bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance of Thermoelectric Based Regenerative Adsorption Cooling System for Harsh Environment
Authors: Sinha Ashish , Joshi Yogendra
Published: July 2010

Performance of a cooling system designed for thermal management of harsh environment electronics has been presented. The system is based on regenerative adsorption-desorption cycle and mainly comprises of two beds with zeolite-water as adsorbent-adsorbate pair, a condenser and an evaporator. Heat regeneration was achieved by a thermoelectric (TE) device placed in between the zeolite beds. Use of a thermoelectric device for heat transfer in between beds allows for miniaturization of usually bulky adsorption cooling systems. This also provides a cooling system with nearly no moving parts, hence suitable for harsh environment electronic cooling applications. Zeolite beds alternately carry out adsorption and desorption depending on the direction of heat flow in between them. Direction of heat flow is governed by the polarity of voltage applied across the TE device. Polarity is switched at fixed time intervals that determine the cycle time. Tests were carried out during which the condenser temperature hovered around 165 °C, heat load was up to 5W, the cycle time kept close to 12 minutes and the targeted evaporator temperature was 140 °C. System was analyzed in terms of the extent of cooling below the heat rejection ambient temperature of 160 °C and coefficient of performance. A COP of 0.2 was obtained. The study could be used to extend the working envelopes of existing electronics towards hotter surroundings. A mathematical model was also prepared and the experimental results have been compared with the simulations.
Heat Transfer and Pressure Drop Correlation for Helicoidal Pipes of Rectangular Cross Section
Authors: Katinas Christopher , Fakheri Ahmad
Published: July 2010

In this study, flow and heat transfer for laminar flow in curved channels of rectangular cross section is examined. The focus of the numerical solutions is on rectangular cross sections with an aspect ratio less than one, since little information is available for heat transfer in curved rectangular pipes whose width is greater than height. The study examines the impact of the aspect ratio and Dean number on both friction factor and Nusselt number. The results show that although both friction factor and Nusselt number increase as a result of curvature effects, the heat transfer enhancements significantly outweigh the friction factor penalty. Numerical solutions in this study consider the more realistic case of hydrodynamically developed and thermally developing flow.
Effect of the Power Generation Unit Operation on the Energy, Economical, and Environmental Performance of CCHP Systems for a Small Commercial Building
Authors: Hueffed Anna K. , Mago Pedro J. , Chamra Louay M.
Published: July 2010

Combined cooling, heating, and power (CCHP) systems generate electricity at or near the place of consumption and utilize the accompanying waste heat to satisfy the building’s thermal demand. CCHP systems have often been cited as advantageous alternatives to traditional methods of power generation and one of the critical components affecting their performance is the power generation unit (PGU). This investigation examines the effect of the PGU on the energy, economical, and environmental performance of CCHP systems. Different size PGUs are simulated under the following operational strategies: follow the building’s electric load, follow the building’s thermal load, and operate at constant load. An internal combustion engine is used as the PGU in the CCHP system to meet hourly electric, cooling, heating, and hot water loads of a typical office building for a year. Annual operational cost, primary energy consumption (PEC), and carbon dioxide emissions (CDE) are found for two cities and compared to a conventional building. Finally, a simple optimization is performed to determine the best engine load for each hour during the simulation. Among the results, the smallest engine generally yielded the lowest costs and lowest PEC; but, no such trend was found with regards to CDE.
Movable Instantaneous Impact Pressure Testing Device
Authors: Han Hongbiao , Li Jishun , Wang Bing , Liu Dandan , Liu Yonggang
Published: July 2010

A movable instantaneous impact pressure test device is designed and achieved, according to the characteristic of instantaneous impact wave such as acutely variation and large range of pressure, adverse conditions on the spot. A piezoresistive transducer of high-frequency an high pressure is selected and used. MEMS technology is adopted to design and manufacture the sensor that is flush packaged. In addition multi-channel analogue amplified circuit and DSP control core circuit are studied. So the multilevel multiple pressure analogue signals can be achieved. The circuit can take charge of high speed sampling, processing and storing of analogue signal too. Software modifying mode, process parameter and data transmission is also developed. The device has the function of scheduling of timing sample, automatic gain of magnification, automatic detection of the beginning of impact pressure, parameterization of working mode and process etc. It is a practical instrument with battery as power supply, the low power consumption of power supply control mode and the solid mental shell for testing explosion shock wave. Pressure test results indicated accurate pressure waves of instantaneous impact can be got with the instrument.
Heat Transfer and Hydrodynamics of Subcooled Inverted Annular Flow Film Boiling on a Single Rod Heater
Authors: Yi Sonny , Warrier Gopinath R. , Dhir Vijay K.
Published: July 2010

