Measurement of temperature profiles in turbulent pipe flow of polymer and surfactant drag-reducing solutions

A device was built to measure temperature profiles of turbulent pipe flows of various drag-reducing fluids. It is easy to use and reliable. We measured temperature profiles over a range of conditions leading to accurate measurements down to $y+≈10$⁠, for tests carried over Reynolds numbers (⁠$Re$⁠) between 10 000 and 90 000. The effects of high heat fluxes and buoyancy, in particular, were quantified to ascertain the parameter range for accurate measurements. Temperature profiles measured for type-A polymer solution and for cationic surfactant solutions allowed us to see strong similarity between velocity and temperature profiles for drag-reducing surfactant solutions. A comparison between the slopes of the thermal and velocity buffer layers resulted in calculated turbulent Prandtl numbers between 6 and 9 for those drag-reducing solutions. We also used this tool to investigate drag reduction for a nonionic surfactant solution, which showed a significantly different fan-type profile, and also for a type-B drag-reducing polymer solution (Xanthan gum).