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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Development of a prototype regeneration carbon dioxide absorber

A prototype regenerable carbon dioxide absorber was developed to maintain the environmental quality of the portable life support system. The absorber works on the alkali metal carbonate-bicarbonate solid-gas reaction to remove carbon dioxide from the atmosphere. The prototype sorber module was designed, fabricated, and tested at simulated extravehicular activity conditions to arrive at optimum design. The unit maintains sorber outlet concentration below 5 mm Hg. An optimization study was made with respect to heat transfer, temperature control, sorbent utilization, sorber life and regenerability, and final size of the module. Important parameters influencing the capacity of the final absorber unit were identified and recommendations for improvement were made.

Patel, P. S.↗
NASA NTRS2004

Experimental and Analytical Investigation of Pressure Differentials for Clean and Loaded Wire Meshes Used in Zeolite Retention

Following failure of the carbon dioxide removal assembly (CDRA) on the ISS, a CDRA teardown, test, and evaluation (TT&E) effort found that the sorbent material was not retained as intended by the packed beds and that presence of the sorbent in the check valve and selector valve was the cause of the failure of these components. This paper documents the development of design data for an in-line filter element. The purpose of the in-line filter is to provide temporary protection for on-orbit CDRA hardware until the bed retainment system can be redesigned and replaced.

Knox, James C.↗
NASA NTRS2009

Investigating Liquid CO2 as a Coolant for a MTSA Heat Exchanger Design

Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is being developed for thermal and carbon dioxide (CO 2) control for a future Portable Life Support System (PLSS), as well as water recycling. CO 2 removal and rejection is accomplished by driving a sorbent through a temperature swing of approximately 210 K to 280 K . The sorbent is cooled to these sub-freezing temperatures by a Sublimating Heat Exchanger (SHX) with liquid coolant expanded to sublimation temperatures. Water is the baseline coolant available on the moon, and if used, provides a competitive solution to the current baseline PLSS schematic. Liquid CO2 (LCO2) is another non-cryogenic coolant readily available from Martian resources which can be produced and stored using relatively low power and minimal infrastructure. LCO 2 expands from high pressure liquid (~5800 kPa) to Mars ambient (0.8 kPa) to produce a gas / solid mixture at temperatures as low as 156 K. Analysis and experimental work are presented to investigate factors that drive the design of a heat exchanger to effectively use this sink. Emphasis is given to enabling efficient use of the CO 2 cooling potential and mitigation of heat exchanger clogging due to solid formation. Minimizing mass and size as well as coolant delivery are also considered. The analysis and experimental work is specifically performed in an MTSA-like application to enable higher fidelity modeling for future optimization of a SHX design. In doing so, the work also demonstrates principles and concepts so that the design can be further optimized later in integrated applications (including Lunar application where water might be a choice of coolant).

Paul, Heather L.↗
NASA NTRS2016

Visible-Light-Responsive Photocatalysis: Ag-Doped TiO2 Catalyst Development and Reactor Design Testing

In recent years, the alteration of titanium dioxide to become visible-light-responsive (VLR) has been a major focus in the field of photocatalysis. Currently, bare titanium dioxide requires ultraviolet light for activation due to its band gap energy of 3.2 eV. Hg-vapor fluorescent light sources are used in photocatalytic oxidation (PCO) reactors to provide adequate levels of ultraviolet light for catalyst activation; these mercury-containing lamps, however, hinder the use of this PCO technology in a spaceflight environment due to concerns over crew Hg exposure. VLR-TiO2 would allow for use of ambient visible solar radiation or highly efficient visible wavelength LEDs, both of which would make PCO approaches more efficient, flexible, economical, and safe. Over the past three years, Kennedy Space Center has developed a VLR Ag-doped TiO2 catalyst with a band gap of 2.72 eV and promising photocatalytic activity. Catalyst immobilization techniques, including incorporation of the catalyst into a sorbent material, were examined. Extensive modeling of a reactor test bed mimicking air duct work with throughput similar to that seen on the International Space Station was completed to determine optimal reactor design. A bench-scale reactor with the novel catalyst and high-efficiency blue LEDs was challenged with several common volatile organic compounds (VOCs) found in ISS cabin air to evaluate the system's ability to perform high-throughput trace contaminant removal. The ultimate goal for this testing was to determine if the unit would be useful in pre-heat exchanger operations to lessen condensed VOCs in recovered water thus lowering the burden of VOC removal for water purification systems.

