On the use of the stratified momentum balance for the deduction of shear stress in horizontal gas-liquid pipe flow

The use of the stratified flow momentum balance for the deduction of interf acial and liquid wall shear stresses from experimental measurements is exam ined. A systematic error analysis is applied to the governing equations usi ng the principle of maximum uncertainty. A series of air-water experiments were conducted in 50 and 80 mm diameter pipes, in which gas pressure drop, liquid height and gas wall shear stress were measured. A framework for the correlation of the deduced shear stresses is proposed from the experimental measurements. The uncertainty analysis is used to show that the definition of mean liquid height does not significantly influence the overall results . The development of empirical equations based on such methods may lead to total uncertainties of up to 40%, irrespective of accuracy of the experimen tal data or the appropriateness of the correlating technique. Comparisons w ith state-of-the-art correlations for the liquid wall and interfacial frict ion factor data showed even larger discrepancies between measurement and pr ediction. (C) 1998 Elsevier Science Ltd. All rights reserved.