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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 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Enzymatic synthesis of 1-caffeoylglycerol with deep eutectic solvent under continuous microflow conditions

1-caffeoylglycerol (1-CG) is a hydrophilic ester with a high solubility, and has a strong activity to prevent skin cancer caused by ultraviolet. However, the current preparation process to synthesize 1-CG via transesterification from methyl caffeate (MC) and glycerin was not economic due to long reaction time or adding extra field. Therefore, an enzymatic synthesis with deep eutectic solvent chloride-urea (ChCl-urea) in a microreactor was firstly applied under continuous microflow condition to improve the productivity. A maximum 1-CG yield of 96.49% was obtained under the optimized conditions: temperature of 65 degrees C, flow rate of 2 $μ$L/min, MC concentration of 50 g/L. Compared to the batch reactor, the reaction time reduced by 75%, the $K_m$ value decreased by 5/6, the reuse times of lipase increased by 2.29-fold, the external mass and transfer coefficients increased 10 times, which process was verified by numerical simulation. In addition, the produced 1-CG of 2 mg/mL has a high UV damage remediation ability of 75.16% using HaCaT cell model, which reveals 1-CG can repair the damage of cells radiated by the UV. Thus, this approach represents a convenient and cost-saving method to produce 1-CG using microfuidic biocatalysis.

09 BIOMASS FUELS↗
DOE OSTI2023

A laboratory-scale compression feed screw for characterizing continuous feeding of dense granular materials

Compression feed screws are commonly used in biorefineries for the continuous feeding of biomass feedstock into reactors. Developing methods to assess the feasibility of feeding granular materials in a compression feed screw is critical for reducing solids handling issues during operation. A laboratory-scale compression feed screw has been built to measure critical process parameters of the feeding operation, namely the driving torque and the mass flow rate. The process parameters of two granular materials, microcrystalline cellulose Avicel PH-200 and milled corn stover are measured using the laboratory-scale feeder. The results show that a larger torque is required to feed corn stover than Avicel PH-200, even though the former consists of more compressible particles. Further, the device can capture real-time fluctuations in the process parameters during operation. Here, the laboratory-scale feeder can be used to compare the feeding of different granular materials and the measured parameters can be used to validate predictive models for a compression screw feeding process.

09 BIOMASS FUELS↗
DOE OSTI2022

Scale-up of microwave-assisted, continuous flow, liquid phase reactors: Application to 5-Hydroxymethylfurfural production

Microwave (MW) technology can be powerful for the electrification and intensification of chemical manufacturing. However, very few examples of scaled MW processes exist. In this work, we build a scaled, MW-assisted, continuous flow reactor for the processing of liquid phase chemistries with specific application to 5-hydroxymethylfurfural (HMF) production. Here, we demonstrate a corresponding computational fluid dynamics model to simulate the reactor’s temperature profile and performance, both of which are in good agreement with experiments. We construct a surrogate model to relate operating parameters to performance for guiding experiments, without demanding simulations, via active learning. Heat recirculation is demonstrated in this scaled reactor, further extending its scale and reducing the energy demand. An HMF yield of ~55 % and a productivity of 0.1 kg/hr, 8x higher than any other reactor, at a flowrate >20x than prior work, are demonstrated while maintaining energy efficiency of >98 %. A basic economic analysis estimates a $1.85/kg cost of HMF from fructose and >60 % reduction in CO 2 emissions than a conventional system without considering the impact of green electricity. We demonstrate that MW technology is well-applied to systems larger than the laboratory scale, and strategies to further reduction in cost and CO 2 are discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Continuous optical in-situ pH monitoring during early hydration of cementitious materials

A luminescent sensor technique for pH analyses has been tested in cementitious media. The optical sensors monitor in-situ pH every 5 s during early hydration reactions over a period of 100 h from initial fluid up to consolidated stage. The pH development was analysed in calcium aluminate, calcium sulfoaluminate and OPC/slag cements up to a pH level of 13.3 and directly correlated with the heat of hydration. Thus tracing the dissolution and formation processes of solid phases via pH sensor monitoring is possible. This measurement technique enables the recording of continuous and highly reproducible pH data sets from slurries, pastes, and hardening materials leading to new vistas for individual (trans)formation pathways of solids, hydration and consolidation reactions in high alkaline cementitious systems.