Photocatalysis↗
NASA NTRS1982

Lewis Pressurized, Fluidized-Bed Combustion Program. Data and Calculated Results

A 200 kilowatt (thermal), pressurized, fluidized bed (PFB) reactor and research test facility were designed, constructed, and operated. The facility was established to assess and evaluate the effect of PFB hot gas effluent on aircraft turbine engine materials that may have applications in stationary powerplant turbogenerators. The facility was intended for research and development work and was designed to operate over a wide range of conditions. These conditions included the type and rate of consumption of fuel (e.g., coal) and sulfur reacting sorbent material: the ratio of feed fuel to sorbent material; the ratio of feed fuel to combustion airflow; the depth of the fluidized reaction bed; the temperature and pressure in the reaction bed; and the type of test unit that was exposed to the combustion exhaust gases.

Rollbuhler, R. J.↗
NASA NTRS2017

Virtual Design of a 4-Bed Molecular Sieve for Exploration

Simulations of six new 4-Bed Molecular Sieve configurations have been performed using a COMSOL model. The preliminary results show that reductions in desiccant bed size and sorbent bed size when compared to the International Space Station configuration are feasible while still yielding a process that handles at least 4.0 kg/day CO2. The results also show that changes to the CO2 sorbent are likewise feasible. Decreasing the bed sizes was found to have very little negative effect on the adsorption process; breakthrough of CO2 in the sorbent bed was observed for two of the configurations, but water breakthrough in the desiccant beds was not observed. Nevertheless, both configurations for which CO2 breakthrough was observed still yield relatively high CO2 efficiency, and future investigations will focus on bed size in order to find the optimum configuration.

Giesy, Timothy J.↗
NASA NTRS1989

Development of an adsorption compressor for use in cryogenic refrigeration

A new compressor with no moving parts has been developed which is able to supply a source of high-pressure gas to a Joule-Thompson based cryogenic refrigerator. The compressor relies on a newly implemented combination of high-surface-area Saran carbon (sorbent) and krypton gas (working fluid). In addition, an integral gas-gap heat switch is used to provide improved overall efficiency. A prototype compressor has been designed, built, and tested as a part of the Jet Propulsion Laboratory effort in sorption refrigeration. Performance data from the prototype unit described here demonstrate successful compressor performance and good agreement with theoretical predictions.

Schember, Helen R.↗
NASA NTRS2017

Virtual Design of a 4-Bed Molecular Sieve for Exploration

Simulations of six new 4-Bed Molecular Sieve configurations have been performed using a COMSOL (COMSOL Multiphysics - commercial software) model. The preliminary results show that reductions in desiccant bed size and sorbent bed size when compared to the International Space Station configuration are feasible while still yielding a process that handles at least 4.0 kilograms a day CO2. The results also show that changes to the CO2 sorbent are likewise feasible. Decreasing the bed sizes was found to have very little negative effect on the adsorption process; breakthrough of CO2 in the sorbent bed was observed for two of the configurations, but a small degree of CO2 breakthrough is acceptable, and water breakthrough in the desiccant beds was not observed. Both configurations for which CO2 breakthrough was observed still yield relatively high CO2 efficiency, and future investigations will focus on bed size in order to find the optimum configuration.

