bluuebunny/crossref_metadata_2025 huggingface dataset:
Biomechanical and Biochemical Study of Muscle-Tendon-Bone in Porcine Digital Flexor Tendon
Authors: Danley Bryan B. , Huang Shadow
Published: March 2016

The musculoskeletal system provides the body with both movement and support. In particular, contractile forces developed in the muscles are transmitted through the muscle-tendon junction (MTJ) into the tendon and then through the tendon-bone insertion into the bone. Each junction occurs between two dissimilar materials (muscle-to-tendon and tendon-to-bone) and neither is fully understood. The current study analyzes the relationship between the tissue microstructure and macro-scale biomechanical properties of the muscle-tendon-bone unit to better understand the anisotropic mechanical behavior of the tissue. Collagen content was assayed at various locations along the porcine digital flexor tendon. Collagen concentration as a percent of the wet weight in the bone end was found to be 20.4±5.2% (n=6), the mid tendon to be 20.6±5.3% (n=6), and the muscle end to be 25.2±3.6% (n=4). No statistical differences were found between these collagen concentrations.

Additionally, to the best of the authors’ knowledge, this is the first study to report cross-sectional stress-strain data for the muscle-tendon-bone unit. Results indicate that the tendon cross-sectional stiffness increases from the proximal end to the distal end. However, no direction dependent anisotropies were found between the mediolateral and dorsopalmar directions. Effects of microstructural components, such as glycosaminoglycans and collagen, and phenomenon such as fibril sliding and cross-linking, are discussed in relation to the reported cross-section stress-strain response. This work provides a synergistic approach for quantifying biomechanical and biochemical properties of biological tissue, and potentially facilitates the development of tissue engineered MTJ and tendon-bone insertion.
Experimental Measurement of Vacuum Assisted Drying of Spent Nuclear Fuel
Authors: Rivera Matthew , Manteufel Randall
Published: March 2016

A prevalent issue within extended long term dry storage units for spent nuclear fuel has always been fuel and cask contamination. This contamination can be the result of the helium within the cask leaking into the atmosphere or inadequate vacuum drying techniques. Once the cask integrity has been compromised, the helium starts to leak, and the resulting space once occupied by helium in the casks is replaced with ambient air. One of the other prominent gases found within ambient air besides oxygen is water vapor which can be a result of both helium leaking and poor vacuum drying techniques. Contact between water and the fuel rods/assemblies for a prolonged amount of time can result in corrosion of the fuel cladding, and the canister if exposed. The potential of corrosion of the fuel cladding increases risk of radioactive fission fragments contaminating the environment, increases the radioactive period of spent nuclear fuel, and decreases the potential for fuel rod repurposing within the future if U.S. law permits.

With literary findings showing liquid water within the inner cask in a long term storage unit of fifteen years or longer, proper drying techniques have not been fully developed. There are a number of projected theories about how water is entering the cask without an external crack or imperfection within the inner cask walls. This case study aims to solve this issue by inspecting the vacuum drying process of the fuel rods/assemblies from the temporary on-site storage pools to their respective long term dry storage casks.

The purpose of this case study is to conduct a laboratory experiment of a scale replica of one dry storage cask and the vacuum drying process before long term storage. The experiment will be focused around the process of applying several cycles of vacuum and backfilling the cask with Helium. The purpose of several cycles of backfilling gas is to simultaneously introduce more of a pressure gradient for water evaporates to depart the pressure vessel and to avoid thermodynamic temperatures that would otherwise freeze the top layer of water. To do this, the vacuuming process must be properly understood, as pulling a vacuum drops pressures instantaneously. There are possibilities of freezing water vapor into its solidified form due to its thermodynamic triple point during this vacuum process. Once water is trapped under a layer of ice within the vessel, water will remain throughout storage time due to restrictions to its own geometries. The importance of developing a scale model and improving the drying process that precedes long term storage of spent nuclear fuel is a necessary solution to existing contamination results for practical future applications within the United States and other countries moving towards long term storage of spent nuclear fuel.
Failure Analysis and Testing of an Overhead Door Design
Authors: Clarke Christopher , Forrest Stephen , Herbst Brian , Bell Lauren
Published: March 2016

Overhead doors see widespread use, primarily in garage door and truck body applications. Although overhead door systems can appear benign to users, there are some types of door system failures that can expose users to potentially injurious hazards. This paper will present the design and operation of an overhead door system in widespread use, the potential hazards of the system, and the possible failure modes of the system. A methodology will be presented that was used to analyze a door system that malfunctioned and resulted in a serious injury to a user. A test matrix which was used to analyze and replicate this malfunction is also presented.
Design of a Screw Heat Exchanger as the Liquid-Suction Heat Exchanger in a Vapor Compression Refrigeration System
Authors: Antonio Francis J. , Berana Menandro S. , Danao Louis Angelo M.
Published: March 2016

The aim of this study is to optimize the design of a screw heat exchanger (SHX) in terms of varying coil aspect ratio (CAR) as a liquid-suction heat exchanger (LSHE) in a vapor compression refrigeration system through Computational Fluid Dynamics (CFD) simulation. The novelty of this study is that it focuses on the fluid-to-fluid heat transfer of SHX to measure its heat transfer effectiveness as compared to many research studies that focus only on helical duct heat exchanger under constant wall temperature and constant heat flux. Optimization of the SHX was done through conjugate heat transfer in a CFD model. High confidence on the computational package was determined as the results of the package on heat transfer between water flows through a shell-and-coil heat exchanger match well with available experimental data of the same setup in related literature.

