bluuebunny/crossref_metadata_2025 huggingface dataset:
Parametric Study of a Combined Power and Cooling Thermodynamic Cycle for Low Temperature Heat Sources
Authors: Vasquez Padilla Ricardo , Demirkaya Gokmen , Goswami D. Yogi , Stefanakos Elias L.
Published: July 2010

A combined power/cooling cycle, which combines the Rankine and absorption refrigeration cycles, uses ammonia-water mixture as a working fluid and produces power and refrigeration while power is the primary goal. This cycle, also known as the Goswami Cycle, can be used as a bottoming cycle using waste heat from a conventional power cycle or as an independent cycle using low temperature sources such as geothermal and solar energy. This paper presents a parametric analysis of the combined cycle. Parametric study of the cycle was carried out in the commercial software Chemcad 6.1. The thermodynamic property data used in simulations were validated with experimental data. Chemcad model was also compared with simulations previously carried out in the process simulator Aspen Plus. The agreement between the two sets has proved the accuracy of the model developed in Chemcad. Then, optimum operating conditions were found for a range of ammonia concentration in the basic solution, isentropic expander efficiency and boiler pressure. It is shown that the cycle can be optimized for net work, cooling output, effective first and exergy efficiencies.
Motion Control of a Nonlinear Single-Rod Hydraulic Actuator via Feedback Linearization
Authors: Moradi Hamed , Hajikolaei Kambiz Haji , Motamedi Mohammad , Vossoughi G. Reza
Published: July 2010

Hydraulic systems are extensively used in many engineering fields where a high degree of both accuracy and performance are required. Due to the highly nonlinear dynamics of hydraulic systems, applying high performance closed-loop controllers is complicated. In this paper, a single-rod hydraulic actuator is considered in which the dynamics of servo-valve is described by first and second order transfer functions. Nonlinear dynamics of hydraulic actuator is represented in the state space configuration. By manipulation of the input voltage to the servo-valve as the control effort, load position is controlled. A controller is designed based on the feedback linearization while its gains are determined using pole placement. Results show that the desired tracking performance and final tracking accuracy are achieved after applying the controller. Required control efforts, load position and velocity are compared for two distinct dynamics of the servo-valve.
Performance and Reliability of High Energy Capacitors in Inverters and DC/DC Converters
Authors: Katsis Dimosthenis C.
Published: July 2010

Emerging alternative energy systems for solar and wind are growing the demand for reliable capacitor technology. Manufacturers presently base the lifetime and reliability of their capacitors on operating temperature, ripple currents, and ambient conditions. Designers of PV inverter systems used are finding that film capacitors are emphasized for their lifetime expectations. This is especially true when compared to aluminum electrolytic capacitors. This paper presents a reliability estimate based on the core temperature of a representative film capacitor. Curves showing the performance of this component in a ripple test fixture will be presented as a reliability estimate.
Intelligent Robotic Arm for Demanufacturing
Authors: Ambuj Ambarish , Ahuja Arun Kumar , Aggarwal Deepak
Published: July 2010

Demanufacturing is the disassembly and recycling of obsolete consumer products. In systematic demanufacturing, we need to disassemble the components from these products, classify these components and send them to different recycling lines. So, we must have an efficient technology for proper sorting and rearrangement of these objects as well as standards for components in terms of shape, size and material etc. The proposed system is to standardize the components and program the robotic arms for disassembling and rearranging those components. Different sensing techniques can be utilized to distinguish objects based on several parameters such as image processing (shape basis), pressure sensor (surface hardness) etc. Subsequently servo motors can be programmed to provide necessary motion to the links. Pulse Width Modulated square wave signal is supplied through the parallel port of desktop to precisely control the angle of rotation of servo motors and hence the motion of the links. In coordination with other automated devices, this system can be used to completely automate the demanufacturing process. This can also be used for developing efficient mechanisms for CIMD i.e. Computer Integrated Manufacturing and Demanufacturing.
Predictions of Structural Testing Characteristics for Wind Turbine Blades
Authors: Desmond Michael , White Darris
Published: July 2010

Static and fatigue structural testing of wind turbine blades provides manufacturers with quantitative details in order to improve designs and meet certification requirements. Static testing entails applying extreme load cases through a combination of winches and weights to determine the ultimate strength of the blade while fatigue testing entails applying the operating design loads through forced hydraulics or resonant excitation systems over the life cycle of the blade to determine durability. Recently, considerable efforts have been put forth to characterize the reactions of wind turbine blades during structural testing in order to develop load and deflection predictions for the next generation of blade test facilities. Incorporating years of testing experience with historical test data from several wind turbine blades, curve fits were developed to extrapolate properties for blades up to one hundred meters in length. Furthermore, conservative assumptions were employed to account for blade variations due to inconsistent manufacturing processes. In short, this paper will outline the predictions of wind turbine blade loads and deflections during static and fatigue structural testing.
On the Development of Solar Drying System
Authors: Chai Adrian Ngu Ming , Ibrahim M. , Chuan Cheah Bin , Yousif B. F.
Published: July 2010

