Flow patterns of two-phase helium in horizontal channels

This paper reports the investigation of the structure of two-phase helium flows used for cryostatically controlling superconducting magnets in installations such as HERA, NET, UNK and KEK. Flow pattern maps for horizontal round channels and rectangular slot channels are plotted on the basis of experimental data obtained for a wide range of flow parameter variations. Some typical features of the flows (e.g. the absence of a slug pattern) are pointed out and attempts are made to explain these features following a theoretical analysis. Methods for estimating stratification and full mix limits are proposed. The position of the limits on the maps obtained for helium is shown to be quite different from that of other two-phase mixtures.