36 MATERIALS SCIENCE↗
DOE OSTI2019

High-speed X-ray investigation of melt dynamics during continuous-wave laser remelting of selective laser melted Co-Cr alloy

The objective of this study is to quantify the melt pool dynamics during continuous-wave laser remelting of a Co-Cr alloy manufactured using selective laser melting. This knowledge will inform process improvement and numerical modeling of laser remelting. A high-intensity x-ray beam imaged a 2 mm × 0.5 mm area of the surface with a 50 kHz framerate. Analysis of these videos quantified the melt pool surface wave movement and compared this to the initial surface features. Here, the results indicate that the keyhole and its characteristic oscillations can suppress large wavelength features on the initial surface.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Adaptive continuity-preserving simplification of street networks

Street network data is widely used to study human-based activities and urban structure. Often, these data are geared towards transportation applications, which require highly granular, directed graphs that capture the complex relationships of potential traffic patterns. While this level of network detail is critical for certain fine-grained mobility models, it represents a hindrance for studies concerned with the morphology of the street network. For the latter case, street network simplification — the process of converting a highly granular input network into its most simple morphological form — is a necessary, but highly tedious preprocessing step, especially when conducted manually. In this manuscript, we develop and present a novel adaptive algorithm for simplifying street networks that is both fully automated and able to mimic results obtained through a manual simplification routine. The algorithm — available in the neatnet Python package — outperforms current state-of-the-art procedures when comparing those methods to manually, human-simplified data, while preserving network continuity.

Python↗
DOE OSTI2023

Conductive overbraid of continuous fiber thermoplastic composite tows

Here, to meet the increasing demand for lightweight materials with multifunctional capabilities, a new high-rate manufacturing method and material system, referred to as M-TOW ® (multifunctional-tow) is introduced. Overbraiding is used to incorporate highly conductive wire onto the continuous fiber reinforced tow (M-TOW ® ), offering a solution for integrating thermal and electrical conductivity into hybrid-molded composite structures. The conductivity performance of different wire configurations are compared before and after forming the M TOW ® , measuring electrical conductivities up to 5.5 x 10 5 S / cm and thermal conductivities up to 21 W / mK. Results conclude that the integration of conductive wires into thermoplastic preforms is a viable means of expanding the functionality of lightweight, high strength composite structures.

3-dimensional reinforcement↗
DOE OSTI2024

Improved stellarator permanent magnet designs through combined discrete and continuous optimizations

A common optimization problem in the areas of magnetized plasmas and fusion energy is the design of magnets to produce a given three-dimensional magnetic field distribution to high precision. When designing arrays of permanent magnets for stellarator plasma confinement, such problems have tens of thousands of degrees of freedom whose solutions, for practical reasons, should be constrained to discrete spaces. We perform a direct comparison between two algorithms that have been developed previously for this purpose, and demonstrate that composite procedures that apply both algorithms in sequence can produce substantially improved results. One approach uses a continuous, quasi-Newton procedure to optimize the dipole moments of a set of magnets and then projects the solution onto a discrete space. The second uses an inherently discrete greedy optimization procedure that has been enhanced and generalized for this work. Further, the approaches are both applied to design arrays cubic rare-Earth permanent magnets to confine a quasi-axisymmetric plasma with a magnetic field on axis of 0.5 T. The first approach tends to find solutions with higher field accuracy, whereas the second can find solutions with substantially (up to 30%) fewer magnets. When the approaches are combined, they can obtain solutions with magnet quantities comparable to the second approach while matching the field accuracy of the first.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2019

A kW-scale, 24-hour continuously operational, radiative sky cooling system: Experimental demonstration and predictive modeling

With the advancement in sub-ambient cooling of water during daytime under the sun with scalable-manufactured radiative cooling metamaterials, the challenge for applications lies in design and building of large-scale radiative cooling systems. Here, we present a kW-scale, 24-hour continuously operational, radiative sky cooling system, with both experimental study and detailed modeling. We first quantitatively show how water flow rate directly affects the system cooling power and inversely affects the water temperature drop. A day-and-night stagnant (flow rate = 0 L/(min·m 2 )) water cooling test of the system shows a consistent sub-ambient water temperature drop of 5–7 °C. A daytime cooling test of the system at a low flow rate of 0.227 L/(min·m 2 ) yields a maximum sub-ambient temperature drop of 4.0 °C with an average net cooling power of around 80 W/m 2 . Further modelling for a typical metrological year (in Phoenix, Arizona) shows that the system could generate as much as 350 kWh cold (or 26 kWh/m 2 ) with a sub-ambient temperature drop of 4–5 °C at a low flow rate of 0.1 L/(min·m 2 ) during a typical summer month. The cold generated could be used to assist AC systems in regions or seasons with high ambient temperatures.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2025

Engineering design of a kW-scale continuous reactor-heat exchanger for high temperature discharge of particle-based thermochemical energy storage

