Study of the intensified heat transfer of longitudinally ridged internal-finned tubes

Through experiments and numerical simulation methods a study has been conducted of the characteristics of convection heat exchange of ridged internal-finned tubes and a comparison of the above characteristics with the flow and heat transfer characteristics of straight internal-finned tubes is performed. The experimental results indicate that the heat exchange characteristics of ridged internal-finned tubes are better than those of straight internal-finned tubes in terms of intensified heat transfer performance, but at the same time there is a corresponding increase in flow resistance. Through the adoption of a turbulent flow model capable of realizing k-ε equation, the flow and heat transfer process of ridged internal-finned tubes have been simulated. The calculation results are in good agreement with the experimental ones. The calculation results indicate that the periodical ridges inside the finned tubes have changed the distribution of the inner-flow fields and temperature ones. Relative to the straight internal-finned tubes, a secondary vortex flow has emerged, which is conducive to an intensified heat exchange and plays a definite destructive role to the flow boundary layer. Meanwhile, by increasing the turbulent kinetic energy of the flow field, the temperature gradient in the neighborhood of the heat exchange wall surfaces has been enhanced, contributing to an intensification of heat transfer.