Flow of Sub-Cooled Cryogens through a Joule-Thomson Device: Investigation of Metastability Conditions

Cryogenic fluid systems are fundamental to space flight architecture. Due to the unique properties of cryogenic fluids and the environments in which they operate for space flight, cryogenic fluid management systems must be developed to maintain these fluids at conditions in which they can be utilized. Liquid oxygen boils at 90 K, and liquid hydrogen boils at 20 K. Significant care must be taken to provide a thermal management system that prevents heat entering these fluids with consequential adverse effects on the performance of the cryogenic fluid systems. One critical component of a cryogenic thermal management system is a Joule-Thomson device. This one small component provides the driving force not only for the production of cryogenic fluids, but for the effective management of thermal loads in many cryogenic fluid systems including those used in space flight architectures. As a fundamental understanding of the Joule-Thomson effect and J-T devices is critical to the effective design of cryogenic fluid management systems, the intent of this work is to examine J-T devices as they relate to space flight systems. This work will examine where these devices are used in space based cryogenic fluid management systems. It will consider research conducted to date that examines both the fundamental fluid physics behind how these devices operate and their application in real systems. Finally, it will report on the potential impact that fluid metastability has as it relates to J-T devices for certain cryogenic fluids. An analytical assessment is made of the stability limits of single phase cryogenic fluids as a J-T device operates on them. This is compared to experimental results for tests conducted in liquid oxygen, and liquid methane. Results show that several factors influence the performance of J-T devices, and that the metastability of single phase cryogenic fluids below the saturation line must be considered in the design of cryogenic fluid management system

Flow of Sub-Cooled Cryogens through a Joule-Thomson Device: Investigation of Metastability Conditions

Cryogenic fluid systems are fundamental to space flight architecture. Due to the unique properties of cryogenic fluids and the environments in which they operate for space flight, cryogenic fluid management systems must be developed to maintain these fluids at conditions in which they can be utilized. Liquid oxygen boils at 90 K, and liquid hydrogen boils at 20 K. Significant care must be taken to provide a thermal management system that prevents heat entering these fluids with consequential adverse effects on the performance of the cryogenic fluid systems. One critical component of a cryogenic thermal management system is a Joule-Thomson device. This one small component provides the driving force not only for the production of cryogenic fluids, but for the effective management of thermal loads in many cryogenic fluid systems including those used in space flight architectures. As a fundamental understanding of the Joule-Thomson effect and J-T devices is critical to the effective design of cryogenic fluid management systems, the intent of this work is to examine J-T devices as they relate to space flight systems. This work will examine where these devices are used in space based cryogenic fluid management systems. It will consider research conducted to date that examines both the fundamental fluid physics behind how these devices operate and their application in real systems. Finally, it will report on the potential impact that fluid metastability has as it relates to J-T devices for certain cryogenic fluids. An analytical assessment is made of the stability limits of single phase cryogenic fluids as a J-T device operates on them. This is compared to experimental results for tests conducted in liquid oxygen, and liquid methane. Results show that several factors influence the performance of J-T devices, and that the metastability of single phase cryogenic fluids below the saturation line must be considered in the design of cryogenic fluid management system

Flow of Sub-Cooled Cryogens through a Joule-Thomson Device: Investigation of Metastability Conditions

Cryogenic fluid systems are fundamental to space flight architecture. Due to the unique properties of cryogenic fluids and the environments in which they operate for space flight, cryogenic fluid management systems must be developed to maintain these fluids at conditions in which they can be utilized. Liquid oxygen boils at 90 K, and liquid hydrogen boils at 20 K. Significant care must be taken to provide a thermal management system that prevents heat entering these fluids with consequential adverse effects on the performance of the cryogenic fluid systems. One critical component of a cryogenic thermal management system is a Joule-Thomson device. This one small component provides the driving force not only for the production of cryogenic fluids, but for the effective management of thermal loads in many cryogenic fluid systems including those used in space flight architectures. As a fundamental understanding of the Joule-Thomson effect and J-T devices is critical to the effective design of cryogenic fluid management systems, the intent of this work is to examine J-T devices as they relate to space flight systems. This work will examine where these devices are used in space based cryogenic fluid management systems. It will consider research conducted to date that examines both the fundamental fluid physics behind how these devices operate and their application in real systems. Finally, it will report on the potential impact that fluid metastability has as it relates to J-T devices for certain cryogenic fluids. An analytical assessment is made of the stability limits of single phase cryogenic fluids as a J-T device operates on them. This is compared to experimental results for tests conducted in liquid oxygen, and liquid methane. Results show that several factors influence the performance of J-T devices, and that the metastability of single phase cryogenic fluids below the saturation line must be considered in the design of cryogenic fluid management system

