Two-phase flow visualization of 4134a in a multi-port microchannel tube

Results are presented from a flow visualization investigation of a multi-port microchannel tube using R134a, a medium pressure refrigerant. The study covers mass fluxes from 50 to 300 kg/s.m2 and qualities ranging from 10% to 90% with a 6-port microchannel tube with a hydraulic diameter of 1.5mm under adiabatic conditions. The results from the flow visualization studies indicate that several flow configurations may exist in multi-port microchannel tubes at the same time while constant mass flux and quality flow conditions are maintained. Based on these observations, development of a typical flow regime map does not appear to be an appropriate manner for describing the flow field. Flow mapping of the fluid regimes in this multi-port microchannel is accomplished by developing functions that describe the fraction of time or the probability that the fluid exists in an observed flow configuration. Pictures from flow visualization results over the mass flux and quality range investigated are included.