bluuebunny/crossref_metadata_2025_split huggingface dataset:
Computational Analysis of Thermal Performance and Entropy Generation of Nanofluid Flow in Microchannels
Authors: Li Jie , Kleinstreuer Clement , Feng Yu 
Published: July 2013

High heat loads of mechanical, chemical, and biomedical microsystems require heat exchangers which are very small, robust, and efficient. Nanofluids are dilute suspensions of nanoparticles in liquids, which may exhibit remarkable heat transfer characteristics, especially for heat removal in micro-devices. Minimization of entropy generation is potentially a design tool to determine best heat exchanger device geometry and operation.
Focusing on microchannel heat sink applications, the thermal performance of pure fluid flow as well as different nanofluids (i.e., Al2O3+water and ZnO+EG) with different volume fractions are discussed. The local and volumetric entropy rates caused by frictional and thermal effects are illustrated for different coolants, geometries and operational parameters. The Feng-Kleinstreuer (F-K) thermal conductivity model, which consists of a base-fluid static part, kbf, and a new “micro-mixing” part, kmm, i.e., knf = kbf + kmm, was adopted in the thermal performance study of nanofluid flow in microchannels. In addition, two effective nanofluid viscosity models have been analyzed and are compared in the current study.
In summary, the friction factor, pressure gradient, pumping power, local heat transfer coefficient, thermal resistance and entropy generation are evaluated for different nanofluids. The experimentally validated computational study provides new physical insight and criteria for design applications towards effective micro-system cooling.
Experimental Study of a High Performance Aligned Graphite Thermal Interface Material
Authors: Zhao Y. , Strauss D. , Chen Y. C. , Liao T. , Chen C. L. 
Published: July 2013

Thermal interface materials (TIMs) play a critical role in microelectronics packaging. In this paper, a novel aligned-graphite/solder TIM is described. Unlike traditional TIMs infiltrated with randomly-oriented high-conductivity fillers, the aligned-graphite/solder TIMs provide both extraordinarily high thermal conductivity along the heat transport direction, and controllable stiffness to conform to surfaces with different roughness and hardness, greatly improving the overall heat transfer performance. In addition, vertically connected solder layers can lock the graphite layers in place and reinforce the strength of the entire package.
Thermal performance of the graphite TIMs was determined experimentally based on the ASTM-D5470 method with comparison to two commercially available TIMs. The graphite TIMs also experienced a thermal cycling test and a high temperature stability test to establish its performance merit in practical applications.
Experiments showed that the overall thermal resistivity of a 150-to-200-μm-thick graphite TIM film was less than 0.035 °C/(W/cm2) when bonding two smooth copper surfaces together at a processing pressure of 30 psi, which corresponds to an approximately 2–3X improvement over a Ag-Sn solder alloy (Indalloy 121). Preliminary thermal cycling and high temperature stability tests showed that the thermal performance of the graphite TIM was very stable, and did not degrade during these tests. The tests also indicated that the presence of surface roughness of 10 μm on one of the copper surfaces reduced the overall thermal resistivity by approximately 30%. A numerical simulation verified this trend.
Study on Condensation of Biomass Pyrolysis Gas by Spray Bio-Droplets
Authors: Cheng Wen-long , Xie Kun , Shi Wen-jing 
Published: July 2013

Bio-oil, produced from biomass feedstock like rice hull, straw, wood flour and other biomass wastes by fast pyrolysis where the biomass feedstock is heated and pyrolized with a rapid rate and the pyrolysis gases produced are condensed rapidly, is an interesting potential alternative fuel oil.
Cooling rate of the biomass pyrolysis gas is an important factor effecting the production of bio-oil. In order to speed up the cooling rate, the high temperature biomass pyrolysis gas is cooled and condensed by spray droplets of produced bio-oil with low temperature in this paper. It was assumed that the chemical reactions among the components of pyrolysis gas can be ignored, a theoretical model based on the classic film model and the Maxwell-Stefan equation was presented to simulate the heat and mass transfer characteristics of the spray condensation of biomass pyrolysis gas. The effects of the initial pyrolysis gas temperatures, the initial bio-oil droplets temperatures and diameters, and the flow ration of the gas and the liquid droplets on the heat and mass transfer between the gas and the liquid droplets were analyzed by the model.
A Study of Small Molecule Absorption in Polydimethylsiloxane
Authors: Brewer Bryson , Gao Yandong , Li Deyu 
Published: July 2013

