A Study of the Flow through Capillary Tubes Tuned for a Cooling Circuit with Saturated Fluorocarbon Refrigerants

Capillary tube expansion devices are widely used in refrigeration equipment; nevertheless, the mechanism of the flow is still not fully described and understood, so the experimental verification ofmost predictions is still necessary.Amodified numerical model of capillary flow has been developed both for standard refrigerants and with emphasis for saturated fluorocarbon (C2F2n+2) refrigerants. These refrigerants have several unique properties (high dielectric performance, chemical stability, and radiation resistance). Therefore, they can be used in some special applications, where other common fluids cannot be applied. The main aim of this study was to prepare a practical capillary flow model, which would improve the procedure of predicting the behavior of capillary tubes for cooling circuits of particle detectors being built at the iInternational CERN laboratory in Geneva. The generated numerical model was verified through available data from the literature and also via measurements performed in a real cooling circuit with pure, oil-free octafluoropropane (C3F8) refrigerant