Visco Jet Joule-Thomson Device Characterization Tests in Liquid Methane

Joule-Thomson (J-T) devices have been identified as critical components for Thermodynamic Vent Systems (TVS) planned for future space exploration missions. Lee Visco Jets (The Lee Company) (Ref. 4) are one type of J-T device that may be used for LCH4 propellant systems. Visco Jets have been previously tested and characterized in LN2 and LH2 (Refs. 6 and 7), but have not been characterized in LOX or LCH4. Previous Visco Jet tests with LH2 resulted in clogging of the Visco Jet orifice under certain conditions. It has been postulated that this clogging was due to the presence of neon impurities in the LH2 that solidified in the orifices. Visco Jets therefore require testing in LCH4 to verify that they will not clog under normal operating conditions. This report describes a series of tests that were performed at the NASA Glenn Research Center to determine if Visco Jets would clog under normal operating conditions with LCH4 propellant. Test results from this program indicate that no decrease in flow rate was observed for the Visco Jets tested, and that current equation used for predicting flow rate appears to under-predict actual flow at high Lohm ratings

Description of Liquid Nitrogen Experimental Test Facility

The Liquid Nitrogen Test Facility is a unique test facility for ground-based liquid nitrogen experimentation. The test rig consists of an insulated tank of approximately 12.5 cubic ft in volume, which is supplied with liquid nitrogen from a 300 gal dewar via a vacuum jacketed piping system. The test tank is fitted with pressure and temperature measuring instrumentation, and with two view ports which allow visual observation of test conditions. To demonstrate the capabilities of the facility, the initial test program is briefly described. The objective of the test program is to measure the condensation rate by injecting liquid nitrogen as a subcooled spray into the ullage of a tank 50 percent full of liquid nitrogen at saturated conditions. The condensation rate of the nitrogen vapor on the subcooled spray can be analytically modeled, and results validated and corrected by experimentally measuring the vapor condensation on liquid sprays

Liquid Oxygen Liquid Acquisition Device Bubble Point Tests with High Pressure LOX at Elevated Temperatures

When transferring propellant in space, it is most efficient to transfer single phase liquid from a propellant tank to an engine. In earth s gravity field or under acceleration, propellant transfer is fairly simple. However, in low gravity, withdrawing single-phase fluid becomes a challenge. A variety of propellant management devices (PMD) are used to ensure single-phase flow. One type of PMD, a liquid acquisition device (LAD) takes advantage of capillary flow and surface tension to acquire liquid. The present work reports on testing with liquid oxygen (LOX) at elevated pressures (and thus temperatures) (maximum pressure 1724 kPa and maximum temperature 122K) as part of NASA s continuing cryogenic LAD development program. These tests evaluate LAD performance for LOX stored in higher pressure vessels that may be used in propellant systems using pressure fed engines. Test data shows a significant drop in LAD bubble point values at higher liquid temperatures, consistent with lower liquid surface tension at those temperatures. Test data also indicates that there are no first order effects of helium solubility in LOX on LAD bubble point prediction. Test results here extend the range of data for LOX fluid conditions, and provide insight into factors affecting predicting LAD bubble point pressures

