bluuebunny/crossref_metadata_2025 huggingface dataset:
A Novel Design for a Jaw-Thrust and Head Immobilization Device and its Successful Testing Using a Human Simulator
Authors: Deshpande Girish , Nair Kalyani , Hand Nick , Magnuson Jesse , Davis Alexa , Morris Martin
Published: March 2012

Jaw thrust is a common maneuver performed by medical care providers to open and maintain an airway in an unconscious patient. This essential procedure not only occupies a significant amount of time for the health care provider, but can also result in physical discomfort (low back pain) or fatigue when it is performed for an extended period of time. A mechanical device would not only prevent fatigue of the provider, but it can also free up time to perform other necessary tasks in management of the critically ill patient. The aim of this study is to develop a novel mechanical device that can perform jaw thrust on older children and adults along with maintaining an open airway. The jaw thrust device includes an extension arm mounted on a base to be placed on each side of the patient’s head. The mandible rest (jaw thruster) is mounted on each extension arm such that it can be positioned under the patient’s jaw. A chinstrap with rubber tubing is placed on four points across the base. A jaw thrusting pressure on the mandible rest causes a rotational force on the chin straps. This opens the mouth without substantially tilting the patient’s head. The device then maintains an open airway without any continuous attention. The supports on each side also immobilize the head in the midline and helps in maintaining the alignment of the cervical vertebrae. Finite element analyses of each of the components were done and a prototype was built for functional evaluation on a patient simulator. The device, when tested and applied to a human patient simulator in an ‘obstructed airway state,’ was able to open the airway evidenced by a cough reflex elicited in response. An ‘airway opened’ timestamp was also noted in the computer attached to the simulator.
Thermochemical Ablation: A Device for a Novel Interventional Concept
Authors: Geeslin Matthew G. , Cressman Erik N.
Published: March 2012

Solid focal and oligometastatic malignancies are appropriate targets for minimally invasive ablative procedures. Thermochemical ablation is an experimental minimally invasive procedure, which exploits certain features of current thermal and chemical tumor ablation therapies. Engineering principles have been used to design a device, which has been research-proven-capable of coagulating tissue through the combination of a thermal and chemical insult. This interventional device completes this assignment by separately guiding the flow of chemical reagents, drawn from auxiliary systems, to a point at the distal tip of an assembled apparatus. At this position, the respective flow-streams converge and undergo an exothermic reaction to produce a heated, hyperosmolar solute, which serves to ablate the targeted tissue. Ex and in vivo studies have confirmed the utility of this device and the physiologic toleration of this interventional concept.
The Impact of Wire Stent Fabrication Technique on the Performance of Stent Placement
Authors: Zhao Shijia , Liu Xiangyi (Cheryl) , Gu Linxia
Published: March 2012

Braided wire stents demonstrate distinct characteristics compared to welded ones. In this study, both braided and welded wire stents with the same nominal dimensions were crimped inside a sheath and then deployed into a stenosed artery using finite element analysis. The braided wire stent was generated by overlapping wires to form crisscross shape. A welded wire stent was created by welding the intersection points of wires to avoid sliding between wires. The effect of fabrication technique on mechanical behavior of Nitinol wire stents was evaluated. The results showed that relative sliding between wires reduced the deformation of the braided stent, which led to less radial strength than the welded one; therefore, the deployed braided stent was more conformed to the anatomic shape of the lesion and much less efficient for restoring the patency of the stenotic artery. Post balloon-dilation was commonly used to improve its performance in terms of lumen gain and deployed shape of the stent. On the contrary, the welded wire stent exhibited a high capacity for pushing the occlusion outward. It reached an approximately uniform shape after deployment. The welded joints caused larger deformation and high strain on the stent struts, which indicate a potential earlier failure for the welded stent. In addition, higher contact pressure at the stent-lesion interface and higher arterial stresses were observed in the artery supported by the welded stent. The peak stress concentration may increase the occurrence of neointimal hyperplasia.
Improving Stability Limits of Natural Gas Buoyant Diffusion Flames With Co-Flow of Air
Authors: Darabkhani Hamidreza G. , Oakey John E. , Zhang Yang
Published: March 2012

