bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of gravity on sintering of 3D‐printed powder components
Authors: Torresani E. , German R. M. , Huff R. , Olevsky E. A.
Published: July 2021

Present technologies of additive manufacturing (such as binder‐jetting, stereolithography, robocasting, etc.) of complex‐shape powder‐components necessitate fine‐tuning of sintering as applied to highly porous 3D‐printing products. The densification of low‐density, complex shapes requires control of the gravity‐related phenomena to ensure a nearly full and distortion‐free densification. The present study addresses these issues through the involvement of comprehensive finite element simulations, the determination of the additively manufactured powder specimens’ sintering behavior, and the experimental validation of the developed models describing sintering of 3D‐printed objects. The paper describes the application of a numerical approach based on continuum mechanics‐based modeling of the gravity‐induced distortions during sintering of 3D‐printed powder components. The validation of the model is conducted through the comparison with the experimental results obtained for the sintering of the beam‐shape components printed using ceramic stereolithography technology. A practical semi‐analytical criterion, which can be used for sintered 3D‐printed parts’ design recommendations applicable to various material systems, is derived. Based on the obtained design criterion, a design map is developed indicating the allowable 3D‐printed elements’ configurations enabling the avoidance of the excessive gravity‐induced shape distortions.
Spray‐dried sol‐gel glass‐ceramic powders based on the tunable thermal expansion of quartz and keatite solid solutions
Authors: Zandona Alessio , Helsch Gundula , Martínez Arias Aurina , Weber Alfred P. , Deubener Joachim
Published: July 2021

Lithium aluminosilicate glass‐ceramic powders were synthesized by the heat treatment of spray‐dried sol‐gel glassy nanobeads, obtaining quartz solid solution (Qss) and keatite solid solution (Kss) crystals. Their composition ranged between 75 mol% SiO2 and pure silica along the spodumene join. The metastable crystals displayed tunable coefficients of thermal expansion ranging from +30 × 10−6 to −2.7 × 10−6 K−1 at room temperature, as obtained from their crystallographic characterization. The solid solution boundaries of Kss could be extended to 85 mol% SiO2. Concurrently, X‐ray diffraction measurements performed in situ at high temperature and at cryogenic conditions confirmed the known linear shift of the high‐low quartz inversion temperature upon increasing Al+Li doping. The obtained results qualify aerosol synthesis as a very versatile method for the production of glass‐ceramic powders in the LAS system.
Jawline reshape technique with suspension threads to improve the effect of blepharoplasty on face rejuvenation
Authors: Bollero Daniele
Published: July 2021

Background

Blepharochalasis, induced by the aging process, is an important esthetic blemish which can be solved by blepharoplasty, the most performed cosmetic surgical procedure in the world today to repair droopy eyelids. Nowadays, there is a greater interest to combine blepharoplasty with minimally invasive treatments to harmonize the oval shape of the face. Therefore, blepharoplasty technique could be associated with face thread lifting, a safe and effective technique that optimizes the rejuvenation of the central and lower part of the face.

Aim

The aim of this study was to assess the overall safety and efficacy of blepharoplasty combined with suspension thread lifting. The author also aimed to demonstrate patients' satisfaction after treatment.

Method

The study involved 12 patients undergoing blepharoplasty plus threads lifting to improve the mandibular line. Patient's satisfaction was valuated with global esthetic improvement score, visual analog scale score, before and after treatment clinical images.

Results

All patients showed optimized face rejuvenation and high satisfaction. Patients experienced an immediate improvement in face harmony in addition to the eye refinement and expressed their satisfaction. The combination of plastic surgery and minimal invasive technique did not cause adverse events to the patients and they would recommend it.

Conclusion

Interest in thread lifting is currently high, and this study highlights the excellent outcome and the visible results of blepharoplasty and threads combination.
Drier, darker and more fertile: 140 years of plant habitat change driven by land‐use intensification
Authors: Finderup Nielsen Tora , Sand‐Jensen Kaj , Bruun Hans Henrik
Published: July 2021

Questions

Land‐use change is a key driver of biodiversity change. Delayed biotic responses to land‐use change impede the establishment of causal links between specific anthropogenic changes and resulting biodiversity change. Therefore, we aimed at investigating changes to plant species pools: (a) at time scales long enough to encompass past land‐use changes, even changes that have ceased from collective memory; and (b) at spatial scales wide enough to encompass landscape‐wide changes to habitat quantity and quality.

Location

Denmark, 10 regions in the range 54°3′–56°7′ N and 10°4′–12°4′ E.

Methods

We assessed changes to regional plant species pools over ca 140 years by comparing high‐quality legacy data to recent re‐surveys in ten Danish regions. To identify anthropogenic drivers of plant compositional change, we assessed ecological properties of winning and losing plant species and compared observed biotic changes to land‐cover data spatially and temporally matching the regional flora data.

Results

Winner species were strongly associated with shaded, fertile, well‐drained conditions. Loser species were associated with open, infertile conditions with either moist or xeric soils. The major land‐use changes driving biotic change were: (a) drainage of moist and wet biotopes; (b) active afforestation and passive scrub overgrowth due to ceased grazing; and (c) landscape‐wide increased nutrient availability. However, the magnitude of increase or decrease in the area of a land‐cover type was a poor predictor of the number of habitat‐associated winner or loser species. This suggests that degradation of extant biotopes and/or low quality of new biotopes limits plant species richness, in particular of habitat specialists.

