Hydraulic resistance to forced two-phase flow of helium in narrow channels

Abstract

Large superconducting magnets with forced circulat ion of coolant through hollow combined conductors have a number of advantages over magnets i m m e r s e d direct ly in a bath of liquid helium [1]. In choosing the pa rame te r s of the coolant and the cryogenic equipment in the f i rs t case, it is important to make a co r r ec t es t imate of the hydraulic res i s tance to the flow of helium in the narrow channels of the cooling sys tem. The development of methods to calculate the p ressu re loss in a s ingle-phase isothermal flow has been adequate. However, the known methods of determining the hydraulic res is tance for s ingle-phase flows with significantly varying proper t ies and for two-phase flows are based on approximate models or are empir ical . The calculational relat ions recommended for these cases are based mainly on experimental data for ordinary (noncryogenic) liquids. Data on the hydraulic res i s tance in a two-phase flow of helium [2, 3] show that the p ressure drop calculated using a homogeneous model of the flow may differ significantly f rom the experimental resul ts .