Mechanical Engineering

El presente trabajo presenta un analisis de pre-factibilidad de un sistema de generacion de energia para satisfacer la demanda residencial en una pequena comunidad islena ubicada en el golfo de Guayaquil, usando HOMER como una herramienta de optimizacion. La comunidad actualmente cuenta con un generador diesel que se encuentra fuera de servicio, el mismo que suministraba energia a los hogares y al alumbrado publico. Dicha comunidad desea contar con un sistema de suministro de energia confiable y amigable con el medio ambiente con la intencion de usar el eco-turismo como una fuente de ingresos. HOMER fue usado para modelar los sistemas de generacion para 5 tipos de demandas diferentes variando la proporcion de casas modelo. La seleccion del sistema esta basada en optimizacion de energia y costos junto a un bajo consumo de diesel y exceso de energia.

neering design education, innovative design, global design, and global engineering education. He has introduced multinational design projects in a freshman introductory engineering design course in collaboration with institutions in Latin America and the Caribbean as part of his effort to contribute to the formation of world class engineers for the Americas. He is actively involved in the International Division of the American Society for Engineering Education and in the Latin American and Caribbean Consortium of Engineering Institution (LACCEI) as Vice-President for Meetings and in the International Federation of Engineering education Societies (IFEES) as VP for the Americas and First VP.

In today's world, it has become very common to find engineers working on multinational projects. As a result, educational institutions need to prepare students to succeed in this global working environment by incorporating global collaborative projects as a learning experience. At the same time, students should be aware of the importance of this experience, recognize its benefit, and be motivated to participate on the projects. It is documented in the literature that students' interest and motivation are important factors contributing to the learning process in any discipline, and of particular importance when students are exposed to a projectbased educational experience in a collaborative and multinational context. Authors have used the multinational collaborative projects to prepare students with global competencies but no formal assessment of the impact of this experience has been done. As part of a formal evaluation of this experience, the main goal of this study is to determine the level of interest and perception of value of engineering students participating in a multinational collaborative project, and make a comparison of such indicators based on gender. For this purpose, a survey based on the Intrinsic Motivation Inventory (IMI) was given to students before starting their participation in the multinational projects. The data collected provides information in five constructs which are: interest, perceived competence, pressure, perceived choice, and value. These constructs provide a perception about students' interests, beliefs, and feelings about the international project that reflect their level of motivation to carry on the tasks.

neering design education, innovative design, global design, and global engineering education. He has introduced multinational design projects in a freshman introductory engineering design course in collaboration with institutions in Latin America and the Caribbean as part of his effort to contribute to the formation of world class engineers for the Americas. He is actively involved in the International Division of the American Society for Engineering Education and in the Latin American and Caribbean Consortium of Engineering Institution (LACCEI) as Vice-President for Meetings and in the International Federation of Engineering education Societies (IFEES) as VP for the Americas and First VP.

A collaborative network of institutions from US and Latin America has developed and executed collaborative global design projects as part of academic experiences for their students. The main goal of these projects is to foster international collaboration and to offer an opportunity to the students to develop professional skills through international teamwork effort in the solution of a design problem. There is anecdotal evidence that students have found the experience rewarding and successful; however, there is no a formal assessment approach to determine the effectiveness of this initiative in reaching the desired goal and objectives. This paper reports an assessment framework and proposed assessment tools for the collaborative global design projects carried out by the international collaborative network with the aim to evaluate the effectiveness of this approach and to explore option to enhance the content and delivery method of the projects.

Dijet angular distributions from the first LHC pp collisions at center-of-mass energy √ s = 7 TeV have been measured with the ATLAS detector. The dataset used for this analysis represents an integrated luminosity of 3.1 pb −1 . Dijet χ distributions and centrality ratios have been measured up to dijet masses of 2.8 TeV, and found to be in good agreement with Standard Model predictions. Analysis of the χ distributions excludes quark contact interactions with a compositeness scale Λ below 3.4 TeV, at 95% confidence level, significantly exceeding previous limits.

1.-Después de un largo día de viaje, tarde por la noche, usted nada en la piscina del hotel donde se hospeda. Cuando se retira a su habitación, se da cuenta de que perdió la llave en la alberca. Consigue una linterna potente y camina alrededor de la alberca dirigiendo la luz hacia ella. La luz ilumina la llave, que yace en el fondo de la alberca, cuando sostiene la linterna a 1.2 m de la superficie del agua y dirigida hacia la superficie a una distancia horizontal de 1.5 m desde el borde. Si el agua en ese punto tiene 4.0 m de profundidad, ¿a qué distancia del borde de la alberca se encuentra la llave?