The performance of SHX with square coil section (SHXSCS) was compared to that of the SHX with circular coil section (SHXCCS). The optimum SHXSCS was then compared to a commercially available LSHE in the form of tube-in-tube heat exchanger (TTHE) which is the most commonly used LSHE in vapor compression refrigeration systems.

The SHXSCS has nominal degrees of superheat of 22.17 °C and nominal degrees of subcool of 17.63 °C. The ratio of the heat of superheating to that of subcooling is seen to increase with increasing CAR and NTU. The RE of SHXSCS is larger by an average of 3.87%, 18.25% and 26.46% compared to those of the SHXCCS, TTHE and the standard vapor compression cycle (VCC), respectively. The COP of the SHXSCS is 2.55%, 10.74% and 5.94% higher than those of the SHXCCS, TTHE and the standard VCC, respectively. The SHXSCS is more capable than SHXCCS in splitting the heat due to the less complicated square cross sections of flows and even less interface materials for heat transfer. Moreover, the SHXSCS is more effective in splitting the heat from subcooling into moderated superheating and largely to the surounding compared to the TTHE mainly due to longer length of interaction of the flows.
Preliminary Analysis of an Innovative Rotary Displacer Stirling Engine
Authors: Bagheri AmirHossein , Bostanci Huseyin , Foster Philip R.
Published: March 2016

The Stirling cycle has recently been receiving renewed interest due to some of its key inherent advantages. In particular, the ability to operate with any form of heat source (including external combustion, flue gases, alternative (biomass, solar, geothermal) energy) provides Stirling engines a great flexibility and potential benefits for many applications. However, several aspects of traditional Stirling engine configurations (i.e., the Alpha, Beta, and Gamma), specifically complexity of design, high cost, and relatively low power to size and power to volume ratios, limited their widespread applications to date. This study focuses on an innovative Stirling engine configuration that features a rotary displacer (as opposed to common reciprocating displacers), and aims to utilize a preliminary analytical analysis to gain insights on its operation parameters. Although the analysis involves idealizations, it still provides useful design guidelines as a first step towards optimization.

This study adopts some of the assumptions from the well-known Schmidt analysis, and follows a similar approach for the innovative rotary displacer configuration. As part of this preliminary analysis the optimum phase (lead) angle is determined to be 90°. In addition, the work ratio normalized for the optimum phase angle is presented. Other studied parameters include the internal volume of rotary displacer over the volume of power cylinder, and the volume of “dead spaces” over the volume of power cylinder at various ratios. Although the dead space have negative effects on overall performance and efficiency, they are dictated by the practical design constraints. Lastly, this study considers work output of the engine over a range of heat sink to heat source temperature ratios, and varies the heat sink or heat source temperatures independently. The analysis addresses both low and high temperature differential situations for the purpose of waste heat recovery and power generation, respectively.
Multi-Reference Interface Inheritance for Concurrent CAD Interoperability Applications
Authors: Staves Daniel R. , Bowman K. Eric , Freeman Robert S. , Red Ed
Published: March 2016

Collaborative CAD promises to solve the major design challenge facing industry relating to interoperability and design sharing: translation between heterogeneous CAD systems. Translation issues alone account for upwards of $1 billion in costs for the US automotive supply chain. With collaborative CAD, parts and assemblies can be viewed and edited simultaneously by multiple users in geographically diverse locations, without the need to manually export and send models as neutral files. In order to attain interoperability between CAD systems, a neutral format is used to pass data between clients. By expanding the traditional neutral format to include interfaces, the object hierarchy more closely resembles the hierarchy employed by native CAD systems — allowing more feature information, and thus design intent, to be preserved. The interface method also enforces referential integrity in the neutral representation of CAD objects by limiting the type of objects to be referenced to valid objects. Corrupt and invalid data can be caught and corrected before being transferred to other users viewing the CAD model.
A Comparative Study of Hydrogen Storage and Hydrocarbon Fuel Processing for Automotive Fuel Cells
Authors: Kazemiabnavi Saeed , Soundararaj Aneet , Zamani Haniyeh , Scharf Bjoern , Thyagarajan Priya , Zhou Xinle
Published: March 2016