In this paper we report on experimental investigation of co-flow air velocity effects on the flickering behavior and stabilization mechanism of laminar natural gas diffusion flames (with more than 96% methane in the fuel composition). In this study, chemiluminescence and high speed photography along with digital image processing techniques have been used to study the change in global flame shape, the instability initiation point, the frequency and magnitude of the flame oscillation. It is found that the co-flow air is able to shift the location of the initiation point of the outer toroidal vortices created by Kevin Helmholtz types of instability. It then reaches a stage when outer toroidal vortices interact only with hot plume of gases further downstream of the visible flame. Once the toroidal structure is out of the flame zone the flickering of the flame will disappear naturally. This is in contrast with the effect of pressure which enhances formation and interaction of outer toroidal vortices with the flame due to essential changes at flow densities. It is observed that a higher co-flow rate is needed in order to suppress the flame flickering at a higher fuel flow rate. Therefore the ratio of the air velocity to the fuel velocity is a stability controlling parameter. It has been found that a non-lifted laminar diffusion flame can be stabilized with a co-flow air velocity even less than half of the fuel jet exit velocity. The oscillation frequency was observed to increase with the co-flow rate. The frequency amplitudes, however, were observed to continuously decrease as the co-flow air was increasing. The oscillation magnitude and the oscillation wavelength were observed to decrease towards zero as the co-flow air was increasing. Whereas the average oscillating flame height behavior was observed to be bimodal. It was initially enhanced by the co-flow air then starts to decrease towards the stabilized level. This height was observed to remain almost constant after stabilization, despite further increase at air flow rate.
Characterization of a Nanofluid Volumetric Solar Absorber / Steam Generator
Authors: Taylor Robert A. , Phelan Patrick , Adrian Ronald , Gunawan Andrey , Otanicar Todd
Published: March 2012

Solar thermal energy has shown remarkable growth in recent years — incorporating many new technologies into new applications [1]. Nanofluids — suspensions of nanoparticles in conventional fluids — have shown promise to make efficient volumetric-absorption solar collectors [2–4]. It has also been shown that concentrated light energy can efficiently cause localized phase change in a nanofluid [5]. These findings indicate that it may be advantageous to create a ‘direct, volumetric nanofluid steam generator’. That is, a solar collector design which could minimize the number of energy transfer steps, and thus minimize losses in converting sunlight (via thermal energy) to electricity. To study this, we use a testing apparatus where concentrated laser light at 532 nm — a wavelength very near the solar spectrum peak — is incident on a highly absorbing sample. The highly absorbing samples compared in this study are black dyes, black painted surfaces, and silver nanofluids — with de-ionized water as a base fluid. Each of these samples converts light energy to heat — to varying degrees — in a localized region. This region is monitored simultaneously with a digital camera and an infrared camera. The resulting observed temperature profile and bubble dynamics are compared for these fluids. For pure water with a black backing, some very high temperatures (>300 °C) are observed with a laser input of ∼75 W/cm2. Using a similar absorption potential, we observed higher temperatures in the nanofluids when compared to black dyes. A simplified boiling heat transfer analysis based on these results is also presented. We also noticed differences in bubble size and growth rates for the different samples. Overall, this study represents a proof-of-concept test for a novel volumetric, direct steam generator. These results of this test indicate that it may be possible to efficiently generate steam directly in a controlled, localized volume — i.e. without heating up passive system components.
Design and Experiment of a Concentrating Transpired Air Heating System
Authors: Shams N. , Mc Keever M. , Mc Cormack S. , Norton B.
Published: March 2012

This paper presents the physical design and experiments of the Concentrating Transpired Air Heating (CTAH) system as a combination of subsystems of parabolic primary and circular secondary reflector that concentrates incident solar radiation onto an inverted perforated absorber. Optical efficiency of the CTAH system has been analysed using a 2D ray tracing model. Experiments have been carried out for 50% perforated black painted aluminium inverted absorber for glazed and unglazed systems. Results show a significant temperature rise of the absorber surface in both cases. The maximum temperature of the absorber for the unglazed system is 52.1°C at 22.5°C ambient temperature, where as for the covered system, it is 67.9°C at 23.2°C ambient temperature.
Configuration of Building Fac¸ade Surface for Seasonal Selectiveness of Solar Irradiation: Absorption and Reflection
Authors: Naraghi Mohammad H. , Harant Adrien
Published: March 2012

A novel building fac¸ade surface configuration is proposed. This fac¸ade consists of grooved cavities that are configured in a manner that reflects summer (cooling season) insolation and absorbs winter (heating season) insolation. The effective absorptivities of the fac¸ade for various cavity reflectance characteristics, i.e., a wide range of diffuse and specular reflectance characteristics, are evaluated using a Monte Carlo model. It was determined the best cavity surface reflectivity is the one with fully diffuse surfaces and absorptivity of 0.7 or more. This reflectance characteristic of cavity results in a small depth of fac¸ade cavity and thicker divider fin between two adjacent cavities. The calculations in the present work are performed for the latitude of 41°N where both heating and cooling loads are significant. The same model can be applied to locations with different latitude which may result in slightly different cavity configurations and effective absorptivities.
Molecular Dynamics Predictions of Thermal Conductivity in Graphene for Phase Change Energy Storage Applications
Authors: Khadem Masoud H. , Wemhoff Aaron P.
Published: March 2012

Additives of highly-conducting nanoparticles such as graphene to a phase change material (PCM) improves PCM heat diffusion, which in turn produces better energy storage than pure PCM. Equilibrium Molecular Dynamics (EMD) simulations with Green-Kubo relations are used to predict the thermal conductivity of graphene sheets of various sizes and using different ensemble formulations. The Tersoff potential function has been implemented to model the covalent bonds between carbon atoms. The MD simulations predict an increase in thermal conductivity with graphene sheet size, and the predictions for the canonical (NVT) ensemble are consistently larger than those using the microcanonical (NVE) ensemble. The autocorrelation functions for the NVT simulations converge to zero for large sampling periods, which is not the case for NVE simulations.
Production of MgO From Residues of Saline Pools in “Las Coloradas” Yucatan, Mex. Using Thermochemical Energy Storage
Authors: Peraza Lizama Jose Carlos , Rubio Atoche Carlos Martin , Garcia Lira Alan
Published: March 2012