Giesy, Timothy J.↗
NASA NTRS2006

Wire-Mesh-Based Sorber for Removing Contaminants from Air

A paper discusses an experimental regenerable sorber for removing CO2 and trace components principally, volatile organic compounds, halocarbons, and NH3 from spacecraft cabin air. This regenerable sorber is a prototype of what is intended to be a lightweight alternative to activated-carbon and zeolite-pellet sorbent beds now in use. The regenerable sorber consists mainly of an assembly of commercially available meshes that have been coated with a specially-formulated washcoat containing zeolites. The zeolites act as the sorbents while the meshes support the zeolite-containing washcoat in a configuration that affords highly effective surface area for exposing the sorbents to flowing air. The meshes also define flow paths characterized by short channel lengths to prevent excessive buildup of flow boundary layers. Flow boundary layer resistance is undesired because it can impede mass and heat transfer. The total weight and volume comparison versus the atmosphere revitalization equipment used onboard the International Space Station for CO2 and trace-component removal will depend upon the design details of the final embodiment. However, the integrated mesh-based CO2 and trace-contaminant removal system is expected to provide overall weight and volume savings by eliminating most of the trace-contaminant control equipment presently used in parallel processing schemes traditionally used for spacecraft. The mesh-based sorbent media enables integrating the two processes within a compact package. For the purpose of regeneration, the sorber can be heated by passing electric currents through the metallic meshes combined with exposure to space vacuum. The minimal thermal mass of the meshes offers the potential for reduced regeneration-power requirements and cycle time required for regeneration compared to regenerable sorption processes now in use.

Perry, Jay↗
NASA NTRS2005

Resistively-Heated Microlith-based Adsorber for Carbon Dioxide and Trace Contaminant Removal

An integrated sorber-based Trace Contaminant Control System (TCCS) and Carbon Dioxide Removal Assembly (CDRA) prototype was designed, fabricated and tested. It corresponds to a 7-person load. Performance over several adsorption/regeneration cycles was examined. Vacuum regenerations at effective time/temperature conditions, and estimated power requirements were experimentally verified for the combined CO2/trace contaminant removal prototype. The current paper details the design and performance of this prototype during initial testing at CO2 and trace contaminant concentrations in the existing CDRA, downstream of the drier. Additional long-term performance characterization is planned at NASA. Potential system design options permitting associated weight, volume savings and logistic benefits, especially as relevant for long-duration space flight, are reviewed. The technology consisted of a sorption bed with sorbent- coated metal meshes, trademarked and patented as Microlith by Precision Combustion, Inc. (PCI). By contrast the current CO2 removal system on the International Space Station employs pellet beds. Preliminary bench scale performance data (without direct resistive heating) for simultaneous CO2 and trace contaminant removal was reviewed in SAE 2004-01-2442. In the prototype, the meshes were directly electrically heated for rapid response and accurate temperature control. This allowed regeneration via resistive heating with the potential for shorter regeneration times, reduced power requirement, and net energy savings vs. conventional systems. A novel flow arrangement, for removing both CO2 and trace contaminants within the same bed, was demonstrated. Thus, the need for a separate trace contaminant unit was eliminated resulting in an opportunity for significant weight savings. Unlike the current disposable charcoal bed, zeolites for trace contaminant removal are amenable to periodic regeneration.

Roychoudhury, S.↗
NASA NTRS2018

Efficacy of FTIR Analysis in Determining CO2 Loading on Diglycolamine

In support of advanced air revitalization technologies to enable human spaceflight beyond low earth orbit, performance studies have been conducted using a liquid amine, Diglycolamine (DGA) between teams at NASA's Johnson Spaceflight Center (JSC) and Ames Research Center (ARC). Liquid amines have been used in regenerable earth-based systems to remove CO2 from industrial systems as well as for closed-environment air revitalization because they can be regenerated at lower temperatures than solid sorbent systems. As an additional advantage to solid sorbent-based systems, liquid sorbents can be cycled between an adsorbing contactor and degassing chamber, thereby reducing system complexity by operation in a continuous loop. In an effort to inform a regeneration system design for micro-gravity applications, ARC has performed a number of tests to characterize the degas mechanics of DGA. In order to accurately measure the amount of CO2 captured or released by the amine, methods such as gravimetric weighing and chemical desorption are reasonable, however the first iteration test setup for a scaled down degas system required analysis on small sample sizes. Fourier-transform infrared spectroscopy (FTIR) analysis was experimentally evaluated to analyze CO2 concentration because it can produce measurements with sample sizes on the order of 100's of μL. Calibration against chemical desorption showed relatively good correlation and test data showed reasonable adherence to expected trends, however more extensive testing should be conducted to fully validate the usage of FTIR to determine CO2 loading on DGA.

