Influences of the inner-surface conditions of circular tubes on the heat transfer in a surfactant drag-reduction system

Cationic surfactant solutions that form rod-like micelles are known to caus e remarkable drag reducing effect. However, heat transfer reduction also oc curs simultaneously in the drag-reducing systems. Application of this drag- reduction technology to the heat transfer medium in a district heating and cooling system may thus decrease the heat transfer capacity of the heat exc hanger in the refrigerator. In this work, we evaluated the heat transfer characteristics of a drag-redu cing aqueous solution containing oleylbis (hydroxyethyl) methylammonium chl oride as the cationic surfactant and sodium salicylate as the counter ion. The heat transfer tubes examined were smooth copper tubes and the internall y grooved tube with spiral ridges inside, both of which are employed in ref rigerators. In the grooved tube with redge of narrow pitch, it was found that heat tran sfer reduction did not occur in the velocity range. It was also found that the heat transfer reduction correlated well with the wall shear rate.