Experimental study of fluid flow and heat transfer in internal helical-rib tubes

Experimental study of fluid flow and heat transfer characteristics in six tubes with internal helical-rib has been conducted. The inside diameters of the studied tubes are 16.25 to 16.69 mm, rib heights 0.28 to 0.44 mm, number of rib 40 to 45, helix angles 43 to 45 deg. It is found that the internal helical-rib tube can effectively enhance heat transfer. The inner heat transfer coefficients of the studied tubes are 1.67 to 2.99 times more than that of smooth tube. A comparison of two methods for evaluating characteristics of internal helical-rib tube is conducted. The fluid flow and heat transfer characteristics are predicted by Webb model and Ravigururajan model, and compared with experimental data of internal helical-rib tube. It is found that the predicted results from the two models deviate appreciably from the present experimental data, with the heat transfer model being relatively better.