Experimental study on cryogenic chilldown performance through a thick-wall tube

Abstract

Cryogenic pipeline chilldown is an inevitable process in cryogenic liquid transfer operation, but the researches on chilldown performance through a thick-wall tube are still insufficient. In the present study, a high-pressure cryogenic chilldown test platform is established to study the tube wall thickness influence on chilldown characteristics. Two stainless steel tubes, with 2 mm thickness wall and 5 mm thickness wall, respectively, are manufactured and tested under different inlet Reynolds numbers (Re) conditions. The temperature decrease curves and heat transfer variations are analyzed and compared. The test results show that a thicker wall tube requires an apparently longer chilldown time and a larger liquid consumption to reach the chilldown purpose. In the present experiments, the mass ratio of the two tubes is about 3.0, but the time cost ratio varies within 3.5–6.0 and the liquid consumption ratio is about 4.5. This performance indicates that in a thicker-wall pipe chilldown event, a lower efficient utilization of liquid cold energy could be speculated. Moreover, increasing inlet Re produces temperature rises both at critical heat flux (CHF) and Leidenfrost point (LFP). For the 2 mm wall tube cases, increasing inlet Re from Re = 5500 to Re = 43000 gives rise to a 39 K temperature rise in LFP and a 32 K temperature rise in CHF. Under the similar inlet Re variation, the temperature rises of LFP and CHF in the 5 mm wall tube cases are 28 K and 46 K, respectively. Comparatively, the 5 mm wall tube experiences a shorter transition boiling-dominated range when increasing the inlet Re. In addition, in the present test cases, the chilldown thermal efficiency varies with 8%–23%, and the 5 mm wall tube cases experience lower thermal efficiency than the 2 mm wall tube cases. To realize a high-efficient chilldown purpose, the approaches of increasing chilldown thermal efficiency should be significantly concerned in the chilldown scheme design, especially when a thick wall tube situation is encountered.