In the present work, solar thermal drying system was developed. The main purpose of solar thermal drying system is to dry local vegetables and fruits. The drying system contained of two main parts as heat collector and the food drying cabinet. It is a force convection indirect type absorbing maximum solar radiation by the heat collector and provides heated air flow to the cabinet via two fans at the air inlet/outlet. The heat collector was inclined at 23.5° angle which suitable to the location for absorption of maximum solar radiation. Experiments were performed to test the efficiency of the solar heat collector and the cabinet at different daily times and operating conditions. The results revealed that 98.8°C temperature was achieved under static air condition. The air temperature at the inlet of the cabinet under both natural and forced air velocities was about 62.8°C. During the experiments, the cabinet was loaded with 426g of banana slices having an initial moisture content of 80%. The designed drying system managed to achieve a final desired moisture content of 15% within effective period of 7 hours without losing the product color.
Reliability of Extracted Modal Parameters by Random Decrement of Acceleration Signatures
Authors: Khodabandelou Babak , Abasi Kaveh , Asayesh Masud
Published: July 2010

Modal parameters provide important information on dynamic properties of structures. In operating condition, since it is difficult to measure input loadings, methods should be applied where don’t require measuring inputs. Such methods which identify modal parameters of structures by measuring their responses are called Operational- or Output Only- Modal Analysis (OMA) techniques. There are many time and frequency domain operational modal analysis techniques. Generally a form of impulse or free vibration response is required to use most of these techniques. However, in practice structures are usually subjected to some immeasurable or unknown random inputs. In these situations Random Decrement (RD) transformation can reduce these responses to equivalent free decay or correlation functions. Therefore, RD technique coupled with those methods, which require a form of impulse or free vibration response offer a valuable tool for identifying the dynamic characteristics of structures from operational or ambient responses. Unfortunately, in the literature there are some constrains on using random decrement signatures. For example by complicated mathematical relations it is shown that random decrement technique is applicable only if the inputs are uncorrelated zero mean Gaussian white noises. In addition, it is proved that only random decrement of displacement and velocity is equivalent to the corresponding free decay responses or correlation functions the random decrement of acceleration response is never equivalent to the corresponding free decay responses or correlation functions. However, there are many papers which have used random decrement of acceleration responses and extracted modal parameters accurately! In this paper it is tried to show simply and clearly whether it is possible to obtain modal parameters from random decrement acceleration signatures or not. To do that, a numerical simulation of a discrete dynamic system with viscous damping is carried out and the results of numerical methods are compared with those come from analytical solution. Numerical simulation is used since it is completely controllable. Finally, it is tried to identify power and the Applicability cases of random decrement method.
Hydrogen and Fuel Cell Education
Authors: Sleiti A. K.
Published: July 2010

This paper is on educational program focused on Hydrogen and Fuel Cell Technology (HFCT) in Engineering Technology Department (ENT) jointly with the Florida Solar Energy Center (FSEC) at University of Central Florida (UCF). The HFCT Program intends to support the need for educated graduates that comprise the next generation workforce needed for research, development, and demonstration activities in government, industry, and academia. The program includes the development and delivery of undergraduate courses at Engineering Technology Department and FSEC within the ABET accredited Bachelor of Science in Engineering Technology program. The mode of course offering is both in class and on line, which will increase the number of students. The program facilitates are located at College of Engineering and Computer Science and at FSEC. The Florida Solar Energy Center has been conducting hydrogen and fuel cell research for 25 years and FSEC has dedicated facilities and a selection of unique laboratory equipment that will be made available to the students for this project. These attributes will allow the students to be trained on the state-of-the-art equipment and facilities. Both ENT and FSEC faculties will participate in the teaching and training of the prospective students.
Experimental Simulation of Solar Flash Desalination
Authors: Abutayeh Mohammad , Goswami D. Yogi
Published: July 2010

Experimental simulations of a sustainable desalination process have been carried out using a small pilot unit at different operating conditions to enhance process analysis and modeling. The proposed desalination process, which employs solar heating and creates vacuum in an innovative passive way, has been theoretically simulated in earlier work. It entails flowing seawater through a condenser to preheat it then through a heater before flashing it in a vacuumed evaporator connected to the condenser where the flashed hot vapor is condensed by the incoming cold seawater forming fresh water. Flashing seawater at higher temperatures increases the vaporization and the production rate of fresh water. In addition, the accumulating non-condensable gases that are slowly eroding the vacuum will decrease the overall vaporization with time which reduces the production rate of fresh water.
Nano-Engineering Silica Aerogel Structure to Determine the Property-Structure Relationship
Authors: Churu Gitogo , Lu Hongbing , Leventis Nicholas
Published: July 2010

