bluuebunny/crossref_metadata_2025 huggingface dataset:
On the Hydrodynamic Analysis and Heat Transfer Investigation of Forced Oscillated Vertical Annular Fluid Column
Authors: Sayar Ersin
Published: February 2017

Heat transfer from a forced oscillated water column is investigated experimentally and theoretically. Further details of the water flow can be given as mini-scale, vertical, annular, internal, reciprocating and single phase. The inner wall of the stationary concentric element is heated and water is oscillated through the annuli. The data is acquired from the measurements both in the initial transient period and in the pseudo-steady (cyclic) period from the experimental set-up. The effect of the oscillations is observed on the measured temperature field and heat transfer. There is minor radial temperature variation in the water column. Experimental study proved that the frequency, wall heat flux and related wall temperatures are important parameters affecting heat transfer. It is understood that, the effective heat transfer mechanism is enhanced in oscillating flows. Cycle and space-averaged heat convection coefficients are calculated for the present oscillating flows. The physical and mathematical behavior of the resulting heat convection coefficients are analyzed using the data acquired from the experiments. The predicted cycle-space averaged heat convection coefficients using the experimental data are shown to have a logical trend with the experimental observations. The analysis is carried out for different oscillation frequencies at various applied wall heat fluxes while the displacement amplitude remains constant. A novel control volume formulation is introduced in order to investigate pressure distribution and energy balance of water over a cycle for the present reciprocating flow and the formulations are reorganized in order to capture the cycle-averaged energy balance of the control volume. The present study is novel because it appears to be the first paper on the analytical hydrodynamic analysis of forced oscillated vertical annular fluid flow. The present investigation has possible applications in moderate sized wicked heat pipes, solid matrix compact heat exchangers compromising of metallic foams (in some other types of heat exchengers as well), possibly in boilers, filtration equipment, and steam generators.
Investigation of the Flexural and Impact Behaviour of the Sand Blasted Duralumin Reinforced FMLs
Authors: Selvadurai Senthil Kumaran , Alagumalai Vasudevan , Ponnusamy Edwin Samson
Published: February 2017

This work focuses on the effect of using sandblasted Aluminum 5052 H36 sheets as reinforcement in fiber metal laminates (FMLs) containing glass fiber - kevlar epoxy layers and glass fiber - carbon fiber epoxy layers. Two sets of 9 layered composites were fabricated using compression moulding technique as follows 1) Sand blasted Aluminum 5052 H36 sheet, S-Glass fiber, Kevlar fiber, with epoxy matrix. 2) Sand blasted Aluminum 5052 H36 sheet, S-Glass fiber, carbon fiber with epoxy matrix. Flexural experimentation of the composites was done to investigate delamination under bending loads. Izod Impact studies were performed to determine the notch toughness of the composites and also to study the debonding under impact loading. Flexural results revealed no delamination between the sandblasted Aluminum 5052 H36 - fiber interlayers owing to the increase in the surface roughness of the duralumin sheets through sand blasting, while pronounced delamination was observed between fiber - fiber interlayers. Impact testing of the composite also showed no delamination between Aluminum 5052 H36 - fiber interlayers and a brittle fracture surface was observed. Thus sand blasting of the Aluminum 5052 H36 layers proves to be a beneficial technique in overcoming the inherent problem of delamination in FMLs.
The Long-Term Viability of Concentrated Photovoltaic Systems in the Southwestern US
Authors: Sahm Aaron , Burnham Laurie , Boehm Robert , Betemedhin Adam , Wood Gary
Published: February 2017

Total lifetime costs of photovoltaic (PV) systems are important determinants of profitability. But such costs are not always accurately measured and compared against fluctuating electricity costs, which can be an important contributor to long-term profitability. In this paper, we consider the economics of concentrated photovoltaics (CPV), which offer significantly higher efficiency and greater energy production over traditional fixed flat-plate PV installations in high-irradiance regions, but are perceived to be risky investments.

Working with two models, one a simple annual model that uses only direct normal solar insolation; the other a more complex hourly model that uses direct normal solar insolation, ambient temperature, and wind speed to predict energy yield, we calculated the energy production and corresponding revenue generation for a 28 kW CPV unit and a comparable single-axis tracker field in Nevada. Our resulting cost matrix shows how much revenue a CPV system can reasonably be expected to generate under different pricing schemes and time periods. While the values vary depending on the assumptions made, the matrix provides an index of profitability, enabling prospective buyers to compare the costs of purchasing, installing and maintaining a system against likely revenue.

