Effect of entrance region and curvature on heat transfer in mini scale curved tubing at constant wall temperature

An experimental study on heat transfer enhancement in short curved tubes for the constant wall temperature boundary condition is presented. Copper tubing with four different radii of curvature (1 cm, 2 cm, 4 cm, and 8 cm) and in four lengths were used. Tubing radii were chosen, so that a constant tube length occurs in different curvatures. Hence, the effect of curvature on heat transfer at a constant length can be studied as well as the effect of heat transfer enhancement by changing the length in a constant curvature. Experimental results are also compared with an existing model for curved tubing. Water and three different silicone oils (0.65 cSt, 1 cSt and 3 cSt) were used in the experiments to examine the effect of Prandtl number on curved tubing heat transfer augmentation.