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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Fluidized bed silicon deposition from silane

A process and apparatus for thermally decomposing silicon containing gas for deposition on fluidized nucleating silicon seed particles is disclosed. Silicon seed particles are produced in a secondary fluidized reactor by thermal decomposition of a silicon containing gas. The thermally produced silicon seed particles are then introduced into a primary fluidized bed reactor to form a fluidized bed. Silicon containing gas is introduced into the primary reactor where it is thermally decomposed and deposited on the fluidized silicon seed particles. Silicon seed particles having the desired amount of thermally decomposed silicon product thereon are removed from the primary fluidized reactor as ultra pure silicon product. An apparatus for carrying out this process is also disclosed.

Hsu, George C.↗
NASA NTRS2003

Numerical Study of Pyrolysis of Biomass in Fluidized Beds

A report presents a numerical-simulation study of pyrolysis of biomass in fluidized-bed reactors, performed by use of the mathematical model described in Model of Fluidized Bed Containing Reacting Solids and Gases (NPO-30163), which appears elsewhere in this issue of NASA Tech Briefs. The purpose of the study was to investigate the effect of various operating conditions on the efficiency of production of condensable tar from biomass. The numerical results indicate that for a fixed particle size, the fluidizing-gas temperature is the foremost parameter that affects the tar yield. For the range of fluidizing-gas temperatures investigated, and under the assumption that the pyrolysis rate exceeds the feed rate, the optimum steady-state tar collection was found to occur at 750 K. In cases in which the assumption was not valid, the optimum temperature for tar collection was found to be only slightly higher. Scaling up of the reactor was found to exert a small negative effect on tar collection at the optimal operating temperature. It is also found that slightly better scaling is obtained by use of shallower fluidized beds with greater fluidization velocities.

Bellan, Josette↗
NASA NTRS1984

Fluidized bed silicon deposition from silane

A process and apparatus for thermally decomposing silicon containing gas for deposition on fluidized nucleating silicon seed particles is disclosed. Silicon seed particles are produced in a secondary fluidized reactor by thermal decomposition of a silicon containing gas. The thermally produced silicon seed particles are then introduced into a primary fluidized bed reactor to form a fludized bed. Silicon containing gas is introduced into the primary reactor where it is thermally decomposed and deposited on the fluidized silicon seed particles. Silicon seed particles having the desired amount of thermally decomposed silicon product thereon are removed from the primary fluidized reactor as ultra pure silicon product. An apparatus for carrying out this process is also disclosed.

Hsu, George↗
NASA NTRS2013

Advanced Magnetic Materials Methods and Numerical Models for Fluidization in Microgravity and Hypogravity

To support long-duration manned missions in space such as a permanent lunar base, Mars transit, or Mars Surface Mission, improved methods for the treatment of solid wastes, particularly methods that recover valuable resources, are needed. The ability to operate under microgravity and hypogravity conditions is essential to meet this objective. The utilization of magnetic forces to manipulate granular magnetic media has provided the means to treat solid wastes under variable gravity conditions by filtration using a consolidated magnetic media bed followed by thermal processing of the solid wastes in a fluidized bed reactor. Non-uniform magnetic fields will produce a magnetic field gradient in a bed of magnetically susceptible media toward the distributor plate of a fluidized bed reactor. A correctly oriented magnetic field gradient will generate a downward direct force on magnetic media that can substitute for gravitational force in microgravity, or which may augment low levels of gravity, such as on the Moon or Mars. This approach is termed Gradient Magnetically Assisted Fluidization (G-MAFB), in which the magnitude of the force on the fluidized media depends upon the intensity of the magnetic field (H), the intensity of the field gradient (dH/dz), and the magnetic susceptibility of the media. Fluidized beds based on the G-MAFB process can operate in any gravitational environment by tuning the magnetic field appropriately. Magnetic materials and methods have been developed that enable G-MAFB operation under variable gravity conditions.

Atwater, James↗
NASA NTRS1975

Fluidized bed regenerators for Brayton cycles

A recuperator consisting of two fluidized bed regenerators with circulating solid particles is considered for use in a Brayton cycle. These fluidized beds offer the possibility of high temperature operation if ceramic particles are used. Calculations of the efficiency and size of fluidized bed regenerators for typical values of operating parameters were made and compared to a shell and tube recuperator. The calculations indicate that the fluidized beds will be more compact than the shell and tube as well as offering a high temperature operating capability.

Nichols, L. D.↗
NASA NTRS1975

Fluidized bed regenerators for Brayton cycles

A recuperator consisting of two fluidized bed regenerators with circulating solid particles is considered for use in a Brayton cycle. These fluidized beds offer the possibility of high temperature operation if ceramic particles are used. Calculations of the efficiency and size of fluidized bed regenerators for typical values of operating parameters have been made and compared to a shell and tube recuperator. The calculations indicate that the fluidized beds will be more compact than the shell and tube as well as offering a high temperature operating capability.