Heat transfer during inverted annular flow boiling of a subcooled liquid was studied in this work. An experiment was set up to simulate flow downstream of a quench front during the reflooding phase of a dried out nuclear core in a loss of coolant accident. Steady-state, subcooled flow film boiling experiments were conducted inside an annular cross section consisting of a single stainless steel rod heater, 71 cm in height and 1.11 cm in diameter, which was placed concentrically within a tube of diameter 1.59 cm. The quench front location was stabilized near the test section inlet using a “hot patch”. The hot patch consisted of a 2.5 cm-long cartridge heater inserted within the inner diameter of the heater tube. All tests were performed with PF-5060 as the test fluid, with mass flux ranging from 200 to 810 kg/m2s, inlet subcooling ranging from 12 to 27 °C, and wall superheat ranging from 200 to 305 °C. The fluid temperature, wall temperature, and pressure were measured at various axial locations. Fluid temperatures in the radial direction were also measured at several axial locations. The data obtained from these experiments were used to determine the wall heat transfer coefficient and liquid side heat transfer rate.
Flow Field Analysis of a Single Piezoelectric Fan
Authors: Eastman Andrew , Kimber Mark
Published: July 2010

Piezoelectrically actuated fans are relatively simple structures consisting of a piezoelectric material affixed to a thin cantilever beam. It is then subjected to a current that causes the beam to oscillate by the constriction and expansion of the piezoelectric material. A common application is that of electronics cooling where the induced flows can greatly augment natural or forced convection. Previous studies have sought to explore the flow field of piezoelectric fans in relation to its heat transfer application. This research seeks to expand upon that knowledge with a focus on measuring the flow parallel to the fan blade. A fan with length and width of 36.5 mm and 12.7 mm, respectively, is excited with an oscillating voltage input of 62.5 Hz and varying amplitudes. A Particle Image Velocimetry system, able to chart particle movement in the x and y directions, is employed to aid in understanding the flow field created by the fan with an emphasis on studying the vortex shed by a single half period of oscillation. This information has the potential to be a starting point for further exploration into a dual fan application and how their interactions alter vortex shedding in both two and three dimensions.
Recrystallization of Lead Free Solder Joints: Confounding the Interpretation of Accelerated Thermal Cycling Results?
Authors: Mayyas Ahmad , Yin Liang , Borgesen Peter
Published: July 2010

A primary concern of any reliability engineer is whether failure in accelerated testing may be caused by a different damage mechanism than the one that determines life in service. The recent suggestion that thermal expansion mismatch induced fatigue and failure of lead free solder joints under realistic service conditions may progress without the recrystallization seen to play a major role in accelerated thermal cycling thus requires systematic investigation. A total different concern is the ever recurring question of to which extent thermal cycling can be replaced by much faster isothermal cycling tests. The observation that the damage mechanisms tend to be completely different, one leading to transgranular cracking the other to intergranular cracking of lead free BGA solder joints, would seem to invalidate such ideas completely. Importantly, most practical service scenarios involve the combination of more than one loading conditions. This may be as simple as thermal excursions to different temperatures or vibrations with two different frequencies or amplitudes, but it may also involve a combination of thermal excursions and vibration, for example. Reliability prediction almost invariably relies on the explicit or implicit assumption of some principle of damage accumulation, most commonly Miner’s rule. These assumptions do, however, break down much more often than commonly recognized. One important reason for this, albeit clearly not the only one, would be the different effects of recrystallization. All of these concerns prompted an ongoing investigation to identify the parameters determining whether recrystallization will affect lead free solder fatigue life and what would be the practical consequences.
Innovative Thermofluids Experiments for Modern Mechanical Engineering Education
Authors: Rodgers Peter , Bojanampati Shrinivas , Goharzadeh Afshin , Molki Arman , Eveloy Valerie
Published: July 2010

One of the primary objectives of the Petroleum Institute (PI) is to prepare future mechanical engineers to assume successful career paths in the oil and gas industry. Hands-on laboratory skills play a vital role in providing students with a sound understanding of the scientific fundamentals and their application in solving real-life engineering problems. The Institute’s undergraduate mechanical engineering curriculum incorporates a one-semester junior level course titled Core Measurements, which is taught in a state-of-the-art measurement laboratory. This course includes two innovative hands-on experiments related to experimental heat transfer and fluid dynamics, with the objective of familiarizing the students, through simple projects, with the characterization of fundamental thermofluid phenomena. Each hands-on project consists of design, fabrication, data acquisition and validation of a simple experiment, with a formal report submitted on completion. Each project is undertaken by groups of four students over a five-week period. The first experiment characterizes conductive heat spread within a heat-source-substrate assembly representative of electronics cooling applications. The effects of heat source foot print, substrate geometry and thermal conductivity, and convective cooling conditions are investigated. The temperature distribution on the source and substrate surfaces are measured using thermocouples and infrared thermography, with substrate thermal resistance calculated and compared with analytical solutions. The second experiment aims to enhance student’s learning of internal pipe flows. Single phase flows in a pipe network are characterized for different flow regimes. The pipe network consists of different diameter lines with valves for regulating and directing the flow to make up various series and parallel piping combinations. The relation between head loss due to fluid friction and velocity, pressure drop empirical laws, valve characteristics, and loss coefficient of fittings are investigated using various pressure and flow measuring techniques, including laser Doppler velocimetry (LDV). The paper documents the experiments and the teaching strategy employed to integrate fundamental theories with hands-on experiences. Sample measurement and analysis results are reported. The effectiveness of the proposed experiments in enhancing student learning of thermofluids, engineering analysis of discrepancies between predictions and measurements, and project management skills is highlighted.
Elastic Effects on Rayleigh-Be´nard-Marangoni Convection in Liquids With Temperature-Dependent Viscosity
Authors: Sekhar G. N. , Jayalatha G.
Published: July 2010