While polydimethylsiloxane (PDMS) has proven to be a popular material in the construction of microfluidic devices, the polymer network structure of PDMS makes it permeable to some molecules. This feature can be problematic for applications where thin PDMS walls are used to separate two different molecular streams or cell populations. Therefore, a better understanding of factors affecting small molecule absorption in PDMS is important for better design and operation of microfluidic devices.
We report on studies of various factors in the absorption of fluorescent dyes in PDMS. Results show significant effects of thermal aging of PDMS on the absorption of the hydrophobic molecule Nile Red. In addition, the short-term hydrophobic recovery of the PDMS devices after being plasma bonded to a glass slide was investigated. Furthermore, we have tested the effects of aspiration and flushing, which show that the wetting property (hydrophilic or hydrophobic) of the flushing solvents can significantly affect the absorption of the Nile Red dye. Finally, parallel tests of PDMS absorption of fluorescein isothiocyanate (FITC) were conducted with no absorption observed.
Microfluidics for Controlled Production of Thin Films and Particles
Authors: Baah David , Tigner Julaunica , Britton Bernard , Floyd-Smith Tamara 
Published: July 2013

Tailored materials with nano to micron dimensions are becoming increasingly important for niche applications in optics, personnel protection and biomedicine. Microfluidics is a robust platform for producing these tailored materials because of the spatial control that can be realized in microfluidic systems due to laminar flow profiles and small dimensions. For this work, a pre-polymer solution, consisting of water, polyethylene glycol diacrylate (PEGDA) and a photo-initiator, flows through a microfluidic channel. For the general scheme, the pre-polymer is exposed to UV light in the microfluidic channel to crosslink the polymer. Depending on the application, the model pre-polymer, PEGDA, may need to be substituted with a different photo-polymerizable pre-polymer to address issues such as chemical compatibility and moisture stability prior to commercialization. Nonetheless, proof-of-concept is demonstrated using PEGDA with results that are transferrable to other photo-polymerizable pre-polymers.
For this work, two distinct applications will be presented. In one application, the pre-polymer has a graded profile of nanoparticles. The nanoparticles modify the refractive index of the heterogeneous material and allow light to be directed through the material according to Snell’s Law. When the pre-polymer solution is polymerized, a thin film with a controlled refractive index profile is produced with potential for waveguiding applications. In a second application, the light is masked during UV exposure to produce particles instead of thin films. The particles can be of any two-dimensional extruded shape. If the pre-polymer solution is loaded with ceramic nanoparticles and sintered, ceramic particles that retain the shape of the original composite particle are produced. To date, numerous particle cross sections of polymeric particles and limited ceramic particles have been demonstrated with applications in liquid body armor, abrasives and drug delivery.
Physics Based Simulation of Large Size Particle Transport in Biomedical Applications
Authors: Chen Zhijian , Przekwas Andrzej , Athavale Mahesh 
Published: July 2013

