 % respectively. In addition it was noted that for the mentioned temperatures, the heat transfer coefficient increased by 234, 275, 304 and 334 % respectively when using tube containing the core insert in comparison to the plain tube. It was also noted that increasing the wall temperature also resulted in increase of friction factor.