Conclusions

We demonstrate a displacement of plant ecospace towards mesic, shaded and fertile conditions, with profound effects on plant diversity, and mainly driven by intensified agricultural/silvicultural use of the landscape matrix, which has strongly affected the main plant habitats in scattered semi‐natural fragments.
Mammal‐bearing gastric pellets potentially attributable to Troodonformosus at the Cretaceous Egg Mountain locality, Two Medicine Formation, Montana, USA
Authors: Freimuth William J. , Varricchio David J. , Brannick Alexandria L. , Weaver Lucas N. , Wilson Mantilla Gregory P.
Published: July 2021

Fossil gastric pellets (regurgitalites) have distinct taphonomic characteristics that facilitate inferences of behavioural ecology in deep time, despite their rarity in the fossil record. Using the taphonomic patterns of both extant and fossil small mammals from more recent geologic deposits as a guide, we assess the taphonomy of three unusual multi‐individual aggregates of mammal skeletons from palaeosols at Egg Mountain, a dinosaur nesting locality from the Upper Cretaceous Two Medicine Formation, Montana, USA. One aggregate consists of two individuals of the multituberculate Filikomys primaevus. This specimen is characterized by brecciated crania, articulated postcrania, and an absence of digestive markings, all suggestive of a non‐predatory origin. Two additional aggregates consist of 3 and 11 individuals, respectively, primarily of the marsupialiform Alphadon halleyi. High proportions of crania and indigestible elements (e.g. teeth), extensive disarticulation and breakage, digestive corrosion patterns, and the absence of a phosphatic ground mass are indicative of regurgitalites and align with features of extant prey in diurnal raptor gastric pellets. We interpret these specimens as the oldest known mammal‐bearing regurgitalites. The discrepancy in taphonomic features implies behavioural separation between the two mammalian taxa at the locality. Abundant shed teeth and nesting evidence at the locality favours the non‐avian theropod Troodon formosus as the predator responsible for the regurgitalites, congruent with previous inferences of a small‐bodied prey diet, manipulation of prey during feeding, heightened metabolic processes, and potential nocturnality for this taxon.
Displaying secrecy in George Gascoigne’s The Adventures of Master F.J.*
Authors: Orgis Rahel
Published: July 2021

George Gascoigne’s The Adventures of Master F.J. (1573/1575) is best known for its elaborate fiction of production and the scandal its 1573 publication supposedly caused due to being read as a roman à clef. This article considers the 1573 version of Gascoigne’s narrative and his 1575 prefatory comments on it in the context of Elizabethan intelligence practices. Interpreting the republication of Gascoigne’s works as a sign of success rather than as a consequence of censorship, I argue that at the heart of the complex narrative lies Gascoigne’s paradoxical endeavour to recommend himself as a government informer through his writing. Gascoigne’s display of the abilities necessary for an informer pervades the very fabric of the text, as he simultaneously puts into practice and reveals his skill at keeping, encoding, transmitting and disclosing secrets. Gascoigne’s contradictory performance of concealment and disclosure results in a narrative in which meanings are both obscured and partly decoded. This manifests itself especially in the narrative’s fiction of production, Gascoigne’s use of roman‐à‐clef strategies and his foregrounding of indirect means of communication, including the coded representation of sexual encounters.
Comparison between tube test and automated column agglutination technology on VISION Max for anti‐A/B isoagglutinin titres: A multidimensional analysis
Authors: Nam Minjeong , Hur Mina , Lee Hyunkyung , Kim Hanah , Park Mikyoung , Moon Hee‐Won , Yun Yeo‐Min
Published: July 2021

Background and Objectives

VISION Max (Ortho Clinical Diagnostics, Raritan, NJ) measures anti‐A/B isoagglutinin titres using automated column agglutination technology (CAT). We compared tube test (TT) and CAT of VISION Max comprehensively, including failure mode and effect analysis (FMEA), turnaround time (TAT) and cost, and suggested modified CAT (MCAT).

Materials and Methods

For 100 samples (each 25 for blood type A, B and O with anti‐A and anti‐B), anti‐A/B isoagglutinin titres were measured by TT and CAT (1:2–1:1024 dilution), as well as by MCAT (with agglutination at 1:32 dilution, then perform additional testing from 1:64 to 1:1024). We assessed the agreement and correlation between TT and CAT and compared FMEA (risk priority number [RPN] score), TAT (h:min:sec) and cost (US dollar, US $) among TT, CAT and MCAT.

Results

TT and CAT showed overall substantial agreement (k = 0.73) and high correlation (ρ ≥ 0.75) except blood type O with anti‐A (ρ = 0.68). Compared with TT, CAT showed lower RPN scores in FMEA and similar TAT and cost (FMEA, 33,700 vs. 184,300; TAT, 15:23:00 vs. 14:26:40; cost, 1377.4 vs. 1312.4, respectively). Regarding FMEA, TAT and cost, MCAT was superior to CAT or TT (43,810; 13:28:00; 899.2, respectively).

