Abstract:

ESDU 01014 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 the engineer with techniques for the assessment of the frictional pressure gradient in gas-liquid mixture flows in horizontal pipes and allows estimates to be made of the accuracy of the predictions.

By means of a statistical analysis, method selection charts are developed that show, for ranges of both the mass quality of the gas component and the mixture mass flux, the order of ranking in accuracy of selected empirical correlations. As a result the best-performing correlation is recommended for any practical set of conditions. Using performance charts the pressure gradient predictions can be made and the likely errors involved for each correlation within those conditions can be assessed.

Specific empirical correlations may be more suitable for a given flow pattern. Thus, where flow pattern data are available, comparisons between the empirical correlations and the pressure drop data are also classified by means of a statistical analysis in terms of flow pattern and mass quality of the gas component. These results are included in further selection and performance charts.

Underpinning the work is a database of gas-liquid frictional pressure drop measurements in horizontal flows. This database contains nearly 6500 carefully selected and evaluated data points and is comparable in size (for the specific case of horizontal flows) with previous databases. In the validation process, many more thousands of data points were rejected as being unreliable.

The use of the methods is illustrated by worked examples.