Der Druckverlust bei nichtisothermer,laminarer Rohrströmung von Potenzgesetz-Flüssigkeiten mit verschiedenartigen thermischen Randbedingungen

This work is concerned with numerical computations of pressure-drops in non-isothermal, laminar flow of power law fluids in circular tubes with various thermal wall conditions (constant and variable wall temperature as well as constant and variable wall heat flux). In the paper both temperature dependent rheological fluid properties and viscous dissipation are included. The results of numerical computations are plotted in 7 figures and selected numerical data are presented tabularly. As a result an extended friction factor formula is derived similar to that one introduced by Metzner and Reed. In addition, an approximative friction factor formula is proposed which enables the calculation of local friction factor if only one value of the so called “film temperature” has been previously measured. This formula is valid for all the thermal wall conditions considered in this work. The results of the present paper are intended to be very helpful for design engineers while calculating the pressure losses in some heat exchangers and pipes for transporting polymer melts.