Adiabatic capillary tube expansion devices: A comparison of the homogeneous flow and the separated flow models

Abstract

Literature shows that the homogeneous flow assumption has been commonly used in most of the adiabatic capillary tube modelling studies. The slip effect between the two phases was often not considered in this small diameter (about 1 mm) capillary tube. Due to the lack of experimental information of the slip ratio in the flow within the capillary tube, the more comprehensive separated two-phase flow model was not frequently used in theoretical studies. This paper attempts to exploit the possibility of the separated flow model. Comparisons of the predicted results between the homogeneous and the separated flow models are presented, together with experimental results from previous workers. The results show that the separated flow model using the Miropolskiy's slip ratio combined with Lin's frictional pressure-gradient correlations gives a better prediction compared to the homogeneous flow model.