Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Utilization”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Utility of Atmospheric Transport Runs Done Backwards in Time for Source Term Estimation

In a general sense, the equations describing transport of an atmospheric contaminant are reversible in time. However, the time reversibility is not perfect. For a source term estimation problem, one atmospheric transport model (ATM) run done backwards in time to represent the influence of a single sample value can yield as much information as hundreds or thousands of forwards ATM runs. Thus, backwards ATM are often used to limit the computational burden of an analysis. A large number of paired ATM runs at 14 release locations were used to explore the agreement between dilution factors for the forward and backwards time directions. Four of the release locations have correlation coefficients between forward and backwards dilution factors greater than 0.9. None of the four have large elevation changes within 100 km of the release location. The two release locations with the lowest correlation coefficients are in mountainous terrain with large elevation differences. Elevation changes have a greater negative influence on the correlations than distance to the sampler or plume transit times. The locations of the releases were estimated using dilution factors from backwards ATM runs. Many of the location estimates are close to the release point, vindicating the general approach of using ATM runs backwards in time. Aggregated over the 14 release points, 26% of the location estimates were within 10 km of the release point, 61% were within 25 km, 80% were within 50 km, and 87% were within 75 km. Most of the remaining 13% (poor matches) occur for two release locations in mountainous terrain. Good time-reversibility cannot be guaranteed for a new analysis, so we recommend that any source term solution using backwards ATM runs should include comparisons based on forward ATM runs. As an example, calculations show good agreement between dilutions in different time-directions for samples taken after the announced nuclear test by the Democratic People’s Republic of Korea in 2013.

Eslinger, Paul W.↗
DOE OSTI2020

Utilizing ink composition to tune bulk-electrode gas transport, performance, and operational robustness for a Fe-N-C catalyst in polymer electrolyte fuel cell

With lower site density and turnover frequency, platinum group metal (PGM)-free catalysts based electrodes are often greater than 50 mu m thick in order to increase performance across the fuel cell operating range. Consequently, PGM-free electrodes have an additional bulk electrode transport resistance beyond the local or aggregate level transport in thin platinum-based electrodes. In parallel to the development of more active and durable PGM-free catalysts, advancements in understanding the interplay between PGM-free electrode fabrication, bulk-electrode transport, proton conductivity and performance are needed. Here, the relationship between ionic and gas phase transport through the electrode thickness is modified by adjusting electrocatalyst and ionomer flocculation/interaction at the ink level. The influence of the ink composition (water/n-propanol content) is examined via various in-situ electrochemical and ex-situ characterization techniques and the resulting electrode structure/performance relationship contrasted with electrode performance robustness across a range of relative humidity (RH). For the electrocatalyst examined here, a water-rich (82 wt% H2O) ink formulation was favorable for operation at high RH due to improved molecular diffusion through larger electrode pores. In contrast, the improved interactions between ionomer and electrocatalyst enabled a more robust electrode and higher performance during low RH operation for the 50 wt% H2O content ink.

08 HYDROGEN↗
DOE OSTI2022

Utilization of the CW magnetrons as coherent RF sources for superconducting RF accelerators

CW magnetrons designed and optimized for industrial heaters, driven by an injection-locking signal, were suggested to power Superconducting RF (SRF) cavities. However, the CW magnetrons, which are regenerative generators, are intended to operate in self-excitation mode, so, for reliable starting they use a large regenerative gain, causing a large regenerative instability in operation. Thus, power supply ripple, even shot noise, etc., lead to multiple sidebands forming a quasi-continuous noise spectrum at the carrier frequency. Therefore, in the traditionally used mode of operation and control, such magnetrons are inapplicable for powering high Q-factor SRF cavities. A new approach to operation and control of CW magnetrons considering non-stationary processes during start-up and operation makes it possible to find a mode of almost coherent RF generation of tubes with a significant reduction in regenerative instability and noise and increased efficiency. In our work is presented substantiation for the newly developed mode with an analysis of the new approach based on experimental results. •In this article, for the first time, non-stationary, regenerative processes are considered during the start-up and operation of CW magnetrons for powering high-Q superconducting RF cavities.•An analytical study, confirmed by experiments, showed that the traditionally used modes of starting and operating CW magnetrons are not suitable for powering high-Q superconducting RF cavities.•In fact, to make CW magnetrons suitable for such cavities, the physics of starting and operating CW magnetrons must be changed. This has been demonstrated in our work.•In developing the Stimulated Coherent Generation Mode [NIM A 980 (2020) 164366], we have shown the suitability of this mode for starting and operating CW magnetrons for high-Q superconducting RF cavities.•Analytical analysis, verified experimentally, substantiates in our article the suitability of the “Mode of stimulated coherent generation” of CW magnetrons for powering high-Q superconducting cavities in pulsed and continuous modes.

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

Analysis and utilization of cryogenic sorption isotherms for high free volume glassy polymers [Analysis and utilization of cryogenic sorption isotherms for high free volume polymers]

The sorption of N 2 , Ar, and CO 2 in the glassy polymer with intrinsic microporosity PIM-1 has been investigated across a broad temperature range, from cryogenic (77 K) to near room temperature (275 K). The data obtained have been interpreted by the non-equilibrium thermodynamic model for glassy polymers (NET-GP), which accurately describes the experimental behaviors, and is used to predict the solubility of the same gases above room temperature. The analysis reveals that the same mechanism drives the sorption process over the broad temperature range inspected, with physical dissolution of the gas in the glassy matrix accompanied by significant swelling of the polymer occurring largely in the central portion of the isotherm at cryogenic temperatures. These findings clearly support the idea that calculation of the BET surface area for amorphous high free-volume glassy polymers does not represent an actual real physical property and suggest that its value is an unsuitable metric of polymer material properties. The gas uptake obtained in the cryogenic sorption isotherm is clearly related to the excess free volume and may instead serve as a more appropriate metric for comparison between different polymers.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Multistage Surface-Heated Vacuum Membrane Distillation Process Enables High Water Recovery and Excellent Heat Utilization: A Modeling Study

Surface-heated membrane distillation (MD) enhances the energy efficiency of desalination by mitigating temperature polarization (TP). However, systematic investigations of larger scale, multistage, surface-heated MD system with high water recovery and heat recycling are limited. Here, we explore the design and performance of a multistage surface-heated vacuum MD (SHVMD) with heat recovery through a comprehensive finite difference model. In this process, the latent heat of condensation is recovered through an internal heat exchanger (HX) using the retentate from one stage as the condensing fluid for the next stage and an external HX using the feed as the condensing fluid. Model results show that surface heating enhances the performance compared to conventional vacuum MD (VMD). Specifically, in a six-stage SHVMD process, 54.44% water recovery and a gained output ratio (GOR) of 3.28 are achieved with a surface heat density of 2000 W m –2 , whereas a similar six-stage VMD process only reaches 18.19% water recovery and a GOR of 2.15. Mass and energy balances suggest that by mitigating TP, surface heating increases the latent heat trapped in vapor. The internal and external HXs capture and reuse the additional heat, which enhances the GOR values. We show for SHVMD that the hybrid internal/external heat recovery design can have GOR value 1.44 times higher than that of systems with only internal or external heat recovery. Furthermore, by only increasing six stages to eight stages, a GOR value as high as 4.35 is achieved. The results further show that surface heating can reduce the energy consumption of MD for brine concentration. As a result, the multistage SHVMD technology exhibits a promising potential for the management of brine from industrial plants.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