Transient cryogenic chill down process in horizontal and inclined pipes

Experimental results are presented that describe the parametric effects of inclination of transfer line and mass flux on cryogenic chill down process. Experiments were performed in a pressurized liquid nitrogen transfer line made of stainless steel. Fluid and wall temperatures were measured at various axial locations of the test section to monitor the chill down process. The local heat transfer coefficient and heat flux were predicted for the transient chill down period using an inverse heat transfer technique. The results show that the chill down period is characterized by three distinct flow regimes at all mass flux rates. However the variation in chill down time is more predominant at low mass fluxes. Heat transfer coefficient and heat flux calculated using the inverse heat transfer technique further confirmed this and showed that peak heat flux increases with increase of mass flux. It is found that the inclination of the chilling line displayed similar temperature profile but accompanied with variation in chill down time. Results suggest the existence of an optimum upward line inclination minimizing the chill down time. (C) 2015 Elsevier Ltd. All rights reserved.