As a result of our calculations, we anticipate that CPV systems will still be viable in high flux areas because they offer the promise of profitability now and continued or increased profitability as cell costs decrease and/or overall efficiency increases. Nonetheless, other factors, such as long-term reliability and O&M costs, must be addressed if CPV is to compete with other simpler technologies, such as single-axis PV trackers, which have lower upfront costs and are therefore becoming more attractive to potential customers.
CAD Integration in Virtual Reality Design Reviews for Improved Engineering Model Interaction
Authors: Freeman Ian J. , Salmon John L. , Coburn Joshua Q.
Published: February 2017

Leveraging virtual reality (VR) technology to enhance engineering design reviews has been an area of significant interest for researchers since the advent of modern VR. The ability to interact meaningfully with 3D engineering models in these VR design reviews is an important, though often neglected, capability due to the difficulty of performing data translation between native CAD data and VR compatible file formats. An automated synchronization interface was developed between a VR design review environment and a commercial CAD package that stream-lines the data translation process and enables enhanced visualization and manipulation tools. User experiments were performed to explore the hypothesis that allowing users to perform CAD-like view transformations and geometric manipulations in VR design reviews improves design understanding and decision making. Analysis of the experiment results show that enhanced interaction tools provide statistically significant advantages over a baseline VR design review environment for complex 3D models.
Simulation of Rotor System Vibrations Using Experimentally Verified Super Elements
Authors: Semenov Sergei , Nikhamkin Mikhail , Sazhenkov Nikolai , Semenova Irina , Mekhonoshin Grigorii
Published: February 2017

A numerical technique based on finite element model reduced by using experimentally verified superelements is presented in the paper. This method can be used for modelling of rotor systems with elements which can produce nonaxisymmetrical vibration modes (fan, flexible disks and etc.) in operating frequency range thus forcing to calculate 3D models without cycle symmetry. Testing of proposed mathematical modeling method is produced using special rotor test rig. The procedure of superelements creation and verification is provided. Critical speeds of test rotor system were determined numerically and experimentally. Comparative analysis of results is provided.
A Numerical Study on Highly Viscous Compound Cancer Cell Microfiltration
Authors: Zhang Xiaolong , Chen Xiaolin , Tan Hua
Published: February 2017

Cancer is a leading cause of death worldwide. There has been extensive research on cancer in recent decades, with many studies focusing on Circulating Tumor Cells (CTCs), i.e., cancer cells shed into the circulating bloodstream from a primary tumor site. CTCs are mainly responsible for initiating metastases, and can be used as an indicator for early cancer detection. Investigating CTCs and the related detection methods such as microfiltration is of great importance. CTCs as well as other cells are normally composed of highly viscous nucleus and cytoplasm which are encapsulated by the outermost layer of cortical membrane. In order to account for the effects of viscous nucleus and cytoplasm on the microfiltration process and study the dynamic characteristics comprehensively, a realistic model is preferred. In this research, we employ the compound droplet model consisting of three layers, the layer of cell membrane, cytoplasm and nucleus, to capture the full range of CTCs behavior during the microfiltration process. The compound cell deformation and pressure signature during microfiltration are studied numerically. Also discussed are the effects of nucleus-cytoplasm ratio (N/C ratio), their viscosity as well as surface tension on the cell behavior when it squeezing through the filter channel. Our results can gain insight into the physics behind the filtering process and provide some guidance to the design and optimization of such devices.
Influence of PIG Mass, Launching Time and Turbulence Model on 3-D CFD Transient Simulation of PIG Motion
Authors: Jaimes Parilli Diego , Blanco Armando , García Janneth
Published: February 2017

Pigging procedures are common maintenance operations used to perform cleaning, draining and pipeline inspection in order to improve flow efficiency and operation cost. Despite these procedures are commonly used, questions still remain regarding the flow and the PIG motion features due to the complex interaction among pig, wall and flow, and the changes in internal fluid pressure and local fluid density. Currently, the PIG dynamic predictions are based on experimental data from short scale laboratory experiments and numerical models founded on physical simplification. So far, the transient of PIG motion calculated by methods that combine CFD and fluid-structure interaction in a 3D model and the influence of the physic and numerical features over the pig dynamics has not been analyzed yet. To provide a better understanding of pigging runs, this paper proposes a CFD methodology to obtain a 3D transient simulation of PIG motion. A moving control volume attached to the PIG let to solve the governing equation in a stationary mesh. This methodology is used to obtain the transient simulation of a PIG launched in a straight water pipeline for different PIG mass, launching time and turbulence models in order to study its influence over the PIG dynamics. The numerical results show a linear relation between the mass and the pressure drop in the transient state, but with no influence over the final stationary state. Also, an asymptotic relation between the transient pressure drop and the launching time was observed with no influence over the PIG terminal velocity. Besides, it is exposed the influence of the turbulence models (κ-ε, SST and BSL Reynolds Stress) in the results of pig motion; appreciable difference between the drop pressure of Omega-Based Stress Models (SST and BSL) and κ-ε turbulent model at steady state is shown, and, finally, a comparison of the velocity profiles at the interstice for each model was developed, this one shows an inaccuracy of the κ-ε model to describe the velocity profile in the walls proximities.
Finite Element Structural Analysis of Commonly Used Horizontal Axis Wind Turbine Airfoils of Various Geometries
Authors: Rahman Mosfequr , Pate David , Sawinski James , Seeloff Tucker , Molina Gustavo , ElShahat Adel , Soloiu Valentin
Published: February 2017