A linear stability analysis of convection in viscoelastic liquids with temperature-dependent viscosity is studied using normal modes and Galerkin method. Stationary convection is shown to be the preferred mode of instability when the ratio of strain retardation parameter to stress relaxation parameter (elasticity ratio) is greater than unity. When the ratio is less than unity the possibility of oscillatory convection is shown to arise. Oscillatory convection is studied numerically for Rivlin-Ericksen, Walters B′, Maxwell and Jeffreys liquids by considering free-free and rigid-free isothermal/adiabatic boundaries. It is found that there is a tight coupling between the Rayleigh and Marangoni numbers, with an increase in one resulting in a decrease in the other. The effect of variable viscosity parameter is shown to destabilize the system. The problem reveals the stabilizing nature of strain retardation parameter and destabilizing nature of stress relaxation parameter, on the onset of convection. The Maxwell liquids are found to be more unstable than the one subscribing to Jeffreys description whereas the Rivlin-Ericksen and Walters B′ liquids are comparatively more stable. Rigid-free adiabatic boundary combination is found to give rise to a most stable system, whereas the free isothermal free adiabatic combination gives rise to a most unstable system. The problem has applications in non-isothermal systems having viscoelastic liquids as working media.
Natural Convective Heat Transfer From an Inclined Isothermal Cylinder With an Exposed Top Surface Mounted on a Flat Adiabatic Base
Authors: Kalendar Abdulrahim , Oosthuizen Patrick H.
Published: July 2010

Natural convective heat transfer from an inclined isothermal cylinder with a circular cross-section and which has an exposed “top” surface has been numerically studied. The cylinder is mounted on a flat adiabatic base plate, the cylinder being normal to the base plate. The situation considered is an approximate model of that which occurs in some electrical and electronic component cooling problems. One of the main aims of the present work was to determine how the diameter-to-height ratio of the cylinder, i.e., D/h, influences the mean heat transfer rate from the cylinder at various angles of inclination between vertically upwards and vertically downwards. The flow has been assumed to be steady and laminar and it has been assumed that the fluid properties are constant except for the density change with temperature which gives rise to the buoyancy forces, this having been treated by using the Boussinesq approach. The solution has been obtained by numerically solving the governing equations, these equations being written in terms of dimensionless variables. These dimensionless governing equations, subject to the boundary conditions, have been solved using the commercial cfd solver, FLUENT. The flow has been assumed to be symmetrical about the vertical center-plane through the cylinder. The solution has been used to derive the values of the mean Nusselt number for the cylinder. The solution has the following parameters: the Rayleigh number, Ra, based on the cylinder height and the cylinder surface to fluid temperature difference; the dimensionless cylinder diameter, i.e., the ratio of the diameter to the height of the heated cylinder; the Prandtl number, Pr; and the angle of inclination of the cylinder relative to the vertical, φ. Because of the applications that motivated this study, results have only been obtained for Pr = 0.7. Values of φ between 0° and 180° and a wide range of Ra and Dh values have been considered. The effects of Dh, Ra, and φ on the mean Nusselt number for the entire cylinder and for the mean Nusselt numbers for the cylinder side wall and the exposed “top” surfaces have been examined.
Fuzzy Sliding Mode Control of a Flexible Spacecraft With Input Saturation
Authors: Bai Shengjian , Ben-Tzvi Pinhas , Zhou Qingkun , Huang Xinsheng
Published: July 2010