Conclusion

This is the first multidimensional analysis on VISION Max CAT for measuring anti‐A/B isoagglutinin titres. The results of anti‐A/B isoagglutinin titres by CAT were comparable with those of TT. MCAT would be a safe, time‐saving and cost‐effective alternative to TT and CAT in high‐volume blood bank laboratories.
Reviewer Acknowledgements
Authors: Walter Andrew
Published: July 2021

Studies in Engineering and Technology (SET) would like to acknowledge the following reviewers for their assistance with peer review of manuscripts for this issue. Many authors, regardless of whether SET publishes their work, appreciate the helpful feedback provided by the reviewers. Their comments and suggestions were of great help to the authors in improving the quality of their papers. Each of the reviewers listed below returned at least one review for this issue.Reviewers for Volume 8, Number 1Girish Upreti, Methodist University, USAHala Abd El Megeed, National Institute for Standards, EgyptHassan Shaaban, Egyption Atomic Authority (EAEA), EgyptHosny Abbas Abouzeid, Higher Technological Institute, EgyptHossam Zaqoot, Ministry of Environmental Affairs, GazaHsienyu Lee, National Taiwan University, USAJose Hernandez, Chilean Nuclear Energy Commission, ChileMarco A Ruano, Economics Department Universidad Carlos III de Madrid, SpainMohammad Reza Barati, Flinders University, AustraliaSimona Rainis, Regional Agency for Rural Development of Autonomous Region of Friuli Venezia Giulia, Italy Andrew WalterEditorial AssistantStudies in Engineering and Technology-------------------------------------------Redfame Publishing9450 SW Gemini Dr. #99416Beaverton, OR 97008, USATel: 1-503-828-0536 ext. 504Fax: 1-503-828-0537E-mail: set@redfame.comURL: http://set.redfame.com
Multiscale Modeling of the Strength and Ductility Paradox for High-Pressure Torsion Samples With Gradient Microstructure
Authors: Hamid Mehdi , Jamalian Maryam , Vincentis Natalia De , Buck Quentin , Field David P.
Published: July 2021

Severely plastically deformed microstructures of pure copper were produced by subjecting cylindrical copper samples to high-pressure torsion. The effects of this procedure on introducing gradient microstructure and subsequent mechanical behavior were investigated by utilizing electron backscatter diffraction and performing Vickers hardness/tensile testing. A crystal plasticity-continuum dislocation dynamics modeling effort was performed to predict the mechanical performance of these samples. The model includes mechanisms based on the gradient of dislocation density and grain size, back stress fields of grain boundaries, dislocation density transmission across grain boundaries, and stress/strain gradient effects.
Effects of Increased Tooth Clearance on the Performance of a Labyrinth Seal With Oil-Rich Bubbly Laminar Flow
Authors: Zhang Min , Childs Dara W.
Published: July 2021

In recent years, multiphase pumps have become more and more popular because of the capability to simplify the process, reduce the footprint, and lower the cost. To compensate for the axial thrust force, an annular seal is normally used as a balance piston seal, and the labyrinth seal is one of the choices. A typical labyrinth seal consists of a surface with teeth and a smooth surface. The teeth are either on the rotor or the stator. To protect the machine, one side (either the teeth or the smooth surface) is made of a material that can be safely sacrificed during a rub. After the rub, the teeth clearance is increased. This paper studies the impact of the increased teeth clearance on the performance of the labyrinth seal under oil-rich bubbly flow conditions. The test fluid is a mixture of silicone oil (PSF-5cSt) and air with inlet gas volume fraction (GVF) up to 9%. Tests are conducted with pressure drop (PD) = 34.5 bars, rotor speed ω = 5 krpm, and radial tooth clearance Cr = 0.102 mm and 0.178 mm. Test results show that, for all test conditions (before and after injecting air bubbles into the oil flow), increasing Cr from 0.102 mm to 0.178 mm increases the mass flow rate by about 40% but barely changes the test seal's rotordynamic coefficients, i.e., the increased tooth clearance would not change the pump vibration performance.
Forced Response Excitation Due to the Stator Vanes of Two and Three Compressor Stages Away
Authors: Miura Toshimasa , Sakai Naoto , Kanazawa Naoki , Nakayama Kentaro
Published: July 2021

State-of-the-art axial compressors of gas turbines employed in power generation plants and aero engines should have both high efficiency and small footprint. Thus, compressors are designed to have thin rotor blades and stator vanes with short axial distances. Recently, problems of high cycle fatigue (HCF) associated with forced response excitation have gradually increased as a result of these trends. Rotor blade fatigue can be caused not only by the wake and potential effect of the adjacent stator vane, but also by the stator vanes of two, three, or four compressor stages away. Thus, accurate prediction and suppression methods are necessary in the design process. In this study, the problem of rotor blade vibration caused by the stator vanes of two and three compressor stages away is studied. In the first part of the study, one-way fluid structure interaction (FSI) simulation is carried out. To validate the accuracy of the simulation, experiments are also conducted using a gas turbine test facility. It is found that one-way FSI simulation can accurately predict the order of the vibration level. In the second part of the study, a method of controlling the blade vibration is investigated by optimizing the clocking of the stator vanes. It is confirmed that the vibration amplitude can be effectively suppressed without reducing the performance. Through this study, ways to evaluate and control the rotor blade vibration are validated.
Carbon Fiber-Based Twisted and Coiled Artificial Muscles (TCAMs) for Powered Ankle-Foot Orthoses
Authors: Kotak Parth , Wilken Jason M. , Anderson Kirsten M. , Lamuta Caterina
Published: July 2021

