bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Dual-VENC Four-Dimensional Flow MRI Framework for Analysis of Subject-Specific Heterogeneous Nonlinear Vessel Deformation
Authors: Concannon J. , Hynes N. , McMullen M. , Smyth E. , Moerman K. , McHugh P. E. , Sultan S. , Karmonik C. , McGarry J. P. 
Published: October 2020

Abstract
Advancement of subject-specific in silico medicine requires new imaging protocols tailored to specific anatomical features, paired with new constitutive model development based on structure/function relationships. In this study, we develop a new dual-velocity encoding coefficient (VENC) 4D flow MRI protocol that provides unprecedented spatial and temporal resolution of in vivo aortic deformation. All previous dual-VENC 4D flow MRI studies in the literature focus on an isolated segment of the aorta, which fail to capture the full spectrum of aortic heterogeneity that exists along the vessel length. The imaging protocol developed provides high sensitivity to all blood flow velocities throughout the entire cardiac cycle, overcoming the challenge of accurately measuring the highly unsteady nonuniform flow field in the aorta. Cross-sectional area change, volumetric flow rate, and compliance are observed to decrease with distance from the heart, while pulse wave velocity (PWV) is observed to increase. A nonlinear aortic lumen pressure–area relationship is observed throughout the aorta such that a high vessel compliance occurs during diastole, and a low vessel compliance occurs during systole. This suggests that a single value of compliance may not accurately represent vessel behavior during a cardiac cycle in vivo. This high-resolution MRI data provide key information on the spatial variation in nonlinear aortic compliance, which can significantly advance the state-of-the-art of in-silico diagnostic techniques for the human aorta.
Modeling of Thermal Contact Resistance of Ball Screws Considering the Load Distribution of Balls
Authors: Gao Xiangsheng , Ma Jiqian , Li Qi , Wang Min , Zan Tao 
Published: October 2020

Abstract
A new analytical method for the modeling of the thermal contact resistance of ball screws considering the load distribution of balls is proposed in this research. The load on balls is analyzed by the force analysis of ball screws, and then, the thermal contact resistance is obtained by the minimum excess principle and Majumdar–Bhushan (MB) fractal theory. The proposed method is validated by experimental results. The comparison with experimental and former results indicates that it is an effective method to evaluate the thermal contact resistance of ball screws. On that basis, effects of axial load, axial pretension, and geometry error of balls are discussed. It is concluded that the thermal contact resistance of ball screws increases along with axial load increase. The load on balls all decreases with axial pretension increase, and the thermal contact resistance of ball screws decreases with the axial pretension increase as well. When the axial load is applied on the nut in an axial-pretension ball screw, the load distribution in Nut A or B becomes less homogenized when the nut moves from nut position parameter ξ = 0 to 1. When the nut moves to ξ = 0.25, the thermal contact resistance will reach a minimum value, and it gets a maximum value at the nut position ξ = 1. The interval range of load and thermal contact resistance are obtained via uncertain analysis. It is concluded that the geometry error has much greater effects on the balls far away from the spacer.
Numerical Investigation on Turbulence Statistics and Heat Transfer of a Circular Jet Impinging on a Roughened Flat Plate
Authors: Alenezi Abdulrahman , Almutairi Abdulrahman , Alhajeri Hamad , Gamil Abdulaziz , Alshammari Faisal 
Published: October 2020