This paper presents the dynamic modeling and fuzzy sliding mode control (FSMC) for a spacecraft with flexible appendages. A first-order approximate model (FOAM) of the flexible spacecraft system is formulated by using Hamilton’s principles and assumed mode method (AMM), taking into account the second-order term of the coupling deformation field. The use of classical Sliding Mode Control (SMC) presents a major problem that appears in the form of chattering. For highly flexible structural models, ideal sliding surface producing pure rigid body motion may not be achievable. In this paper, the discontinuity in the sliding mode controller is smoothened inside a thin boundary layer by using fuzzy logic (FL) techniques so that the chattering phenomenon is effectively reduced. The robustness of SMC only holds in the sliding mode domain (SMD). However, when the amplitude of the actuators is limited, SMD will be restricted to some local domain near zero on the switching surface. Control input saturation is also explicitly considered in the FSMC approach. The new features and advantages of the proposed approach are the use of new dynamic equations of motion of flexible spacecraft systems, and the design of FSMC by taking into account the control input saturation. To study the effectiveness of the corresponding control scheme, the classical SMC case is also developed for the control system. Numerical simulations are performed to show that rotational maneuvers and vibration suppression are accomplished in spite of the presence of disturbance torques, model uncertainty and control saturation nonlinearity.
Non-Destructive Characterization of Multi Layer Objects by Thermal Tomography
Authors: Erturk Hakan
Published: July 2010

Multi layered systems are frequently used for thermal management where the quality of the layers and the interfaces are critical in achieving desired operating conditions. Defects that introduce an additional thermal resistance in the thermal path must be prevented. Non-destructive characterization tools such as computerized tomography or scanning acoustic microscopy have been used to identify such problems, and help improve manufacturing process to ensure product quality. In a system with opaque solids, thermal tomography that relies on a thermal signal diffusing through the layers can be used to identify the defects in the system. Such a technique can constitute a practical and low cost alternative to the other non-destructive testing methods necessitating expansive equipment. Feasibility of thermal tomography for characterization of multilayer systems is tested considering different measurement configurations based on areal and discrete measurements. The configurations are compared considering different geometric parameters with Levenberg-Marquard method used for image reconstruction.
Global Engineering Ethics: A Marketing Approach
Authors: Peirson Bradley , Barakat Nael
Published: July 2010

There is no doubt that the world is shrinking in many ways, including the ways that engineers from various nations collaborate and share ideas. Along with major international projects such as the international space station, corporations in the United States and abroad are carrying out international engineering tasks on a daily basis. Such collaborations have been of great benefit to the engineering profession because of the free exchange of ideas and engineering talents. One of the main problems facing engineers in the international arena, however, is the lack of a common ethical background. The debate about how to create a common, global code of ethics for engineers has been carried out for several years. The aim of this paper is not add to the arguments about what should be included in a global code of ethics. The purpose of this paper is, in fact, to present a method by which an international organization tasked with the development and administration of such a code could go about attracting potential members. A common code of ethics, containing tenets that most engineering societies around the world already agree upon, is laid down as the framework. From this the basic operation of an international engineering society is outlined. With this basic starting point established the discussion proceeds to the techniques that an international society would need to employ in order grow in numbers and gain credibility among the profession. Further discussion leads to incorporation of these ideas into the education of engineers at the undergraduate level. Ethical training is currently incorporated into undergraduate curricula at many universities in the US. In many cases, however, this portion of the curriculum is limited to western ethical philosophies and the codes of ethics of the American engineering societies. Undergraduate engineering education is designed to develop the next generation to lead their engineering fields. With the prevalence of international collaboration in engineering it is almost assured that these future engineers will be international engineers, to some degree. This paper presents not only a method for attracting potential members to an international engineering society, but also means to prepare future engineers to be responsible members of the international engineering community.
Reducing Scale Deposition by Surface Modification and Magnetic Water Treatment
Authors: Si Xiuhua , Youn Sungmin , Xi Jinxiang
Published: July 2010

Scale deposition (or fouling) on metal surfaces from salt-containing water considerably reduces the efficiency and performance of heat transfer equipments. In industrial practices, scale deposition could be reduced through physical or chemical methods. However, in some cases chemical methods are unpractical due to cost and contamination issues, rendering the physical methods the only feasible options. The objective of this study was to evaluate the effectiveness of two physical treatments in reducing scale depositions. One is to decrease the surface energy of the heat exchanger wall through surface modification; the other one is to change the crystallography of the small solid particles formed in the solution by applying a magnetic field. For the first method, the scale deposition on PTFE surfaces, SAMs (self-assembly monolayers) surfaces, polished copper surfaces, and polished stainless steel surfaces are investigated respectively. Copper and stainless steel surfaces were modified by micro-scale (μm thickness) PTFE (Poly-Tetrofluorethylene) films and nano-scale (nm thickness) thiolate SAMs. The surface energy of PTFE films and SAMs layers based on copper and stainless steel were significantly reduced compared with the untreated metal surfaces. To study the magnetic treatment effect on the formation of the calcium carbonate scale, a magnetic field up to 0.6 T was implemented in a simulated recirculation cooling water system. A large number of experiments were performed to study the effects of fluid velocity, heat flux, and the bulk concentration of the solution on the fouling rate and induction period of calcium carbonate on various modified surfaces. The experiments showed that the formation rate of the calcium carbonate scale was decreased on modified surfaces and the induction period was prolonged with the decrease of the surface energy. The study also showed that the nucleation and nucleate growth of calcium carbonate particles were enhanced through magnetic water treatment. In addition, using a higher flow rate and/or filtration of suspended calcium carbonate particles achieves a longer induction period.
Numerical Evaluation and Optimization of the Combined Solar Thermal and Electric Desiccant Cooling System
Authors: Enteria Napoleon , Yoshino Hiroshi , Satake Akira , Mochida Akashi , Yoshie Ryuichiro , Mizutani Kunio
Published: July 2010