Horizontal axis wind turbines (HAWTs) are the dominating technology in large scale energy production utilizing the wind power. With these structures, HAWTs continually becoming more massive in size to produce the most energy possible, greater stresses are imposed on the blades of these turbines. The purpose of this study was to analyze the stresses and deformation imposed on the blades of commonly used airfoils under varying materials and blade arrangements of HAWTs. This structural analysis was performed by the use of ANSYS Workbench software. The pressures applied to the blades were determined by previous studies which used ANSYS Fluent for blade pressure analysis created under varying wind speeds. Use of the airfoil designs denoted as S811, S822, and S826 were implemented, with structural analysis performed solely on the blade, on three and five blades arrangements. The materials used for each of these setups were Aluminum Alloy and Structural Steel. Furthermore, varying mesh types within ANSYS were applied to each of the geometries for comparison. It has been found from this study that the S811 profile models had the lowest stress and deformation for both blade configurations, meshing methods, and materials.
Numerical Simulation of Manifold Microchannel Heat Exchanger
Authors: Ali Muhammad Ansab , Khan Tariq S. , Al Hajri Ebrahim
Published: February 2017

The quest to achieve higher heat transfer rate, smaller size and minimum pressure drop is a main area of focus in the design of heat exchangers. Plate heat exchangers are one of viable candidates to deliver higher heat duties but still have a drawback of higher pressure drop due to long restricted flow path. Motivated by demand of miniaturization and cost reduction, a novel design of tubular microchannel heat exchanger for single phase flow employing ammonia water mixture is proposed. Numerical simulation of unit fluid domain is conducted in ANSYS Fluent. Parametric study of the different flow geometries is evaluated in terms of Nusselt number and pressure drop. The salient features of the design include ultra-compact size with higher heat transfer rate and acceptable pressure drop.
A New Model for Predicting Flow Boiling Heat Transfer Coefficients in Horizontal Microfin Tubes
Authors: Merchant Reem , Mehendale Sunil
Published: February 2017

The objective of the current work is to present a new correlation for predicting heat transfer coefficients (HTCs) for flow boiling in horizontal microfin tubes. Correlations to predict HTCs have been proposed by numerous authors such as Yu et al., Thome et al., Cavallini et al., Yun et al., Chamra and Mago, Wu et al., and other researchers. The correlations proposed are semi-empirical due to the difficulties associated with modeling the physics of flow boiling in microfin tubes. The above correlations are based on smooth tube flow boiling correlations which are modified to capture the effect of the inner grooves in the microfin tubes on the boiling process. In a previous work, it has been demonstrated that no single correlation can reasonably predict the flow boiling HTCs over a wide range of operating conditions and tube geometric parameters (Merchant and Mehendale). A new model has been proposed and validated using an experimental database of 1576 points from published literature. For the full dataset, the new correlation has X30% of 67.3%, compared to Cavallini et al. and Wu et al. with X30% of 44.2% and 40.6% respectively. The performance of the new model for tube diameters less than and greater than 5 mm has also been discussed for halogenated refrigerants and CO2.
An Optimum Design Approach for Textured Thrust Bearing With Elliptical-Shape Dimples Using CFD and DOE Including Cavitation
Authors: Fu Gen , Untaroiu Alexandrina
Published: February 2017

Surface texturing has been used to enhance contact performance for decades since 1960s. Surface structures can tremendously change the friction coefficient of the contact surface. These structures have been widely used in bearings and seals. According to previous studies, textured thrust bearings provide more loading capacity than non-textured bearings. Compared to tapered and step bearings, the dimples can also reduce the friction torque. However, most previous optimization efforts for texturing geometry were focused on rectangular dimples and employed Reynolds equation. Limited studies have been done to investigate the effects of partially textured thrust bearings with elliptical dimples. This study proposes a new optimization approach to find the optimal partially texture geometry with elliptical dimples, which maximize the loading capacity and minimize the friction torque. In this study, a 3D computational fluid dynamics model for a parallel sector-pad thrust bearing is built using ANSYS CFX software instead of solving Reynolds equation with simplified field assumptions. Only one sector of the thrust bearing is modeled. Mass conserving cavitation model is used to simulate the cavitation region inside the dimples. Energy equation for Newtonian flow is also solved. Realistic boundary conditions are applied. The results of the model are validated by the experimental data from the literature. Based on this model, the flow pattern and pressure distribution inside the dimples are analyzed. Then, the geometry of elliptical dimple is parameterized and analyzed using the method of design of experiments (DOE). In this study, all the dimples have identical geometry. The selected geometry parameters include the length of major axis, the length of minor axis, dimple depth, circumferential space between two dimples, radial space between two dimples, radial extend and circumferential extend. The design space is sampled using central composite method. A temperature threshold is set to exclude the design points which result in high temperatures. A quadratic response surface model is created based on the results of the DOE process. Next, a multi-objective optimization scheme is used to find the optimal texture structure with the load force and friction torque set as objective functions. The results show that the shape of dimples has a crucial effect on the performance of the textured thrust bearings. This optimization approach proposed is expected to be useful in typical texture design process of thrust bearing.
Morphological Characterization of Fouling on Air Cooled Fin Fan Heat Exchangers
Authors: Sharma Arjun , Khan Tariq S. , Al Hajri Ebrahim , Islam Md.
Published: February 2017