Abstract
A detailed heat transfer numerical study of a three-dimensional impinging jet on a roughened isothermal surface is presented and is investigated from flow physics vantage point under the influence of different parameters. The effects of the Reynolds number, roughness location, and roughness dimension on the flow physics and heat transfer parameters are studied. Additionally, the relations between average heat transfer coefficient (AHTC) and flow physics including pressure, wall shear and flow vortices with thermodynamic nonequilibrium are offered. This paper studies the effect of varying both location and dimension of the roughness element which took the shape of square cross-sectional continuous ribs to deliver a favorable trade-off between total pressure loss and heat transfer rate. The roughness element was tested for three different radial locations (R/D) = 1, 1.5, and 2 and at each location its height (i.e., width) (e) was changed from 0.25 to 1 mm in incremental steps of 0.25. The study used a jet angle (α) of 90 deg, jet-to-target distance (H/D = 6), and Re ranges from 10,000 to 50,000, where H is the vertical distance between the target plate and jet exit. The results show that the AHTC can be significantly affected by changing the geometry and dimensions of the roughness element. This variation can be either an augmentation of, or decrease in, the (HTC) when compared with the baseline case. An enhancement of 12.9% in the AHTC was achieved by using optimal location and dimensions of the roughness element at specific Reynolds number. However, a diminution between 10% and 30% in (AHTC) was attained by the use of rib height e = 1 mm at Re = 50k. The variation of both rib location and height showed better contribution in increasing heat transfer for low-range Reynolds numbers.
Performance Evaluation of a Single-Stage Two-Bed Adsorption Chiller With Desalination Function
Authors: Sztekler Karol , Kalawa Wojciech , Nowak Wojciech , Mika Łukasz , Krzywański Jarosław , Grabowska Karolina , Sosnowski Marcin , Alharbi Ahmed A. 
Published: October 2020

Abstract
Energy efficiency is one of the most important topics nowadays. It is strictly related to the problem of energy demand, energy policy, environmental pollution, and economic issues. Because of the technological development, using more advanced processes in almost every part of industry and increasing demands both for a high standard of living and simplification of processes, the energy demand is growing. This can be observed, e.g., in the building sector—air conditioning is present in almost every new building and people expect high quality thermal conditions. At the same time, many technological processes result in dissipating energy to the environment. Energy efficiency can be increased and operation costs reduced by using waste heat in other processes. One of the possibilities is to use sorption chillers to produce cool and desalinated water. Low temperature waste heat is not easy to utilize because of low energy potential. Using adsorption chillers in low temperature conditions allows utilizing waste heat and producing useful products in many regions of the world. The paper presents the results of experimental study carried out on three-bed adsorption chiller with desalination, using silica gel and water as the working pair. The chiller was equipped with plate-fin tube heat exchanger filled with silica gel with a grain size of 0.5–1.5 mm. The laboratory test stand included one evaporator, one condenser, and three separate tanks for water, desalinated water, and brine, respectively. The test stand scheme and description were presented. All results were obtained during a few hours test with stable temperature conditions in the range of 55–85 °C for the heating water.
Investigation of Southern California Natural Gas Infrastructure to Transport and Store Hydrogen to Meet Electric Demand Based on a 100% Renewable Energy Portfolio
Authors: Heydarzadeh Zahra , Brouwer Jack 
Published: October 2020

Abstract
In this research, we utilize Southern California (SoCal) natural gas transmission pipelines and underground storage resources for transporting and storing hydrogen gas for a 100% renewable energy penetration. The goal is to determine to what extent natural gas infrastructure can be used to deliver and store hydrogen to meet SoCal electric demand for a 100% renewable energy portfolio. Hydrogen is produced from solar power generation using electrolysis next to the gas transmission pipelines whenever it is available in quantities greater than the electricity demand. It was found that using four main transmission pipelines owned by Southern California Gas company (SoCalGas) to transport hydrogen from the point of production to the four underground storage fields to store and later generate electricity through fuel cells can transport and store hydrogen sufficient to meet 40% of the SoCal electricity demand. That is, without any investment in additional transmission and distribution infrastructure, and without any investment in energy storage, the idea of building solar farms in the desert and using only the gas system for storage and transmission and distribution leads to a 40% increase in renewable electricity for the state.
Prediction of Ultra-Lean SI Engine Performance by QD-Combustion Model With an Improved Laminar Flame Speed
Authors: Sok Ratnak , Kusaka Jin , Yamaguchi Kyohei 
Published: October 2020