Nichols, L. D.↗
NASA NTRS1979

Acoustic fluidization - A new geologic process

A number of geologic processes, particularly seismic faulting, impact crater slumping, and long runout landslides, require the failure of geologic materials under differential stresses much smaller than expected on the basis of conventional rock mechanics. This paper proposes that the low strengths apparent in these phenomena are due to a state of 'acoustic fluidization' induced by a transient strong acoustic wave field. The strain rates possible in such a field are evaluated, and it is shown that acoustically fluidized debris behaves as a newtonian fluid with a viscosity in the range 100,000 to 10,000,000 P for plausible conditions. Energy gains and losses in the acoustic field are discussed, and the mechanism is shown to be effective if internal dissipation in the field gives a Q approximately greater than 100. Whether such values for Q are realized is not known at present. However, acoustic fluidization provides a qualitatively correct description of the failure of rock debris under low differential stresses in the processes of faulting, crater slumping, and long runout landslides. Acoustic fluidization thus deserves serious consideration as a possible explanation of these phenomena.

Melosh, H. J.↗
NASA NTRS1986

Agglomeration-Free Distributor for Fluidized Beds

New gas distributor for fluidized beds prevents hot particles from reacting on it and forming hard crust. In reduction of iron ore in fluidized bed, ore particles do not sinter on distributor and perhaps clog it or otherwise interfere with gas flow. Distributor also relatively cool. In fluidized-bed production of silicon, inflowing silane does not decompose until within bed of hot silicon particles and deposits on them. Plates of spiral distributor arranged to direct incoming gas into spiral flow. Turbulence in flow reduces frequency of contact between fluidized-bed particles and distributor.

Ouyang, F.↗
NASA NTRS1981

Fluidized bed heating process and apparatus

Capacitive electrical heating of a fluidized bed enables the individual solid particles within the bed to constitute the hottest portion thereof. This effect is achieved by applying an A. C. voltage potential between dielectric coated electrodes, one of which is advantageously the wall of the fluidized bed rejection zone, sufficient to create electrical currents in said particles so as to dissipate heat therein. In the decomposition of silane or halosilanes in a fluidized bed reaction zone, such heating enhances the desired deposition of silicon product on the surface of the seed particles within the fluidized bed and minimizes undesired coating of silicon on the wall of the reaction zone and the homogeneous formation of fine silicon powder within said zone.

McHale, Edward J.↗
NASA NTRS2010

Extracting Oxygen from Lunar Simulant Using a Transparent Furnace Pulsed Fluidized Bed

In the event that humans return to the moon, utilizing the local materials will be beneficial for extended stays. Rather than transporting resources, such as oxygen, from Earth, NASA is investigating methods of extracting it from lunar regolith. One promising process is hydrogen reduction. In the hydrogen reduction process, lunar regolith is heated to 1000 C in the presence of hydrogen. The iron oxide (Fe-O) bonds, found in lunar material, are broken and the hydrogen attracts the oxygen to produce water vapor [Allen et al., 1996]. FeO + H2 (right arrow) Fe +H2O. The water vapor is then captured, cleaned, and electrolyzed. The hydrogen is recycled back to the reduction process and the oxygen is stored until consumed by an end user (propulsion, life support, etc.). To obtain a good oxygen yield, the majority of lunar regolith must be exposed to the hydrogen gas and have a high rate of heat transfer from heat source to particle. This is achieved with good solids mixing via fluidization or mechanical agitation. In Generation II of the ROxygen program, the ROxygen Team at Johnson Space Center (JSC) investigated the feasibility of gas only pulsed fluidization as the only means to mix synthetic lunar regolith (simulant) at high temperatures. Fluidized beds have been used in industry to effectively process powders for decades. They consist of gas flowing upward through a bed of particles. The stirring action continuously moves the grains around to achieve uniform mixing of gas, solids, and heat [Geldart, 1986]. A transparent furnace unit was developed by Thoughventions Unlimited LLC (TvU) to aid in the qualitative observation of the fluidization behavior at high temperatures. Multipoint thermocouples and pressure sensors provided quantitative information regarding the quality of mixing. The water produced was measured using humidity sensors and captured using a NASA designed and built condenser. Once the simulant was processed, pneumatically transporting the 'hot' simulant out of the furnace was investigated.

Oryshchyn, L.↗
NASA NTRS2003

Model of Fluidized Bed Containing Reacting Solids and Gases

A mathematical model has been developed for describing the thermofluid dynamics of a dense, chemically reacting mixture of solid particles and gases. As used here, "dense" signifies having a large volume fraction of particles, as for example in a bubbling fluidized bed. The model is intended especially for application to fluidized beds that contain mixtures of carrier gases, biomass undergoing pyrolysis, and sand. So far, the design of fluidized beds and other gas/solid industrial processing equipment has been based on empirical correlations derived from laboratory- and pilot-scale units. The present mathematical model is a product of continuing efforts to develop a computational capability for optimizing the designs of fluidized beds and related equipment on the basis of first principles. Such a capability could eliminate the need for expensive, time-consuming predesign testing.