Novel solar thermal desiccant cooling system has been developed. Experimental operation and evaluation of the system was conducted. System optimization and parametric investigation are so important for the improvement of system performance. However, inasmuch as evaluation through experimentation is time consuming and very expensive, numerical model is made and developed for the system. The developed model is implemented in TRNSYS program. The model is validated using the experimental data of the system. Based on the result of the numerical evaluation is conducted the area of the installed solar collector area must be reduced to 8m2. The needed electric heater heating operation is 2 hours. Reduction of the solar collector inclination angle to 30° improved the solar energy collection. Improvement of the desiccant wheel dehumidification rate increased the system total performance. Increasing the heat exchanger (HEX 2) efficiency lowered the supply air temperature with improvement of system performance. Reduction of the system electric energy consumption increased the system electric COP (ECOP). These results of the study are of great importance for the improvement of the design of the developed system, operational procedure, and performance. The relationship and effects of the variables in the study are applicable for other researches seeking the effects of the operational parameters for the solar thermal desiccant cooling system design and processes.
Effect of Buoyancy Driven Stream Loop Numbers on Heat Transfer and Entropy Generation
Authors: Heidary H. , Davoudi M. , Kermani M. J.
Published: July 2010

Free convection in a cavity filled with a fluid-saturated porous medium is from prime importance in many technological applications. Transient free convection in a rectangular cavity filled with a porous medium is numerically studied in this paper. Uniformly and non-uniformly sinusoidal heated bottom wall and adiabatic side walls maintaining constant temperature of cold top wall has been performed. Investigation of problems with this boundary condition is very complicated, as there are a limited number of studies available in the literature dealing with this problem. The finite volume numerical method is used to solve the non-dimensional governing equations. The numerical procedure has been done over a range of Rayleigh number, Ra, 10 ≤ Ra ≤ 103 and Prandtl number, Pr, 0.71 and Aspect ratio, AR, 0.25≤ AR ≤8 and effect of them is investigated on heat transfer and entropy generation. For uniform heating of the bottom wall, the heat transfer rate or Nub is high at the edges of the bottom wall due to the discontinuities present in the temperature boundary conditions at the edges and reduces towards the center of the bottom wall with the minimum value at the center. Effect of streamline loop numbers on heat transfer is shown for various aspect ratios in this study. The present paper analyzes entropy generation induced by free convection and effect of different parameters on entropy generation is studied. Relation of Nusselt number and Bejan number with aspect ratio is given that is due to effect of stream loops number. In lower Ra, because of weak stream, entropy generation is more due to heat transfer irreversibility (HHI).
Turbulent Transport of a Passive Scalar Additive in Spanwise Rotating Channel Flow With Zero Intrinsic Vorticity
Authors: Koppula Karuna S. , Be´nard Andre´ , Petty Charles A.
Published: July 2010

In spanwise rotating channel flows, the turbulent kinetic energy near the high pressure and the low pressure walls is primarily associated with longitudinal velocity fluctuations. Consequently, the primary normal Reynolds momentum flux difference is positive and the secondary normal Reynolds flux difference is negative. In the outer region on the high pressure side of the symmetry plane, the energy is redistributed with the result that the signs of both the primary and of secondary normal differences flip. This redistribution of energy by Coriolis forces occurs in a region of zero intrinsic vorticity. In this paper, the dispersion of a passive additive within the zero intrinsic vorticity region is examined by using a recently developed universal, realizable, anisotropic prestress closure for the normalized Reynolds stress. For low rotation numbers (i.e., | Ωx | ≪ ε / k), the theory shows that the transverse component of the passive additive flux is mitigated by a coupling between the shear component of the Reynolds stress and the longitudinal gradient of the mean passive additive field. At high rotation numbers (i.e., | Ωx | ≫ ε / k), the dispersion coefficient in the transverse (cross flow) direction is four times larger than the dispersion coefficient in the spanwise direction. Surprisingly, the dispersion coefficient in the longitudinal direction is relatively small. The geophysical and the engineering significance of these theoretical conclusions will be highlighted in the presentation.
An Evaluation of the Effectiveness of Traveling Engineering Activity Kits in Pre-College Classrooms
Authors: DeBartolo Elizabeth A. , Bailey Margaret B. , Gillow Sheryl A. , Scorse William , Liccion Richard
Published: July 2010