Diglycolamine↗
NASA NTRS2018

Efficacy of FTIR Analysis in Determining CO2 Loading on Diglycolamine

In support of advanced air revitalization technologies to enable human spaceflight beyond low earth orbit, performance studies have been conducted using a liquid amine, Diglycolamine (DGA) between teams at NASA?s Johnson Spaceflight Center (JSC) and Ames Research Center (ARC). Liquid amines have been used in regenerable earth-based systems to remove CO2 from industrial systems as well as for closed-environment air revitalization because they can be regenerated at lower temperatures than solid sorbent systems. As an additional advantage to solid sorbent based systems, liquid sorbents can be cycled between an adsorbing contactor and degassing chamber, thereby reducing system complexity by operation in a continuous loop. In an effort to inform a regeneration system design for micro-gravity applications, ARC has performed a number of tests to characterize the degas mechanics of DGA. In order to accurately measure the amount of CO2 captured or released by the amine, methods such as gravimetric weighing and chemical decomposition are reasonable, however the initial design for a scaled down degas system required analysis on small sample sizes. In order to accomplish CO2 loading measurements with a sample size of approximately 500µL, Fourier-transform infrared spectroscopy (FTIR) was used. Calibration against acid decomposition showed relatively good correlation and test data showed reasonable adherence to expected trends, however more extensive testing should be conducted to fully validate the usage of FTIR to determine CO2 loading on DGA.

Diglycolamine↗
NASA NTRSDate not supplied

Diglycolamine Material Compatibility through Mechanical Testing

One promising candidate for use as a liquid sorbent in air revitalization technologies is a mixture of diglycolamine and water. This solution can react heavily with certain materials, putting a constraint on what materials can be used when designing and operating a liquid amine air revitalization system. Initial testing on materials has been done in the Air Revitalization labs at NASA Ames Research Center (ARC) through dunk testing of materials and physically checking for swelling, cracking, or any sort of corrosion of the material at hand. While this approach allowed for a quick way of material testing, a more thorough approach is favorable to allow for a database of compatible materials and their properties after contact with the solution for extended periods of time to be compiled. With this database, an air revitalization system intended for long-duration space flight can be designed and operated with confidence that the materials chosen will not degrade and need to be replaced over time.

Tiago Faria Costa↗
NASA NTRS2009

Transient Modeling and Analysis of a Metabolic Heat-Regenerated Temperature Swing Adsorption (MTSA) System for a PLSS

A Metabolic heat-regenerated Temperature Swing Adsorption (MTSA) system is being developed for carbon dioxide, water and thermal control in a lunar and martian portable life support system (PLSS). A previous system analysis was performed to evaluate the impact of MTSA on PLSS design. That effort was Mars specific and assumed liquid carbon dioxide (LCO2) coolant made from martian resources. Transient effects were not considered but rather average conditions were used throughout the analysis. This effort takes into further consideration the transient effects inherent in the cycling MTSA system as well as assesses the use of water as coolant. Standard heat transfer, thermodynamic, and heat exchanger methods are presented to conduct the analysis. Assumptions and model verification are discussed. The tool was used to perform various system studies. Coolant selection was explored and takes into account different operational scenarios as the minimum bed temperature is driven by the sublimation temperature of the coolant (water being significantly higher than LCO2). From this, coolant mass is sized coupled with sorbent bed mass because MTSA adsorption performance decreases with increasing sublimation temperature. Reduction in heat exchanger performance and even removal of certain heat exchangers, like a recuperative one between the two sorbent beds, is also investigated. Finally, the coolant flow rate is varied over the cycle to determine if there is a more optimal means of cooling the bed from a mass perspective. Results of these studies and subsequent recommendations for system design are presented.

