A prediction method of frictional pressure drop during two-phase flow in small diameter channels

Two-phase flow in minichannels is widely present in evaporators and condensers, such as, for example, air-cooled condensers for automotive and air-conditioning applications. It is crucial to have reliable pressure drop prediction methods for two-phase heat transfer modeling and optimization because pressure drop have a strong influence on the two-phase heat transfer. In this work, a model to calculate the frictional pressure gradient during two-phase flow in small diameter channels is presented: it accounts for the effects of surface roughness on the internal surface. Predictions by the present model are compared against a new two-phase pressure drop database to enlarge its validity range. The new pressure drop database is obtained from experimental tests with refrigerants R290 (propane), R1234ze(E), and two mixtures R32/R1234ze(E) (23/77% and 50/50% by mass composition) at mass flux ranging between 200 and 800 kg m-2 s-1.