Two-phase separated flow model of refrigerants flowing through capillary tubes

Capillary tubes are often used as an expansion and controlling device in refrigeration systems. The homogeneous two-phase flow model has been used exclusively in capillary tube flow studies and has not changed appreciably since the 1950ʹs. However, some experimental results show that two-phase flow in small diameter tubes may be not entirely homogeneous due to phase interaction. In this paper, a separated flow model of refrigerants through capillary tubes is derived. The effects of various correlations of relevant parameters; frictional pressure gradient and slip ratio, on the prediction of a separated flow model are investigated. The results calculated by this separated flow model are compared with the measured data reported in the literature. Finally suitable correlations of relevant parameters for a flow model are proposed.