Ankle foot orthoses (AFOs) control the position and motion of the ankle, compensate for weakness, and correct deformities. AFOs can be classified as passive or powered. Powered AFOs overcome the limitations of passive AFOs by adapting their performance to meet a variety of requirements. However, the actuators currently used to power AFOs are typically heavy, bulky, expensive, or limited to laboratory settings. Thus, there is a strong need for lightweight, inexpensive, and flexible actuators for powering AFOs. In this technical brief, carbon fiber/silicone rubber (CF/SR) twisted and coiled artificial muscles (TCAMs) are proposed as novel actuators for powered AFOs. CF/SR TCAMs can lift to 12,600 times their weight with an input power of only 0.025 W cm−1 and are fabricated from inexpensive materials through a low-cost manufacturing process. Additionally, they can provide a specific work of 758 J kg−1 when an input voltage of 1.64 V cm−1 is applied. Mechanical characterization of CF/SR TCAMs in terms of length/tension, tension/velocity, and active-passive length/tension is presented, and results are compared with the performance of skeletal muscles. A gait analysis demonstrates that CF/SR TCAMs can provide the performance required to supplement lower limb musculature and replicate the gait cycle of a healthy subject. Therefore, the preliminary results provided in this brief are a stepping stone for a dynamic AFO powered by CF/SR TCAMs.
Proposal of an Improved Contactless Measurement Method Using an Advanced Light Emitting Diode Displacement Sensor for Vibration Stress of Piping Systems
Authors: Maekawa Akira , Tsuji Takashi , Takahashi Tsuneo
Published: July 2021

This paper proposes an improved contactless measurement method for vibration stress of piping systems, by which the measurement time is shorter and the measuring works are more simple. The proposed method includes two processes, in which the bending mode shape of piping vibration is identified by a transmission-type light emitting diode (LED) displacement sensor and the vibration stress is calculated based on beam theory using the approximated curve of the bending mode shape. The proposed method uses one advanced LED displacement sensor to measure the vibration stress in contrast to multiple conventional LED sensors, which must be used in the previous method developed by the authors. Therefore, the measuring system could be reduced in size and a light-weight and portable measurement instrument was developed. The measurement accuracy and reliability of the new method were validated by the vibration experiment using a mockup piping system.
Evaluation of the Influence of 1,4-Dioxane and Exhaust Gas Recirculation on the Performance and Emission Values of a Diesel Engine Fuelled With Low Viscous Biofuel Blend
Authors: Samuel Panithasan Mebin , Venkadesan Gnanamoorthi
Published: July 2021

The world greatly relies on the usage of liquid fuels for its energy needs, especially in the transportation sector, which is very high in developing countries. In countries like India, diesel fuel is mainly used for all its transportation requirements (considering its higher efficiency), leading to higher pollution. Many kinds of research works are conducted to find a replacement for diesel fuel. In which biodiesel is considered to be a potential replacement for diesel. However, the challenges like higher viscosity, lower calorific value, higher NOx emission stands as a huge barrier. To overcome this, this study proposes using a low viscous biofuel, which has a higher calorific value close to diesel. To reduce NOx emission, the exhaust gas recirculation (EGR) technique is used in this study. A single-cylinder, constant speed, water-cooled stationary engine setup is used for this study. 20% of pine oil is blended with diesel, and 10ml of 1,4, dioxane additive is added. These blends are tested in the engine for different load conditions (0, 25, 50, 75 and 100%) with and without 10% EGR. The results showed that pine oil usage negatively affected the performance characters but significantly reduced CO, HC, and Smoke emissions (15.94, 17.04 and 2.47% respectively). The 10ml of 1,4, dioxane further enhanced this reduction (32.61, 28.15 and 4.36% respectively). The 10% EGR usage negatively affected both performance and emission characters, but it reduced NOx emissions significantly (11.53%). This study provides an integrated way to overcome the challenges seen in biodiesel usage with a low viscous biofuel and exhaust gas recirculation technique.
Experimental Investigation of Latent Heat Thermal Energy Storage System Enhanced by Annular and Radial Fins
Authors: Tiari Saeed , Hockins Addison , Moretti Samantha
Published: July 2021

In the current study, the thermal characteristics of a latent heat thermal energy storage system enhanced with annular and radial fins are investigated experimentally. Rubitherm RT-55 is used as the phase change material (PCM) and is enclosed within a vertical cylindrical container. Water is used as the heat transfer fluid (HTF) which is circulated in a copper pipe that passes through the center of the container. The hot HTF is circulated through the system until the entire mass of solid PCM inside the container is melted. Twelve k-type thermocouples are inserted into the container at different levels to monitor the PCM temperature during the charging processes. A thermal imaging camera is used to take thermal images of the latent heat thermal energy system as it operates. The effects of different number of annular and radial fins attached to the central pipe on the thermal performance of the latent heat thermal energy storage system during the charging processes have been studied. It was found that the inclusion of 10 and 20 annular fins decreased the charging time by 79.5% and 82.8%, respectively. The two radial fin designs of 4 fins and 8 fins were assessed and found to decrease charging time by 81.9% and 86.6%, respectively.
A Comparative Study of the Influence of Different Wake Models on Wind Farm Layout Optimization
Authors: Yang Puyi , Najafi Hamidreza
Published: July 2021