We characterize mechanically strong nano/meso-porous cross-linked templated silica aerogels that were synthesized through the sol gel process and reinforced by nano casting a 4–10nm thick conformal layer of isocynate derived polymer. Tri-block co-polymer (pluronic P123) was used as a structure directing agent to produce ordered mesoporous walls while 1, 3, 5 trimethylbenzene (TMB) was added as micelle-swelling reagent to regulate the size of the pores. The shape and size of the micro and meso pores were nano engineered by varying the amount of chemical surfactant as well as the concentration of the cross-linking solution used to form the polymer nano layer. In so doing we manipulated the structure at the molecular level to develop an optimized structure that closely resembles the honeycomb structure found in nature. Dynamic mechanical analysis (DMA) test results established that the material had an α-grass transition temperature of about 130°C while quasi-static compression tests showed that the optimized nano-structured silica aerogel had a Young’s modulus of about 800MPa. We present the synthesis protocol as well as chemical, physical and mechanical characterization of cross-linked templated silica aerogel (CTSA). ). In addition, material point method (MPM) simulation results are highlighted.
Study on the Application of Multi-Step Predictive Self-Tuning Arithmetic in Hybrid Isolation System
Authors: Hu Shifeng , Zhu Shijian , Zhong MinJun , He Qiwei
Published: July 2010

The radiated noise caused by the vibration of the power plant equipment is in the low frequency band and contains discrete lines in the noise spectrum. Insertion of resilient isolators between the machinery and the base is one of the most common methods for controlling unwanted vibration and hence reducing the radiated noise. Passive and active vibration isolation systems have their own relative merits. Therefore, hybrid vibration isolation, a combination of passive and active isolation technique, is a solution to improve the vibration isolation effectiveness. In order to offset the deficiency of passive vibration isolation system of power equipment on ship, the control system of multi-step predictive self-tuning arithmetic in hybrid vibration isolation system was build. The model of the system was obtained and the design of control system was given. And the same time a example of system design was simulated and analyzed. The result showed that the control system of multi-step predictive self-tuning arithmetic in hybrid vibration isolation system can effectively offset the deficiency of passive vibration isolation system and the system have the well performance of robustness.
Effect of a Permanent Magnet on CHS (Compost Heating System)
Authors: Toriyama H. , Asako Y.
Published: July 2010

Effect of a permanent magnet on ventilation of an air duct through compost have been investigated numerically. Some compost yield heat over 60 Celsius in fermentation process. That exothermic reaction produces a considerable amount of heat, which could be a potential heating source. Fermentation reaction requires ventilation, abundant supply of paramagnetic oxygen gas and exhaust of metabolized diamagnetic carbon dioxide gas. Continuous and forced air supply is more efficient rather than the conventional manual turn or stirring as ventilation means. In magneto-fluid-dynamics, the magnetizing force acting on a paramagnetic oxygen gas is applied for the enhancement of air flow, heat and mass transfer. In this research, the enhancement of the air flow of various size air ducts have been numerically investigated by applying a permanent magnet on an air duct. Numerical results shows that a permanent magnet enhances the air flow. The application of a permanent magnet to an air duct is useful for CHS, a promising alternative energy system.
A Comparison of the Relative Effectiveness of Fin Aspect Ratio Under Natural Convective Heat Transfer With Top Mounted Fins
Authors: Pruszenski Anthony S.
Published: July 2010

Mechanical engineers often design fins on metal enclosures to dissipate an internal heat load using natural convection. This paper gives the results of a series of CFD (Computational Fluid Dynamics) studies, and, supporting calculations for the maximum temperature rise on a plate with a constant heat load of 100 watts applied to the bottom of the plate. Vertical fins are formed on the top surface of the plate. In this study, the horizontal dimensions and thickness of a square plate are held constant, while, the aspect ratio of the top surface fins are varied between studies. The aspect ratio is defined as the ratio of the height of the fin to the width of the base of the fin. The study compares aspect ratios from 1:1 to 40:1 with a constant base width. In addition, comparisons between 20:1 aspect ratio fins with the same height but with different fin counts due to changes in fin separation distances are compared. Closely spaced fins are not always the best solution for natural convection.
Laminar Fluid Flow Around Two Wall-Mounted Blocks of Different Size
Authors: Tavakol Mohammad Mehdi , Eslami Mohammad
Published: July 2010