In recent years, there has been increased interest in fuel cells as a promising energy storage technology. The environmental impacts due to the extensive fossil fuel consumption is becoming increasingly important as greenhouse gas (GHG) levels in the atmosphere continue to rise rapidly. Furthermore, fuel cell efficiencies are not limited by the Carnot limit, a major thermodynamic limit for power plants and internal combustion engines. Therefore, hydrogen fuel cells could provide a long-term solution to the automotive industry, in its search for alternate propulsion systems. Two most important methods for hydrogen delivery to fuel cells used for vehicle propulsion were evaluated in this study, which are fuel processing and hydrogen storage. Moreover, the average fuel cost and the greenhouse gas emission for hydrogen fuel cell (H2 FCV) and gasoline fuel cell (GFCV) vehicles are compared to that of a regular gasoline vehicle based on the Argonne National Lab’s GREET model. The results show that the average fuel cost per 100 miles for a H2 FCV can be up to 57% lower than that of regular gasoline vehicles. Moreover, the obtained results confirm that the well to wheel greenhouse gas emission of both H2 FCV and GFCV is significantly less than that of regular gasoline vehicles. Furthermore, the investment return period for hydrogen storage techniques are compared to fuel processing methods. A qualitative safety and infrastructure dependency comparison of hydrogen storage and fuel processing methods is also presented.
Enhanced Light Absorption in Thin Crystalline Silicon Solar Cells With Silica Nanoparticles
Authors: Yang Huan , Li Ben Q. , Liu Changhong
Published: March 2016

In this paper, numerical simulations are performed to investigate the effects of different configurations of dielectric SiO2 particles on the improvement of light absorption in 2-μm single crystal silicon photovoltaic solar cells. The numerical model is developed on the basis of the FDTD solution of the transient Maxwell equations and checked with analytical solutions for simple configurations and against experimental measurements of light absorption in bare Si films. The numerical model is also checked for mesh sensitivity such that the computed data are approximately mesh-insensitive. Computed results are analyzed and the short circuit current of the Si films is used as a measure of the efficiency for light trapping in Si films. Results show that with SiO2 nanoparticles closely packed atop the Si film, good improvement in light absorption efficiency is achieved if the particle is 700 nm in diameter. This is considered to be attributed to the anti-reflection effect of the particle layer and the whispering gallery mode of SiO2 particles excited by the incident light. If the closely arranged SiO2 nanoparticles are embedded half-way into a Si film through its top surface, the light absorption is enhanced by ∼120%, approaching to the Yablonovitch limit. The structured surface of the Si film can almost realize 100% anti-reflection of incident, because the use of the half embedded SiO2 particles in the top layer of the Si film creates a graded transition of the effective refractive index along the direction of incident; and as a result almost all the light with the wavelength below or near 500nm are absorbed due to the higher imaginary part of the refractive index. The improvement in light absorption with the wavelength greater than 500nm comes, however, from the resonance behavior of the SiO2 nanoparticles. Experiments are now planned and measurements of light absorption will be conducted with a photospectrometer to validate the above calculations.
The Reliability and Sensibility Analysis for an Aircraft Lock Mechanism Based on the Surrogate Models
Authors: Guo Wei , Cui Weimin , Yu Tianxiang , Song Bifeng
Published: March 2016

In order to analyze the reliability of the new lock mechanism which is an important part of aircraft cabin door system, this paper studies the reliability and sensitivity for the lock mechanism based on surrogate models and variance methods respectively. Function hazard analysis (FHA) and failure mode effects analysis (FMEA) of lock mechanism is studied firstly. Then, based on dynamics simulation model, performance function and various random variables, the widely used surrogate models of lock mechanism is established and verified. Based on the most accurate metamodel which has been established, the unlocking reliability which is the most hazardous function is calculated. Finally, the variance-based sensitivity method is used for sensitivity analysis of influence factors, the result shows that the tension of lock-hook from lock-ring is the largest influence factor on the unlocking reliability, which could contribute to the analysis and further improvement of lock mechanism.
Transient Response of a Cross Flow Heat Exchanger Subjected to Temperature and Flow Perturbations
Authors: Silaipillayarputhur Karthik , Idem Stephen A.
Published: March 2016

The transient performance of a multi-pass cross flow heat exchanger subjected to temperature and mass flow rate perturbations, where the heat exchanger flow circuiting is neither parallel flow nor counter flow, is considered in this work. A detailed numerical study was performed for representative single-pass, two-pass, and three-pass heat exchangers. Numerical predictions were obtained for cases where the minimum capacity rate fluid was subjected to a step change in inlet temperature in absence of mass flow rate perturbations. Likewise, numerical predictions were obtained for the heat exchangers operating initially at steady state, where a step mass flow rate change of the minimum capacity rate fluid was imposed in the absence of any fluid temperature perturbations. The transient performance of this particular heat exchanger configuration subjected to these temperature and flow disturbances has not been discussed previously in the available literature. In the present study the energy balance equations for the hot and cold fluids and the heat exchanger wall were solved using an implicit central finite difference method. A parametric study was conducted by varying the dimensionless quantities that govern the transient response of the heat exchanger over a typical range of values. Because of the storage of energy in the heat exchanger wall, and finite propagation times associated with the inlet perturbations, the outlet temperatures of both fluids do not respond instantaneously. The results are compared with previously published transient performance predictions of multi-pass counter flow and parallel flow heat exchangers.
Reconfigurable Compliant Cellular Material With Programmable Compliant Cellular Structure
Authors: Kang Ye , Kim Kwangwon , Ju Jaehyung
Published: March 2016