In today’s fast growing world where availability of energy has become a major concern, the cost of performance demands optimum heat exchange performance over extended periods of operational times. Fouling is one major factor that drastically affects heat exchanger performance. Most of the oil & gas processing plants in the Middle East are located in deserts. Due to scarcity of water most of the installed heat exchangers are air-cooled. These heat exchangers are at high risk of low performance due to dusty/sticky particulate fouling. In order to identify possible active/passive methods to control or ideally eliminate particulate fouling, as a first step, it is desirable to know exact morphology of such particulate fouling. This study presents morphological characterization of selected fouling samples from eight different installed fin fan heat exchangers. The scanning electron microscope (SEM) tests are carried out to determine standard characteristics and size of sample foulant powder. Variability in sizes and shapes is found between samples perhaps due to different working temperature ranges of the selected heat exchangers. The semi quantitative sample composition measured by energy dispersion x-ray micro analysis was as following: 26.50% Si, 26.12% Ca, 10.07% C and 9% Al with traces of Fe, Na, Mg, Cl, and some other salts. X-ray diffraction analysis revealed presence of quartz, calcite and alumina with traces of halite and hematite. The diversity of these fouling samples reflects complexity with respect to their potential removal and effects on heat transfer.
Vibration Reduction by Active Control of Flexible Marine Riser Angle Subjected to Time-Varying Distributed Force
Authors: Bakhtiari-Nejad F. , Azimi A.
Published: February 2017

In this research, boundary control is developed at the upper end of the riser based on the Lyapanuv’s direct method to reduce top angle and transverse vibration of the riser subjected to time-varying disturbance. First, ocean surface current is assumed to be linearly declined to zero from the ocean surface to the ocean floor and then it is assumed to be exponentially declined to zero. The riser is modeled as a distributed parameter system with one partial differential equation (PDE) coupled with boundary conditions (ODE). Since all of the control signals can be measured by sensors or can be calculated by a backwards difference algorithm, so the boundary control is practical and implementable with existing instrumentation. The Lyapunov’s direct method is applied to stability analysis of the closed-loop system. Finally, efficiency of the controller is verified and results of linear and exponential profiles are compared to each other.
A New Model for Predicting Falling Film Evaporation Heat Transfer Coefficients
Authors: Baruah Apurva , Mehendale Sunil
Published: February 2017

For falling film evaporation, the most important considerations from a thermal design standpoint are the onset of film dryout and the local heat transfer coefficients in partially and fully wet conditions. Previous methods developed for the prediction of (i) pool boiling heat transfer coefficient (HTCs), (ii) the onset of dryout, and (iii) falling film heat transfer coefficient consist of empirical, tube-specific constants which are quite difficult, if not impossible, to determine, and hence have limited utility. New methods to predict these parameters have been developed in the present study, which eliminate the special constants by incorporating dimensionless parameters that capture the effect of refrigerant properties and macro-level tube-geometry. The predictions of the new model have been found to be better than or comparable to those of the best available existing models.
Design Optimisation and Life Estimation of Split Hub Geometry of FSAE Car
Authors: Raju Suraj , Kumar Asu Vijaya Pavan , S. Kumar Varun , Manjunath Nikhil , Nagaraj Harish
Published: February 2017