This paper proposes a method of thermochemical-energy storage from magnesium sulfate recovered from salt ponds of sea water. The idea develops from a project originally thought to obtain magnesium oxide from a salt plant in the Yucatan Peninsula, Mexico. The new idea is based on the exploitation of the heat of decomposition of magnesium sulphate. In the traditional literature, closed-loop, reversible reaction is considered, whereas in this work, an open-loop is proposed; that is, sulphur dioxide is separated from the magnesium oxide before cooling down to 700°C; in this way, magnesium oxide is obtained by thermal decomposition, and at the same time, the high heat of decomposition is used to store thermal energy for electricity generation; magnesium oxide, sulfuric acid and hydrogen are co-products of the process if another iodine reaction cycle is considered. This second process is again a modification of an open-loop traditional process, to a closed-loop process where no sulphuric acid is required.
Experimental Comparison and Economic Analysis of PV Technologies for Utility Scale Installations
Authors: Realmuto Jonathan D. , Sadineni Suresh B. , Madala Srikanth , Boehm Robert F.
Published: March 2012

The photovoltaic (PV) industry has seen remarkable progress in recent years, especially considering the advancement in materials and cell architecture. The potential of these technologies is investigated in a high insolation region of Southwestern United States, namely Las Vegas, where there is an abundance of surrounding barren land available for large scale installations. An experimental comparison of different PV technologies (HIT-Si, poly-c-Si, a-Si, and triple junction a-Si) under identical climatic conditions is the basis of this study. All tested modules have identical operating conditions, i.e. fixed installation plane, geographic location, and climatic conditions. The experiment verifies thin-film’s temperature independency, HIT-Si’s superior performance, and summarizes winter energy production of popular technologies in our climate. Lastly, an economic analysis is performed to compare the different technologies for prospective utility scale PV installations in southern Nevada, or similar climatic regions.
The Development of the Heliostat Focusing and Canting Enhancement Technique: An Optical Heliostat Alignment Tool for the National Solar Thermal Test Facility
Authors: Sproul Evan , Chavez Kyle , Yellowhair Julius
Published: March 2012

A heliostat array is a field of heliostats that focuses sunlight continuously on a central receiver in a power tower solar concentration system. Each heliostat consists of a structurally mounted mirror surface capable of reflecting sunlight onto a given target throughout the day. Typically, most heliostats are actually a group of individual mirror facets on a single moving frame. To achieve highly concentrated solar flux on a central receiver, each heliostat mirror facet has to be properly aligned (both canted and focused) when attached to the heliostat frame. In order to accurately evaluate and correct heliostat facet alignment, Sandia National Laboratories (SNL) and New Mexico Tech (NMT) have developed the Heliostat Focusing and Canting Enhancement Technique (H-FACET), a new and unique heliostat alignment tool that allows technicians to make fast and effective adjustments to facet canting and focusing. H-FACET uses a high resolution digital camera mounted on top of a receiver tower to observe the image of a stationary target reflected by a heliostat. Custom image processing software compares specific measurement points on the actual target reflection image with the corresponding measurement points on an ideally reflecting heliostat. Deviations between the actual and ideal reflection points reveal facet misalignments. Additionally, a live image of the ideal and theoretical points provides real-time feedback during the alignment correction process. SNL has implemented H-FACET at the National Solar Thermal Test Facility (NSTTF). Technicians have used the canting portion of the software to successfully cant a large section of the SNL NSTTF heliostat field. Visual inspections of reflected heliostat beam patterns have demonstrated noticeable improvements in beam size and shape resulting from the use of H-FACET. Preliminary quantitative analyses of H-FACET have shown beam diameter reductions of up to fifty percent. The beam reductions resulting from the use of H-FACET will assist in minimizing beam spillage and increasing flux densities. As a result, H-FACET may be a valuable tool in increasing the annual performance of a heliostat field. This paper details the computational algorithms used in H-FACET. These algorithms include accurate models of heliostat field geometries, sun position, facet orientations and facet shapes. This paper also discusses the optical methods used to determine the orientations and surface shapes of ideally aligned facets. Lastly, it investigates probable sources of error and ways to improve H-FACET.
Multi Objective Optimization of Lifecycle Cost, Unmet Load, and Renewable Energy Capacity for an Expansion of Existing Standalone Internal Combustion Generator (ICG) Systems
Authors: Perera A. T. D. , Attalage R. A. , Perera K. K. C. K.
Published: March 2012