Cellular materials have two important properties: structures and mechanisms. This property enables one to design structures with proper stiffness and flexibility. Recent advance in 3D printing technologies enable engineers to manufacture complex cellular structures. In addition, use of smart materials, e.g., shape memory polymers (SMPs), for 3D printing enables us to construct mesostructures actively responsive to environmental stimuli with a programmable function, which may be termed ‘4D Printing’ referring to additional dimension on time-dependent shape change after 3D printing. The objective of this study is to design and synthesize active reconfigurable cellular materials, which enables the advance of technology on intelligent reconfigurable cellular structures with 4D printing. A two-layer hinge of a CPS functions through a programmed thermal expansion mismatch between two layers and shape memory effect of an SMP. Starting with thermo-mechanical constitutive modeling of a compliant porous hinge consisting of laminated elastomer composites, macroscopic behaviors of a reconfigurable compliant porous structure (CPS) will be constructed using the strain energy method. A finite element (FE) based simulation equipped with a user subroutine will be implemented with ABAQUS/Standard to simulate time-dependent thermo mechanical behaviors of a CPS.

The designed CPS with polymers shows an extremely high negative Poisson’s ratio (∼ −120) and negative thermal expansion coefficient (−2,530 × 10−6/C). When programmed with an appropriate thermo-mechanical procedure, the hinge of the CPS bends either in positive and negative sign, which enables to tailor the CPS into desired intermediate and final configurations, ending up with achieving a reconfigurable CPS. This paper demonstrates that actively reconfigurable compliant cellular materials (CCMs) with CPSes can be used for next-generation materials design in terms of tailoring mechanical properties such as modulus, strength, yield strain, Poisson’s ratios and thermal expansion coefficient together with programmable characteristics.
Development of Charge Electrochemical Accumulator of Conductive Polypyrrole/ Cassava Starch Biopolymers
Authors: Acosta Humánez Manuel F. , Arrieta Almario Alvaro Angel , Ávila Gómez Adrián Enrique , Martínez Guarín Arnold Rafael , Palacio Vega Mario Andrés , Nova Casares Víctor Antonio
Published: March 2016

The development of electrochemical accumulators of charge starting from biopolymer conductors of cassava starch chemically synthesized from cassava and adding plasticizers (glycerol. polyethylene glycol and glutaraldehyde) as well as lithium perchlorate in varying concentration and the addition of polypyrrole, which was prepared electrochemically by chronoamperometry. Each of these polymers is used as a polymer solid electrolyte and electrode respectively. Paratoluensulfonic acid and indigo-carmine was used as counterion. Surface response methodology was implemented in order to maximize experimental conditions for accumulators assembly (chemical compositions of biopolymers) as well as electric properties. For all compositions it shows optimal values of electric properties. Comparing desirability between chemical compositions, it showed that best conditions for assembly of electrochemical accumulator were obtained with composition 2.
Characterization of a Fast Responding Composite Thermal Bimorph Film Actuator Based on Carbon Nanotube Sheets
Authors: Bever Alaina M. , Brown Peter J. , Lane Kerry V. , Levy-Wendt Benjamin L. , Yasuda Nathan K. , Han Yen-Lin , Shih Frank J.
Published: March 2016

As the extraordinary thermal, electrical, and mechanical properties of carbon nanotubes (CNTs) have become better understood, they have found their way into a wide range of engineering applications. Used in conjunction with fiber-reinforced composite materials, CNTs provide enhanced thermal conductivity, interlaminar strength, and ballistic resistance of laminar composite materials. However, the direct application of the macro form of CNT sheet as a heating element for use in a thermal actuator has not been reported. In the present study, CNT sheets are used as a flexible, efficient, and fast-responding heating element that induces transverse motion in a multilayered functional polymer composite based on thermal expansion mismatch between layers. The CNT heating element is designed to have a specific cross-sectional area to length aspect ratio, giving it a specific resistance and power consumption characteristic. The heating element is bonded to a compliant silicone elastomer substrate and a stiff constraining polyimide thin film, forming a flap-like actuator. The robust design and simple operation of the actuator makes it a potential candidate for control surfaces on micro air vehicles and actuating elements in microscale fluid pumps. The heating response rate of the actuator is measured experimentally using an infrared thermal imager. The temperature change in the thermal actuator is measured as a function of input voltage. The edge deflection of the actuator is also measured as function of the applied voltage. Finally, finite element modeling of the thermal actuator, a parametric study of material selection, and deflection analysis are conducted to better understand the result of these experiments.
Elastic Turbulence Effects on the Performance of a Miniature Viscous Disk Pump
Authors: Lund Benjamin , Brown Maria , Jennerjohn Mary , Ligrani Phil , Fatemi Arshia
Published: March 2016