Hub in the car faces high vibrations and centrifugal stresses. This calls for proper design and analysis. The life cycle of any formula car should be less which is adequate for racing purpose. This work is focused in analyzing low cycle fatigue and conducting vibratory analysis of a split hub of FSAE car. Stress concentration factor is significant in machine elements which give rise to localized stresses for any change in design of surface or abrupt change in cross section. This member acts as stress riser which leads to localized stresses in turn leading to peak stresses introducing cracks. These cracks may propagate and leads to catastrophic failure of machine elements and these conditions leads to fatigue analysis to calculate life. Two approaches are employed here. Based on linear elastic finite element analysis Neuber stresses are calculated from fictive elastic results. Strain Amplitude approach is followed by Coffin-Manson equation to determine Fatigue life. The failure induced by fretting fatigue due to two contact surfaces subjected to an oscillatory loading serves as premature crack nucleation which will gradually become a prominent issue during the running of car. In some cases it reduces the life due to micro slip at the edge of contact. The split pieces of hub talk to each other and create wear which is calculated by fretting. These rotary parts call for structurally rigid geometry. Modes with relatively high mode participation factor can be readily excited by the base vibrations. Vibratory stresses arise due to engine and rotating wheels acts like excitation frequencies which may lead to possible resonance. Campbell diagram is effectively used to modify the stiffness in turn design. Also an approach is done for design optimization of fillet stresses at Sharp edges caused due to bending strength of the split pieces. Optimization of diameter, contact region, root land dimensions is done to ensure stress distribution is uniformly spread along the fillet radius on both pieces of hub which otherwise may lead to crack initiation considering all peak stresses. Design of Experiments technique and optimization methods are used to improve structural integrity by finding the peak sectional stress. Design optimization is done using screening method to ensure strength of material.
Effect of Alignment on Thermal Conductivity Enhancement of Polyethylene/Graphene Nanoplatelet Composite Materials
Authors: Saeidijavash Mortaza , Garg Jivtesh , Wang Bin
Published: February 2017

In this work we investigate the effect of molecular alignment on thermal conductivity (k) enhancement of polyethylene/graphene nanoplatelet (PE/GNP) composites. Enhancement of thermal conductivity of polymers can pave way for their application in heat exchangers leading to significant energy savings as processing of polymers is more energy efficient than metals. Such energy savings will drive down costs and will have the additional benefit of considerably reducing the environmental effects of energy production. Such high k polymers will also enable improved thermal management in electronic devices in servers, automobiles, high brightness LEDs and mobile applications. Stretching is known to induce alignment of molecular chains in a polymer system thereby increasing thermal conductivity. In this work we explore mechanical stretching of polyethylene-graphene nanocomposites to enhance their k.
Effect of Upstream Cylinder’s Oscillation Frequency on Downstream Cylinder’s Vortex Induced Vibration
Authors: Tofa M. Mobassher , Maimun Adi , Ahmed Yasser M.
Published: February 2017

Vortex induced vibration or widely known as VIV, is a very complex hydrodynamic phenomenon. There are relatively very few experimental and numerical references for oscillating pair of cylinders because of the early assumption that the interference between the two cylinders is weak and thus each of the cylinders may have the same behavior as found in the case of a single cylinder, but recent researches showed this assumption was not true. For tandem arrangement, several parameters govern the nature of VIV of downstream cylinders, such as spacing, upstream cylinders VIV amplitude etc. The nature of downstream cylinders response isn’t same as classical VIV or WIV (wake induced vibration). Oscillation frequency of a cylinder subjected to flow induced vibration is one of the important characteristics Oscillation frequency is highly dependent on natural frequency of the cylinder. By changing spring stiffness or mass ratio, natural frequency can be altered. The aim of this study is to investigate the effect of upstream cylinder’s oscillation frequency on the vibration of downstream cylinder. Numerical simulations have been conducted to understand the nature of vortex induced vibration (VIV) of a pair cylinder in tandem arrangement at high Reynolds numbers. Cylinders were subjected to uniform flows in sub-critical flow regime and have been allowed to oscillate in cross flow direction only. The spacing between the upstream and downstream cylinders was four times of the cylinder diameter. The oscillation frequency of the upstream cylinder has been altered by varying the mass ratio of the upstream cylinder. It was found that for same Reynolds number, downstream cylinder’s VIV amplitude is increased quite significantly if the upstream cylinder oscillates relatively slowly. The shear stress transport detached eddy turbulence model has been used for simulating the turbulent flow around the two cylinders. An advanced mesh movement known as “mesh morphing” model was employed to lessen the requirement for re-meshing which help to increase the accuracy of the prediction. Calculation of accurate results due to large domain deformations was achieved by re-positioning existing mesh points. The numerical results of a single cylinder subjected to one degree of freedom (1DOF) vibration have been compared with the available experimental results to validate the present study. The study is important in terms of designing VIVACE (Vortex Induced Vibration for Aquatic Clean Energy) converter for low speed current. In recent past, multiple cylinders have been used for VIVACE converter. So, the study of VIV of two equal-diameter cylinders in tandem arrangement at low current speed is very significant.
Techno-Economic Study of Installing 10 MW PV Power Plant in Sudan
Authors: Abuelyamen Ahmed , Mohamed Mohand H.
Published: February 2017

