Hydraulic and thermal analysis for cryodistribution lines of cryopumps for NBI system of SST-1

Abstract

Cryo-pumps had been developed for the long duration continuous pumping (∼4000sec) with pumping speed of 2x105l/sec of hydrogen for the Steady state Superconducting Tokamak-1 (SST-1) Neutral Beam Injection (NBI) system[1][2]. Two pumps have been placed in the vacuum chamber along with the components required for the test and operation of NBI system. A liquid helium plant is used to produce and circulate liquid helium in the cryo-condensing panels at temperature ∼4K. Chevron-baffles, around this panel are cooled by liquid nitrogen (LN2) to reduce the external heat loads on the panels. It is necessary that, both pumps should get equal and required flow rates of helium and nitrogen as both pumps are identical. Detailed analysis is required as flow regimes will be different for different segments of the distribution system. In nominal operations, for certain segments, it may be single-phase flow and for certain others it may be two-phase flow. This two-phase flow can be affected due to the heat loads on these cryo-lines. In this report, we discuss the hydraulic as well as thermal analysis including the routing of the cryodistribution lines.