Flow and heat transfer in drag-reducing polymer solution flow through the corrugated tube and circular tube

Flow and heat transfer characteristics of xanthan gum (XG) solutions are experimentally studied to compare the drag reduction (DR) and heat transfer reduction (HTR) behavior in the corrugated tube with that in the circular tube. Effects of XG concentration (C) and bulk velocity (v) on drag enhancement (DE), heat transfer enhancement (HTE) and comprehensive performance index (xi) in the corrugated tube are also examined. The results show that the DR in the corrugated tube increases and then decreases until becomes negative with increasing bulk velocity under the intense turbulent disturbance of the corrugated wall, which is different from the DR behavior in the circular tube, and the onset of DR is found to occur earlier. In addition, the variation trend of HTR is consistent with that of DR's absolute value, which is closely related to the interaction between drag reduction property and high viscosity property of XG solutions. Furthermore, the HTE and xi increase with increasing XG concentration and decreasing bulk velocity, and the maximum HTE and xi can be up to 25 and 1600, which proves the corrugated tube has a specific applicability in terms of energy saving and heat transfer enhancement for high-concentration XG solutions at low velocity.