This work investigates the installation of a 10 MW solar PV power plant in a sustainable city in Sudan. Initially, the climatic data such as relative humidity, temperature and horizontal solar radiation over 30 cities in Sudan were collected from NASA web page, then the behavior of all climatic data was analyzed. Annual daily solar radiation on a tilted surface was also calculated over the 30 locations around the country. It was found that the maximum value of tilted average solar radiation is 6.61 KWh/day at Dungola from fixed mode and 8.93 kWh/m2/day from tracking mode. Consequently, the location was selected as an optimum spot for building the solar PV power plant. Additionally, the available solar PV panels on the market were judged according to the maximum module efficiency and high ratio value of module capacity to frame area. The project lifetime is considered as 25 years. RETScreen v.4 software was used to simulate the feasibility analysis of the project based on electric power generated from fixed and tracking modes of operation, financial analysis and greenhouse gas emissions. The study showed that, technically, the proposed plant can generate up to 16.209 GWh of electric energy annually from the fixed system and 21.828 GWh from the tracking system. Environmentally, the annual net GHG reduction is 16,000 and 21,600 tons of CO2 from fixed and tracking systems respectively. From a financial standpoint, the cost-effective indicators were calculated and it was found that the IRR and payback period for the fixed system plant were 0.6% and 23.6 years, respectively. While for tracking system plant, figures were 2.66% and 19.4 years, respectively.
Evaluation of Techniques to Describe Device Complexity in Pre and Post Design Stages
Authors: Mountain Philip J. , Bohm Matt R. , Riggs Marie K.
Published: February 2017

Electro-Mechanical device complexity exists in everyday items from cell phones to automobiles to vacuum cleaners. Generally, product complexity is one of the least quantifiable characteristics in the design cycle with arguably some of the greatest implications. A high level of device complexity carries a negative connotation and is usually considered an attribute a designer should attempt to mitigate. Alternatively, a low level of device complexity may induce designers and marketers to question a product’s usefulness. Whether complexity is a necessary aspect of a design or a hindrance needing to be minimized or eliminated, depends upon how complexity is framed. Some instances in literature attempt to measure complexity yet there is no unified measure that captures the complexity of a product or system during design phases or upon product/system realization. Complexity is defined in many ways, at different levels of abstraction, and different stages of design therefore, becoming highly contextual and subjective at best. An established and repeatable methodology for calculating complexity of existing products in the marketplace is necessary. Once a measure of complexity is agreed upon at the post design stage we can look to earlier phases in design to see whether insights are observable. Identifying complexity early in the design cycle is paramount to strategic resource allocation. This study considers the Generalized Complexity Index (GCI) measure put forth by Jacobs [1] and expands upon it to include functional modeling as a key component in determining an indicative complexity metric. Functional modeling is a method used to abstract system or product specifications to a general framework that represents a function based design solution. Complexity metrics are developed at the functional and completed design levels and used for comparison. Thirty common household products retrieved from an online design repository [2] as well as seven senior capstone design projects were evaluated using the GCI. A modification to the GCI equation is proposed and to gain a relative scale of complexity within the data, a ranked complexity metric was developed and utilized. The magnitude of the ranked complexity metric was only indicative of hierarchical status of a product within the data set and therefore is not comparable to GCI values. Though Jacobs GCI worked well in his study, the GCI does not represent a meaningful complexity measure when applied to the data in this study. This study is an initial attempt to apply an independent data set to Jacobs GCI model with perhaps greater implications, with respect to products, that complexity is multifaceted and is not accurately represented by only interconnectedness, multiplicity, and diversity.
A CFD Study of Water Condensation Inside the Tubes of an Automotive Compact Charge Air Cooler Using Large Eddy Simulation Approach
Authors: Cash Robin , Talekar Apoorv , AbdulNour Bashar
Published: February 2017

The usage of compressed air generated by supercharger or turbocharger by automotive Original Equipment Manufacturers (OEM) is growing with the aim to increase engine performance by increasing the density of the air charge being drawn into the cylinder. Denser air coupled with more fuel pulled into the combustion chamber results in increased engine performance. The inlet air is heated during compression which can cause pre-ignition, which leads to reduced engine functionality. The charge air cooler (CAC) is a heat exchanger introduced to extract heat created during the compression process. Previous research developed a 3-D Computational Fluid Dynamics (CFD) model using the k-epsilon turbulent model with near wall treatment to resolve turbulence in the small channels of the CAC. [1] The present research uses a refined computational scheme with a Large Eddy Simulation (LES) model to solve local data as a function of time and location and correlates the result to the experimental measurements, as well as compare to the k-epsilon approach. Using LES resulted in the ability to correlate any portion of the experimental data and take a closer look at local heat transfer between the outside surface of the tube and the cooling air. Large Eddy Simulation for heat transfer gave more information required for design of CACs which is difficult to collect for various operating conditions by experiment. The overall benefit presented is a validated simulation methodology that predicts condensation, which is then used to evaluate and design CACs that function outside the condensate formation zone during various vehicle operation modes.
Aircraft Turbine Sound and Vibrations Signatures for a Synthetic Kerosene Fuel
Authors: Soloiu Valentin , Knowles Aliyah , Simons Emerald , Muinos Martin
Published: February 2017

