Experimental Investigation of Thermal and Hydrodynamic Development Regions for Drag-Reducing Surfactant Solutions

The reductions in friction and heat transfer exhibited by a surfactant solution in the entry region of a circular pipe were measured and analyzed, with special attention paid to the relationship between the local heat transfer and friction. Two entrance configurations were used, a cone contraction and wire mesh plugs used as a device for velocity profile flattening. Both the simultaneous development of temperature and velocity profiles and the development of temperature profile with hydrodynamically predeveloped flow were studied. Interestingly, the local heat transfer measurements for surfactant solutions matched very well a correlation developed for polymer solutions, but for surfactants the development of the heat transfer and velocity profiles appear coupled, unlike what is thought to happen for polymer solutions. The development patterns appear to be independent of velocity and entrance type at low disturbance levels. At high disturbance levels, however, some striking changes in the fluid itself, likely due to temporary micellar structure degradation by high local shear stress in the inlet region, were observed as well, and quantified.