The focus of this paper is assessment of the effectiveness of Traveling Engineering Activity Kits (TEAK) in engaging pre-college students in engineering-related activities. This includes a discussion of the challenges in assessing such a brief interaction with groups of middle school students with widely varying backgrounds as well as a discussion of how past assessment has led to modifications in TEAK activities. Program assessment has evolved from pre- and post-visit quizzes on technical content and interest in engineering to instructor observation of student engagement during TEAK visits relative to engagement during a typical class period. Initial results from pre- and post-visit quizzes showed that the vast majority of students self-reported an increased interest in engineering but that the percentage of students showing an increased understanding of engineering topics was highly dependent on the background of the students. Students who did well on the pre-visit quizzes would show less improvement after a TEAK visit, because their initial level of knowledge was higher. In the present model of rating levels of student engagement during TEAK visits, results seem much more promising, with teachers indicating that, during TEAK activities, their students are more engaged and ask more and better questions than during a typical class.
Improving Mechanical Engineering Education Through Use of Case Studies
Authors: Rajan Pramod , Raju P. K. , Sankar Chetan S.
Published: July 2010

Business is increasingly conducted in a global environment, and mechanical engineering students are expected to be proficient in leadership skills as well as strong technical skills. Many authors state that instead of adding more material and more courses to the engineering curriculum, which would likely turn students away from engineering, engineering educators need to respond by opening up access to engineering with the larger world. We found that one of the effective ways of bringing real-world issues related to the areas of manufacturing and design, thermal engineering, acoustics, vibration, welding and nondestructive evaluation into classrooms is through the use of case study methodology. The Laboratory for Innovative Technology and Engineering Education (LITEE) at Auburn University has developed eighteen multimedia case studies over the past ten years. Faculty and students partnering with various industries develop these case studies. The case studies focus on real-world problems that actually occurred in the chosen industry. All the technical and business details related to the problem are provided in the case study. Through the use of information technologies we created multi-media case studies that bring real-world decision making from the engineering industry into the classrooms. The students analyze the problem in the class using role-playing, thereby simulating the decision-making scenario that occurred in the industry. The students also have an opportunity to compare their solutions to what happened in the industry. This paper describes the steps involved in developing a LITEE case study, administering this case study in engineering classrooms, and the results of evaluating the effectiveness of this method of instruction. This paper also discusses the details of different case studies related to the above-mentioned areas available through LITEE.
Towards a Self-Tunable, Wide Frequency Bandwidth Vibration Energy Harvesting Device
Authors: Challa Vinod R. , Prasad M. G. , Fisher Frank T.
Published: July 2010

Vibration energy harvesting is increasing in popularity due to potential applications such as powering wireless sensors and ultra low power devices. For efficient energy harvesting, matching the device frequency to the source frequency is a major design requirement. Since mechanical vibrations differ in characteristics (frequency and acceleration amplitude), it is difficult to design an individual energy harvesting device for every source. Recently, several groups have pursued techniques to tune the resonance frequency of the vibrating structure through active and passive methods. In this paper, work has been done to attain a self-tunable energy harvesting device, which utilizes a magnetic force resonance frequency tuning technique to tune the device. The device is successfully tuned with in a bandwidth of ± 27% of its untuned resonance frequency, considering root mean square of the peak power output as the cutoff for frequency bandwidth. Since the technique is semi-active, energy is only consumed to tune the resonance frequency and is not required to remain at that specific frequency. The device consists of a piezoelectric cantilever beam array which is displaced to the desired distance to induce magnetic stiffness and to match the source frequency using a DC motor. The device has a power output of approximately 0.7 mW to 1 mW in the designed cutoff frequency range. The amount of energy consumed by the actuator to displace the beam is approximately 3.5 W to 4.5 W, which requires approximately 150 minutes to reclaim the expended energy.
An Acceleration Technique for the Computation of Participating Radiative Heat Transfer
Authors: Mathur Sanjay R. , Murthy Jayathi Y.
Published: July 2010

It is known that the finite volume and discrete ordinates methods for computing participating radiation are slow to converge when the optical thickness of the medium becomes large. This is a result of the sequential solution procedure usually employed to solve the directional intensities, which couples the ordinate directions and the energy equation loosely. Previously published acceleration techniques have sought to employ a governing equation for the angular-average of the radiation intensity to promote inter-directional coupling. These techniques have not always been successful, and even where successful, have been found to destroy the conservation properties of the radiative transfer equation. In this paper, we develop an algorithm called Multigrid Acceleration using Global Intensity Correction (MAGIC) which employs a multigrid solution of the average intensity and energy equations to significantly accelerate convergence, while ensuring that the conservative property of the radiative transfer equation is preserved. The method is shown to perform well for radiation heat transfer problems in absorbing, emitting and scattering media, both and without radiative equilibrium, and across a range of optical thicknesses.
Thermal Conductivity and Phonon Transport Properties of Silicon Using Perturbation Theory and the Environment-Dependent Interatomic Potential
Authors: Pascual-Gutie´rrez Jose´ A. , Murthy Jayathi Y. , Viskanta Raymond
Published: July 2010