Expanding existing Internal Combustion Generator (ICG) systems by incorporating renewable energy sources is getting popular due to its potential to reduce the emission of Green House Gases (GHG) and fuel consumption. Designing such Hybrid Energy System (HES)s become challenging due to the seasonal variation of renewable energy sources resulting either poor reliability of power supply or higher expenditure, which makes it essential to optimize Levelized Energy Cost (LEC), unmet load fraction and renewable energy capacity at the early design stages. This study evaluates the results obtained through such optimization based on evolutionary algorithm. In order to accomplish this, mathematical modeling and simulation of a stand-alone HES was carried out along with the optimization. Obtained results shows that both wind and Solar PV (SPV) capacity is having a significant impact on LEC, unmet load fraction and fuel consumption.
Comparison of Blower Door and Tracer Gas Testing Methods for Determination of Air Infiltration Rates Through Building Envelopes at Normal Operating Conditions
Authors: Patel Tapan , Mitsingas Constandinos , Miller James P. , Newell Ty A.
Published: March 2012

Tracer gas and blower door testing are two widely used methods to determine the rate of air infiltration through a building envelope. Blower door testing is performed at elevated pressure differentials across the building envelope whereas tracer gas testing is conducted at near zero differential pressures, better reflecting the air leakage rate at near normal building operating conditions. The primary objective of this study was to determine whether extrapolation of blower door test data to normal building operating conditions provides a good estimate of annual average air infiltration at those conditions. Two methods were used to extrapolate the data and were then compared to the baseline tracer gas tests. A secondary objective was to determine the ventilation rate of a residential facility using tracer gas tests. Tracer gas testing seems to be more reliable in determining the air leakage rate at normal operating pressures, but is sensitive to the tracer gas and ambient weather conditions. Regardless, for the subject facility, the ACH50/20 rule and Sherman’s ACH50/N correlation, extrapolated from the blower door tests, are within 6%–33% and 4%–38% of the tracer gas results, respectively. However, these errors are dependent on the assumptions used. Nevertheless, it appears that simple blower door testing can provide a reasonable measure of a building’s annual average air infiltration rate regardless of ambient conditions, whereas the more expensive and complex tracer gas tests may better reflect seasonal variations in air infiltration rates.
Affordable Universal Solar Tracker
Authors: Dehmlow Michael R.
Published: March 2012

With the global growth of solar technologies, the general public is beginning to utilize these efficient power sources in their everyday lives. In response, the NMSU Solar team is developing a product to help the enthusiasts and businesses that fuel this green movement. The NMSU Solar team is developing an affordable, standalone digital solar tracker that can be mounted to any device (e.g. solar panels, parabolic dish, etc.). The digital solar tracker is being designed to fit the needs of price conscious businesses and the abilities of hobbyists wanting to build their own personal tracker. The device utilizes a digital clock chip for the date and time, a simple magnetometer as a digital compass, and an accelerometer to detect the acceleration of gravity to locate the sun by its geographical location. Once the system has its target face within a few degrees of being normal to the sun, it employs a quadrant-photo-diode to precisely calculate the sun’s direction. By coupling the system with two multiplexers, an Arduino board, and an X-Bee chip, the system can be remotely controlled and monitored from a single command post up to a mile away. The use of the Arduino’s 10 bit resolution analog-to-digital converter allows the unit to have a remote DAQ system capable of reading temperatures, pressures, and power from the solar device. The results can be sent back to a computer for data logging or monitoring. Because these components are in water resistant housing with a small battery and a 10 watt solar panel, the system can give years of service. This basic design is an effective tool for large businesses or a “must have” upgrade for the enthusiast looking to gain every ounce of power from existing solar panels. By releasing the code and design to the public after its final development, the NMSU Solar team hopes to aid in the sustainability of a power hungry world.
Hybrid Solar System for Stationary Electric Power Generation
Authors: Hotz Nico
Published: March 2012

The present study investigates the feasibility, efficiency, and system design of a hybrid solar system generating electric power for stationary applications such as residential buildings. The system is fed by methanol and combines methanol steam reforming and Proton Exchange Membrane (PEM) fuel cells with solar collectors to generate the required heat for the steam reforming. The synergies of these technologies lead to a highly efficient system with significantly larger power densities compared to conventional systems and generate tremendous advantages in terms of installation and operation costs. The present investigation describes the entire proposed system and its components and presents first analytical, numerical, and experimental results of a larger project to prove the feasibility of such a system by analyzing first a bench test demonstrator generating around 10 W of electric power and finally a prototype for an entire single family household. It is shown that the methanol-to-electricity efficiency of the entire system is above 50%.
Design and Construction of a Dual Axis Passive Solar Tracker, for Use on Yucata´n
Authors: Pe´rez Sa´nchez Mari´a M. , Balam Tamayo David , Cruz Estrada Ricardo H.
Published: March 2012