This study investigates the theoretical design parameters and thermal performance of a kW-scale continuous oxidation reactor for high temperature (~1000 °C) thermochemical energy storage (TCES) applications. The concept comprises a counter-current particle-based system that includes a reaction zone with a heat exchanger to extract the heat produced from the oxidation reaction. Both above and below the hot reactive volume are sensible heat recuperation zones to enable the feed and removal of particles and oxidizing gas near ambient temperature during steady state operation. Two operation types for the reaction zone are studied, a fluidized bed reactor (FBR) and a moving bed reactor (MBR). The results of the parametric analysis suggest that the MBR requires a smaller volume per kW of heat produced, achieving power densities in excess of 2500 kW/m3 compared to ~ 900 kW/m 3 in the FBR. Additionally, the MBR achieves between 0.71 and 0.99 oxidation conversions compared to between 0.23 and 0.38 conversions in the FBR with the same volumes and flowrates. However, the FBR has the potential to maintain a uniform reactor temperature which can produce heat transfer fluid (HTF) outlet temperatures as high as the reactor temperature, i.e., ~1000 °C, whereas the MBR produces variable reactor temperatures that can create overheating zones and low HTF outlet temperatures (< 800 °C) depending on the operating conditions selected. Future work should aim at understanding the coupled fluid dynamics, heat and mass transfer, and thermochemical reaction for any given combination of reactor volume and contacting patterns. Here, these studies should be complemented by experimental work on particle-gas TCES reactors.

25 ENERGY STORAGE↗
DOE OSTI2018

Exploring the effects of climatic variables on monthly precipitation variation using a continuous wavelet-based multiscale entropy approach

Highlights: • Developed a wavelet transform entropy approach to study precipitation. • Multiscale entropy values were the basis for precipitation regionalization. • Various entropy-based bands were introduced to segregate the CWME values for each cluster. • The relationship between changes of CWME and mean monthly precipitation were investigated. • Central rain gauges of each cluster were used for further analysis. Understanding precipitation on a regional basis is an important component of water resources planning and management. The present study outlines a methodology based on continuous wavelet transform (CWT) and multiscale entropy (CWME), combined with self-organizing map (SOM) and k-means clustering techniques, to measure and analyze the complexity of precipitation. Historical monthly precipitation data from 1960 to 2010 at 31 rain gauges across Iran were preprocessed by CWT. The multi-resolution CWT approach segregated the major features of the original precipitation series by unfolding the structure of the time series which was often ambiguous. The entropy concept was then applied to components obtained from CWT to measure dispersion, uncertainty, disorder, and diversification of subcomponents. Based on different validity indices, k-means clustering captured homogenous areas more accurately, and additional analysis was performed based on the outcome of this approach. The 31 rain gauges in this study were clustered into 6 groups, each one having a unique CWME pattern across different time scales. The results of clustering showed that hydrologic similarity (multiscale variation of precipitation) was not based on geographic contiguity. According to the pattern of entropy across the scales, each cluster was assigned an entropy signature that provided an estimation of the entropy pattern of precipitation data in each cluster. Based on the pattern of mean CWME for each cluster, a characteristic signature was assigned, which provided an estimation of the CWME of a cluster across scales of 1–2, 3–8, and 9–13 months relative to other stations. The validity of the homogeneous clusters demonstrated the usefulness of the proposed approach to regionalize precipitation. Further analysis based on wavelet coherence (WTC) was performed by selecting central rain gauges in each cluster and analyzing against temperature, wind, Multivariate ENSO index (MEI), and East Atlantic (EA) and North Atlantic Oscillation (NAO), indeces. The results revealed that all climatic features except NAO influenced precipitation in Iran during the 1960–2010 period.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Investigation of two concrete thermal energy storage system configurations for continuous power production

Two Modelica concrete thermal energy storage (CTES) models are built to analyze potential CTES system designs. One design is the single pipe network design wherein a heat transfer fluid (HTF) flows in one direction during heat deposition and the opposite direction during heat removal. All pipes in the network are used for either deposition (charging) or removal (discharging). The second design is a dual pipe network design in which a network of HTF pipes carries charging fluid and a separate piping network carries discharging HTF. Operation of these two configurations to produce constant steam is evaluated. Here, results indicate that the designs are likely appropriate for different applications with the single pipe network appearing appropriate for batch energy applications and the dual pipe network for continuous energy applications.

