Effect of cryogenic feed line thermal mass distribution and orientation on chill-down performance

• Published in: Cryogenics (Guildford) 2024-03, Vol.138, p.103781, Article 103781
• Main Authors: Venkatesh, N., Agarwal, Deepak Kumar, Salih, A., Sunil Kumar, S.
• Format: Article
• Language: English
• Subjects: Chilldown; Chilldown performance index; Chilldown time; Cryogen; Feed line orientation; Flow visualisation; Mass flux; Thermal mass distribution
• ISSN: 0011-2275; 1879-2235
• DOI: 10.1016/j.cryogenics.2024.103781

•Analysed the experimental data reported by authors earlier along with fresh set of data generated as part of present study to estimate the chilldown time and a non dimensional parameter called Chilldown performance Index.•Compared the chilldown time and CPI for different test section orientation and mass flux to understand their influence on chilldown performance of cryogenic feed lines.•Influence of thermal mass distribution on chilldown performance of cryogenic feed lines is studied by conducting experiments with varying mass distribution and cryogen mass flux.•Experiments are performed using a double jacked vacuum insulated view glass to capture the flow structure prevailing in the test section during tests with varying feed line orientation. Chilldown performance of cryogenic systems is highly influenced by parameters like feed line orientation, thermal mass of the feed system and its distribution, mass flux of the cryogen and heat in-leak. In this work, the impact of feed line orientation and mass flux of cryogen on chilldown is evaluated through a parameter defined as Chilldown Performance Index. A set of experimental data generated with Liquid Nitrogen employing a test section insulated with poly-isocynurate foam is used for this study. Chilldown Performance Index is found to be lower with downward inclination upto 60° downward orientation of test section as compared to that of horizontal orientation. Beyond this, at 90° downward orientation, it is seen to be better as compared to 60° orientation. Chilldown performance improves significantly with upward inclination of test section. Chilldown time is found to be highly sensitive to mass flux, whereas effect on Chilldown Performance Index is not so significant. Experiments also show that chilldown performance is significantly influenced by the distribution of feed line thermal mass. Chilldown is faster in experiments with higher thermal mass distributed near to the inlet to the test section as compared to the case wherein they are distributed near to the exit of the test section. Flow visualisation studies are also conducted employing a vacuum jacketed view glass made of borosilicate material to capture the flow structure prevailing in experiments with different upward and downward orientation and to assess its influence on chilldown. Flow structure is observed to be significantly different in experiments with upward inclination, compared to those with horizontal and downward orientation. Observation