Heisenberg vortex for light-weight refrigeration of liquid hydrogen

This research has demonstrated that a Heisenberg Vortex Tube (HVT) can be used to reduce liquid hydrogen boil-off in cryogenic propellant tanks. A cryogenic propulsion stage has never been fired outside earth’s orbit and current technology is suitable to support missions with a time scale of a few days without large mass penalties. Heisenberg Vortex Tubes (HVT) are special types of counter-flow vortex tubes that have a parahydrogen-orthohydrogen catalyst on the inner wall. Counter-flow vortex tubes separate a compressed gas into hot and cold streams with no moving parts and light-weight characteristics. This project focused on the fundamental understanding and experimental proof of concept of the Heisenberg Vortex Tube (HVT) concept which takes advantage of the endothermic parahydrogen-orthohydrogen conversion to aid in cooling. To demonstrate this concept numerical and experimental methods were used to model and measure the fundamental physics occurring in the ruthenium coated HVT. 1st order models were built including parahydrogen-orthohydrogen conversion and simplified 2-phase near vapor dome performance. Since then progress towards a qualitatively verified High-Performance Computing (HPC) transient 3D Computational Fluid Dynamics (CFD) model has been made possible from allocation time on the National Renewable Energy Laboratory (NREL) Peregrine HPC system. Experimental proof of concept was accomplished with a bench top scale test in the Cryocatalysis Hydrogen Experiment Facility (CHEF) at WSU. This system liquefies 5L of liquid parahydrogen that is then boiled-off through the HVT where temperature, flowrate, and orthohydrogen-parahydrogen composition are measured. The test plan was driven by the most impactful variables in the 1st order model sensitivity analysis. A total of 6 tests were planned for the spring of 2018 including 3 catalyzed and 3 non-catalyzed spanning the temperature range of 30K to 50K amenable to boil-off temperatures in-space. However, based on the initial results, 3 more tests were allocated to the catalyzed tests to achieve more definition based off the unexpected cooling observed from both hot and cold outlets of the HVT. Approximately 40% increase in cooling capacity can be realized if the 100% parahydrogen boil-off can be converted to the equilibrium 77% parahydrogen at 50K. Figure 3: Experimental catalyzed HVT “hot” and cold end temperature differentials as a function of vortex tube inlet temperature. Both outlets of the vortex tube cooled relative to the inlet temperature. The 1st order Extended Heat Exchanger (EHE) model dashed line represents the average temperature of the hot and cold sides in the model at the corresponding parahydrogen-orthohydrogen conversion fraction. Figure 3 demonstrates the experimental results of the catalyzed HVT tests. At the 50.56K inlet temperature condition, the HVT produced 5.16x more cooling than an isenthalpic Joule Thomson (JT) expansion valve in the same pressure ratio conditions (3.82). The non-catalyzed test resulted in the traditional hot and cold separation at the hot and cold HVT outlets. This fundamental modeling and experimental research helped characterize flow behavior and predict the cooling potential of the HVT. The CFD model will be used to give sweeps of parameters over a wider range of performance characteristics than testing allows. This will allow the development of more efficient thermodynamic refrigeration or venting cycles applicable to all liquid hydrogen propellant tanks including those to be used on liquid hydrogen in-space propellant storage systems such as NASA’s Exploration Upper Stage (EUS), ULA’s Advanced Cryogenic Evolved Stage (ACES), cis-lunar propellant aggregation, and other applications such as propellant production from lunar water ice. This research addresses NASA Technology Area Breakdown Structure (TABS) 14.1 – Cryogenic Thermal Management Systems.