Within the present investigation, a miniature viscous disk pump (VDP) is utilized to characterize and quantify non-Newtonian fluid elastic turbulence effects, relative to Newtonian flow behavior. Such deviations from Newtonian behavior are induced by adding polyacrylamide to purified water. The VDP consists of a 10.16 mm diameter disk that rotates above a C-shaped channel with inner and outer radii of 1.19 mm, and 2.38 mm, respectively. A channel depth of 230 μm is employed. Fluid inlet and outlet ports are located at the ends of the C-shaped channel. Within the present study, experimental data are given for rotational speeds of 1200–3500 rpm, pressure rises of 0 to 700 Pa, and flow rates up to approximately 0.00000007 m3/sec. As such, the overall intent is enhancement of fundamental understanding of the associated physical processes associated with elastic turbulence, as it is induced in liquids by polymers subject to stretching and constriction by flow strain. Different amounts of flow strain are induced by changing the rotational speed of the disc. As rotational speed increases, overall magnitudes of flow strain increase, and the polymer strings become locally more agitated. The result is growth in the local elastic stress, and development of the Weissenberg instability as the Weissenberg number increases. Overall consequences include increased mixing, increased transport levels, and larger static pressure rise magnitudes. Also considered are changes to effective viscosity from the presence of elastic turbulence.
Modeling and Optimization of a Novel Heat Recovery Design for Thermoelastic Cooling Systems
Authors: Qian Suxin , Ling Jiazhen , Hwang Yunho , Takeuchi Ichiro , Radermacher Reinhard
Published: March 2016

The traditional refrigerants used in the vapor compression cycles have significant environmental impacts due to their high global warming potential. To address this challenge, solid-sate cooling technologies without using any aforementioned fluids have been developed rapidly during the past decades. Thermoelastic cooling, a.k.a. elastocaloric cooling, is a new concept, and thus no systematic studies of it have been conducted to date. Heat recovery plays an important role in the performance of the cooling systems, affected by the parasitic internal latent heat loss inside the cycle. A novel heat recovery (HR) scheme was been proposed in our previous study to minimize such parasitic internal latent heat loss. The objective of this study is to further investigate the performance improvement potential of the proposed heat recovery method by introducing the optimization study using the previously validated heat recovery model. The dynamic model details are revisited. The assumptions behind the model are re-examined by using the real thermoelastic cooling prototype geometries and materials properties of nickel-titanium tubes. A multi-objective optimization problem was formulated for the model and solved by MatLab. The heat recovery efficiency and the heat recovery duration were used as optimization objectives. A well-spread Pareto solutions were obtained, and a final solution was chosen with a 6.7% penalty in HR efficiency but six times faster cycle.
Optimization of Biporous Micropillar Array for Enhanced Heat Transfer Performance
Authors: Wei Mengyao , Somasundaram Sivanand , He Bin , Liang Qian , Raj Rishi , Tan Chuan Seng , Wang Evelyn N.
Published: March 2016

Biporous evaporator wicks for heat pipe and vapor chambers can perform superiorly by reducing the viscous drag with larger pores or channels and simultaneously generate higher capillary pressure with smaller pores radius. Unlike conventional sintered metal biporous wicks, cylindrical silicon micropillar based evaporator with microchannels, possess the following advantages: mature and easily controllable fabrication process, possibility of direct integration with semiconductor devices and no risk of thermal expansion mismatch. In this work, we investigated a biporous wick for the evaporator design, which consists of micro pillar arrays interspersed within micro channels. This design was systematically studied by constructing a mathematical model, by coupling Brinkman’s equation with mass and energy conservation equations, to predict the biporous wicks’ heat transfer performance. In order to find the best combination of geometric factors that give the highest heat flux at a certain superheat value, optimization in Matlab was done. The effect of diameter to pitch ratio, aspect ratio, channel width and contact angle on wick’s permeability, capillary pressure and evaporative heat flux were also investigated. Conclusion was drawn that a higher diameter to pitch ratio of 0.57, reasonable aspect ratio of 1.75∼3.22, island to channel width ratio of around 1.96 are preferred in this kind of biporous wick’s design. Biporous wick show potential to dissipate heat flux of 515.7 W/cm2 at superheat of 40 °C, which is 134 % higher compared to monoporous wick.
Quantifying the Directionality of Liquid Crystalline Polymers in Extrusion Processes Using an Order Parameter
Authors: Sullivan Anthony , Saigal Anil , Fragoudakis Roselita , Zimmerman Michael A. , Ahmadzadegan Arash
Published: March 2016

Liquid crystalline polymers (LCPs) are among a high-performance class of materials, which derive unique mechanical, chemical, and electrical characteristics from their long-range molecular order. The evolution of anisotropic orientation in the LCP microstructure during processing, however, can adversely affect the macroscopic polymer behavior. Simulation of this anisotropy is crucial to the design of manufacturing processes producing the desired material properties, and the ability to quantify the polymer directionality is a necessary metric of the model. Using a Monte-Carlo approach introduced by Goldbeck-Wood et al., a practical method for simulating LCP orientation is used to model the polymer flow, and the directionality results are then used to calculate a quantitative molecular degree of order. This metric, known as the order parameter, is an ideal candidate for measuring the LCP orientation, ranging from zero to unity between the isotropic and perfectly aligned states, respectively, as it is sensitive to both the direction of the average molecular orientation, as well as to the distribution of crystals around the average orientation. The effects of varying process parameters in the directionality model on the order parameter are shown. Understanding of these relationships will ultimately drive the design of manufacturing processes for more isotropic materials.
Application of Two-Parameter Non-Diffusive Heat Conduction Model to Nanoscale Transient Grating Experiments
Authors: Qu Zhengxian , Wang Dadong , Ma Yanbao
Published: March 2016