Iacomini, Christie↗
NASA NTRS2012

Performance of a Water Recirculation Loop Maintenance Device and Process for the Advanced Spacesuit Water Membrane Evaporator

A water loop maintenance device and process to maintain the water quality of the Advanced Spacesuit Water Membrane Evaporation (SWME) water recirculation loop has been undergoing a performance evaluation. The SWME is a heat rejection device under development at the NASA Johnson Space Center to perform thermal control for advanced spacesuits. One advantage to this technology is the potential for a significantly greater degree of tolerance to contamination when compared to the existing Sublimator technology. The driver for the water recirculation maintenance device and process is to further enhance this advantage through the leveraging of fluid loop management lessons-learned from the International Space Station (ISS). A bed design that was developed for a Hamilton Sundstrand military application, and considered for a potential ISS application with the Urine Processor Assembly, provides a low pressure drop means for water maintenance in a recirculation loop. The bed design is coupled with high capacity ion exchange resins, organic adsorbents, and a cyclic methodology developed for the Extravehicular Mobility Unit (EMU) Transport Water loop. The maintenance process further leverages a sorbent developed for ISS that introduces a biocide in a microgravity-compatible manner for the Internal Active Thermal Control System (IATCS). The leveraging of these water maintenance technologies to the SWME recirculation loop is a unique demonstration of applying the valuable lessons learned on the ISS to the next generation of manned spaceflight Environmental Control and Life Support System (ECLSS) hardware. This

Rector, Tony↗
NASA NTRSDate not supplied

Design for an Integrated Open-Loop System for Carbon Dioxide Removal using Liquid Amine

Manned Space missions require maintaining a safe environment for the crew that can both sustain a breathable atmosphere and remove pollutants. Carbon dioxide, while not toxic in low concentrations, accumulates as crew members work and breath and can eventually affect the crew’s health. Therefore, a constant, passive system to remove the carbon dioxide build up is necessary for long-term missions. Currently, the prevailing liquid sorbent used in submarines and industrial flue gas utilizes the primary amine, monoethanolamine (MEA), to capture, transfer, and remove carbon dioxide from air. Diglycolamine (DGA) is an alternate primary amine that has similar performance and less volatility. It is currently being studied at Ames Research Center (ARC) and is the primary candidate for the operation of the sub-scale liquid amine test stand. The test stand is used to investigate liquid flow and liquid gas interfaces to assist in a system design for microgravity applications. The test stand includes a wedge design utilizes capillary action to hold the liquid while allowing gas-liquid interaction for carbon dioxide transfer. These wedge trays are placed in a contactor unit to remove carbon dioxide from the air stream, a degasser unit to replenish the liquid amine, and a capillary condensing heat exchanger (CCHX) to recapture water lost in the degasser unit. Nominal operating conditions for the contactor are a gas flow rate of 26scfm enriched with pure CO2 to 2600ppm and a liquid mixture of 65/35 vol% DGA/H2O at 0.65mL/min while the degasser was operated at 100°C and 1 atm. This paper discusses the challenges and limitations of a fully integrated system which will influence the design of a new subscale test stand.

Adrian Cortez↗
NASA NTRS1985

Space station trace contaminant control

Different systems for the control of space station trace contaminants are outlined. The issues discussed include: spacecabin contaminant sources, technology base, contaminant control system elements and configuration, approach to contaminant control, contaminant load model definition, spacecraft maximum allowable concentrations, charcoal bed sizing and performance characteristics, catalytic oxidizer sizing and performance characteristics, special sorbent bed sizing, animal and plant research payload problems, and emergency upset contaminant removal. It is concluded that the trace contaminant control technology base is firm, the necessary hardware tools are available, and the previous design philosophy is still applicable. Some concerns are the need as opposed to danger of the catalytic oxidizer, contaminants with very low allowable concentrations, and the impact of relaxing materials requirements.

Olcutt, T.↗