Experimental investigation on the effect of geometry on cryogenic transfer line chilldown

Abstract

In order to analyze the effect of geometry on cryogenic chilldown, experiments were performed on straight, one twisted and twin twisted copper tubes using liquid nitrogen. Data presented in this paper is for the experiments conducted under terrestrial gravity conditions at supply pressures of 1.2 bar and 1.3 bar. Test sections considered were copper tubes (7.9375 mm OD, 0.8128 thick) of straight, one twisted and twin twisted geometry traversing a distance of 220mm under Polyurethane foam insulation. Pressure measurements at test section inlet and outlet was monitored using transducers. Temperature measurement at four equidistant sections along the length were tracked in real-time using a data acquisition system. Temperature and pressure profiles were obtained. The results of the experiment indicated that, for a given mass flux, the transition during chilldown occurs earlier in one twisted transfer lines compared to straight and twin twisted tubes. This indicates the earlier occurrence of film boiling for the one twisted channels. Thereby, changing the transfer line geometry from straight tubes to one twisted sections, the chilldown time can be reduced to a considerable extend further resulting in reduction of cryogen consumption during the initial stages of transfer process.