25 ENERGY STORAGE↗
DOE OSTI2021

Geomechanical and flow implications with continued bioconversion of coal to methane: Experiments and modeling

Microbial conversion of coal to methane is a promising technology during transition of coal-based energy from conventional coal mining to natural gas recovery from coal. Significant research advances have been made towards engineering ideal microbial communities and nutrients for bio-stimulation of coal. However, actual field applications require geomechanical and flow behavior characterization of coal during the bioconversion process as well as gas production over the life of the created “biogenic gas reservoirs”. This work presents the results of an experimental investigation to estimate gas/methane production using bioconversion of coal and analyses of variations in bulk modulus, strain and permeability. Bulk modulus of coal demonstrated time-dependent behavior with continued bioconversion of solid coal. The phenomenon was modeled using mass balancing in a closed environment and the logistic equation based biogenic gas production with time. The modeled gas production and changes in modulus of coal showed excellent agreement with the corresponding experimental results. Next, numerical simulation of biogenic conversion of coal in a constant stress in-situ condition, replicating the Huff ‘n Puff method under field conditions, was carried out. The results showed that bioconversion can lead to decrease in effective stress, increase in permeability and decrease in the modulus of coal with time. Repeated recharge of coal with nutrients and recovering the produced gas, that is, sequential cycles of Huff n’ Puff, showed further increase in permeability and decrease in coal strength, potentially leading to coal failure in-situ, further increasing the permeability, thus enhancing the prospect of field application of the technology.

01 COAL, LIGNITE, AND PEAT↗
DOE OSTI2021

Analysis of digitized herbarium records and community science observations provides a glimpse of downy mildew species diversity of North America, reveals potentially undescribed species, and documents the need for continued digitization and collecting

Downy mildew diseases caused by Peronosporaceae cause significant crop losses globally, with several emerging and resurgent threats in recent decades. Biodiversity data from digitized herbarium specimens provide an opportunity to develop a baseline census of species diversity, however, these resources may represent aggregations of nonrandom and opportunistic collecting efforts, which could lead to spurious results. Here, the MyCoPortal census of digitized herbarium records for downy mildew species collected from North America 1800 to present were analyzed. From 9838 unique records, 196 species were identified, reflecting ~28% of known species diversity. Temporal and geographic collecting biases were observed, with 90% of the collections made prior to 1960 and the efforts of six “super-collectors” accounting for 25% of the collections. The presence of 50–100 undescribed species in North America was inferred from the records. Together, these results highlight the need for continued downy mildew collections, taxonomic research and digitization efforts.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Investigation of methane and ethane pyrolysis with highly active and durable iron-alumina catalyst to produce hydrogen and valuable nano carbons: Continuous fluidized bed tests and reaction rate analysis

The goal of this research work was to evaluate a novel iron-alumina catalyst for methane and ethane pyrolysis with high conversion rates to H 2 with a long life time to address two major issues reported with previous catalysts. Fluidized bed tests demonstrated continuous hydrogen production while collecting carbon containing fines. During the 230 h fluid bed test the methane conversion rate to hydrogen at 700 °C remained above 80% for 160 h while creating valuable nano carbons. Similarly high catalyst lifetimes with high methane conversions have not been reported before. Ethane was more active than methane for pyrolysis with 100% conversion to H 2 . Transmission electron microscopy and Raman analysis of the carbon showed single and multiwall nanotubes and conglomerate nano-fibers. Ethane did not impact the allotrope of carbon formed. TGA was used to create a data array that was used for kinetic analysis and reaction model parametric regressions. Ethane had a higher rate of pyrolysis that was 2.3–2.8 times that of methane. Ethane pyrolysis was found to be more sensitive to temperature with a higher activation energy of 62 kJ/mol as compared to methane at 43 kJ/mol. The frequency factor, A i , was significantly higher for ethane at 0.73 [[kmol/m 3 -sec]/[N/m2] n ] compared to 0.03 for methane on the same basis. Both gases had a functional partial pressure order dependence of ~0.6 based on the regression analysis.

08 HYDROGEN↗
DOE OSTI2011

Induction Chemotherapy and Continuous Hyperfractionated Accelerated Radiotherapy (CHART) for Patients With Locally Advanced Inoperable Non-Small-Cell Lung Cancer: The MRC INCH Randomized Trial