In biomedical microdevices and medical applications there is a need to analyze fluid transport of solid structures with sizes comparable to channel dimensions. Examples include manipulation of biological cells in microfluidic devices or transport of thrombin particles in blood vessels. Computational modeling of such macroparticles is very difficult when the particle size is bigger than the size of the computational control volume (mesh element). In performing such simulations, conventional Lagrangian model of micro particles is not suitable since this approach doesn’t account particle’s volume blockage of the supporting Eulerian computational mesh. Other approaches such as deforming mesh or volume of fluid are either impractical of computationally very intensive or limited to structured meshes. We have developed a ‘macroparticle’ methodology where the large particle is represented as a large cluster of smaller particles (marker particles) that is “embedded” on a background computational grid. The macroparticle is then represented by blocking the cells in the background mesh that are overlapped by individual micro-particles. The discrete surface of the macroparticle is represented by partially or fully blocked cells of the background computational mesh. The translation /rotation/deformation motion of the macroparticle is calculated using a 6-DOF model with fluid pressure and shear forces acting on the particle surface used as forces and moments in calculating macroparticle position, velocity, acceleration and rotation. The size of the background grid determines the accuracy of the particle shape definition and the flow solution. The relevant physics and chemical conservation laws for each macroparticle are solved in a coupled, iterative method with the equation systems governing the background fluid domain.
This methodology has been successfully used for simulations of macroparticle-laden fluids in micro channels in biochips. As an application of this novel method, we have applied this technology to simulate a moving clot in blood flow and process of clot mechanical dissolution (thrombolysis).
A Study on the Effects of Ceramic Content of CNT / Metal Composite Surface Coatings Fabricated by Cold Spray for Boiling Heat Transfer Enhancement
Authors: Pialago Edward Joshua , Zheng Xi Ru , Ada Kristian Arvin , Kwon Oh Kyung , Cha Dong An , Park Chan Woo 
Published: July 2013

In this study, the enhancement of boiling heat transfer through surface modification of heat transfer materials by surface coating was investigated. Specifically, the study evaluated how the boiling heat transfer performance of CNT/metal composite coatings, fabricated by the cold gas dynamic spray process, was affected by the addition of different ceramic particles on the raw materials of these surface coatings. These raw materials were composite powders of CNT, Cu powder, and ceramic powders (SiC, AlN, and BN) that were mechanically alloyed using an attrition ball mill.
The boiling heat transfer tests were performed in a pool of R134a at a gauge pressure of 2.5 kg/cm2 and liquid temperature of 4.8°C. Test results showed that the addition of ceramic particles in the CNT/Cu composite powders can further augment boiling heat transfer. The augmented boiling heat transfer performance varied with the kind of ceramic powder added and with their quantity. The highest enhancement ratio was 2.57. This was exhibited by a Cu plate specimen that was cold spray coated with (5 vol.% CNT + 95 vol.% Cu) + 20 vol.% AlN composite powder.
Convection, Evaporation, and Condensation of Simple and Binary Fluids in Confined Geometries
Authors: Qin Tongran , Grigoriev Roman O. 
Published: July 2013

Rayleigh-Bénard and Marangoni convection in a layer of a homogeneous fluid with a free surface in the absence of phase change is a classic (and extensively studied) problem of fluid mechanics. Phase change has a major effect on the convection problem. Most notably, significant latent heat generated at the free surface as a result of phase change can dramatically alter the interfacial temperature, and hence, the thermocapillary stresses. Furthermore, differential evaporation in binary fluids can lead to considerable variation in the concentration field, producing solutocapillarity stresses, which can compete with thermocapillarity and buoyancy.
This talk describes numerical studies of convection in alcohol and alcohol-water mixtures due to a horizontal temperature gradient in the presence of phase change. We illustrate how the composition of the liquid and the presence of non-condensable gases (e.g., air) can be used to alter the balance of the dominant forces. In particular, by adding or removing air from the test cell, the direction of the flow can be reversed by emphasizing either the thermocapillary or the solutocapillary stresses.
Carbon Monoxide Emission Improvements From Combustion System Upgrades at the Wheelabrator Portsmouth Refuse Derived Fuel Plant
Authors: Pethe Samit J. , Britt Michael L. , Morrison Scott A. 
Published: July 2013

