Experimental studies on cool-down and mass flow characteristics of a demountable liquid nitrogen transfer line

Abstract

A demountable transfer line has been designed and fabricated to carry out experimental studies on cool-down time and mass flow characteristics of a liquid nitrogen transfer line held in a horizontal position. The effects of varying degrees of vacuum in the interspace on the cool-down time and mass flow rates have been evaluated. It has been found that during the initial phase of cool-down, lines with coarse vacuum perform better than high-vacuum-insulated lines. The performances of multilayer-insulated lines and lines with interspace medium of carbon dioxide have been evaluated as well as that of bare line exposed to an ambient environment. An experimental correlation has been developed to predict the cool-down time as a function of vacuum level and supply dewar pressure.