In this investigation, we propose to use the thermal expansion properties of metals in a bimetallic strip as a base of operation of a passive solar tracker. The design process involved the determination of all aspects necessary to make a first prototype based on requirements and operating conditions previously identified. Predictive mathematical models were used to decide critical aspects. Certainly, some aspects of the design were determined experimentally to ensure the proper functioning of the solar tracker. The product of this research was the construction of a prototype with the ability to be placed with an average angular difference of 25 degrees to the position of the sun, under controlled conditions. The device created is a passive solar tracker with two degrees of freedom, one used to track the sun daily, operates automatically actuated by the bimetallic strip, the other one is manually adjusted in seasonal changes to compensate the variation in the decline of the sun along the year. Although the accuracy of the system is low, the cost of production is well below the purchase price of any commercial solar tracker, and its construction is simple, making it an economical alternative to increase the production of photovoltaic energy on a PV panel currently fixed.
Thermal Recuperation Modeling of a Solar Thermochemical Reactor
Authors: Mayer Luke J. , James Darryl L.
Published: March 2012

The United States spends over 700 billion dollars on foreign oil every year. A promising method to reduce this dependence, and be carbon-neutral as well, is concentrated solar thermochemical technology. Concentrated solar thermochemical technology has the potential to directly convert sunlight into a useable, carbon-neutral fuel that can be easily stored and integrated into our existing forms of energy demand such as transportation and heating fuels. Research is being performed by several groups at Sandia National Laboratories to fundamentally understand the complex physics and chemistry occurring within a solar thermochemical reactor prototype named the CR5 [counter-rotating-ring receiver/reactor/recuperator]. The objective of the work presented in this paper is to understand recuperative heat transfer within the CR5 as a function of reactor geometry and operational conditions. The CR5 vessel utilizes counter-rotating disks to provide for thermal energy recuperation, which is a necessity for an efficient reactor. Initially a simplified steady-state two-dimensional recuperation analysis was made to evaluate the relationship between the reactive material fin height and recuperation. The results from the simplified two-dimensional model indicate that recuperation is a strong function of fin height. Next, a more detailed, but still simplified, transient, three-dimensional model was developed. The initial three-dimensional simulations presented in this paper were performed to determine recuperator effectiveness and mesh density requirements for a generic case that had 2.5 kW energy input, fin height to gap ratio of 0.9, and finned reactor disks rotating at 1 rpm. A recuperator effectiveness of 88% and 85% was calculated from the finer and coarser meshes, suggesting that the coarser mesh (lumped in the fin thickness direction) is adequate for future parametric analysis simulations. This analysis will lead to a better understanding of recuperation as a function of reactor geometry, energy input, rotational speed, and thermophysical properties.
A New Approach to Maximize the Potential of Reciprocating Engines Operating on Bio-Fuel Energy
Authors: Lam Henry , Richter Mark , Ashton Geoff
Published: March 2012

Since the Industrial Revolution one of the oldest and “greenest” bio-fuel energy sources has been the byproduct of sewage and landfill. These biogases also known as Land Fill Gas or Digester Gas can be used as a fuel in an internal combustion engine, the clear choice for their efficiency in heat recovery and utility as a prime mover. The problem with bio-fuels is their unpredictable and varying fuel heating values which creates a challenge for maintaining air fuel ratio (AFR). If AFR is not controlled this can lead to engine instability and an increase in NOx, CO and THC emissions. With today’s ever increasing scrutiny of combustion pollutants this could spell the end of these types of fuels in combustion engines. AETC has embraced this challenge to provide a system that addresses the seasonal fuel gas quality, Low Heating Value (LHV) fluctuation to operate engines at best achievable emissions. This case study focuses on two Caterpillar 3516 Generator Engines rated 1000VA, at 1200 rpm, lean burn gas and turbocharged, running on renewable energy source supplementing power to a waste water treatment facility in California. The engines operate on wide range of fuel mixture including landfill, digester gas and air blended natural gas over a heating value range from 350–650 BTU. The fuel gas LHV constantly varies depending on fuel availability controlled by pressure switches within the individual fuel headers. Determining fuel heating values by using a gas calorimeter is not a viable option due to its high cost and poor reliability when operating in the environment of unfiltered Digester and landfill gas. AETC installed their Advanced Monitoring System (AMS) to utilize the engine as a calorimeter and to determine the fuels LHV. As part of the AMS functionality, the system acquired all the existing AFRC parameters such as kilo-Watt, RPM, Fuel Flow, Air Manifold Pressure and Temperature to determine the combustion performance. This simple approach offers surprisingly good performance while tying together basic thermodynamics, combustion performance and emissions. The system can also be used to parametrically determine engine emissions, based on the calculated combustion pressure without installing pressure sensors. The AMS monitors and determines emissions based on Trapped Equivalence Ratio, Effective Bulk Temperature or Pressure Ratio on single or multiple fuels providing a green/red light as an indicator of in/out of compliance accurately meeting today’s most stringent regulatory conditions.
A Novel Metric for Evaluation of Solar Forecasting Models
Authors: Marquez Ricardo , Coimbra Carlos F. M.
Published: March 2012

