F-17 Tubeside and Shellside Shear Stress for Single-Phase Flow

C. A. Bennett

Anecdotal and laboratory evidence suggest that high shear stresses mitigate fouling. This report presents methods for calculating isothermal and diabatic shear stresses for single-phase fluids on both the tube side and the shell side of shell-and-tube heat exchangers. There are limitations to these methods, however. The tubeside shear stress calculation technique applies only to fully developed velocity profiles. The shellside shear stress method, which is based on a rigorous CFD analysis of shellside flow, provides an estimate of the average shear stress on the shell side because it does not account for variations around the circumference of the tubes or for the stagnation zones near the baffles. A comparison between tubeside and shellside crossflow isothermal shear stresses reveals that the shellside crossflow average shear stress is approximately two to three times higher than the tubeside shear stress at a given (B-stream) velocity.