Comparative analysis of calculation methods of pressure drops for two-phase flow through pipelines

Despite the importance of an adequate and correct sizing of emergency relief systems, a high level of uncertainty is still present when two-phase liquid-vapor flow can establish. In such a case, no single correlation is presently generally applicable to calculate the pressure drop through a relief pipeline in a wide range of relief conditions. In the present paper a large number of new experimental data have been produced and compared with two of the most widely known and adopted calculation methods: the Friedel model and the classical Lockhart-Martinelli model. They belong to either of the two main groups of prediction models, the homogeneous and non-homogeneous models. The results provide useful insights in their accuracy and range of applicability, and are expected to be of help in the correct sizing of these fundamental safety systems.