The effect of reduced gravity on cryogenic nitrogen boiling and pipe chilldown.

Samuel Darr,Jason Hartwig,Jacob Chung,Jun Dong,Alok Majumdar,Neil Glikin,Andre Leclair

doi:10.1038/npjmgrav.2016.33

Samuel Darr, Jason Hartwig + Show 5 more

Open Access

https://doi.org/10.1038/npjmgrav.2016.33

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Abstract

Manned deep space exploration will require cryogenic in-space propulsion. Yet, accurate prediction of cryogenic pipe flow boiling heat transfer is lacking, due to the absence of a cohesive reduced gravity data set covering the expected flow and thermodynamic parameter ranges needed to validate cryogenic two-phase heat transfer models. This work provides a wide range of cryogenic chilldown data aboard an aircraft flying parabolic trajectories to simulate reduced gravity. Liquid nitrogen is used to quench a 1.27 cm diameter tube from room temperature. The pressure, temperature, flow rate, and inlet conditions are reported from 10 tests covering liquid Reynolds number from 2,000 to 80,000 and pressures from 80 to 810 kPa. Corresponding terrestrial gravity tests were performed in upward, downward, and horizontal flow configurations to identify gravity and flow direction effects on chilldown. Film boiling heat transfer was lessened by up to 25% in reduced gravity, resulting in longer time and more liquid to quench the pipe to liquid temperatures. Heat transfer was enhanced by increasing the flow rate, and differences between reduced and terrestrial gravity diminished at high flow rates. The new data set will enable the development of accurate and robust heat transfer models of cryogenic pipe chilldown in reduced gravity.

Highlights

Future orbiting propellant depots and human-carrying orbital transfer vehicles to Mars will need to utilize the high thrust and efficiency of liquid cryogenic chemical propulsion or nuclear thermal propulsion.[1,2,3,4] The transfer of cryogenic propellants in space, has yet to be accomplished, partly owing to the limited availability of cryogenic two-phase heat transfer data in reduced gravity.[4]
Results showed that the reduced gravity conditions during each test were high quality as there was negligible angular asymmetry in the pipe wall temperature compared with 1-g horizontal flow during chilldown
The increasing mass flow rate enhanced the wall-to-fluid heat transfer, which resulted in a faster chilldown rate

Summary

Introduction

Future orbiting propellant depots and human-carrying orbital transfer vehicles to Mars will need to utilize the high thrust and efficiency of liquid cryogenic chemical propulsion or nuclear thermal propulsion.[1,2,3,4] The transfer of cryogenic propellants in space, has yet to be accomplished, partly owing to the limited availability of cryogenic two-phase heat transfer data in reduced gravity.[4] When a cryogenic propellant like liquid hydrogen or liquid oxygen is transferred from a supply tank to an engine or receiver tank, a transient two-phase heat transfer process ensues where the cryogen boils into vapor until the transfer pipe and the receiving hardware are cooled to the liquid temperature. There is a current lack of accurate heat transfer correlations for cryogenic chilldown

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