Fluid flow around single or multiple bluff bodies mounted on a surface has great significance in science and engineering. Understanding the characteristics of different vortices formed around wall-mounted bodies is quite necessary for different applications. Although the case of a single surface mounted cube has been studied extensively, only little attention has been paid to the flow around two or more rectangular blocks in array. Therefore, a CFD code is developed to calculate three dimensional steady state laminar fluid flow around two cuboids of arbitrary size and configuration mounted on a surface in free stream conditions. The employed numerical scheme is finite volume and SIMPLE algorithm is used to treat pressure and velocity coupling. Results are presented for two rectangular blocks of the different size mounted on a surface in various inline arrangements. Streamlines are plotted for blocks of different size ratio. Velocity and pressure distributions are also plotted in the wake region behind the obstacles. It is shown that how the behavior of flow field and vortical structures depend on the respective size and location of the larger block in comparison with the case of two inline wall mounted cubes of the same size.
Numerical Simulation of Natural Convection in a Cavity With Vertically Partial Filled Porous Media
Authors: Dai Chuanshan , Chen Yan , Ma Qiang-Yun , He Guang-Xun , Sun Ping-Le
Published: July 2010

Natural convection in a 2D rectangular cavity with vertically partial filled porous media was numerically simulated by using lattice Boltzmann method (LBM). The cavity was enclosed with four non-slip flow boundaries, and its left part was filled with porous media, and the remained right part open free. The natural convection behaviors of fluid flow and temperature distribution were numerically studied for a configuration with a heating surface at left and a cooling surface at right, and the top and bottom surfaces were adiabatic. The local heat transfer coefficient at the cooling surface of right side was analyzed in detail at conditions with various types of filled porous media. The interface function that separates the fluid in open free space from porous media was numerically studied.
Entropy Generation in Thin Films Evaluated From Phonon Radiative Transport
Authors: Bright T. J. , Zhang Z. M.
Published: July 2010

One of the approaches for micro/nanoscale heat transfer is to use the Boltzmann transport equation, which reduces to the equation of phonon radiative transfer under the relaxation time approximation. Transfer and generation of entropy are processes inherently associated with thermal energy transport, yet little has been done to analyze entropy generation in solids at length scales comparable with or smaller than the mean free path of heat carriers. This work extends the concept of radiation entropy in a participating medium to phonon radiation, thus providing a general theory of entropy generation that is applicable to both large and small length scales. The conventional formula for entropy generation in heat diffusion can be derived under the local equilibrium assumption. Furthermore, the phonon brightness temperature is introduced to describe the nature of nonequilibrium heat conduction. A fundamental understanding of the entropy generation processes will broaden the knowledge of heat transport in solids, which is particularly important for thermal analysis in nanoelectronics.
Impacts of Industrial Assessment Centers on Energy Engineering Education
Authors: Mehta D. Paul
Published: July 2010

The need for energy efficiency captured the attention of all sectors of our society in the 1970s when energy supplies dwindled and prices increased. Interest in energy efficiency continued during the 1980s primarily due to environmental concerns and secondarily because of economic and industrial competitiveness issues. Energy supply disruptions caused by hurricanes Katrina and Rita, and recent hikes in energy prices have generated a renewed interest in energy efficiency. An example of this renewed interest is that the U. S. Department of Energy (DOE) initiated, developed, and implemented a national campaign to save energy now in 2006. In the past, the industrial sector has responded to energy shortages and its price increases with varying effectiveness, but small and medium-sized plants generally lacked the resources to cope effectively. One of the U. S. government’s responses to this situation was to offer these small and medium-sized plants technical assistance such as Industrial Assessment Center (IAC) program. One such center was established at Bradley University in 1993. Since its inception, the Bradley University Industrial Assessment Center (BU IAC) has functioned very successfully. Periodically BU IAC has been doing an in-house critical review of its performance and effectiveness. These reviews included outcomes such as total assessment recommendations, (ARs); diversity of ARs; quantifications of identified opportunities to save energy, minimize waste, and enhance productivity; implementation rates analysis; and impacts on energy engineering education. The purpose of this paper is to describe the impacts of the Industrial Assessment Center program on energy engineering education. The impacts on employment, salaries, and job performance of BU IAC graduates are discussed in this paper. The impacts of the BU IAC in improving the quality of in-class instruction by its Director(s) are explained in this paper.
Analysis of Energetic, Design and Operational Criteria When Choosing an Adequate Working Fluid for Small ORC Systems
Authors: Faca˜o Jorge , Oliveira Armando C.
Published: July 2010

