ESDU 04006:2012

ESDU 04006 is one of a group of Data Items on the prediction of
pressure drop in two-phase gas-liquid mixtures in piping
systems.

It provides techniques for the assessment of the frictional and
gravitational pressure gradient for fluids flowing upwards in
smooth vertical pipes. This assessment requires a knowledge of the
phase flow rates, phase physical properties and pipe diameter. It
also provides methods for estimation of the accuracy of the
predictions.

Within ESDU 04006, the basic generic methodologies for the
empirical prediction of total pressure gradient are reviewed. A
description is then given of the development of a database of data
on vertical two-phase flows. This database contains nearly 6000
carefully selected and evaluated data points and is comparable in
size with previous databases. In the validation process, many more
thousands of data points were rejected as being unreliable. The
performance of a number of correlations for void fraction (hold-up)
and frictional pressure gradient was tested against the database,
and performance comparisons underpins a methodology for the
selection of the best-performing correlation under given flow
conditions. The results of the performance comparisons with the
database are reviewed and the methodology for applying the results
is described.

Worked examples illustrate the selection methodology and the
calculation of total pressure gradient for air-water and
steam-water flows.