Abstract
A quasi-dimensional (QD) simulation model is a preferred method to predict combustion in the gasoline engines with reliable results and shorter calculation time compared with multi-dimensional simulation. The combustion phenomena in spark ignition (SI) engines are highly turbulent, and at initial stage of the combustion process, turbulent flame speed highly depends on laminar burning velocity SL. A major parameter of the QD combustion model is an accurate prediction of the SL, which is unstable under low engine speed and ultra-lean mixture.
This work investigates the applicability of the combustion model for evaluating the combustion characteristics of a high-tumble port gasoline engine operated under ultra-lean mixture (equivalence ratio up to ϕ = 0.5) which is out of the range of currently available SL functions initially developed for a single component fuel. In this study, the SL correlation is improved for a gasoline surrogate fuel (5 components). Predicted SL data from the conventional and improved functions are compared with experimental SL data taken from a constant-volume chamber under micro-gravity condition. The SL measurements are done at reference conditions at temperature of 300K, pressure of 0.1MPaa, and at elevated conditions whose temperature = 360K, pressure = 0.1, 0.3, and 0.5 MPaa. Results show that the conventional SL model over-predicts flame speeds under all conditions. Moreover, the model predicts negative SL at very lean (ϕ ≤ 0.3) and rich (ϕ ≥ 1.9) mixture while the revised SL is well validated with the measured data. The improved SL formula is then incorporated into the QD combustion model by a user-defined function in GT-Power simulation. The engine experimental data are taken at 1000 RPM and 2000 RPM under engine load IMEPn = 0.4–0.8 MPa (with 0.1 increment) and ϕ ranges are up to 0.5. The results shows that the simulated engine performances and combustion characteristics are well validated with the experiments within 6% accuracy by using the QD combustion model coupled with the improved SL. A sensitivity analysis of the model is also in good agreement with the experiments under cyclic variation (averaged cycle, high IMEP or stable cycle, and low IMEP or unstable cycle).
Thermo-Economic Optimization of the Dual-Pressure Condenser for 700 °C Ultra-Supercritical Coal-Fired Power Plants
Authors: Fu Yue , Liu Ming , Wang Liyuan , Yan Junjie 
Published: October 2020

Abstract
Pulverized coal power is one of major contributor in power production, whose efficiency can be enhanced by increasing the main steam parameters and adjusting the cold end system parameters. The thermo-economic optimization of the cold end system for 700 °C ultra-supercritical coal-fired power plants were carried out in this study. The condenser pressure was thermo-economically optimized for the single-pressure condenser systems. Then, with the same heat transfer area of the optimized single-pressure condenser, the dual-pressure condenser system was thermo-economically optimized. The distributions of heat transfer area and exhaust steam mass flow between the high-pressure and low-pressure chambers in the dual-pressure condenser system were optimized. The results show that the optimal vacuum pressure of the single-pressure condenser is 3 kPa and the optimal heat transfer area is 27 km2. For the dual-pressure condenser system, the cost of dual-pressure condenser is reduced to the minimum value 1.3 million CNY/year. The power plant efficiency is increased by the maximum value 0.1% when the heat transfer area and exhaust steam mass flow rate are distributed equally between two chambers, compared with that of the single-pressure condenser system. The optimal values of the low-pressure and high-pressure chamber are 2.4 kPa and 3.2 kPa, respectively. This paper provides the reference for the design optimization of cold end system for high parameter power units.
Numerical and Experimental Study of Geometry Effects on Fuel/Air Mixing and Combustion Characteristics of a DLN Burner
Authors: Zhao Yan , Shao Weiwei , Liu Yan , Tang Xiaodi , Xiao Yunhan , McDonell Vincent 
Published: October 2020