Wheelabrator Technologies Inc. (WTI) operates a waste-to-energy facility in Portsmouth, Virginia. At full capacity, a total of 2,000 tons/day of refuse derived fuel (RDF) can be fired in four identical boilers to generate a total of 600,000 lb/hr of steam and 60 MW of electricity. The boilers were originally designed to co-fire RDF and coal; however, coal burning capability was removed a few years after commissioning. The plant provides all of the process/heating steam and the majority of the electrical power to the nearby Norfolk Naval Shipyard.
Historically, the boilers had not been able to reliably achieve carbon monoxide (CO) emissions compliance. CO emissions experienced during normal boiler operation would be more than twice the mandated emission limit. WTI’s goal was to improve the boilers’ CO emissions performance while achieving sustained boiler operation at higher steam generation and RDF firing rates.
WTI contracted Jansen Combustion and Boiler Technologies, Inc. (JANSEN) to evaluate the operation of the boilers, to assess the overall feasibility of meeting WTI’s goals, and to develop design concepts to overcome boiler limitations. The project was initiated by an engineering site visit where boiler operating data was collected and evaluated to develop a baseline of boiler operation.
Current and new combustion system arrangements were evaluated with Computational Fluid Dynamics (CFD) modeling. The results confirmed that the root cause of the poor CO emissions performance was the inadequate penetration and mixing of the original overfire air (OFA) system (comprised of multiple rows of small ports on the front and rear furnace walls). CFD modeling also showed increased CO emissions to result from non-uniform RDF delivery profiles generated by the original fuel distributors that were installed at a high elevation over the grate. Modeling of the furnace with larger and fewer OFA nozzles placed on the side walls in an interlaced pattern, and the installation of “new-style” RDF distributors at a lower elevation where the boiler’s original coal distributors formerly were located was shown to significantly improve CO burnout.
From December 2010 to May 2011, the new combustion systems were installed on all four boilers. Subsequent testing has shown that CO levels have been lowered by more than 70% and boiler availability has been significantly improved. Nitrogen oxides (NOx) emissions, although slightly higher following the upgrade, are still within the NOx compliance limit.
This paper describes the process that led to a successful project, including: data collection and analyses, CFD modeling, equipment design and supply, operator training, and start-up assistance.
Air Permitting of New WTE Projects
Authors: Henderson Thomas M. , Hanisch John L. , Scott Kevin R. , Cohn Joel S. 
Published: July 2013

Two major new Waste-To-Energy (WTE) Projects have received Air Construction Permits under the Prevention of Significant Deterioration (PSD) program during the past two years and a third is scheduled to receive its permit prior to NAWTEC 20. These new facilities are being required to operate with significantly lower emissions of nitrogen oxides (NOx) and other major air pollutants than similar existing US facilities. This paper will explore the permitting process on these three projects and the divergent approaches being taken by the applicants to meet the stringent emission requirements imposed by the PSD permits.
The Palm Beach County (Florida) Renewable Energy Facility No. 2 (PBREF No. 2) will be a three unit, 3,000 ton per day (tpd) mass burn facility which will utilize Selective Catalytic Reduction (SCR) systems similar to that used in many recent European WTE facilities for NOx control. The Fairfield (Maryland) Renewable Energy (Fairfield) and Aercibo (Puerto Rico) Renewable Energy (Aercibo) Projects are each two unit, 2,106 tpd Refuse Derived Fuel (RDF) facilities which will utilize regenerative SCR (RSCR®) systems. This will be the first time RSCR® has been used in a WTE application. All three permits require achievement of a NOx emission rate of 45 parts per million by volume at 7% O2 dry basis (ppmvd).
PBREF No. 2 and Fairfield received PSD permits from delegated state programs prior to the new Greenhouse Gas (GHG) and condensable PM2.5 permitting rules going into effect at the beginning of 2011. Aercibo is being permitted by United States Environmental Protection Agency (EPA) Region II and will reflect new GHG and condensable PM2.5 permitting rules. This paper discusses the approach to the Best Available Control Technology (BACT) and Lowest Achievement Emission Rate (LAER) determinations and differences in final permit requirements.
Modeling and Design of a High Temperature Chamber Fed by a Plasma Torch for Removal of Tars
Authors: Demarthon Romain , Marias Frédéric , Fourcault Alice , Robert-Arnouil Jean Paul 
Published: July 2013