Perturbation theory is used to compute the strength of three-phonon and isotope scattering mechanisms in silicon using the Environment-Dependent Interatomic Potential (EDIP) without resorting to any parameter-fitting. A detailed methodology to accurately find three-phonon processes satisfying energy- and momentum-conservation rules is described. Bulk silicon thermal conductivity values are computed across a range of temperatures and shown to match experimental data well. It is found that about two-thirds of the heat transport in bulk silicon may be attributed to transverse acoustic modes. Effective relaxation times and mean free paths are computed in order to provide a more complete picture of the detailed transport mechanisms and for use with carrier transport models based on the Boltzmann transport equation.
Particle Dispersion and Deposition in a Curved Duct
Authors: Winkler C. M. , Vanka S. P.
Published: July 2010

Particle transport in ducts of square cross-section with constant streamwise curvature is studied using numerical simulations. The flow is laminar, with Reynolds numbers of Reτ = 40 and 67, based on the friction velocity and duct width. The corresponding Dean numbers for these cases are 82.45 and 184.5, respectively, where De = Rea/R, a is the duct width and R is the radius of curvature. A Lagrangian particle tracking method is used to account for the particle trajectories, with the particle volume fraction assumed to be low such that inter-particle collisions and two-way coupling effects are negligible. Four particle sizes are studied, τp+ = 0.01, 0.05, 0.1, and 1. Particle dispersion patterns are shown for each Dean number, and the steady-state particle locations are found to be reflective of the Dean vortex structure. Particle deposition on the walls is shown to be dependent upon both the Dean number and particle response time, with the four-cell Dean vortex pattern able to prevent particle deposition along the center of the outer wall.
Performance of Bi-Unit Impact Vibration Absorbers With Staggered and Identical Clearances
Authors: Ekwaro-Osire S. , Alemayehu F. M. , Durukan I. , Ca´rdenas-Garci´a J. F.
Published: July 2010

Impact vibration absorbers have been used extensively to control vibrations of mechanical systems. This paper deals with an experimental study on the performance of bi-unit impact vibration absorbers. The objective of this research was to study the performance of staggered versus identical clearances for two impact balls. This means that in the staggered clearance, the two impact balls had different distances to travel before impacting the limit walls whereas the clearances were identical for the other case. An experimental setup was designed and constructed. A novel digital image system, consisting of high speed camera and image acquisition software, was designed. The primary system was tuned to have a natural frequency of 5 Hz. A time series data of the location of the impact wall and both balls was acquired through constant frequency and constant amplitude excitation. This data was used to obtain motion plots and frequency responses. It was demonstrated that the vibration absorber with staggered clearances was more effective than the vibration absorber with identical clearances.
Impinging Jet Cooled Plate Fin Heat Sinks With Turbulators Enhancement
Authors: Subbuswamy Ganesh , Li Xianchang
Published: July 2010

Extended surfaces (fins) and impinging jets have been used to enhance heat transfer in many applications. In electronic thermal management, heat sinks can be designed to take advantage of the combined effect of fins and jet impingement such as jets impinging on an array of pin fins or plate fins. Significant studies have been focused on the thermal resistance, pressure drop, and the parametric effect of Reynolds number, fin thickness, density, and height. To further improve the heat sink performance, ribs/turbulators, which are widely employed in internal cooling of gas turbine blades, can be integrated into the plate fins, especially close to the surface area with low heat transfer coefficient. Numerical study is performed in this paper to examine the flow and heat transfer behavior of plate fin heat sinks cooled by an impinging jet and enhanced by the ribs. The height and shape of the turbulators are investigated to achieve the best performance. Parametric studies also include the flow Reynolds number and the spacing between the ribs. Heat transfer mechanism is explored for the confined turbulence jet with and without turbulators. It is expected that the rib enhancement can lead to a more cost-effective heat sink for cooling of electronic components. Further enhancement and optimization are discussed in this paper.
Optimal Vibration Control of Flexible Structures Using Multiple Tuned Mass Dampers
Authors: Yang Fan , Sedaghati Ramin , Esmailzadeh Ebrahim
Published: July 2010

The structural vibration suppression of beam-type structures using Tuned Mass Damper (TMD) and Multiple Tuned Mass Dampers (MTMD) technologies will be investigated in this study. A vibration suppression strategy for beam-type structures based on TMD and MTMD technologies, in which a light beam with attached masses (secondary structure) is connected to the primary structure (beam), will be presented. The beam is modeled by utilizing the Timoshenko beam theory, and then the governing differential equations of motion have been cast into the finite element form by using the Galerkin method. The derived finite element formulation of beam-type structures with the attached TMD and MTMD systems has been combined with a designed optimization procedure to find the optimum design variables in the developed TMD and MTMD systems to suppress the vibration effectively. The effectiveness of the developed methodologies is verified through an experimental study, where the structural responses for the uncontrolled structure and that with the attached optimal TMD and MTMD systems were compared.
Review of Reliability of the Cooling Technologies in the Telecommunications Systems
Authors: Mynampati Venkata Naga Poornima , Mariam Feroz Ahamed Iqbal , Muralidharan Bharath Krishnan , Agonafer Dereje
Published: July 2010

