Experimental investigations on turbulent heat transfer of carbon dioxide in a helically coiled tube

Experimental investigations on turbulent heat transfer of carbon dioxide in a helically coiled tube were performed under constant wall heat flux conditions. A computational program was compiled in a helical coordinate system to calculate the inner wall temperatures based on the directly measured outer wall temperatures by thermocouples. It was found that the wall temperatures increased with the increasing heat flux and the decreasing mass flux, while the heat transfer coefficients increased with the increasing heat flux and mass flux. The circumferential temperature and heat transfer coefficient distributions for a fixed cross section displayed the non-uniform character. Generally, the outer side had a relatively lower temperature and higher heat transfer coefficient than the inner side due to the secondary flow induced by the centrifugal force.