A simplified method for calculating heat transfer coefficients and friction factors in laminar pipe flow of non-newtonian fluids

Abstract

In this work, we propose an approximate methodology to estimate the Nusselt number and friction factor in fully developed non-Newtonian laminar flow in circular pipes for a constant wall heat flux. The methodology was tested using several constitutive equations, including generalized Newtonian fluids and viscoelastic models such as the simplified Phan-Thien-Tanner (sPTT), Herschel-Bulkley, Bingham, Casson, and Carreau-Yasuda constitutive equations. The error of the approximate methodology was found to be smaller than 3.2%, except for the fluids with yield stress for which the maximum error increased to about 8% for the cases analyzed, which cover a wide range of shear viscosity curves. [DOI: 10.1115/1.4006288]