The accuracy of analytical wake models applied in wind farm layout optimization (WFLO) problems plays a vital role in the present era that the high-fidelity methods such as LES and RANS are still not able to handle an optimization problem for large wind farms. Based on a verity of analytical wake models developed in the past decades, FLOw Redirection and Induction in Steady State (FLORIS) has been published as a tool integrated several widely used wake models and the expansions for them. This paper compares four wake models selected from FLORIS by applying three classical WFLO scenarios. The results illustrate that the Jensen wake model is the fastest one but the defect of underestimation of velocity deficit is obvious. The Multi Zone model needs to be applied additional tunning on the parameters inside the model to fit specific wind turbines. The Gaussian-Curl wake model as an advanced expansion of the Gaussian wake model does not perform an observable improvement in the current study that the yaw control is not included. The default Gaussian wake model is recommended to be used in the WFLO projects which implemented under the FLROIS framework and has similar wind conditions with the present work.
Performance Considerations for Ground Source Heat Pumps in Cold Climates
Authors: Garber-Slaght Robbin
Published: July 2021

Remote, cold climates present challenges to finding safe and affordable space heating options. In Alaska, residential ground source heat pumps (GSHPs) have been gaining in popularity, even though there is little research on their long-term performance or their effect on soil temperatures. The extended heating season and cold soils of Alaska provide a harsh testing ground for GSHPs, even those designed and marketed for colder climates. The large and unbalanced heating load in cold climates creates a challenging environment for GSHPs. In 2013 the Cold Climate Housing Research Center (CCHRC) installed a GSHP at its Research and Testing Facility (RTF) in Fairbanks, Alaska. The heat pump replaced an oil-fired condensing boiler heating an office space via in-floor hydronic radiant piping. The ground heat exchanger (GHE) was installed in moisture-rich silty soils underlain with 0°C permafrost. The intent of the project was to observe and monitor the system over a 10-year period to develop a better understanding of the performance of GSHPs in sites with permafrost and to help inform future design. As of this writing, the heat pump system has been running for eight heating seasons. The efficiency in those eight heating seasons has been variable with ups and downs that have been difficult to explain. This paper seeks to understand the variability in performance as well as make recommendations for GSHP use in other cold climates.
Sensitivity Analysis of Occupant Preferences on Energy Usage in Residential Buildings
Authors: Pattawi Kaleb , Munankarmi Prateek , Blonsky Michael , Maguire Jeff , Balamurugan Sivasathya Pradha , Jin Xin , Lee Hohyun
Published: July 2021

Residential buildings, accounting for 37% of the total electricity consumption in the United States, are suitable for demand response (DR) programs to support effective and economical operation of the power system. A home energy management system (HEMS) enables residential buildings to participate in such programs, but it is also important for HEMS to account for occupant preferences to ensure occupant satisfaction. For example, people who prefer a higher thermal comfort level are likely to consume more energy. In this study, we used foresee™, a HEMS developed by the National Renewable Energy Lab (NREL), to perform a sensitivity analysis of occupant preferences with the following objectives: minimize utility cost, minimize carbon footprint, and maximize thermal comfort. To incorporate the preferences into the HEMS, the SMARTER method was used to derive a set of weighting factors for each objective. We performed week-long building energy simulations using a model of a home in Fort Collins, Colorado, where there is mandatory time-of-use electricity rate structure. The foresee™ HEMS was used to control the home with six different sets of occupant preferences. The study shows that occupant preferences can have a significant impact on energy consumption and is important to consider when modeling residential buildings. Results show that the HEMS could achieve energy reduction ranging from 3% to 21%, cost savings ranging from 5% to 24%, and carbon emission reduction ranging from 3% to 21%, while also maintaining a low thermal discomfort level ranging from 0.78 K-hour to 6.47 K-hour in a one-week period during winter. These outcomes quantify the impact of varying occupant preferences and will be useful in controlling the electrical grid and developing HEMS solutions.
Cost and Technical Profiling of Geothermal District Heating Using GEOPHIRES and Comsof Heat Simulation Software
Authors: Fry Nicholas
Published: July 2021

The heating of commercial and residential buildings in the United States is mostly dependent on fossil fuel sources such as natural gas. GeoVision, a U.S. Department of Energy study from 2019, found a tremendous market potential for geothermal district heating systems (GDHS). To date, most of the GDHS development, conventional or with heat pumps, has taken place in China and Europe. GDHS component manufacturing capacity in North America is not mature and significant increases in construction would likely require importation of European goods. This project attempts to expand market intelligence by simulating the cost for installation of modern European pipe, control, substations, and heat interface units serving a conventional GDHS in Helena, Montana. A shallow, low-temperature (< 75°C) surface manifestation, 2 kilometers from the service area, is the heat source.