This work presents an alternative, time-window invariant metric for evaluating the quality of solar forecasting models. Conventional approaches use statistical quantities such as the root-mean-square-error and/or the correlation coefficients to evaluate model quality. The straightforward use of statistical quantities to assign forecasting quality can be misleading because these metrics do not convey a measure of the variability of the time-series included in the solar irradiance data. In contrast, the quality metric proposed here, which is defined as the ratio of solar uncertainty to solar variability, compares forecasting error with solar variability directly. By making the forecasting error to variability comparisons for different time windows, we show that this ratio is essentially a statistical invariant for each forecasting model employed, i. e., the ratio is preserved for widely different time horizons.
Analysis of Thermo-Active Foundations With U-Tube Heat Exchangers
Authors: Rouissi Khaled , Krarti Moncef , McCartney John
Published: March 2012

This paper presents a heat transfer model for thermally active drilled-shaft foundations used for heating and cooling buildings. Specifically, this paper presents a numerical approach to evaluate the unsteady temperature distribution within the ground medium surrounding the foundation as well as indoor/outdoor heat fluxes. In particular, a 2-D numerical solution was obtained using the finite difference technique with a purely implicit solution scheme. The results of the sensitivity analysis indicate that the efficiency of the thermo-active foundation can be significantly improved with a proper selection of design parameters including flow velocity, foundation depth, and foundation materials.
Photolytic Nanostructures for Hydrogen Production
Authors: Maclaskey Sean K. , Ramachandriya Karthikeyan D. , Topal C¸. O¨zge , Wilkins Mark R. , Yasar Murat , Kalkan A. Kaan
Published: March 2012

The present work demonstrates hydrogen generation by nanowire-nanoparticle conjugate structures under visible radiation. The mechanism of hydrogen generation is attributed to photolytic cleavage of water. The nanostructures are synthesized by sol-gel and reduction chemistries and characterized by XRD, SEM, TEM, and optical spectroscopy. Photolysis is analyzed by gas chromatography. We discuss the possible mechanisms involved in the observed photolysis in terms of unique attributes of the multifunctional nanostructures, such as efficient channeling of photocarriers to redox reactions at the interfaces and self-alignment of energy levels leading to efficient charge transfer. We demonstrate conversion and quantum efficiencies of 10.6% and 22.5%, respectively, for the first hour of photolysis, under 470 nm excitation.
Bioclimatic and Energy Efficiency Considerations for Social Housing: A Case Study in Hot Dry Climate
Authors: Ochoa Jose M. , Marincic Irene , Alpuche Maria G. , Canseco Sofia , Borbon Ana C.
Published: March 2012

The development of social housing In Mexico during the last decade has been supported by the different levels of government (federal, state, and municipal) in order to assist low-income families. The accelerated construction that takes place in order to address the housing deficit causes a reduction in the quality of design and construction, which is also affected by rising building costs. Environmental comfort conditions inside the dwellings are reduced drastically when houses are constructed without considering climate conditions, especially in hot arid regions. This situation generates uncomfortable thermal conditions for users and high-energy costs due to the unavoidable need of air conditioning. User profiles, architectural program, comfort preferences and guidelines for design and construction of future dwellings in the city of Hermosillo, in northwest Mexico, were determined by surveying beneficiaries of government affordable housing programs. One survey measured the degree of satisfaction of inhabitants in a sample of over 370 households; a second survey sampled 200 households and was aimed at determining aspects of comfort. This paper describes the results of thermal simulations carried out on two housing models. The first model represents the type usually constructed by commercial developers, and the second is a proposal developed by the research team according to guidelines based on the results of the research project described before. This study is a preliminary step in the construction of a physical model for experimental research and demonstration.
Design, Manufacturing and Testing of an Aperture Mechanism for a Solar Reactor
Authors: Al Hamidi Yasser , Abdulla Shameel , El Zamli Mahmoud , Rizk Ihab , Ozalp Nesrin
Published: March 2012

This study presents the test results of our variable aperture mechanism which allows a solar reactor to dynamically respond to the changes in incoming solar radiation. Virtual prototyping was used to check the control system implemented, while experimental testing helped us to identify the drawbacks of the mechanism and the loop holes in the control system. A comparison of variable aperture verses fixed aperture is given to show the benefits of this mechanism. Numerical methods such as Euler and the trapezoidal rule were used in modeling. Tests results show that varying aperture size saves 2.2% energy during a cloudy day and 0.3% on a sunny day. The results from these experiments have also shown that there is a slight deviation of the aperture blades from their required position (by ±0.5 mm to ±1 mm). But overall, the combination of the control system and the selected hardware along with the aperture assembly responded to the changes successfully. The results of our experimental findings and theoretical calculations showed that this variable aperture concept is able to provide more stable internal temperature inside a solar reactor compared to fixed aperture concepts.
Simulation Study of Tokyo Tech Rotary-Type Solar Reactor on Solar Field Test at CSIRO in Australia
Authors: Kaneko Hiroshi , Ishikawa Yosuke , Lee Chong-il , Hart Glenn , Stein Wesley , Tamaura Yutaka
Published: March 2012