Aero gas turbine engines generate high levels of sound across a wide frequency spectrum. The total sound energy produced by the engine is composed of multiple thermodynamic sources, including the air intake, combustion, and exhaust. The focus in this research is the investigation of the combustion noise. The combustion process is complex and dependent upon the properties of the fuel being used. Different fuels have different reaction and evaporation times, indicating that the noise may increase or decrease between each type of fuel. Fuels can affect how a turbine produces a sound output that will eventually be perceived by the human ear. In this study, two fuels were used in the operation of an aircraft gas turbine in the Georgia Southern University’s Aerospace Engine Laboratory. The SR-30 gas turbine is capable of operating at a maximum speed of 80,000 rpm, produce a maximum thrust of 40 lbf, has a pressure ratio of 3.4 to 1, and a specific fuel consumption of 1.22 lbfuel/lbthrust per hour. The fuels used were Jet-A fuel and two synthetic kerosene fuels. Synthetic fuels are attractive in the aviation industry because of their potential for reducing energy dependence and the growing need for higher efficiencies, while reducing emissions. While synthetic fuels show multiple benefits for their use over traditional jet fuels, the sound and vibration signatures were less investigated and this brought the need of this paper. This is especially important if the sound shows a noticeable decibel difference of three decibels or more. The three decibels difference is key, since humans can perceive a difference in sound, based on the logarithmic scale for decibel, of three decibels or more. Hence, A-weighting would be used for the determination of a noticeable difference in sound. This study investigates the vibrations characteristics within the 1/3 octave band of 400 Hz. The sound and vibrations of the engine were measured with an advanced Bruel & Kjaer condenser microphone and piezoelectric tri-axial accelerometer. The sound and vibration characteristics in the mid frequency range is of particular interest regarding combustion of the gas turbine. It has been determined that a 7 dB(A) difference between the reference fuel and the synthetic fuel was achieved at 400 Hz on a 1/3 octave band analysis. Overall, sound signals coming from one of the synthetic kerosene fuels was higher than Jet-A. The highest fuel throughout the vibrations signals overall was Jet-A and at least one of the synthetic kerosene fuels. All data was processed using a Constant Percentage Bandwidth analysis. Understanding the combustion from the sound and vibrations point-of-view can help to foresee the potential danger to the components of the engine, understand the potential effects of sound on the human passenger, and work towards a design to mitigate these phenomena, if necessary.
Numerical Simulations of Airborne Particle Removal Rates for Air-Ventilated Spaces of Different Obstacle Setups
Authors: Javadpour Sina , Delfanian Fereidoon , Saadeddin Khaled
Published: February 2017

As a result of industrialization, human activities and consequently the time spent in indoor spaces has significantly increased. As airborne particles, especially those of relatively small sizes (less than 2 μm), can easily enter human respiratory tract and cross the thin air-blood barrier inside the lungs, necessary measures need to be taken to minimize exposure to these particles. In this study numerical simulations were done by coupling the “Laminar” and “Turbulent Flow” and the “Particle Tracing for Fluid Flow” interfaces in COMSOL Multiphysics to investigate the effects of obstacle setup on air flow profile and particle removal rate in a confined space of an air-ventilated office using 3D models. Particle tracing for fluid flow was used with a Newtonian formulation to simulate and trace particles with diameter of 0.5 μm and density of 1086 kg/m3. A total of 100,000 particles were simulated to reduce the uncertainty in particle concentration calculations and also to yield statistically more accurate results. Simulations were done for a control model with no obstacles, and 3 other models of different obstacle setups in a cubic room of 2.5 m * 4 m * 1 m with the same inlet and outlet configurations and a maximum interval of 180 minutes (3 hours). All cases had a monodisperse particle distribution, where particles were released transiently and evenly distributed through the entire space at the initial time step (t = 0 min). All models reached a steady-state stage after 180 minutes, with the remaining particles circulating and trapped. Analyzing the results revealed that a positive correlation exists between path-length and particle removal rate. Thus, it was concluded that an obstacle orientation and setup leading to increased flow path-length would greatly enhance the particle removal rate and pollutant dilution. Also, regions of recirculation and stagnation proved to have a negative impact on particle removal by trapping the particles and hence should be avoided in obstacle configuration.
High Temperature Interfacial Adhesion Strength Measurement in Electronic Packaging Using the Double Cantilever Beam Method
Authors: Sankarasubramanian Santosh , Cruz Jaime , Yazzie Kyle , Sundar Vaasavi , Subramanian Vijay , Cetegen Edvin , McCoy David , Malatkar Pramod
Published: February 2017