Small cogeneration (CHP) systems may lead to a significant reduction of primary energy consumption and harmful emissions. Low temperature Rankine cycles, that can be assisted by solar energy, are a possible solution for producing combined electricity and useful heat. These cycles usually use an organic working fluid. This study presents an analysis of the energetic, design and operational features, that have to be taken into account when choosing an adequate working fluid for these Organic Rankine Cycles (ORC). When using renewable energies as a heat source, like solar or geothermal, the cycles may operate at temperatures between 120°C and 230°C. A system producing 5 kW of electricity was considered as a basis of comparison. Several fluids were analysed: n-dodecane, water, toluene, cyclohexane, n-pentane, HFE7100, R123, isobutane and R245fa. The organic dry fluids, with a positive slope of the saturated vapor curve in a T-s diagram, are in principle desirable for low temperature applications, simplifying turbine design. The degree to which the fluids are drying, is generally related to their molecular weight or molecular complexity. Practical issues, like thermal stability, toxicity, flammability and cost are considered. The thermodynamic cycle efficiency is also important. The saturated vapor specific volume gives an indication of condenser size, which is related to system initial cost. A super-atmospheric (>100 kPa) saturation pressure eliminates infiltration gases, which is important for operational reasons, because infiltration reduces system efficiency. The degree of superheating was optimized for maximum cycle efficiency, with a quadratic approximation method. This optimization makes it possible to decide if it is better to have saturated vapor or superheated vapor at turbine inlet, for a fixed turbine inlet temperature. For a heat source temperature of 120°C, only toluene and isobutane present a small advantage in superheating. It is difficult to find the best fluid, which has simultaneously: high cycle efficiency, low vapor specific volume at turbine outlet, super-atmospheric saturation pressure, good thermal stability, small environmental impact, small toxicity and no flame propagation. From the point of view of cycle efficiency, n-dodecane presents the best performance. However, this fluid presents the highest saturated vapor specific volume (resulting in a larger condenser) and the smallest condenser saturation pressure (resulting in infiltration of gases). The best candidates for the cycle regarding all the aspects are: toluene, cyclohexane and n-pentane. Comparing the three fluids, toluene presents the highest efficiency, the highest impact in environment and the biggest vapor specific volume. N-pentane presents the smallest cycle efficiency and smallest vapor specific volume, but is the unique fluid with super-atmospheric saturation pressure. Cyclohexane is the fluid with lowest impact in environment.
Flight Characteristics of Flapping Wing Miniature Air Vehicles With “Figure-8” Spherical Motion
Authors: Trabia Mohamed B. , Yim Woosoon , Rehmat Zohaib , Roll Jesse
Published: July 2010

Hummingbirds and some insects exhibit “Figure-8” flapping motion that allows them to go through a variety of maneuvers including hovering. Understanding the flight characteristics of Figure-8 flapping motion can potentially yield the foundation of flapping wing UAVs that can experience similar maneuverability. In this paper, a mathematical model of the dynamic and aerodynamic forces associated with Figure-8 motion generated by a spherical four bar mechanism is developed. For validation, a FWMAV prototype with the wing attached to a coupler point and driven by a DC servo motor is created for experimental testing. Wind tunnel testing is conducted to determine the coefficients of flight and the effects of dynamic stall. The wing is driven at speeds up to 12.25 Hz with results compared to that of the model. The results indicate good correlation between mathematical model and experimental prototype.
A Unified Method of Modeling a 3-Phase Induction Motors
Authors: Snell Antony
Published: July 2010

Many textbooks on electro-mechanical machines introduce the induction motor using a transformer circuit model connected to a fictitious load resistor, the value of which changes as a function of the slip speed. The method is essentially a power based analysis, which yields some neat, quick results. The developed torque is calculated in terms of the power developed in that fictitious resistor. Although clever in its simplicity, the method fails to provide much physical insight into how the developed torque comes about. One is just expected to trust the circuit model. The approach described in this paper is based on theory of Lorentz force and Faraday’s Law used successfully to explain the operation of DC commutator machines. The method is readily understood and it provides direct insight into how the torque is developed. The paper will introduce a torque angle, which can be useful in visualizing how the machines work. It will also be shown that the traditional transformer model of the motor can be derived from the new analysis.
The Effect of Geometrical Features on Air-Side Heat Transfer and Friction Characteristics, and Optimization of a Large-Size Plain Fin-and-Tube Heat Exchanger by 3-D Numerical Simulation
Authors: Izadi M. , Aidun D. K. , Marzocca P. , Lee H.
Published: July 2010

The effect of geometrical features on the air-side heat transfer and friction characteristics of an industrial plain fin-and-tube heat exchanger is investigated by 3-D numerical modeling and simulations. The heat exchanger has been designed and employed as an intercooler in a gas power plant and is a large-size compact heat exchanger. Most of the available design correlations developed so far for plain fin–and–tube heat exchangers have been prepared for small-size exchangers and none of them fits completely to the current heat exchanger regarding the geometrical limitations of correlations. It is shown that neglecting these limitations and applying improper correlations may generate considerable amount of error in the design of such a large-size heat exchanger. The geometry required for numerical modeling is produced by Gambit® software and the boundary conditions are defined regarding the real operating conditions. Then, three-dimensional simulations based on the SIMPLE algorithm in laminar flow regime are performed by FLUENT™ code. The effect of fin pitch, tube pitch, and tube diameter on the thermo-hydraulic behavior of the heat exchanger is studied. Some variations in the design of the heat exchanger are suggested for optimization purposes. It is finally concluded that the current numerical model is a powerful tool to design and optimize of large-size plain fin-and-tube heat exchangers with acceptable accuracy.
The Experimental Investigation of Fouling Phenomenon in Heat Exchangers by Heat Transfer Resistance Monitoring (HTRM) Method
Authors: Izadi M. , Aidun D. K. , Marzocca P. , Lee H.
Published: July 2010