This paper describes the performance evaluation of the Tokyo Tech Rotary-Type Solar Reactor (TTR-Solar reactor) by simulation study on the solar field test (20kW input) conducted at CSIRO in Australia. The rector is developed for solar hydrogen production by two-step water splitting with reactive ceramics. The simulation design of the solar reactor consists of three parts (1) release of oxygen, (2) heat exchange (generation steam), and (3) hydrogen evolution. In the solar field test at CSIRO, the O2-releasing step was examined, and the data obtained by the test were analyzed using an FEM simulation software (COMSOL multiphysics) in terms of concentration flux, reaction temperature, oxygen releasing reaction, and heat conductance. For a practical operation of the proto-type model at a solar field, we have investigated a desirable operation condition which achieved sufficient reaction temperature of the reactive ceramics in the reactor.
Efficient Solar Methane Reforming Using Spectrally Controlled Thermal Radiation Produced by Concentrated Solar Radiation
Authors: Maegami Yuriko , Iguchi Fumitada , Yugami Hiroo
Published: March 2012

Hydrogen energy infrastructure is expected to be a key technology for developing a sustainable society. However, the production route of hydrogen is still an important open problem. One prospective route of hydrogen production is a solar hydrogen system. In such a system, the thermal radiation spectrum, which plays an important role in chemical reactions, can be controlled by applying a two-dimensional surface grating to radiative materials. We used spectrally controlled thermal radiation to promote methane-steam reforming. Therefore, we demonstrated that hydrogen production strongly depends on the spectral intensity within the particularly resonant wavelength range, and that the amount of hydrogen produced is 5.8 times greater than that using normal thermal radiation. The conceptual design of a solar hydrogen system using spectrally controlled radiation is presented.
A Demonstration of Intelligent Control Technology in Tactical Power Grids
Authors: Curtiss Peter S. , Massie Darrell D. , Miller Michael A.
Published: March 2012

The concept of energy sharing is made difficult by the need to rapidly reconfigure military hardware in support of varied missions. Military equipment must have the ability to operate independently, even if not at optimal operating points, but then share power when opportunities exist. Dynamic reconfiguration of power systems has historically been difficult for mechanically or digitally controlled systems equipped with traditional technologies. This report describes a fundamental step in building an energy-sharing infrastructure, effectively creating redundant sources of energy supply and significantly reducing the logistical burdens associated with providing power. The authors have developed and tested an intelligent power management and power grid system that optimizes performance and efficiency through local and system-level autonomous control. The grid system was based on existing military, trailer-mounted, mobile power equipment. A reduction in fuel consumption of 36 percent was observed. In addition, prioritized load shedding was demonstrated as a means to prevent the generators from being overloaded.
Ultimate Trough: The New Parabolic Trough Collector Generation for Large Scale Solar Thermal Power Plants
Authors: Riffelmann Klaus-Ju¨rgen , Graf Daniela , Nava Paul
Published: March 2012

From 1984 to 1992, the first commercial solar thermal power plants — SEGS I to IX — were built in the Californian Mojave desert. The first generation of trough collectors (LS1) used in SEGS I showed an aperture area of about 120 m2 (1’292 ft2), having an aperture width of 2.5 m (8.2 ft). With the second generation collector (LS2), used in SEGS II to VI, the aperture width was doubled to 5 m (16.4 ft). The third generation (LS3) has been increased regarding width (5.76 m or 18.9 ft) and length (96 m or 315 ft) to about 550 m2 (5’920 ft2) aperture. It was used in the last SEGS plants VIII and IX, those plants having a capacity of 80 MW each. After more than 10 years stagnancy, several commercial plants in the US (the 64 MW Nevada Solar One project) and Spain (the ANDASOL projects, 50 MW each with 8 h thermal storage) started operation in 2007/2008. New collectors have been developed, but all are showing similar dimensions as either the LS2 or the LS3 collector. One reason for this is the limited availability of key components, mainly the parabolic shaped mirrors and heat collection elements. However, in order to reduce cost, solar power projects are getting larger and larger. Several projects in the range of 250 MW, with and without thermal storage system, are going to start construction in 2011, requiring solar field sizes of 1 to 2.5 Million m2. FLABEG, market leader of parabolic shaped mirrors and e.g. mirror supplier for all SEGS plants and most of the Spanish plants, has started the development of a new collector generation to serve the urgent market needs: lower cost and improved suitability for large solar fields. The new generation will utilize accordingly larger reflector panels and heat collection elements attended by advanced design, installation methods and control systems at the same time. The so-called ‘Ultimate Trough’ collector is showing an aperture area of 1’667 m2 (17’944 ft2), with an aperture width of 7.5 m (24.6 ft). Some design features are presented in this paper, showing how the new and huge dimensions could be realized without compromising stiffness, and bending of the support structure and improving the optical performance at the same time. Solar field layouts for large power plants are presented, and solar field cost savings in the range of 25% are disclosed.
Numerical Analysis of Heat Loss From a Parabolic Trough Absorber Tube With Active Vacuum System
Authors: Roesle Matthew , Coskun Volkan , Steinfeld Aldo
Published: March 2012