Advanced microelectronic packages utilize a multitude of materials with dramatically different mechanical properties. Delamination occurring at the interfaces between these materials, due to poor adhesion and/or moisture exposure, is an important failure mode affecting the thermomechanical reliability of the package. The adhesion strength of these interfaces is a critical mechanical property that plays a role in the reliability performance of these packages. A good adhesion strength metrology is required to perform material selection and enable assembly process optimization in order to avoid the need for expensive assembly builds, followed by reliability testing which leads to long development times. This paper discusses the use of the Double Cantilever Beam (DCB) method for characterizing the adhesion strength of interfaces in advanced microelectronic packages at both room and high temperatures. Previous work in this area was focused only on room temperature testing. However, in order to characterize the adhesion strength of these interfaces at elevated temperatures seen during package assembly and reliability testing, an environmental chamber was designed and fabricated to rapidly and uniformly heat the DCB samples for testing at high temperatures. Depending on the interface tested and the testing temperature, DCB samples failed in one of three fail modes: (1) adhesive (at the interface), (2) cohesive (within the adhesive layer), and (3) brittle cracking of the substrate. Two case studies describing high temperature DCB testing on silicon-capillary underfill samples are presented. With adhesive failure being the desired fail mode in order to rank order materials and processes, it was found that for the underfills tested in this study, the DCB samples failed cohesively within the underfill at room temperature but started failing adhesively at temperatures near 150°C. Adhesion strength also showed a clear degradation with temperature. It is suspected that the change in failure mode from cohesive to adhesive with increasing temperature is due to competing trends of degradation in cohesive strength of the underfill versus degradation in adhesive strength of the interface with temperature.
Temperature-Staged Thermal Energy Storage Enabling Low Thermal Exergy Loss Reflux Boiling in Full Spectrum Solar Systems
Authors: Hendricks Terry J. , Nesmith Bill J. , Grandidier Jonathan
Published: February 2017

Hybrid full spectrum solar systems (FSSS) designed to capture and convert the full solar wavelength spectrum use hybrid solar photovoltaic/thermodynamic cycles that require low thermal exergy loss systems capable of transferring high thermal energy rates and fluxes with very low temperature differentials and losses. One approach to achieving this capability are high-heat-flux reflux boiling systems that take advantage of high heat transfer boiling and condensation mechanisms. Advanced solar systems are also intermittent by their nature and their electrical generation is often out-of-phase with electric utility power demand, and their required power system cycling reduces efficiency, performance (dispatchability), lifetime, and reliability. High temperature thermal energy storage (TES) at 300–600°C enables these reflux boiling systems to simultaneously store thermal energy internally to increase the energy dispatchability of the associated solar system, as this can increase the power generation profile by several hours (up to 6–10 hours) per day. Many TES phase change materials (PCM’s) exist including KNO3, NaNO3, LiBr/KBr, MgCl2/NaCl/KCl, Zn/Mg, and CuCl/NaCl, which have various operating melting points and different latent heats of fusion. Common, cost effective TES PCM’s are FeCl2/NaCl/KCl mixtures, whose phase change temperature can be varied and controlled by simple composition adjustments. This paper presents and discusses unique “temperature-staged” thermal energy storage configurations using these TES materials and analysis of such systems integrated into high-heat-flux reflux boiling systems. In this specific application, the TES materials are designed to operate at staged temperatures surrounding an operating design point near 350°C, while providing 18 kW of source heat transfer to operate a thermoacoustic power system during off-sun conditions (e.g., temporary cloud conditions, after sun-down). This work discusses relevant configurations, and critical thermal and entropy models of the TES configurations, which show the inherent minimization of thermal exergy during critical heat transfers within the configurations and systems envisioned.
Microfluidic Synthesis of Polymer Ionic Liquid Gel Beads for Energy Harvesting Applications
Authors: Kudtarkar Kaushik A. , Smith Thomas W. , Iglesias Patricia , Schertzer Michael J.
Published: February 2017

In the operation of many common devices and processes, more than 60% of consumed energy is wasted in many common processes. These loses come in many forms including heat, friction, and vibration. Energy harvesters are devices that can recapture some of this waste energy and convert it into electrical energy. This work will focus on electrostatic energy harvesting devices that recapture vibrational energy. Electrostatic energy harvesters recapture mechanical energy when a conductive mass translates or deforms in an electric field. Polymer ionic liquid gel beads may serve as a useful replacement for fluid droplets in electrostatic energy harvesters.

This work uses a recently developed method for reliable synthesis of polymer gel beads. These beads are synthesized using a micro-reactor, which generates monomeric droplets in a silicon oil carrier fluid. The monomer solution also contains a photoinitiator and cross linker, which enables the monomer to polymerize when exposed to UV light. The present work demonstrates a method to rapidly synthesize uniform beads with a variety of chemical compositions. These chemical compositions can be used to tune the electromechanical properties of the beads to improve performance in applications such as energy harvesting devices.