The aim of this paper is to describe a monitoring system for fouling phenomenon in tubular heat exchangers. This system is based on a physical model of the fouling resistance. A mathematical model of the fouling resistance is developed based on the applied thermal heat, the inside heat transfer coefficient, and geometrical characteristics of the heat exchanger under consideration. The resulting model is a function of measured quantities such as water and tube wall temperatures, fluid flow velocities, and some physical properties of the fluid flowing inside the tubes such as viscosity, conductivity, and density. An on-line fouling evaluation system was prepared and the heat transfer resistance for selected solutions was measured in real time by this system. The effect of concentration and chemical reactions on fouling is studied experimentally by using different contaminants such as sodium bicarbonate, calcium chloride, and their mixture. Accelerated corrosion was observed for the calcium chloride-0.4g/l solution due to the presence of chlorine ions. This corrosion-fouling can be mitigated by adding sodium bicarbonate. However, calcium carbonate is formed as the result of the chemical reaction between calcium chloride and sodium bicarbonate which activates two other fouling categories, particulate fouling and crystallization. The inside surface of the tube is analyzed by analytical microscopy after the experiment to investigate different fouling categories. Experimental results provide quantitative information of liquid-side fouling on heat transfer surfaces, and its effects on the thermal efficiency. Experimental data is significantly important for the design, and for formulating operating, and cleaning schedules of the equipment.
Using Meshfree Weak-Strong Form Method for a 2-D Heat Transfer Problem
Authors: Zahiri S. , Daneshmand F. , Akbari M. H.
Published: July 2010

In this work, the numerical simulation of 2-D heat transfer problem is studied by using a meshfree method. The method is based on the local weak form collocation and the meshfree weak-strong (MWS) form. The goal of the paper is to find the temperature distribution in a rectangular plate. The results obtained are compared by those obtained by use of other numerical methods. Two types of boundary conditions are considered in this paper: Dirichlet and Neumann types. The Local Radial Point Interpolation Method (LRPIM) is used as the meshfree method. It is shown that the essential boundary conditions can be easily enforced as in the Finite Element Method (FEM), since the radial point interpolation shape functions posses the Kronecker delta property. It is also shown that the natural (derivative) boundary conditions can be satisfied by using the MWS method and no additional equation or treatment are needed. The MWS method as presented in this paper works well with local quadrature cells for nodes on the natural boundary and can be generated without any difficulty.
Numerical Investigation of Turbulent Convection in Al2O3/Water Nanofluid With Temperature Dependent Properties
Authors: Bianco Vincenzo , Manca Oronzio , Nardini Sergio
Published: July 2010

In this paper turbulent forced convection flow of a water–Al2O3 nanofluid in a circular tube subjected to a constant and uniform heat flux at the wall is numerically analyzed. Two different approach are taken into account: single and two-phase models, with particle dimension equal to 38 nm. Temperature dependant thermophysical properties are considered for both the approaches. The CFD commercial code Fluent is employed to solve the problem by means of finite volume method. It is found that convective heat transfer coefficient for nanofluids is greater than that of the base liquid. Heat transfer enhancement is increasing with the particle volume concentration and Reynolds number. A good agreement is found with the correlation of Xuan and Li.
Nonlinear Disturbance Observer Based Impedance Control for a Teleoperation System Under Time Delay
Authors: Monemian Esfahani A. , Rezaei S. M. , Zareinejad M.
Published: July 2010

In this paper a nonlinear disturbance observer (NDO) based impedance control is proposed for a teleoperation system. The unknown friction and uncertainties will be estimated by the observer and added to the control input for compensation. Although friction will improve the stability, it worsens the transparency of the system which is another major point in teleoperation systems. The stability of the system is guaranteed by Lyapunov stability criterion and selecting the best design parameters. Tracking of force/position is achieved by these parameters. Also a fixed time delay is added to the system because of delays in the cables and other sources, it is then compensated with the designed controller. Performance of the proposed control is validated by experimental results.
CFD Analysis of Natural Convection in a Cubic Enclosure Heated From a Side Wall With Experimental Verification Using PIV
Authors: Ku¨rekci Nuri Alpay
Published: July 2010