Liquid Acquisition Device Testing with Sub-Cooled Liquid Oxygen

When transferring propellant in space, it is most efficient to transfer single phase liquid from a propellant tank to an engine. In earth s gravity field or under acceleration, propellant transfer is fairly simple. However, in low gravity, withdrawing single-phase fluid becomes a challenge. A variety of propellant management devices (PMD) are used to ensure single-phase flow. One type of PMD, a liquid acquisition device (LAD) takes advantage of capillary flow and surface tension to acquire liquid. Previous experimental test programs conducted at NASA have collected LAD data for a number of cryogenic fluids, including: liquid nitrogen (LN2), liquid oxygen (LOX), liquid hydrogen (LH2), and liquid methane (LCH4). The present work reports on additional testing with sub-cooled LOX as part of NASA s continuing cryogenic LAD development program. Test results extend the range of LOX fluid conditions examined, and provide insight into factors affecting predicting LAD bubble point pressures

Bubble Point Measurements with Liquid Methane of a Screen Capillary Liquid Acquisition Device

Liquid acquisition devices (LADs) can be utilized within a propellant tank in space to deliver single-phase liquid to the engine in low gravity. One type of liquid acquisition device is a screened gallery whereby a fine mesh screen acts as a bubble filter and prevents the gas bubbles from passing through until a crucial pressure differential condition across the screen, called the bubble point, is reached. This paper presents data for LAD bubble point data in liquid methane (LCH4) for stainless steel Dutch twill screens with mesh sizes of 325 by 2300 and 200 by 1400 wires per inch. Data is presented for both saturated and sub-cooled LCH4, and is compared with predicted values

Promoting Policy Advocacy in Nursing via Education

Nurses have a professional, ethical, and social responsibility to advocate for optimal healthcare and an optimal professional environment. However, nurses often default on that responsibility. Leadership at a national nursing organization\u27s state affiliate (SNO) perceived a need to optimize its members\u27 policy advocacy. To meet that need, the Policy Advocacy Toolkit for Nurses (PATN) was developed for this doctoral project. The evidence-based PATN relied on established theories and frameworks, notably Knowles\u27 adult education theory and Kingdon\u27s multiple streams approach; research specific to this project; evidence from other researchers, healthcare organizations, and government websites; and input from a statistician, nursing education experts, and SNO personnel. The PATN\u27s creation had 2 research questions. The first research question asked what SNO members\u27 motivators and barriers to advocacy were. Chi square tests of survey results addressing this issue found significant relationships between advocacy levels and perceived speaking skills (χ2[4, N = 176] = 30.435, p = .000), understanding of SNO\u27s daily advocacy activities (χ2[4, N = 176] = 17.814, p=.001), and understanding of policy creation (χ2[4, N = 176] = 33.830, p = .000). The second research question asked if the PATN\u27s design was significantly improved after incorporating SNO design-stakeholders\u27 input. A paired sample t test revealed no significant difference (p\u3e.05) in the PATN with the stakeholders\u27 input added. Details for evaluating the PATN\u27s sustained effect on political astuteness, as offered in this doctoral project, were provided to the SNO. The PATN, evidence-based and built on the perceived needs of its intended users, should promote positive social change by promoting nurse advocacy

Inverted Outflow Ground Testing of Cryogenic Propellant Liquid Acquisition Devices

NASA is currently developing propulsion system concepts for human exploration. These propulsion concepts will require the vapor free acquisition and delivery of the cryogenic propellants stored in the propulsion tanks during periods of microgravity to the exploration vehicles engines. Propellant management devices (PMD's), such as screen channel capillary liquid acquisition devices (LAD's), vanes and sponges have been used for earth storable propellants in the Space Shuttle Orbiter and other spacecraft propulsion systems, but only very limited propellant management capability currently exists for cryogenic propellants. NASA is developing PMD technology as a part of their cryogenic fluid management (CFM) project. System concept studies have looked at the key factors that dictate the size and shape of PMD devices and established screen channel LADs as an important component of PMD design. Modeling validated by normal gravity experiments is examining the behavior of the flow in the LAD channel assemblies (as opposed to only prior testing of screen samples) at the flow rates representative of actual engine service (similar in size to current launch vehicle upper stage engines). Recently testing of rectangular LAD channels has included inverted outflow in liquid oxygen and liquid hydrogen. This paper will report the results of liquid oxygen testing compare and contrast them with the recently published hydrogen results; and identify the sensitivity of these results to flow rate and tank internal pressure