Parametric study of the hydraulic performance of counter flow LN2 cooled cold dielectric HTS cable

Abstract

A hydraulic analysis is promising to perceive the complex turbulent flow behavior of sub-cooled liquid nitrogen (LN2) through counter flow cold dielectric high temperature superconducting (HTS) cables. Such counter flow HTS cables comprise of an annular (cryostat) and a central corrugated pipe separated by a HTS conductor layer. Flow of sub-cooled liquid nitrogen through central and annular corrugated pipe affects the hydraulic performance of HTS cable due to the sudden expansion and contraction in the corrugated pipes shape. Therefore, in the present work, the hydraulic performance in terms of friction factor, pressure drop, pumping power and flow pattern of LN2 through central (forward flow) and annular (return flow) corrugated pipe (cryostat) are investigated computationally. Moreover, the effect of various parameters (corrugation pitch and depth) on hydraulic performance is also examined. In order to analyze the effect of corrugation pitches (6, 8, 10 and 12mm) and depths (4, 6 and 8mm), ten different two dimensional (2-D) axisymmetric model of counter cooled HTS cable are developed and solved using computational fluid dynamics (CFD). Additionally, two-equation turbulence model (k-ϵ) is being used to accurately predict the complex flow pattern of LN2 in corrugated pipes. Furthermore, the results of pressure drop are validated with available experimental results. Hence, the hydraulic analysis results are beneficial in opting the corrugated pipes configuration and the allied cryo-units for fluid pumping.