Natural convection of air in a cubical volume is investigated experimentally and numerically. A cubical volume of 20×20×20 cm dimensions was built for the experimental study. One of the vertical walls covering the volume is hot, the other one is cold and the rest are adiabatic. Three walls are made of aluminum and the others are made of heat-resistant glass. The hot wall temperature is kept constant during the experiments by means of an electrical heater. The cold wall is at the ambient temperature. Other adiabatic surfaces are insulated with polyurethane foam. Experiments are performed in an air-conditioned room at 21°C. PIV (Particle Image Velocimetry) is used for velocity measurements. The FLUENT CFD software package is used for the numerical study. A three-dimensional solution is obtained for the laminar flow case for a 61×61×61 grid. The numerical and experimental results are compared with each other for the validation of the numerical solution under the testing conditions of TH = 69°C, TC = 41°C and Ra = 1.3×107. Results obtained from the numerical and experimental studies are in a reasonably good agreement with each other.
A Novel Composite Neural Network for Hysteresis Modeling in Piezoelectric Actuators
Authors: Fazli Mohamad , Rezaei Seyed Mahdi , Zareienejad Mohamad
Published: July 2010

Piezoelectric actuators are convenient for micro positioning systems. Inherent hysteresis is one of the drawbacks in use of these actuators. Precise control of this actuator under changing of environmental and operational conditions, without modeling of hysteresis, is impossible. Neural networks can be used for this modeling. The ordinary feed forward neural networks can not train time dynamic relationship between input and output. Thus a certain type of networks called time delay feed forward neural networks (TDNN), are developed and is used in this paper. In the previous researches in this field, the important effect of loaded force on the actuator is ignored. This can increase the positioning error remarkably. Especially when these actuators are used in the precise grinding or machining operations. In this paper, neural network is used for hysteresis modeling with attention to the important effect of loaded force. After modeling, inverse hysteresis model is used as compensator in a feed forward way to linearize the input-output relationship. Then using PI closed loop controller and selecting suitable coefficient for it, the maximum error was decreased to less than 2 percent of the working amplitude.
Gravity Scaling Parameter for Pool Boiling Heat Transfer
Authors: Raj Rishi , Kim Jungho , McQuillen John
Published: July 2010

The effect of low gravity on pool boiling heat flux has been studied by researchers, but pool boiling heat flux data over a continuous range of gravity levels (0g–1.8g) was unavailable until recently. The current work uses the results of a variable gravity subcooled pool boiling experiment to develop a gravity scaling parameter for prediction purposes. The heat flux prediction at various gravity levels was found to be in good agreement with the measured heat flux data. The scaling parameter can be used as a tool to predict boiling heat flux at any gravity level if the data under similar experimental conditions are available at any other gravity level. The scaling parameter has been demonstrated to be valid for pool boiling of n-perfluorohexane in heater size independent boiling regime (Lh/Lc>2.8).
H
∞ Robust Control of Continuous Fluidized Tea Bed Dryer
Authors: Moradi Hamed , Motamedi Mohammad , Hajikolaei Kambiz Haji , Vossoughi G. Reza
Published: July 2010

During drying processes, moisture control of food products, such as dried tea, is of great importance. Improving dryer control, results in consistent production and reduction of energy consumption. However, the dryer is a complex system associated with model uncertainties. In this paper, a realistic uncertain model of a fluidized tea bed dryer is considered. Moisture content and temperature of tea leaves (or other products) are controlled at desired values by manipulating tea leaves heating rate. Developing a code by Robust Control Toolbox of MATLAB and modeling uncertainties, a robust controller is designed based on μ-synthesis with DK-iteration algorithm. Results show that in the presence of model uncertainties, designed controller guarantee robust performance of the system; with appropriate behavior in tracking desired set points.
Evaluating Lifelong Learning
Authors: Bryan April , Brackin Patricia , Sanders Wayne
Published: July 2010

One of the required ABET outcomes is “a recognition of the need for, and an ability to engage in lifelong learning.” Although students must demonstrate this recognition and ability at graduation, data from alumni can strengthen a program’s assertion that its graduates actually engage in lifelong learning. Several strategies for demonstrating lifelong learning are presented and discussed. In addition, a case study from the Mechanical Engineering Department at Rose-Hulman Institute of Technology is presented. For the case study, several assessment instruments were used: an alumni survey, employer focus groups, an Advisory Board survey, and feedback from senior students. Each component will be discussed, results will be presented, and conclusions will be drawn. The alumni survey was made via the internet. The 760 respondents included graduates from the 1940s through the 2000s. Respondents were asked to indicate the number of additional courses or workshops that they had taken and whether or not they had received any additional degrees. Furthermore, respondents were asked to rate the importance of lifelong learning to their current job. In addition, they were asked to rate how well Rose had prepared them for lifelong learning. Employer perspective was gained through focus groups and the advisory board. Companies who were present at career fairs were asked to answer questions about Rose graduates in general. The ME Advisory Board contains members from institutions who are major employers of our graduates. Advisory board members gave feedback based on their knowledge of graduates’ performances. As in the alumni survey, both groups were asked to rate the importance of lifelong learning, along with how well Rose prepared them. Finally graduating seniors were asked to rate how important they felt lifelong learning would be in their careers. In addition, they were asked how well prepared they thought they were. All groups surveyed rated the ability to continue to learn and educate one’s self as being important, and all groups felt that RHIT graduates met the required standard.
Deformation and Strain Measurement of Flip-Chip Solder Bump Under In-Situ Thermal Loading
Authors: Kwak Jae B. , Lee Dong Gun , Nguyen Tung , Park Seungbae
Published: July 2010

