Drag reduction and heat transfer of surfactants flowing in a capillary tube

Pressure drop and heat transfer were measured in fully developed laminar flow in a pipe of inner diameter 1.07 mm in the range of Reynolds numbers 10 less than or equal to Re less than or equal to 450. The study was performed for water and water-surfactant solution of 530 and 1060 ppm. It was shown that these surfactant solutions increase the pressure drop in adiabatic and diabatic flows. The dependence of friction coefficients as a function of solvent Reynolds number was used to predict the ability of certain surfactant solutions to increase drag in laminar flows. The experimental values of the Nusselt number depend significantly on the thermal conduction through the tube wall. They become lower than theoretically predicted for tubes heated with constant heat flux on the wall. The heat transfer coefficients with surfactant solutions were higher than that in water flow at the same bulk velocity. The results showed that the Peclet number is an additional parameter needed for a description of the averaged Nusselt number in laminar pipe flow of water and surfactant solution. (C) 2004 Elsevier Ltd. All rights reserved.