Investigation of helium injection cooling to liquid oxygen under pressurized condition

Sub-cooling of cryogenic propellant by helium injection is one of the most effective methods for suppressing bulk boiling and keeping sub-cooled liquid oxygen before rocket launch. Compared with the helium injection cooling under atmospheric condition, helium injection cooling under pressurized condition has advantage that it can greatly reduce re-warming time of the sub-cooled liquid oxygen. Helium injection cooling under pressurized condition is characterized by cooling of initially sub-cooled cryogenic liquid, which is significantly different from that of the atmospheric condition where liquid oxygen usually exists at saturated condition. In this paper, we discuss the characteristics of helium injection cooling under pressurized condition, with the associated physical understanding of the process. Experimental results are presented along the simulations of variously combined system parameters based on the finite heat transfer and instantaneous diffusion mass transfer model. A non-dimensional parameter for identifying the cooling regime is conceived. The critical values of the non-dimensional parameters and injected helium temperatures are also estimated. (C) 2006 Elsevier Ltd. All rights reserved.