Three production simulations with varying wellhead flow rates were made, then projected across a heat network using two simulation tools: GEOthermal energy for Production of Heat and electricity (GEOPHIRES) and Comsof Heat. Correlations between flow rates, heat losses, utilization factors, and costs indicate important variables for developer consideration. A cost profile was made using the average of these simulations. Exploiting a shallow, low-temperature heat source for a GDHS often requires greater investment in the heat network than the wellfield.

This project suggests North American geothermal developers must prepare for interdisciplinary GDHS projects that fall outside of their current business models. European DH operators and manufacturers can provide surface system expertise and materials while North America assesses subsurface exploitation targets. Bringing European DH professionals together with North American geothermal experts may help realize the potential of the GeoVision study, unlocking new business opportunities.
Effects of Vortex Generators on the Impingement Jet Arrays Heat Transfer
Authors: Yang Yue , Mao Junkui , Wang Feilong
Published: July 2021

In the jets array cooling system of the gas turbine, the downstream jets will be deflected by the crossflow and the heat transfer in the downstream will be suppressed. In this paper, the rectangular vortex generators are arranged in the jet arrays to enhance the jet impingement heat transfer. Through the numerical simulations, the configuration of rectangular vortex generators (Common-flow-down CFD and Common-flow-up CFU) and the relative position (l2) between the impingements and the rectangular vortex generators are studied. The results show that both of configurations are beneficial to the suppression of the crossflow and enhance the heat transfer in the downstream. The maximum enhancement of the whole regional average Nusselt numbers in CFD-VGs configuration can reach up to 9.09% with lower than 5% increase of the pressure loss and that in CFU-VGs configuration can reach up to 10.8% with lower than 4.8% increase of the pressure loss. From the perspective of the whole regional average Nusselt numbers and the overall thermal efficiency, the CFD-VGs with l2 = 0 has the best performance. However, from the perspective of the whole regional average Nusselt numbers, the CFU-VGs with l2 = 0 has the best performance, while from the perspective of the overall thermal efficiency, the CFU-VGs with l2 = 3 has the best performance.
Machine Learning for Chaotic Rayleigh Transitions
Authors: Tribelhorn Ben , Dillon H. E.
Published: July 2021

This paper is a preliminary report on work done to explore the use of unsupervised machine learning methods to predict the onset of turbulent transitions in natural convection systems. The Lorenz system was chosen to test the machine learning methods due to the relative simplicity of the dynamic system. We developed a robust numerical solution to the Lorenz equations using a fourth order Runge-Kutta method with a time step of 0.001 seconds. We solved the Lorenz equations for a large range of Raleigh ratios from 1–1000 while keeping the geometry and Prandtl number constant. We calculated the spectral density, various descriptive statistics, and a cluster analysis using unsupervised machine learning. We examined the performance of the machine learning system for different Raleigh ratio ranges.

We found that the automated cluster analysis aligns well with well known key transition regions of the convection system. We determined that considering smaller ranges of Raleigh ratios may improve the performance of the machine learning tools. We also identified possible additional behaviors not shown in z-axis bifurcation plots. This unsupervised learning approach can be leveraged on other systems where numerical analysis is computationally intractable or more difficult.

The results are interesting and provide a foundation for expanding the study for Prandtl number and geometry variations. Future work will focus on applying the methods to more complex natural convection systems, including the development of new methods for Nusselt correlations.
Near Infrared Radiative Properties of Thermal Barrier Coatings
Authors: Wang Yao , Hsu Pei-feng , Wu Yingsang
Published: July 2021

Thermal barrier coatings are widely used in gas turbines to protect the gas turbine metal components against very high combustion product temperature. To improve energy efficiency, higher combustion temperatures are needed. A limiting factor at present is the stability under extreme and prolonged heating of thermal barrier coatings. The coatings are typically made by the air plasma sprayed process in which fine particles of yttria-stabilized zirconia (YSZ) are melted or partially melted and ejected from plasma jet at high speed onto the bond coated substrate metal. With increasing combustion temperature and pressure in the modern gas turbine engines radiative heat transfer is becoming an important portion of the overall heat transfer in the thermal barrier coating. This study has demonstrated that the commonly used Kubelka-Munk method in the radiative property reduction from the measured transmittance and reflectance spectra of YSZ coatings will incur inaccurate result when the coating optical thickness is not sufficiently large. An alternative method — the discrete ordinates method with the asymmetric spherical ring angular quadrature — is used instead. The absorption and scattering coefficients of air plasma sprayed YSZ films are determined over the wavelength range from 1 to 2.6 μm at room temperature. Over this near infrared wavelength range, the scattering coefficient decreases with the increasing wavelength and the absorption coefficient is very small overall. The pore size distributions before and after the 50-hr temperature gradient, thermal cycling are compared. The sintering effect as well as the crack growth will impact the coating radiative properties. These results point to a clear need for better understanding of the radiative heat transfer process, which includes the microstructure-property relationship, progressive changes of the radiative properties with the operation condition and time.
The Effects of Bending on Heat Pipes
Authors: Mahdavi Mahboobe , Faghri Amir
Published: July 2021