With the development of technology, in smaller and smaller length scale, emerging non-diffusive heat transfer has been challenging the traditional Fouriers law of heat conduction. Consequently, lots of models have been constructed. In this paper, a novel two-parameter non-diffusive heat conduction (TPHC) model was applied to decode the physics in nanoscale transient grating experiments. Better fitting with the experiment was shown in the numerical simulation and newly discovered collective diffusive effect was observed by this TPHC model.
Oscillating Heat Pipes for Waste Heat Recovery in HVAC Systems
Authors: Mahajan Govinda , Cho Heejin , Thompson Scott M. , Rupp Harrison , Muse Kevin
Published: March 2016

Oscillating heat pipes (OHPs) were experimentally assessed as a passive-type heat transfer device for air-to-air heat exchange in a typical Heating Ventilation & Air conditioning system (HVAC) with adjacent air streams at different temperatures. The objective is to utilize, otherwise wasted thermal energy to pre-heat or pre-cool air in order to reduce the payload on HVAC systems, thus reducing energy consumption. OHPs can achieve effective thermal conductivities on-the-order of 10,000 W/m-K via no internal wicking structure and hence can perform aforementioned heat transfer task while providing an aerodynamic form factor. A unique working fluid with limited research inside OHPs, but with properties desirable for low grade heat fluxes, i.e. n-pentane with 70 % fill ratio, was chosen as the working fluid to achieve maximum heat transfer. Aerodynamic performance, in terms of pressure drop, was evaluated and juxtaposed with heat transfer gain/loss. The OHP thermal performance and total heat transfer for hot-environment HVAC operation was benchmarked with an empty/evacuated OHP with same overall dimensions. Results indicate that the current, atypically-long OHP is fully-capable of operating in the air-to-air convection mode for waste heat recovery for typical HVAC operating conditions. Since the OHP is passive, cost effective, and relatively aerodynamic (no fins were used), the potential cost savings for its integration into HVAC systems can be significant.
Modeling of Carbon Nanotube Reinforced Rubber Seals
Authors: Zhang Haitao , Li Ke , Ito Masaei , Collins Tony
Published: March 2016

The increasing demand for oil and gas has incited exploration and production of deeper wells that reach high pressure and high temperature (HPHT) reservoirs. One critical element that is required to this end is rubber seals that can withstand HPHT conditions while meeting the requirements of sealability and structural integrity. Novel nanocomposites that comprise of natural rubber (NR) reinforced by well dispersed, high-concentration carbon nanotubes (CNTs) were recently developed to achieve the desired performance and were experimentally shown to exhibit significantly higher storage modulus than the matrix material. Understanding of the underlying reinforcing mechanism of this class of nanocomposites subjected to large deformation, especially in the real application conditions, has been very limited. In this study, a multiscale modeling method is developed to understand the mechanical behavior of CNT-rubber seals installed in a groove and subjected to high pressure. A micromechanics model is first constructed to evaluate the effective stress-strain responses of a representative volume element under different loading conditions, including uniaxial tension, equal biaxial extension, and planar tension. The effective properties thus established are then inputted into an appropriate hyperelasticity model, which is then used to model a CNT-rubber O-ring installed and pressurized. Sealability and structural integrity are evaluated in terms of contact pressure and strain. The numerical results are compared with the available experimental data. A parametric study is then conducted to assess the effects of CNT concentrations.
Development of Haptic-Enabled Virtual Reality Applications for Engineering, Medicine and Art
Authors: Medellín-Castillo Hugo I. , González-Badillo Germánico , Govea Eder , Espinosa-Castañeda Raquel , Gallegos Enrique
Published: March 2016

The technological growth in the last years have conducted to the development of virtual reality (VR) systems able to immerse the user into a three-dimensional (3D) virtual environment where the user can interact in real time with virtual objects. This interaction is mainly based on visualizing the virtual environment and objects. However, with the recent beginning of haptic systems, the interaction with the virtual world has been extended to also feel, touch and manipulate virtual objects. Virtual reality has been successfully used in the development of applications in different scientific areas ranging from basic sciences, social science, education and entertainment. On the other hand, the use of haptics has increased in the last decade in domains from sciences and engineering to art and entertainment. Despite many developments, there is still relatively little knowledge about the confluence of software, enabling hardware, visual and haptic representations, to enable the conditions that best provide for an immersive sensory environment to convey information about a particular subject domain.