Bellan, Josette↗
NASA NTRS1968

Characteristics of fluidized-packed beds

Study of fluidized-packed bed includes investigation of heat transfer, solids-gas mixing, and elutriation characteristics. A fluidized-packed bed is a system involving the fluidization of small particles in the voids of a packed bed of larger nonfluidized particles.

Gabor, J. D.↗
NASA NTRS1971

Rotating Fluidized Bed Reactor for Space Nuclear Propulsion: Design Studies and Experimental Results - Annual Report

The rotating fluidized bed reactor concept is being investigated for possible application in nuclear propulsion systems. Physics calculations show U-233 to be superior to U-235 as a fuel for a cavity reactor of this type. Preliminary estimates of the effect of hydrogen in the reactor, reflector material, and power peaking are given. A preliminary engineering analysis was made for U-235 and U-233 fueled systems. An evaluation of the parameters affecting the design of the system is given, along with the thrust-to-weight ratios. The experimental equipment is described, as are the special photographic techniques and procedures. Characteristics of the fluidized bed and experimental results are given, including photographic evidence of bed fluidization at high rotational velocities.

Source record↗
NASA NTRS1973

Parameters critical to the morphology of fluidization craters

In order to study further the role of fluidization on the moon, a laboratory investigation was undertaken on two particulate material size fractions to determine the effect of variables, such as, duration of gas streaming, gas pressure, and 'regolith' thickness on the morphology of fluidization craters. A 3.175-mm cylindrical vent was used to simulate a gas streaming conduit. Details of the fluidization chamber are discussed together with questions of experimental control, aspects of nomenclature, crater measurements, and the effect of variables.

Siegal, B. S.↗
NASA NTRS1978

Fluidized combustion of coal

A combustion technology that permits the burning of low quality coal, and other fuels, while maintaining stack emissions within State and Federal EPA limits is discussed. Low quality fuels can be burned directly in fluidized beds while taking advantage of low furnace temperatures and chemical activity within the bed to limit SO2 and NOx emissions. The excellent heat transfer characteristics of the fluidized beds also result in a reduction of total heat transfer surface requirements. Tests on beds operating at pressures of one to ten atmospheres, at temperatures as high as 1600 F, and with gas velocities in the vicinity of four to twelve feet per second, have proven the concept. The progress that has been made in the development of fluidized bed combustion technology and work currently underway are discussed.

Pope, M.↗
NASA NTRS1980

The preparation of calcium superoxide in a flowing gas stream and fluidized bed

Superoxides can be used as sources of chemically stored oxygen in emergency breathing apparatus. The work reported here describes the use of a low-pressure nitrogen gas sweep through the reactant bed, for temperature control and water vapor removal. For a given set of gas temperature, bed thickness, and reaction time values, the highest purity calcium superoxide, Ca(O2)2, was obtained at the highest space velocity of the nitrogen gas sweep. The purity of the product was further increased by flow conditions that resulted in the fluidization of the reactant bed. However, scale-up of the low-pressure fluidized bed process was limited to the formation of agglomerates of reactant particles, which hindered thermal control by the flowing gas stream. A radiofrequency flow discharge inside the reaction chamber prevented agglomeration, presumably by dissipation of the static charges on the fluidized particles.

Wood, P. C.↗
NASA NTRS1981

Solar heated fluidized bed gasification system

A solar-powered fluidized bed gasification system for gasifying carbonaceous material is presented. The system includes a solar gasifier which is heated by fluidizing gas and steam. Energy to heat the gas and steam is supplied by a high heat capacity refractory honeycomb which surrounds the fluid bed reactor zone. The high heat capacity refractory honeycomb is heated by solar energy focused on the honeycomb by solar concentrator through solar window. The fluid bed reaction zone is also heated directly and uniformly by thermal contact of the high heat capacity ceramic honeycomb with the walls of the fluidized bed reactor. Provisions are also made for recovering and recycling catalysts used in the gasification process. Back-up furnace is provided for start-up procedures and for supplying heat to the fluid bed reaction zone when adequate supplies of solar energy are not available.

Qader, S. A.↗
NASA NTRS1985

Design and evaluation of fluidized bed heat recovery for diesel engine systems

The potential of utilizing fluidized bed heat exchangers in place of conventional counter-flow heat exchangers for heat recovery from adiabatic diesel engine exhaust gas streams was studied. Fluidized bed heat recovery systems were evaluated in three different heavy duty transport applications: (1) heavy duty diesel truck; (2) diesel locomotives; and (3) diesel marine pushboat. The three applications are characterized by differences in overall power output and annual utilization. For each application, the exhaust gas source is a turbocharged-adiabatic diesel core. Representative subposed exhaust gas heat utilization power cycles were selected for conceptual design efforts including design layouts and performance estimates for the fluidized bed heat recovery heat exchangers. The selected power cycles were: organic rankine with RC-1 working fluid, turbocompound power turbine with steam injection, and stirling engine. Fuel economy improvement predictions are used in conjunction with capital cost estimates and fuel price data to determine payback times for the various cases.

Hamm, J. R.↗