RECENT PROGRESS ON EXPERIMENTAL RESEARCH OF CRYOGENIC TRANSPORT LINE CHILLDOWN PROCESS

Chilldown or quenching is a complicated process that initiates the cryogenic fluid line transport, and it involves unsteady two-phase heat and mass transfer. To advance our understanding of this process, we have reviewed recent experimental investigations. The chilldown process can be generally divided into three regimes: film boiling, transition boiling and nucleate boiling, and each regime is associated with a different flow pattern and heat transfer mechanism. Under low flow rate conditions, it is concluded that the two-phase flow regime is dispersed flow in the film boiling regime. The dispersed liquid phase is in the form of long filaments as the transport line is chilled down, and the vapor phase is generally superheated. Microgravity experiment for line chilldown was conducted basically in the film boiling region. Bottom wall heat flux was found to decrease under microgravity condition. Under the experimental condition, the gravity effect does not show a strong dependence on wall temperature and inlet flow rate.