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Results for “P-W”

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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8 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

The period-pulse-width distribution of pulsars and their division into three classes

The period-pulse-width (P-W) distribution of sample of 41 pulsars has been reanalyzed under two versions of a model where radiation is beamed from magnetic polar caps which are isotropically oriented with respect to the rotation axis of the neutron stars (IOPC models). It is found that neither IOPC model can explain the P-W distribution of the entire sample. Pulsars with simple unimodal (U) or complicated multimodal (M) pulse shapes show significantly different P-W distributions. Class M pulsars have a narrower P-W distribution than do class U pulsars and, taken separately, are compatible with either IOPC model. Class U pulsars divide into two subgroups, those with relatively narrower pulses (UN) and those with relatively wider pulses (UW), each of which is compatible with either IOPC model. One interpretation of these results is that the pulsars in classes UN, M, and UW have different intrinsic beam sizes, roughly in the ratios 1:2:4, respectively. The possible origins of the three classes are discussed in terms of the force-balance magnetosphere model (Roberts et al., 1972, 1973), where the differences may be attributed to different-mass neutron stars and the structure of the polar caps. An alternative interpretation is that the angle between the rotation and emission axes is not isotropically distributed, but can take only certain preferred values.

Roberts, D. H.↗
DOE OSTI2025

Thermal Analysis of a Solid Particle Light-Trapping Planar Cavity Receiver Using Computational Fluid Dynamics

Concentrated solar power (CSP) is one of the most effective ways of harnessing solar power to create efficient, durable, and resilient energy systems. This study entails thermal modeling and analysis of a novel central tower receiver configuration. This receiver uses solid particles as the heat transfer fluid (HTF), a promising option for third-generation CSP systems. The configuration considered here is the light-trapping planar cavity receiver (LTPCR) introduced by the National Renewable Energy Laboratory. While heat transfer studies of various LTPCR subsystems have been done, system-level thermal analysis of the LTPCR receiver has not been attempted. This study also presents important sensitivity analyses of the operating parameters of the CSP system, which can help guide the design of future central tower receivers. This study employs Ansys Fluent as a computational fluid dynamics (CFD) tool to model fluid dynamics and heat transfer in the receiver, intending to quantify its thermal performance. The model seamlessly integrates Monte Carlo ray tracing data, which generates absorbed solar flux profiles from the heliostat field design, with the heat transfer characteristics of the fluidized particle bed. This unified model is designed to accurately predict the thermal behavior of the LTPCR. Analysis of preliminary results reveals that the primary loss mechanisms are radiative and natural convective losses, in that order. Based on observations from a baseline case, several strategies are suggested and numerically tested. These solutions include selective cooling of high-temperature regions and manipulation of particle bed parameters. Selective cooling of high-temperature regions reduced the peak temperature by 151 degrees C and decreased thermal losses by 0.9%. Improving the particle-wall heat transfer coefficient (P-W HTC) of the particle bed decreased the thermal losses by 1.7% and decreased the peak temperatures by 57 degrees C. Decreasing the particle inlet temperature (PIT) also reduced thermal losses by 3.5% and decreased peak temperatures by 29 degrees C. Compounding these strategies improved the thermal losses of the receiver from 13.5% in the baseline case to 7.5%. Additionally, the study explores the variation in thermal performance across different locations of the receiver, where a variation of thermal losses from 12.9% to 17.3% is found. This allows a comprehensive evaluation of potential improvements in efficiency and temperature management.

computational fluid dynamics↗
DOE OSTI2020

Materials Data on P2W by Materials Project

WP2 crystallizes in the orthorhombic Cmc2_1 space group. The structure is three-dimensional. W6+ is bonded to seven P3- atoms to form a mixture of distorted corner, edge, and face-sharing WP7 pentagonal bipyramids. There are five shorter (2.50 Å) and two longer (2.51 Å) W–P bond lengths. There are two inequivalent P3- sites. In the first P3- site, P3- is bonded in a 5-coordinate geometry to four equivalent W6+ and one P3- atom. The P–P bond length is 2.17 Å. In the second P3- site, P3- is bonded in a distorted rectangular see-saw-like geometry to three equivalent W6+ and one P3- atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on P2W by Materials Project

WP2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. W6+ is bonded in a 8-coordinate geometry to eight P3- atoms. There are a spread of W–P bond distances ranging from 2.48–2.65 Å. There are two inequivalent P3- sites. In the first P3- site, P3- is bonded in a 4-coordinate geometry to three equivalent W6+ and three equivalent P3- atoms. There are one shorter (2.20 Å) and two longer (2.65 Å) P–P bond lengths. In the second P3- site, P3- is bonded in a 5-coordinate geometry to five equivalent W6+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PW by Materials Project

WP is Modderite structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. W3+ is bonded to six equivalent P3- atoms to form a mixture of distorted edge, corner, and face-sharing WP6 pentagonal pyramids. There are a spread of W–P bond distances ranging from 2.48–2.56 Å. P3- is bonded in a 6-coordinate geometry to six equivalent W3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PW3 by Materials Project

W3P crystallizes in the tetragonal I-42m space group. The structure is three-dimensional. there are three inequivalent W sites. In the first W site, W is bonded in a 2-coordinate geometry to two equivalent P atoms. Both W–P bond lengths are 2.53 Å. In the second W site, W is bonded in a distorted bent 120 degrees geometry to two equivalent P atoms. Both W–P bond lengths are 2.44 Å. In the third W site, W is bonded in a 4-coordinate geometry to four equivalent P atoms. All W–P bond lengths are 2.51 Å. P is bonded in a 8-coordinate geometry to eight W atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on P3W by Materials Project

WP3 is alpha bismuth trifluoride structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. W6+ is bonded in a distorted body-centered cubic geometry to fourteen P2- atoms. There are eight shorter (2.63 Å) and six longer (3.03 Å) W–P bond lengths. There are two inequivalent P2- sites. In the first P2- site, P2- is bonded in a body-centered cubic geometry to four equivalent W6+ and four equivalent P2- atoms. All P–P bond lengths are 2.63 Å. In the second P2- site, P2- is bonded in a 8-coordinate geometry to six equivalent W6+ and eight equivalent P2- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on PW3 by Materials Project

W3P crystallizes in the tetragonal I-4 space group. The structure is three-dimensional. there are three inequivalent W sites. In the first W site, W is bonded in a 2-coordinate geometry to two equivalent P atoms. There are one shorter (2.53 Å) and one longer (2.54 Å) W–P bond lengths. In the second W site, W is bonded in a 4-coordinate geometry to four equivalent P atoms. There are a spread of W–P bond distances ranging from 2.50–2.53 Å. In the third W site, W is bonded in a distorted bent 120 degrees geometry to two equivalent P atoms. There are one shorter (2.44 Å) and one longer (2.46 Å) W–P bond lengths. P is bonded in a 8-coordinate geometry to eight W atoms.

36 MATERIALS SCIENCE↗