In current designs of parabolic trough collectors for concentrating solar power plants, the absorber tube is manufactured in segments that are individually insulated with glass vacuum jackets. During the lifetime of a power plant, some segments lose vacuum and thereafter suffer from significant convective heat loss. An alternative to this design is to use a vacuum pump to actively maintain low pressure in a long section of absorber with a continuous vacuum jacket. A detailed thermal model of such a configuration is needed to inform design efforts for such a receiver. This paper describes a combined conduction, convection, and radiation heat transfer model for a receiver that includes the effects of nonuniform solar flux on the absorber tube and vacuum jacket as well as detailed analysis of conduction through the rarefied gas in the annular gap inside the vacuum jacket. The model is implemented in commercial CFD software coupled to a Monte Carlo ray-tracing code. The results of simulations performed for a two-dimensional cross-section of a receiver are reported for various conditions. The parameters for the model are chosen to match the current generation of parabolic trough receivers and the simulation results correspond well with experimental measurements.
Thermochemical Conversion of Palm Kernel Shell (PKS) to Bio-Energy
Authors: Okoroigwe Edmund C. , Li Zhenglong , Unachukwu Godwin , Stuecken Thomas , Saffron Christopher
Published: March 2012

Palm kernel shell is an important by-product of oil palm production. It is often neglected and handled as waste in the product mix of palm oil production. One kilogram of PKS was pyrolized in a bench scale pyrolysis screw reactor at temperature range of 450°C to 500°C in 10mins. The process yielded 61 wt%, 24.5 wt% and 14 wt% bio-oil, bio-char and non condensable flammable gas respectively. Palm Kernel shell is relatively abundant in the tropical West Africa and Asia. Until recently PKS is commonly combusted for cooking purposes which contributes to total GHG emission. The products were characterized by determining their physical and chemical properties using standard methods. The thermochemical conversion shows that there is 29% and 26% increase in the higher heating values and lower heating values (on dry basis) respectively, of the bio-oil obtained when compared with the energy values of the original PKS. Similarly, the HHV of the bio-char is 62% higher than that of the original PKS. In addition the results of the GC-MS analysis of the bio-oil show that it contains useful chemicals that can be harnessed for industrial applications. The ash content of the bio-oil and the original PKS sample are 0.37% and 8.68% respectively, on as received, while the results of the elemental analyses show that there is < 0.08% and < 0.05% sulphur content of the PKS and its bio-oil respectively. This makes the products an environmentally suitable fuels for transportation and power generation. The results of this work show that the products compare well with those of other woody samples used for commercial pyrolysis process. PKS bio-char possesses the potential to be used as industrial absorbent in water treatment and process technology. Hence, PKS can be harnessed as potential future source of bio-energy and Activated carbon, and as such should be given adequate attention as a major product of oil palm processing for sustainable economic development of emerging economies.
Hydrogen Production and Utilization in Petroleum Refineries: A Study of the U.S. Oil and Gas Industry
Authors: Mohamed Mohamed A. , Soelem Radwa , Attar Fares , Ozalp Nesrin
Published: March 2012

Petroleum refining industry in the United States is the largest in the world operating 148 refineries. These refineries contribute a major economic value to the U.S. market for providing the chemical industry with vital products. The economic gain, however, is challenged by the increasing competitiveness within the refining sector as well as the unpredictable oil prices. Furthermore, environmental obligations also have been recently advocating low emission rates that may entail additional operating costs to refineries. In this study, we analyze hydrogen production and utilization in the U.S. oil and gas industry to characterize its key role and trends in this energy-intensive industry. We referred to U.S. Department of Energy data and statistics of hydrogen production rates as well as we considered other elementary factors of refineries productivity such as; economics of crude oil, power consumption and chemical outputs. Considering the fact that hydrogen-dependent processes in refining count as a key element in oil refining; it is certainly that efficient production and implementation of hydrogen in processes such as hydro-cracking and hydro-desulfurization will result in cost saving opportunities for refineries. From this point of view, we highlight the economic and environmental advantages of solar cracking of natural gas as an alternative way of hydrogen production. Hydrogen production in refineries could possibly benefit from utilizing this alternative method on both local and global levels. Economically, this study explains how solar cracking could save about $62 million in hydrogen production for U.S. refineries. Even though the momentum of desulfurization acts are not yet strong in the U.S., major European refining investments are in jeopardy if not soon to utilize enhanced desulfurization facilities in response to demands of lower sulfur content of refined products. A comprehensive expenditures model is presented in this study to monitor primary areas of saving in hydrogen production from the early stages of establishing a hydrogen production plant. Further alternatives showing potential are also included as future considerations for the refinery sector.
From Sulfenylation to Sulfhydration: What a Thiolate Needs to Tolerate
Authors: Finkel Toren
Published: March 2012

New techniques have revealed the dynamics of posttranslational modifications triggered by redox signaling that target cysteine residues.
Smoke Signals
Authors: VanHook Annalisa M.
Published: March 2012

Closely related hydrolases allow plants to distinguish between chemically similar compounds that elicit distinct physiological responses.