NEW INSIGHTS INTO THE BEHAVIOR OF THE METASTABLE REGION OF AN OPERATING CAPILLARY-TUBE

This study examines the mass flow rate of R-22 in an adiabatic capilla ry tube, with an emphasis on the nature of the metastable region. The metastable region of and operating capillary tube was found to be much more predictable than previously reported in the literature. A new da ta acquisition technique, which takes the history of the system into a ccount, revealed a hysteresis effect in the mass flow rate as the leve l of inlet subcooling is increased and decreased. This result is attri buted to the fact that, as the inlet level of subcooling is decreasing , it is possible to create and lengthen a metastable region in which l iquid flow exists where it might otherwise be two phase. It is predict ed that this finding will have an impact on the future of capillary tu be data acquisition, modelling efforts, and the fundamental understand ing of capillary tube flow.