Jacob Leachman

Fundamental Equations of State for Parahydrogen, Normal Hydrogen, and Orthohydrogen

If the potential for a boom in the global hydrogen economy is realized, there will be an increase in the need for accurate hydrogen thermodynamic property standards. Based on current and anticipated needs, new fundamental equations of state for parahydrogen, normal hydrogen, and orthohydrogen were developed to replace the existing property models. To accurately predict thermophysical properties near the critical region and in liquid states, the quantum law of corresponding states was applied to improve the normal hydrogen and orthohydrogen formulations in the absence of available experimental data. All three equations of state have the same maximum pressure of 2000MPa and upper temperature limit of 1000K. Uncertainty estimates in this paper can be considered to be estimates of a combined expanded uncertainty with a coverage factor of 2 for primary data sets. The uncertainty in density is 0.04% in the region between 250 and 450K and at pressures up to 300MPa. The uncertainties of vapor pressures and satura...

Revised Standardized Equation for Hydrogen Gas Densities for Fuel Consumption Applications.

An equation for the density of hydrogen gas has been developed that agrees with the current standard to within 0.01 % from 220 K to 1000 K with pressures up to 70 MPa, to within 0.01 % from 255 K to 1000 K with pressures to 120 MPa, and to within 0.1 % from 200 K to 1000 K up to 200 MPa. The equation is a truncated virial-type equation based on pressure and temperature dependent terms. The density uncertainty for this equation is the same as the current standard and is estimated to be 0.04 % (combined uncertainty with a coverage factor of 2) between 250 K and 450 K for all pressures, and 0.1 % for lower temperatures. Comparisons are presented with experimental data and with the full equation of state.

Fundamental Equation of State for Deuterium

World utilization of deuterium is anticipated to increase with the rise of fusion-energy machines such as ITER and NIF. We present a new fundamental equation of state for the thermodynamic properties of fluid deuterium. Differences between thermodynamic properties of orthodeuterium, normal deuterium, and paradeuterium are described. Separate ideal-gas functions were fitted for these separable forms together with a single real-fluid residual function. The equation of state is valid from the melting line to a maximum pressure of 2000 MPa and an upper temperature limit of 600 K, corresponding to available experimental measurements. The uncertainty in predicted density is 0.5% over the valid temperature range and pressures up to 300 MPa. The uncertainties of vapor pressures and saturated liquid densities are 2% and 3%, respectively, while speed-of-sound values are accurate to within 1% in the liquid phase.

A Technique for Producing Large Dual-Layer Pellets in Support of Disruption Mitigation Experiments

Abstract A special single-shot pellet injection system that produces and accelerates large cryogenic pellets (~16mm diameter and composed of D2 or Ne) to relatively high speeds (>300 and 600 m/s, respectively) was previously developed at the Oak Ridge National Laboratory. Subsequently, a similar system was installed on DIII-D and used successfully in disruption mitigation experiments. To circumvent some operational issues with injecting the large Ne pellets, a technique has been developed in which a relatively thin layer (0.1 to 1.0 mm) of D2 is frozen on the inner wall of the pipe-gun barrel, followed by filling the core with solid Ne.A fast solenoid valve operating with a light gas (H2 or He) at relatively high pressure (~70 bar) provides the force necessary to break away the dual-layer pellet and accelerate it. The technique and the initial laboratory tests are described, as well as the implementation and operational issues for fusion experiments.

THERMODYNAMIC PROPERTIES STATUS OF DEUTERIUM AND TRITIUM

Deuterium and tritium are seeing increased use in cryogenics as a fuel for nuclear fusion energy machines. The current Equation of State (EOS) for deuterium is based on work completed before the mid 1980s and tritium does not have an EOS available in the literature. In order to assess the need for new property correlations and experimental measurements, this paper presents a review and comparison of the available thermodynamic property measurements and models for deuterium and tritium. The comparisons extend a wide range of temperatures and pressures from the onset of solidification to the highest temperature and pressure measurements available. Based on the comparisons, recommendations for new experimental measurements and thermophysical property correlations are made.