A comprehensive three-dimensional numerical model is developed to evaluate the effect of bending on water-copper cylindrical heat pipes. This model distinguishes itself from other models by its ability to uniquely determine the operating pressure of the heat pipe based on the operating and physical conditions. The effects of one 90-degree bend and two 90-degree bends are evaluated on the performance of a heat pipe. Two types of wicks are considered: a screen mesh wick and a sintered powder wick. The obtained results show that bending does affect the vapor pressure drop; however, the changes are not significant when compared to the operating pressure of the heat pipe. If the bending is performed in a manner where the wick is not damaged and the liquid is not blocked from returning to the evaporator, the performance of the heat pipe will not be affected significantly. In addition, if the heat pipe is operating in the horizontal direction, where both evaporator and condenser legs are at the same level, bending does not affect the liquid pressure drop significantly; however, the screen mesh does provide a higher capillary limit. The results also showed that the effects of gravity can be important when bending heat pipes and consideration should be given for this factor. When the bent heat pipe works against gravity, the sintered powder wick heat pipes showed higher capillary limits.
Flow Boiling of Deionized Water in Ultrahigh-Aspect-Ratio Microchannel Heat Sink
Authors: Cui Peilin , Liu Zhenyu
Published: July 2021

Microchannel heat sinks have attracted much attention due to its superiority of removing high heat flux with a very small size, which recently have been applied in the electronic cooling. The flow boiling of deionized water in the ultrahigh-aspect-ratio copper microchannels was experimentally investigated in this work. The heat sink consists of 20 rectangular straight microchannels (5000μm × 200μm) with the hydraulic diameter of 385 μm and the aspect ratio of 25. The experiment was conducted with the heat flux range of 39.7–1368 kW/m2 and the mass flow range of 21.3–41.6 kg/(m2·s) (the inlet temperature of 30°C). The flow patterns in the ultrahigh-aspect-ratio microchannels were captured using the visualization technique and four flow regimes (bubbly flow, slug flow, churn flow and annual flow) were clearly observed. The nucleate boiling sites increase significantly in the depth direction on the large-area side wall at bubbly flow. An obvious delay for flow patterns transformation in the upper regions compared with the lower region of microchannel was found. The bubble sliding was observed with a large sliding distance compared to the conventional low-aspect-ratio microchannels, which leads to an enhanced the heat transfer. It shows that the higher effective heat flux and the lower pressure drop were achieved in ultrahighaspect-ratio microchannel due to its special flow patterns in the channel and large surface area in the limited volume.
Influence of Flue Gas Turbulence Intensity on the Heat and Mass Transfer and Pressure Drop Inside a TMC Based Heat Exchanger
Authors: Al-rifai Saja , Lin Cheng-Xian
Published: July 2021

In this study, a numerical analysis of turbulent flow heat and mass transfer in the cross-flow transport membrane condenser (TMC) based heat exchange was carried out. The heat exchanger under investigation was designed to recover both sensible and latent heat due to transport of heat and mass through a nanoporous ceramic membrane in the bundle of tubes of the heat exchanger. The shear stress transport SST k-ω turbulence model was used to model the turbulent flow of the flue gas mixture. The condensation rate of the water vapor from the flue gas were calculated using a mixed condensation model. The mixed model was based on the capillary condensation and wall condensation in the membrane tube. The numerical study was focused on the investigation of the impact of the turbulence intensity of the flue gas at various inlet conditions, such as Reynolds numbers and temperatures, on the heat and mass transfer and pressure drop characteristics. The numerical results were validated against the experimental results reported in the literature. Different tube diameters were used in the simulation, with the Reynolds number varied from 3000 to 10000. The results showed that an increase in turbulence intensity led to a significant increase in the turbulent kinetic energy, condensation rate, average convective Nusselt number and change on the pressure drop in the heat exchanger. The effects of inlet flow Reynolds number and tube diameter on the heat and mass transfer were also presented and discussed.
Numerical Analysis on the Leading Edge Film Cooling of Bifurcation Holes for Gas Turbine Blade
Authors: Tang Zhonghao , Xie Gongnan , Li Honglin , Gao Wenjing , Tan Chunlong , Li Lei
Published: July 2021

Film cooling performance of the cylindrical film holes and the bifurcated film holes on the leading edge model of the turbine blade are investigated in this paper. The suitability of different turbulence models to predict local and average film cooling effectiveness is validated by comparing with available experimental results. Three rows of holes are arranged in a semi-cylindrical model to simulate the leading edge of the turbine blade. Four different film cooling structures (including a cylindrical film holes and other three different bifurcated film holes) and four different blowing ratios are studied in detail. The results show that the film jets lift off gradually in the leading edge area as the blowing ratio increases. And the trajectory of the film jets gradually deviate from the mainstream direction to the spanwise direction. The cylindrical film holes and vertical bifurcated film holes have better film cooling effectiveness at low blowing ratio while the other two transverse bifurcated film holes have better film cooling effectiveness at high blowing ratio. And the film cooling effectiveness of the transverse bifurcated film holes increase with the increasing the blowing ratio. Additionally, the advantage of transverse bifurcated holes in film cooling effectiveness is more obvious in the downstream region relative to the cylindrical holes. The Area-Average film cooling effectiveness of transverse bifurcated film holes is 38% higher than that of cylindrical holes when blowing ratio is 2.
High-Throughput Screening of Aperiodic Superlattice for Minimum Thermal Conductivity Based on Atomistic Simulation-Informed Effective Medium Theory and Genetic Algorithm
Authors: Lin Shangchao , Liu Yixuan , Cai Zhuangli
Published: July 2021

