Frictional pressure drop in single-phase flow in narrow channels

An evaluation of frictional pressure drop in micro-conduits was carried out, taking into consideration such quantities as channel diameter, shape and aspect ratio, inclination, working fluid and heat input. Experiments took place at three different institutions and results were confronted with classical theory, using a simulation model where necessary. Excellent agreement was verified between the experimental friction factor data and the Hagen-Poiseuille and Blasius equations for all conditions and diameters. The difference in behaviour between circular and rectangular channels is minimal within the aspect ratios considered, but in the case of large temperature variation the effect of viscosity change must not be disregarded. For inclined channels, the frictional contribution to the total pressure drop exceeds the gravitational part only after a given value of the mass flux. This value increases for larger diameter and fluid density.