Line Chilldown and Flow Boiling Heat Transfer Characteristics of Stainless Steel Tubes

As part of the ongoing efforts to develop and test a two-phase flow chilldown experimental setup onboard the International Space Station (ISS), experiments are conducted to analyze the line chilldown and flow boiling heat transfer characteristics of SS-316 using a simulant fluid PF-5060 in this study. The cryogenic transfer line chilldown process is pre-dominated by the film boiling regime for most of the duration followed by transition and nucleate boiling regimes. The line chilldown tests performed in this study are designed to mimic the cryogenic transfer line chilldown by heating the tubes to around 250 °C and then allowing the PF-5060 liquid flow to cool down the tubes. The test module consists of the main heated section, and a bypass section to maintain the flow rate while the test section preheating is undergoing. The main heating section is 60 cm long with wall temperature measurements at top and bottom sides of the tubes placed at equal distances. A fibre-glass insulated Nichrome tape heater achieves the desired initial temperature conditions, and a three-way valve activates to divert flow from the bypass section to the main test section when all the wall thermocouples read 250 °C or above. The present experimental design captured the entire chilldown curve from film boiling to single phase liquid regions.