Superlattices with suppressed thermal conductivity are of great significance in the field of thermoelectricity and can improve the thermoelectric conversion efficiency of materials. Due to Anderson localization of coherent phonons, aperiodic superlattices have lower thermal conductivity than their periodic counterparts. At present, the thermal conductivity of superlattices is mostly predicted through ab initio or molecular dynamics simulations, which is computationally expensive and limits the size of the system. Meanwhile, there are many layered structural combinations for aperiodic superlattices, making it difficult to efficiently screen through all the combinations to search structures with the minimum thermal conductivity. In this work, based on a modified series thermal resistance model (STRM), a new effective medium theory (EMT) is established to predict the thermal conductivity of periodic and aperiodic superlattices. An adjacency factor near the maximum-resistance layers and a correction function, respectively, are introduced to account for the phonon coherence effect and the degree of randomization in the layer thickness. Combined with the genetic algorithm, EMT enables high-throughput screening of millions of aperiodic superlattice structures. This work demonstrates that the thermal conductivities of aperiodic superlattices at a wide range of system size can be constantly reduced to 1.4∼1.8 W/(m·K), which occurs at averaged periodic thicknesses in a stable range of 2.0∼2.5 nm.
The Use of Variational Bayes Compared to Markov Chain Monte Carlo in The Estimation of Thermal Properties
Authors: Emery Ashley F.
Published: July 2021

Estimating the parameters that describe a thermal problem using Bayes statistics requires the specification of appropriate prior probabilities. That is p(P|D) = p(D|P)p(P)/p(D) where P = parameters, D = data and p(P) is the prior probability. For thermal problems this requires prior probabilities for density, specific heat, thermal conductivities, surface convective coefficients, radiative properties, and local heat release, Q. For many problems it is common to choose Gaussian probabilities to represent the errors. If the standard deviation is large, then the predictions can lead to negative values — a result that is not possible except for Q. Variational Bayes (VB) is an alternative to Markov Chain Monte Carlo (MCMC) and assumes that complex distributions p(a,b) can be replaced by factorization, p(a,b) = p(a)p(b), the mean field theory of physics. Overall Variational Bayes is particularly important for posterior probabilities, p(a|D), that have multiple maxima distributions.
Visualization of Heat Transfer Characteristics of 1EHT and Smooth Surface Tubes
Authors: Santos Humberto , Alves Ailson , Kukulka David , Smith Rick , Li Wei
Published: July 2021

High efficiency heat transfer tubes play a major role in industrial applications due to its benefits in recovering more energy, smaller footprint and lower operational costs. Given the importance of enhanced heat transfer tubes, an experimental investigation was carried out to compare the performance of the Vipertex 1EHT tube with an equivalent smooth tube using Particle Image Velocimetry (PIV). For the experimental setup a Dantec Dynamics PIV system was considered, and both tubes used had an outer diameter of 19.05 mm and inner diameter of 17.09 mm. Heat transfer experiments were conducted at 100% of the heater power capacity, i.e. 750 W, and observations were made in terms of boiling visualization, particle velocity vector field, and seeding particle velocity. The results obtained from the visualization showed higher density of bubble formation on the surface of 1EHT tube compared to the smooth tube, as well as a more frequent formation of bubbles. Moreover, the high-speed camera films recorded for comparison between smooth and enhanced tubes, showed that the dimples provided nucleation sites. Additionally, the average particle velocity for the 1EHT tube was 0.300 m.s−1 and for the smooth tube it was only 0.230 m.s−1, as a result of the higher heat transfer of the enhanced tube. These results suggest that the 1EHT tube performs better in boiling heat transfer application, which can be attributed to the enhanced heat transfer area produced by the series of dimples/protrusions and petals distributed over its surface.
The Simulation of Water Transports in Proton Exchange Membrane Fuel Cell Based on Lattice Boltzmann Method
Authors: Zhou Shikun , Zhang Yingchun , Xie Gongnan
Published: July 2021

The proton exchange membrane fuel cell (PEMFC) has many advantages, such as low operating temperature, fast reaction, and high energy density, etc. It is a very potential energy source. During battery operation, PEMFC will produce a large amount of water in the catalyst layer where the reaction occurs. The catalyst layer and gas diffusion layer (GDL) inside the battery are made of porous media. The water produced during the reaction will be discharged through these porous media structures, but the narrow gaps of the porous media structures will complicate the process. For example, too much water will flood the internal structure of the battery, making liquid water unable to drain smoothly. The above process may cause the reaction rate of the battery to decrease or even stop. Studying and understanding the water transportation process inside PEMFC is of great help in solving the above problems. Lattice Boltzmann method (LBM) is a promising numerical method for simulating the flows in porous media. Compared with the traditional CFD method, the lattice Boltzmann method (LBM) can deal with the pore structure of fine-scale better. In this paper, the lattice Boltzmann method (LBM) is employed to simulate the flow in the PEMFC. In order to reconstruct the porous media structure in PEMFC, the numerical reconstruction technique is used to generate porous media structures with different porosity. By simulating the flow of water in porous media, the transport laws of water in different porosity rates can be obtained. It provides a reference for improving the operating efficiency of proton exchange membrane fuel cells.