Thermo-mechanical behavior of solder joints, especially the solder bumps located at the chip corners where most failures usually occur was investigated. Digital Image Correlation (DIC) technique with optical microscope was adopted to quantify the deformation behavior and strains of a solder bump of flip-chip package subjected to thermal loading. A flip-chip specimen was cross-sectioned after manual polishing process followed by wet etching method in order to generate natural speckle patterns with high enough contrast on the measuring surface for employing DIC technique. The sample was placed in a miniature heating chamber and subjected to in-situ thermal loading from 25 °C to 100°C. During the heating, sequential microscopic images of the cross-sectioned surface of a solder bump were acquired, and the deformation behavior and strain distributions were successfully measured with submicron accuracy by applying DIC technique on the captured images. The computed full-field displacement fields clearly depicted both normal and shear deformation of the solder bump under the thermal loading. In addition, from the strain fields, it was observed that strains were mostly concentrated on the bottom portion of solder bump near the pad connected to substrate. In order to assess the thermo-mechanical strains of the flip-chip interconnections more quantitatively, the average strains of solder joints at different locations were also measured and compared to one another. By doing so, the strain trends of solder bumps were effectively analyzed with respect to the distance to neutral point (DNP). Finally, finite element analysis was conducted by simulating the thermal loading applied in the experiments, and comparison between the simulation and experimental results of displacements and strains was made. The comparison results exhibited satisfactory agreement, which ensured the validity of the experimental data and methodology. This study can further expedite the studies of electronic-package reliability through fatigue and crack failure analysis of the solder joints due to thermal cyclic loading.
Ultra Low Carbon Dioxide Emission MCFC Based Power Plant
Authors: Andreassi Luca , Chiappini Daniele , Jannelli Elio , Ubertini Stefano
Published: July 2010

The application of high temperature fuel cells in stationary power generation seems to be one of the possible solutions to the problem related to the environment preservation and to the growing interest for distributed electric power generation. Great expectations have been placed on both simple and hybrid fuel cell plants, thus making necessary the evolution of analysis strategies to evaluate thermodynamic performance, design improvements and acceleration of new developments. This paper investigates the thermodynamic potential of combining traditional internal combustion energy systems (i.e. gas turbine and internal combustion engine) with a Molten Carbonate Fuel Cell (MCFC) for medium and low-scale electrical power production with low CO2 emissions. The coupling is performed by placing the fuel cell at the exhaust of the thermal engine. As in MCFCs the oxygen-charge carrier in the electrolyte is the carbonate ion, part of the CO2 in the gas turbine flue gas is moved to the anode and then separated by steam condensation. Plant performance are evaluated in function of different parameters to identify optimal solutions. The results show that the proposed power system can be conveniently used as a source of power generation.
Cold Welding Phenomenon in Adhesively Bonded Flip-Chip Interconnects
Authors: Sinha K. , Farley D. , Kahnert T. , Solares S. , Dasgupta A. , Caers J. F. J. , Zhao X. J.
Published: July 2010

In the conversion to Pb-free electronics, there has been increasing interest in conductive adhesive interconnects, as they combine Pb-free materials with the added benefit of low temperature processing. This work explores the degradation mechanisms and kinetics in adhesively bonded Au-bumped flip chip interconnects. Earlier researchers have suggested that electrical contact is by mechanical interfacial compression caused cure-induced shrinkage of the adhesive and degradation is by stress relaxation of the adhesive material during temperature and moisture cycling throughout the life cycle. However, temperature cycling conducted here raises questions about the validity of this hypothesis since no such progressive degradation is found under temperature cycling. Instead, overstress failures were found at cold temperatures. The alternate interconnection mechanism between the Au bumps, suggested by this study, is metallurgical bonding by cold welding or mechanical interlocking. Experimental and modeling results showing evidence of this cold welding phenomenon are presented here. First, the surface roughness of unmated and mated Au bumps are characterized on flip-chip dies, since the amount of surface flattening provides insights into both mechanical interlocking as well as propensity for cold-welding. A corresponding elastic-plastic, large-deformation finite element modeling with nonlinear contact surfaces is used to further understand and quantify this surface-flattening phenomenon. Next, pull tests for flip-chip to flip-chip assemblies were designed to measure the bond strength and observe the temperature & time dependence of the strength at the interface. The results clearly showed strong evidence that the bonding mechanism may be either diffusionassisted metallurgical bonding or increase in contact area over time due to new bond formation. This work is somewhat novel, as prior examples of low-temperature cold welding are mostly for very thin gold films.