In this paper, the state of the art of the research work regarding virtual reality and haptic technologies carried out by the authors in the last years is presented. The aim is to evidence the potential use of these technologies to develop usable systems for analysis and simulation in different areas of knowledge. The development of three different systems in the areas of engineering, medicine and art is presented. In the area of engineering, a system for the planning, evaluation and training of assembly and manufacturing tasks has been developed. The system, named as HAMS (Haptic Assembly and Manufacturing System), is able to simulate assembly tasks of complex components with force feedback provided by the haptic device. On the other hand, in the area of medicine, a surgical simulator for planning and training orthognathic surgeries has been developed. The system, named as VOSS (Virtual Osteotomy Simulator System), allows the realization of virtual osteotomies with force feedback. Finally, in the area of art, an interactive cinema system for blind people has been developed. The system is able to play a 3D virtual movie for the blind user to listen to and touch by means of the haptic device. The development of these applications and the results obtained from these developments are presented and discussed in this paper.
Confinement Effects on Phase Behavior of Hydrocarbon in Nanochannels
Authors: Alfi M. , Nasrabadi H. , Banerjee D.
Published: March 2016

Several researchers have recently studied the phase behavior of petroleum fluids in shale systems. There is a general agreement that the confined PVT properties in shale are substantially different from the corresponding bulk properties. These differences have significant impact on the prediction of well performance and ultimate recovery in shale reservoirs. Experimental measurements of fluid properties in shale rocks are currently not available. This has led to significant amount of uncertainty in phase behavior calculations for shale reservoirs.

In this study, experimental validation of numerical predictions for phase behavior of various hydrocarbons confined in nanochannels was performed using a nanofluidics platform. The nanofluidics platform was designed, fabricated and tested at different temperatures. Design of the nanochannel is described in this paper.

In this study, a nanochannel device (similar to Duan and Majumdar 2010) was designed, fabricated, packaged and tested. The reservoirs in the nanofluidic chip were filled with various hydrocarbon liquids (e.g. n-decane). The temperature was varied at a constant pressure, during which epifluorescence imaging was performed to measure the bubble nucleation temperature, i.e., the temperature corresponding to the formation of the first bubble of gas (i.e., to determine bubble-point pressure and temperature relationship).
Comparison of Modeling Approaches for Open-Fire Hearth Furnace Heat Transfer
Authors: Kurzawski Andrew , Ezekoye Ofodike A. , Baldea Michael , Edgar Thomas F.
Published: March 2016

Modeling of heat transfer processes for controls applications requires that the modeler make a set of assumptions that strikes a balance between accuracy and simulation run time. Common points of consideration include choosing the appropriate dimension of the model, the importance of transient effects, numerical and temporal discretization, etc. The results of these decisions directly impact the speed and accuracy of the model. It can be useful for the modeler to build a framework containing a set of models for a given system where each model contains a different set assumptions. This allows for easy comparison of different classes of models and aids in the decision process for selecting the model that best fits the needs of the user.

This work takes the modeling of an open-flame hearth furnace as a case study and examines the implications of different modeling simplifications. This scenario is similar to plug-flow reactors (PFRs) and continuous stirred-tank reactors (CSTRs) in that reactions are occurring in a chamber where mass is flowing in to and out of the system. Modeling of these systems focuses on the concentration of the reactants, whereas the hearth furnace model seeks to capture the heat transfer to the work-piece and walls. Numerous models of PRFs and CSTRs exist in literature as well as several open-fire furnace models using Hottel’s zone method. This work builds off of these modeling techniques by testing several types of models for speed and accuracy.

Both steady-state and transient operation are considered and each of the different heat transfer phenomena are modeled in varying dimensions. The open-flame environment inside the furnace produces gases that participate in radiative heat transfer for which there are a number of different models. The P1 approximation to the method of spherical harmonics is used, both in three dimensions and a simplification to one dimensional radiation. The flow of gases inside the furnace is considered to be plug flow with a series of burners injecting hot gases along the length of the furnace. Conduction to the walls and work-piece occurs at much longer time scales than convection, i.e. the combustion gases are moving through the furnace much faster than the characteristic thermal response time of the walls and work-pieces (τgas ≪ τwall). This brings the modeler to the question of how to model transient effects at such disparate time scales. A model is posited that is a combination of quasi-steady radiative heat transfer, transient fluid evolution, and lumped transient conduction. This formulation takes advantage of the disparity in time scales to take large steps in time when solving the radiation equation while solving the energy equation at each time step for the internal gas control volumes. This model is then compared on the grounds of speed and accuracy to the more traditional explicit advancement of a consistent time step in both the gas energy balance and radiative transfer solution.
Evaluation of Wave Energy in the Pacific Ocean for Baja California State in Mexico
Authors: Tapia Olivas Juan Carlos , Delgado Rendón René , Hernández Martínez Emilio , Noh Pat Felipe , Villanueva Vega Eric Efrén , Castañón Bautista María Cristina
Published: March 2016

According to the World Energy Council (WEC) the estimated energy of the wave power in the world is in the range of 8,000 to 80,000 TWh/year to depths of 100 meters or higher and actually the utilization of wave energy resource it is possible because it has been implemented in countries like Australia, Indonesia, Nigeria, United Kingdom, Norway, Portugal and Colombia evaluating different types of marine technologies that take the advantage of the kinetic energy in the ocean waves.