Abstract
Swirling flow is widely used in gas turbine burners to promote fuel/air mixing uniformity and to stabilize lean premixed flames. In this study, numerical and experimental methods are utilized to investigate the effects of burner geometry on fuel/air mixing and combustion performance and to optimize the burner geometry. The premixed burner geometry parameters including air swirling angle and fuel injection diameter/angle are modified to achieve fuel/air mixture uniformity. Laser Doppler Velocimetry (LDV) and Particle Image Velocimetry (PIV) are adopted to examine the flow field, Planar Laser Induced Fluorescence (PLIF) for detecting OH radical distribution thus investigating the characteristics of the reaction field. Burners of different configurations are manufactured to conduct combustion experiments. The burner with the worst mixing performance can‘t ignite successfully. However, burners with better mixing performance have a homogeneous reaction field with less perturbance, and the NOX emission stays at a relatively low level around 2.5 ppm (15% O2) at the designed operating condition.
Combining a Fuel Cell and Ultracapacitor Bank to Power a Vertical Take-Off and Landing Unmanned Aerial System
Authors: Laddusaw Justin A. , Pollman Anthony G. , Yakimenko Oleg A. , Gannon Anthony J. 
Published: October 2020

Abstract
This research investigated the combination of a fuel cell and ultracapacitors to create a hybrid powertrain for a vertical take-off unmanned aerial system (UAS). This replaced the more common battery-only powertrain or the hybrid fuel cell-battery powertrain. A secondary power source, such as a battery or ultracapacitors, is required to assist a fuel cell with immediate load requests because fuel cells are unable to supply instantaneous power. The fuel cell-ultracapacitor was tested using a power profile that was experimentally determined using a battery-powered vertical take-off UAS during take-off, hover, and landing. This tabletop experiment is meant to lead to a more refined solution that can be easily scaled to fit into a smaller future vertical take-off UAS. Two separate ultracapacitor banks were made to be put in parallel with the fuel cell. The first was a series of 14, 650 Farad ultracapacitors and the second was a series of 14, 350 Farad ultracapacitors. Both fuel cell-ultracapacitor powertrains were able to meet the power requirements while also supplying power to the fuel cell itself, without an external power supply. Future work opportunities include scaling for implementation into a UAS platform and coding the power management software to optimally manage the proposed hybrid powertrain.
Modeling of Micro-Tubular Flame-Assisted Fuel Cells
Authors: Ghotkar Rhushikesh , Milcarek Ryan J. 
Published: October 2020

Abstract
Direct flame fuel cells were developed in 2004 and there have been many iterations of them ever since. One of the latest iterations are the micro-tubular flame-assisted fuel cells. Even though there has been significant experimental research characterizing the performance and polarization losses of flame-assisted fuel cells, there is no model that describes their polarization losses. A model is thus developed and presented in this paper to assess the polarization losses and performance of flame-assisted fuel cells. Voltage and power density variation with current density are the main parameters that are analyzed in this paper. A model for calculating activation, ohmic and polarization losses is developed. Experimental parameters from previously published work like dimensions of the fuel cell layers, the fuel and oxidizer flow rates, the charge transfer coefficient and the exchange current density are used to optimize the model. The FFC is assumed to be a lumped system and a zero dimensional model is thus developed. The model was able to achieve an accuracy up to 95%, which adds to its credibility. The fuel-rich combustion exhaust composition is predicted using chemical equilibrium analysis for the equivalence ratios of 1.25 to 1.4 with intervals of 0.5 at 800°C. The model predicts that the open circuit voltage decreases from 0.94 to 0.89 for the equivalence ratios of 1.4 to 1.25, respectively, which matches experimental results. The model also predicts that the maximum power density decreases with decrease in equivalence ratio. Negligible activation loss was observed in the results while the ohmic loss didn‘t vary significantly with equivalence ratio. The concentration loss increased with decrease in equivalence ratio, which also matches with experimental results.
Investigation of Mycelium Growth Network As a Thermal Transpiration Membrane for Thermal Transpiration Based Pumping and Power Generation
Authors: Willsey Aliza M. , Hartwell Alexander R. , Welles Thomas S. , Park Daekwon , Ronney Paul D. , Ahn Jeongmin 
Published: October 2020