Purpose: Recent clinical trials and meta-analyses have shown that both CHART (continuous hyperfractionated accelerated radiation therapy) and induction chemotherapy offer a survival advantage over conventional radical radiotherapy for patients with inoperable non-small cell-lung cancer (NSCLC). This multicenter randomized controlled trial (INCH) was set up to assess the value of giving induction chemotherapy before CHART. Methods and Materials: Patients with histologically confirmed, inoperable, Stage I-III NSCLC were randomized to induction chemotherapy (ICT) (three cycles of cisplatin-based chemotherapy followed by CHART) or CHART alone. Results: Forty-six patients were randomized (23 in each treatment arm) from 9 UK centers. As a result of poor accrual, the trial was closed in December 2007. Twenty-eight patients were male, 28 had squamous cell histology, 34 were Stage IIIA or IIIB, and all baseline characteristics were well balanced between the two treatment arms. Seventeen (74%) of the 23 ICT patients completed the three cycles of chemotherapy. All 42 (22 CHART + 20 ICT) patients who received CHART completed the prescribed treatment. Median survival was 17 months in the CHART arm and 25 months in the ICT arm (hazard ratio of 0.60 [95% CI 0.31-1.16], p = 0.127). Grade 3 or 4 adverse events (mainly fatigue, dysphagia, breathlessness, and anorexia) were reported for 13 (57%) CHART and 13 (65%) ICT patients. Conclusions: This small randomized trial indicates that ICT followed by CHART is feasible and well tolerated. Despite closing early because of poor accrual, and so failing to show clear evidence of a survival benefit for the additional chemotherapy, the results suggest that CHART, and ICT before CHART, remain important options for the treatment of inoperable NSCLC and deserve further study.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2013

Radiation-Free Weekend Rescued! Continuous Accelerated Irradiation of 7-Days per Week Is Equal to Accelerated Fractionation With Concomitant Boost of 7 Fractions in 5-Days per Week: Report on Phase 3 Clinical Trial in Head-and-Neck Cancer Patients

Purpose: To report long-term results of randomized trial comparing 2 accelerated fractionations of definitive radiation therapy assessing the need to irradiate during weekend in patients with head and neck squamous cell carcinoma. Methods and Materials: A total of 345 patients with SCC of the oral cavity, larynx, and oro- or hypo-pharynx, stage T2-4N0-1M0, were randomized to receive continuous accelerated irradiation (CAIR: once per day, 7 days per week) or concomitant accelerated boost (CB: once per day, 3 days per week, and twice per day, 2 days per week). Total dose ranged from 66.6-72 Gy, dose per fraction was 1.8 Gy, number of fractions ranged from 37-40 fractions, and overall treatment time ranged from 37-40 days. Results: No differences for all trial end-points were noted. At 5 and 10 years, the actuarial rates of local-regional control were 63% and 60% for CAIR vs 65% and 60% for CB, and the corresponding overall survival were 40% and 25% vs 44% and 25%, respectively. Confluent mucositis was the main acute toxicity, with an incidence of 89% in CAIR and 86% in CB patients. The 5-year rate of grade 3-4 late radiation morbidity was 6% for both regimens. Conclusions: Results of this trial indicate that the effects of accelerated fractionation can be achieve by delivering twice-per-day irradiation on weekday(s). This trial has also confirmed that an accelerated, 6-weeks schedule is a reasonable option for patients with intermediate-stage head-and-neck squamous cell carcinoma because of the associated high cure rate and minimal severe late toxicity.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2015

Continuous Monitoring and Intrafraction Target Position Correction During Treatment Improves Target Coverage for Patients Undergoing SBRT Prostate Therapy

Purpose: To compare the potential benefits of continuous monitoring of prostate position and intervention (CMI) using 2-mm displacement thresholds during stereotactic body radiation therapy (SBRT) treatment to those of a conventional image-guided procedure involving single localization prior to treatment. Methods and Materials: Eighty-nine patients accrued to a prostate SBRT dose escalation protocol were implanted with radiofrequency transponder beacons. The planning target volume (PTV) margin was 5 mm in all directions, except for 3 mm in the posterior direction. The prostate was kept within 2 mm of its planned position by the therapists halting dose delivery and, if necessary, correcting the couch position. We computed the number, type, and time required for interventions and where the prostate would have been during dose delivery had there been, instead, a single image-guided setup procedure prior to each treatment. Distributions of prostate displacements were computed as a function of time. Results: After the initial setup, 1.7 interventions per fraction were required, with a concomitant increase in time for dose delivery of approximately 65 seconds. Small systematic drifts in prostate position in the posterior and inferior directions were observed in the study patients. Without CMI, intrafractional motion would have resulted in approximately 10% of patients having a delivered dose that did not meet our clinical coverage requirement, that is, a PTV D95 of >90%. The posterior PTV margin required for 95% of the dose to be delivered with the target positioned within the PTV was computed as a function of time. The margin necessary was found to increase by 2 mm every 5 minutes, starting from the time of the imaging procedure. Conclusions: CMI using a tight 2-mm displacement threshold was not only feasible but was found to deliver superior PTV coverage compared with the conventional image-guided procedure in the SBRT setting.

62 RADIOLOGY AND NUCLEAR MEDICINE↗