Mexico according to the National Institute of Statistics and Information (INEGI) has a land area of 1,972,550 km2 of which has a coastline of 11,150 km having potential for the use of their coasts. Baja California with a land area of 71,445 km2 (3.6% of the country) is located on a peninsula in northwest Mexico and has 720 km of coastline on the Pacific Ocean (6.4% nationally) with a range of depths of 25.6 m to 650 m at a distance of the coastline of 15 km, which makes it suitable to evaluate the use of wave energy at local sites.

With the completion of this work will contribute to the characterization of the sites that will present the best technical and economic conditions for its implementation, considering the physical characteristics of the site as well as connection points on the transmission lines operated by the Federal Electricity Commission (CFE).

For the preparation of this study was carried out in three stages: a) Site Selection, b) Evaluation of Wave Energy and c) Economic evaluation of sites using RETScreen.

Based on the characteristics of the coast of Baja California the results obtained are the following: 1) 18 sites were selected with a sea depth averaged of 50 m, the annual density power was 7.5 kW/m, this represents a potential of 210 MW considering an average length of 2 km in each site, 2) The economic evaluation of this type of project was for a period of 30 years in RETScreen, considers an annual inflation rate of 5% and obtains an investment cost of 9,538 US $/kW for this type of generation. We conclude that this source of energy will reduce dependence on fossil fuels and contribute to the generation of electricity in the state of Baja California diversifying the energetic matrix state by the use of clean and renewable sources, which represents an investment opportunity between the public and private sector.
Improved Thermal Comfort of Office Occupants Through Better Air Diffuser Designs
Authors: Liu Yu-Cheng , Burzo Mihai G. , Sier Scott , Ellis Cassandra
Published: March 2016

In this work we are exploring the influence of the design of air diffusers on a number of parameters that influence the thermal comfort of building occupants. In particular we are looking at calculating the Air Diffusion Performance Index (ADPI) and vertical temperature difference as well as the throw and drop parameters for various diffuser designs. The results show that while a complex radial vane diffuser that uses the Coanda effect could offer good performance if the HVAC system is used for cooling, the same design might not give any advantage as compared to a regular multi-cone design while the system is used for heating. This is mostly due to the strong air stratification observed for both diffuser designs, while the HVAC system is in the heating mode. Consequently we propose a better alternative, namely, to use a variable geometry (angle) air diffuser. To prove this concept we performed a CFD analysis of several diffusers, each delivering the air at different angles, for both heating and cooling mode, and we show that indeed using a design that allows changing the angle of the air jets between the heating and cooling season is the optimal way of delivering air to a room.
Effect of Competing Mechanisms on Fracture Toughness of Polycrystalline Metals
Authors: Li Yan , Zhou Min
Published: March 2016

Fracture toughness in ductile materials is the combined effect of the plastic dissipation and the energy spent in creating new surfaces. The design of polycrystalline metals with improved fracture toughness requires in-depth understanding of two levels of competitions: the competition between plastic deformation and crack formation as well as the competition between transgranular and intergranular fracture. Currently, no systematic approach exists to address the two competitions. The fundamental challenges lie in the difficulty in separating the two energy dissipations and inadequate knowledge about the correlation between fracture mechanisms and material fracture toughness. In this paper, a Cohesive Finite Element Method (CFEM) based multiscale framework is introduced to quantify the two levels of competitions. The fracture toughness of ductile materials is predicted by calculating the J-integral at the macroscale. The fracture surface energy for different type of failure mechanisms is evaluated through explicit simulation of crack propagation at the microstructure level. The calculations carried out here concern AZ31 Mg alloy. Results indicate that the mixed transgranular and intergranular failure can lead to optimized fracture toughness. Microstructures with refined grain size and grain boundary bonding strength can best promote the favorable failure mechanisms.
The Evolution of Streamwise Counter-Rotating Vortices in Flat Plate Boundary Layer With Leading Edge Pattern
Authors: Hasheminejad Seyed Mohammad , Mitsudharmadi Hatsari , Winoto S. H. , Lua Kim Boon , Low Hong Tong
Published: March 2016

The evolution of streamwise counter-rotating vortices induced by different leading edge patterns is investigated quantitatively using hot-wire anemometer. A notched and triangular leading edge with the same wavelength and amplitude were designed to induce streamwise vortices over a flat plate at Reynolds number (based on the wavelength of the leading edge patterns) of 3080 corresponding to free-stream velocity of 3 m/s. The streamwise velocity at different streamwise locations collected and analyzed using a single wire probe hot-wire anemometer showed reveal different characteristics of boundary layer flow due to the presence of these two leading edge patterns. The major difference is the appearance of an additional streamwise vortex between the troughs of the notched pattern. Such vortices increase the mixing effect in the boundary layer as well as the velocity profile.