Frictional pressure drop in a boiling refrigerant flow in pipes

Abstract
Two methods are used in this country to calculate pressure drops in a boiling two-phase flow through smooth pipes. The transition to new refrigerants and the increase of their mass flow rate in evaporators call for the need to improve the accuracy of calculating frictional pressure drop during evaporation of different refrigerants. Based on the analysis of foreign sources, four generalized correlations were selected. They take into account the properties of the boiling liquid and are based on specific experimental data sets. For the sake of comparison, calculations of pressure drops were made using the homogeneous model and four models of separate phase movement at different combinations of refrigerant boiling conditions. The calculation results show that sufficient accuracy and relative simplicity is provided by the Müller-Steinhagen and Heck correlation. The model which takes into account the change of flow regimes during the movement of boiling liquid seems promising but too complicated. The most credible is the result of pressure drop calculations for given conditions when it appears roughly similar for two or three methods.