One way of biomass and/or waste recycling is its thermochemical conversion into combustible gas. Mainly composed of CO,H2 and CH4, the gas may also contain varying amounts of impurities (dust, polluting products, tar or soot). Specifically, there is a tar problem: their high condensation temperature is incompatible with an industrial utilization. They can cause rapid fouling, corrosion and abrasion into turbines or engines.
Proposed by EUROPLASMA, the CHO-Power process aims to generate electricity from a mixture of municipal waste and biomass using a fixed bed gasifier with conventional gas treatment. Its specificity consists of an unit called Turboplasma. This stage allows to reach very high temperature in order to obtain temperature around 1600K, and so to degrade all tars present, even heavier.
Indeed, EUROPLASMA built a gasification pilot unit based on fluidized bed technology, (called KIWI) to qualify the synthesis gas produced. TURBOPLASMA pilot scale will be installed there. The objective of this work is the design of this high temperature stage thanks to numerical modeling.
Reaction scheme used previously [4] to modelize tar degradation in the Turboplasma of CHO-Power, has been improved: a discrete phase modeling has been added providing a better view of the TURBOPLASMA internal behavior. Indeed, char particles from syngas can significantly change the reactor performance. This study shows that char particles react primarily with the H2O and CO2. Char gasification takes place in areas of high velocity and temperature gradient. Increased understanding of aerodynamics inside the reactor allows a better estimate of the overall performance of the reactor. Performance evaluation of the reactor is based on a set of parameters such as levels of heat loss, velocity gradient, mixing quality, residence time.
Comparison of Environmental Performance Expectations: Gasification Versus Mass-Burn WTE Facilities Currently Under Construction in North America
Authors: Rice Elizabeth A. 
Published: July 2013

In recent years, factors including limited landfill capacity, increasing costs of fossil fuels, and increased pressure to actively recover value from waste in the form of materials and energy have encouraged municipalities throughout North America to advance waste management strategies that utilize waste-to-energy (WTE) technologies as an alternative to landfilling. Currently, utilization of alternative conversion technologies, including gasification, is limited to small-scale or pilot municipal solid waste (MSW) to energy facilities in North America. Though limited history of environmental performance when using MSW as a primary feedstock has delayed public acceptance of facility proposals, municipalities are now moving forward with alternative conversion technology applications.
In Florida, two entities have received permits from the Department of Environmental Protection to proceed with construction of gasification facilities — Geoplasma, Inc. in St. Lucie County, and INEOS New Planet BioEnergy in Vero Beach. In Edmonton, Alberta, Canada, Enerkem GreenField Alberta Biofuels has received a permit from Alberta Environment to begin construction of a gasification facility that will produce bioethanol from post-recycled MSW.
Since 1996, no new greenfield MSW-processing mass burn facility has been constructed in the U.S., though facilities in Hillsborough County, FL; Lee County, FL; and Olmstead County, MN have undergone expansions, and in Honolulu, FL, a 900 TPD unit is currently under construction. In recent years, two municipalities have received permits to proceed with construction of mass burn WTE facilities and have made significant progress toward implementation: The municipalities of Durham and York, Ontario, Canada and The Solid Waste Authority of Palm Beach County, Florida.
This paper will provide a direct comparison of the expected environmental performance of the recently permitted gasification facilities to the expected environmental performance of the recently permitted mass burn WTE facilities, as established by permit applications and emissions modeling studies. Comparison of emissions of particulate matter, sulfur dioxide, nitrogen oxides, carbon monoxide, volatile organic compounds, and hydrogen chloride will be performed on the basis of one ton of feedstock processed. Emission of these pollutants at the recently permitted facilities discussed above will be contrasted with emissions experienced at currently operating WTE facilities within North America.