Tensile strengths of polyamide based 3D printed polymers in liquid nitrogen

Advances in additive manufacturing technology have made 3D printing a viable solution for many industries, allowing for the manufacture of designs that could not be made through traditional subtractive methods. Applicability of additive manufacturing in cryogenic applications is hindered, however, by a lack of accurate material properties information. Nylon is available for printing using fused deposition modeling (FDM) and selective laser sintering (SLS). We selected 5 SLS (DuraForm® EX, DuraForm® HST, DuraForm® PA, PA 640-GSL, and PA 840-GSL) and 2 FDM (Nylon 12, ULTEM) nylon variants based on the bulk material properties and printed properties at room temperature. Tensile tests were performed on five samples of each material while immersed in liquid nitrogen at approximately 77 Kelvin. Samples were tested in XY and, where available, Z printing directions to determine influence on material properties. Results show typical SLS and FDM nylon ultimate strength retention at 77 K, when compared to (extruded or molded) nylon ultimate strength.

Development of the Genii-UAS Demonstrator: a Small-Class Vehicle with Low Wing Loading and Fuel Cell Propulsion

A sub 25 kg class unmanned aerial system has been developed with the intent of flying with power derived from alternative energy systems. The aircraft has a wingspan of 5.5 m; its expected top speed is 23 m/s, maximum takeoff weight is 25 kg, and minimum takeoff distance is 87 m. This paper is focused on the aircraft design and performance calculations. An overview is also given on the aircraft’s construction technique and design of the hybrid drive train to incorporate alternative energy systems. Results of simplified design techniques for the aircraft performance are compared with numerical modeling for the wing lift coefficient and induced drag. Limited performance data of the initial flight with battery power is presented. Plans for future testing with gaseous and liquid hydrogen through a PEM fuel cell, and gasoline-electric generator are discussed.

Parahydrogen-Orthohydrogen Conversion for Enhanced Vapor-Cooled Shielding of Liquid Oxygen Tanks

Long-term space missions require minimized boil-off from liquid hydrogen and oxygen tanks to increase the payload mass fraction at launch. Vapor-cooled shielding technologies can use liquid hydrogen boil-off vapors to refrigerate and potentially eliminate boil-off from liquid oxygen tanks. Statistical thermodynamic calculations estimate that the amount of refrigeration provided by hydrogen for a liquid oxygen tank can be increased up to 50% through catalysis of parahydrogen–orthohydrogen conversion. Based on this prediction, a cryocatalysis hydrogen experiment facility was developed as a proof of concept. Hydrogen is liquefied in a noncatalytic condenser and vapor venting controlled via a proportional-integral-derivative controller. The effective heat capacity of the effluent is measured directly through a change in temperature of the known mass flow and applied heater power. The change in parahydrogen–orthohydrogen composition is validated independently with a thermal conductivity probe calibrated in sit...

Design of a reconfigurable liquid hydrogen fuel tank for use in the Genii unmanned aerial vehicle

Long endurance flight, on the order of days, is a leading flight performance characteristic for Unmanned Aerial Vehicles (UAVs). Liquid hydrogen (LH2) is well suited to providing multi-day flight times with a specific energy 2.8 times that of conventional kerosene based fuels. However, no such system of LH2 storage, delivery, and use is currently available for commercial UAVs. In this paper, we develop a light weight LH2 dewar for integration and testing in the proton exchange membrane (PEM) fuel cell powered, student designed and constructed, Genii UAV. The fuel tank design is general for scaling to suit various UAV platforms. A cylindrical vacuum-jacketed design with removable end caps was chosen to incorporate various fuel level gauging, pressurizing, and slosh mitigation systems. Heat and mechanical loadings were modeled to compare with experimental results. Mass performance of the fuel tank is characterized by the fraction of liquid hydrogen to full tank mass, and the insulation performance was characterized by effective thermal conductivity and boil-off rate.

Development of a Diagnostic Twin Screw Extruder to Characterize Fuel Production for Tokamaks

Abstract Twin screw extrusion is anticipated to meet the pellet fueling demands of tokamak fusion devices. The twin-screw design principle has been proven by a functional prototype extruder at Oak Ridge National Laboratory (ORNL); however numerical models necessary for design optimization have yet to be validated due to system complexity. Characteristic measurements of solid flow during extrusion are difficult for any extruder and are exacerbated by the cryogenic environment necessary to solidify solid hydrogen. In this paper, we first discuss current modeling efforts to establish needs for experimental measurements and then present the design and construction status of a diagnostic twin-screw extruder to address these needs. Development is underway of a mass transfer analysis that predicts volumetric efficiency and augments an existing 1st order model of extrudate temperature. These predictive models are necessary for design and operation of hydrogenic twin screw extruders for fueling tokamaks, including ITER.