The present trends in the cooling technologies have marked a significant improvement in the outdoor telecommunications systems and the need of cooling has marked an important requirement for the proper functioning of these cabinets. This aim of this paper is to review all of the articles and to gather the information regarding the different cooling technologies used and their reliability in the outdoor telecommunication systems especially the telecommunication cabinets.
Microfluidic Device for Transport and Observation of Single Cells
Authors: Merza Saeed A. , Posner Jonathan D. , Anis Yasser H. , Young A. Cody , Johnson Roger H. , Meldrum Deirdre R.
Published: July 2010

A fluidic device capable of aspirating microparticles in aqueous medium and transporting them under controlled conditions to a chosen destination is reported. The device is fabricated through repeated stacking of aligned, laser cut acrylic, mylar and adhesive layers. The rectangular cross-section of the primary flow chamber within the device follows a specific mathematical function to achieve a desired velocity profile for improved particle tracking. Flow is controlled into and out of the chamber by three-way solenoid valves to allow changes in flow direction and to minimize capacitance in the fluidic circuit. The valves are connected to syringe pumps which generate positive and negative pressures within the device. Aspirated microparticles can be accurately transported by controlling the ON/OFF state of the solenoid valves. Computational fluid dynamic (CFD) models are employed to compare the theoretically derived velocity field and pressure distributions with analytical solutions and observations. Processed imagery showed the positions versus time of microparticle flowing through the chamber channel.
Analysis of Flow in a Concentric Cylindrical Vessel Using Stream and Vorticity Function
Authors: Rakshit Sukanta , Bojja Harsha
Published: July 2010

This paper reports the numerical results of flow in a concentric cylindrical vessel. Velocity plots are shown to illustrate the swirling cylinder flow inside the cylinder having free surface on top and constant rotating bottom wall. The analysis is carried out axisymmetric using Stream function and Vorticity method by writing Navier-Stokes equation and continuity equation in cylindrical coordinates in form of stream functions and azimuthal vorticity components eliminating the pressure component. Using Finite Difference Schemes, modified Navier-Stokes equation and continuity equations are solved by explicit methods. No-slip boundary condition is assumed at wall to minimize the discontinuity. Vortex formation is shown using contour plots and variation in Reynolds number and dimensions are considered as variable for the system. As the Reynolds number is increased the system undergoes vortex breakdown. Result clearly indicates the formation of another vortex near the free surface illustrating the phenomena of vortex breakdown. Effect of aspect ratio in the nature flow is also shown in the paper. Comparison of numerically achieved results and experimental results are done for validation.
A Coupled Thermal and Mechanical Model of a Thermal Energy Harvesting Device
Authors: Bulgrin Katherine E. , Ju Y. Sungtaek , Carman Greg P. , Lavine Adrienne S.
Published: July 2010

In this paper, a two-step thermal energy harvester is analyzed. “Two-step” refers to thermal to mechanical energy conversion followed by mechanical to electrical conversion. A numerical code is developed to predict the behavior and thermomechanical performance of the device. The physical motion of the device is dependent on both temperature and the position of an actuator plate, so equations based on multiple physical forces are solved simultaneously to find the operational characteristics. To verify the accuracy of the code, numerical predictions of device frequency are compared to experimental results. Furthermore, four parameters are varied in a parametric study to observe the effect on the predicted temperature, power output, and efficiency of the device.
Design Algorithm of a Multi-Effect Humidification–Dehumidification Solar Distillation System
Authors: Gonza´lez R. , Pieretti P. , Diaz H.
Published: July 2010

Water is an abundant resource; however, there is an upcoming water shortage. In order to face this situation, conventional desalination plants have been built; nevertheless, these plants contribute to the emission of greenhouse gases. A way to stop this trend is to use renewable sources, especially in coastal areas where solar irradiation is abundant. Due to the large coastal line of Venezuela, and the particular troubles with water distribution in these areas, the Energy Institute of the Simon Bolivar University proposed to develop and test a solar humidification–dehumidification (MEH) distillation pilot unit to provide small communities of the isolated or insular regions of Venezuela with 25 liters of drinking water per day. This project initiates a research branch that aims to produce a commercial size solar humidification desalination plant for these areas. Considering the lack of a known design procedure for solar desalination systems, and in view to optimize future developments in the field, a design algorithm was proposed for single stage MEH units which, by setting some of the design temperatures, gives the entire flux diagram of the unit, providing the designer the possibility to start the sizing process with a strong empirical basis.