Abstract
Micro combustion and power generation systems have increasingly been investigated as potential alternatives to electrochemical energy storage thanks to hydrocarbon fuel’s high energy density, but electrical componentry for pumping significantly limits the overall system efficiency. These components must be eliminated to allow for widespread adoption of micro combustion and power generation systems, and so the development of an alternative pumping technique is required.
By taking advantage of the thermal transpiration phenomenon, small-scale pumping can be obtained in the presence of a temperature gradient. Initial work has been done to investigate the efficacy of this system, but a major issue has arisen due to the lack of low-cost thermal transpiration membranes with desirable pore characteristics. Research has revealed that vessel hyphae present in the roots of mushrooms (mycelium) form a network which could meet the requirements of an effective thermal transpiration membrane. Proper growing conditions could also allow for an application specific mycelium structure providing a highly effective and low-cost thermal transpiration membrane for micro combustion systems.
Life Cycle Assessment of Hydrogen Fuelcell-Based Commercial and Heavy-Duty Vehicles
Authors: Tahir Shahbaz , Hussain Muzafar 
Published: October 2020

Abstract
This paper focuses on FuelCell-based electromobility (Commercial and Heavy-Duty Vehicles) to judge its ability to reduce GHG (Greenhouse Gas) emissions in the Transport sector as to fulfill Paris Agreement demands to struggle against Global warming. Current LCA studies and literature show that BEVs (Battery Powered Vehicles) offer lesser emissions and better driving experience to users compared to FCEVs (Fuel Cell Vehicles) with existing German’s energy mix, but in the longer run transformation is needed in transportation sector and infrastructure to diminish emissions arising from this sector. Since most of the developed nations are looking beyond 2030 with a vision of renewables integration for Power and Energy so, LCA results proved that: In upcoming decades, FCEVs offer lesser or zero-emissions with same driving experience as provided by BEVs. H2 (Hydrogen) here plays a significant role because its production is very energy-intensive; hence, future Fuel Cell mobility is only beneficial if H2 supply is ensured by renewables. From the historical point of view, Europe always acted as a leader among all continents to fight against climate change, and Germany is the prime economy in Europe and a foremost contributor to GHG emissions. Therefore, it has been chosen for our LCA study.
Convolutional Neural Network Model for the Prediction of Plenum Temperature in a Waste Glass Melter
Authors: Abboud A. W. , Guillen D. P. , Pokorny R. 
Published: October 2020

Abstract
Legacy radioactive tank waste is slated to undergo vitrification at the Waste Treatment and Immobilization Plate (WTP) using Joule-heated, ceramic-lined melters. A high-fidelity, computational fluid dynamics (CFD) model of the pilot-scale DM1200 melter has been developed to provide an understanding of the heat transfer and fluid dynamics within the WTP melters. Monitoring of the non-radioactive pilot-scale system has been primarily done through visual observations. However, visual observations will not be possible in the full-scale radioactive melter and process control will be based upon the measured plenum temperatures. Using the CFD model, the effect of the cold cap coverage on the plenum temperature can be assessed. The plenum temperature within the DM1200 is primarily driven by the amount and distribution of the cold cap coverage on the melt pool, since thermal radiation is the dominant mode of heat transfer at these temperatures. Plenum temperatures in the DM1200 obtained during pilot-scale testing by the Vitreous State Laboratory were used for model validation. A standard LeNet-1 convolutional neural network (CNN) is used to predict the spatial cold cap coverage of the model from the computed plenum temperature distributions derived from known cold cap topologies. With a 16 cm × 16 cm filter applied, an accuracy of 89% was achieved.