An analysis of thermal performance of a vertical Borehole Heat Exchanger (BHE) from a close loop Ground Source Heat Pump (GSHP) located in Guayaquil-Ecuador is presented. The project aims to assess the influence of using novels heat transfer fluids such as nanofluids, slurries with microencapsulated phase changematerialsandamixtureofboth. TheBHEssensitiveevaluation is performed by a mathematical model in a finite element analysis by using computational tools; where, the piping array isstudiedinonedimensionscenariomeanwhileitssurroundings grout and ground volumes are presented as a three dimensional scheme. Therefore, an optimized model design can be achieved which would allow to study the feasibility of GSHP in buildings and industries in Guayaquil- Ecuador.

The paper presents the results of the first experimental measurement of soil thermal properties in Guayaquil, Ecuador. The experimental point is located at UTM (0622853/09755713) and the test was carried out during the Ecuadorian dry season.  This location is geologically composed of sediments of estuarine-deltaic nature from River Guayas.  A boring of 113 mm diameter and 50 m deep was drilled to perform the test.  The experiment consists of heating and water pumping during a period of between 48 and 72 hours.  The power input to the system is 2746.03 W which heats a water flow of 1.36 m3/h, corresponding to a value of 54.92 W/m. A linear source model was used to obtain the thermal conductivity and diffusivity of the soil.  In order to reduce errors in the calculations it is important to allow the system to reach steady state . In our case steady state was reached after the first 12 hour s of measurement.  Thermal conductivity of the soil was calculated to be 1.310–1.312 W/m K, thermal diffusivity between 0.017–0.046 m2/day.  The core material of the drilling was recovered and used for a lithological, mineralogical and geotechnical analysis of the samples using X-ray diffraction, optical microscopy, grain size analysis. Silts containing 45.3% illitemotmorillonite and 32.1% anortite, 18.2% cuarzo and 4.4% amorphous minerals. Mineralogy in sand is cuarzo and plagioclasa anortite type. Finally, an assessment of the suitability of the soil for the use of underground heat exchangers with the potential of replacing cooling towers in buildings’ climatization systems is performed.

An assessment of the use of engineered heat transfer fluids working under constant wall temperature conditions in the turbulent regime is presented. An analysis of entropy generation and pumping power on the system working with different engineered heat transfer fluids is performed. Three types of fluids are considered: multiwalled carbon nanotube (MWCNT) based nanofluids, slurries with microencapsulated phase change materials (MPCM) and a mixture of both fluids. Specific heat, thermal conductivity and viscosity of the fluids are included in the analysis using theoretical and experimental results available in literature. Nanofluids in the system result on greater entropy generation and pumping power consumption when compared with base fluid. MPCMs slurries produce the minimum entropy generation and pumping power consumption. Mixtures are affected by the content of nanofluids resulting in a performance below of MPCMs slurries. The improvement on the heat capacity of the fluid produced by the Microencapsulated phase change material is the main factor in reducing entropy generation and pumping power consumption for the system. Under the conditions assessed, the increase in viscosity offsets the increase in thermal conductivity on the MWCNT based nanofluids. On the other hand in the case of MPCM slurries, the increase in heat capacity outweighs the reduction in thermal conductivity and increase in viscosity.

Abstract A study of heat transfer and film dynamics caused by single and multiple streams of
impinging droplets using HFE-7100 as the cooling liquid under constant heat flux conditions
is presented. Single and multiple streams of mono-dispersed droplets were produced using
a piezoelectric droplet generator with the ability to adjust parameters such as droplet
impingement frequency, droplet diameter, droplet velocity, and spacing between adjacent
impinging droplet streams.

Current microflowmeters can be used accurately in laminar flow conditions for Reynolds (Re) number greater than 50 or when μPIV trace particles are used. However, many applications require accurate measurement of very low flow rates using a simple and ...

ABSTRACT Spray cooling is one of the most promising technologies in applications which require large heat removal capacity in very small areas. Previous experimental studies have suggested that one of the main mechanisms of heat removal in spray cooling is forced convection with strong mixing due to droplet impingement. These mechanisms have not been completely understood mainly due to the large number of physical variables, and the inability to modulate and control variables such as droplet frequency and size. Our approach consists of minimizing the number of experimental variables by controlling variables such as droplet direction, velocity and diameter. An experimental study of single and multiple droplet impingements using HFE 7100 as the cooling fluid under constant heat flux conditions is presented. A monosized droplet train is produced using a piezoelectric droplet generator with the ability to adjust droplet frequency, diameter and velocity. In this study, heaters consisting of a layer of Indium Tin Oxide (ITO) as heating element, and silicon substrates are used. Film morphology was characterized using a Laser Induced Fluorescence (LIF) technique with a focus on the droplet impact zone by measuring variables such as film thickness and diameter of the impact zone. Infrared thermography was used to measure surface temperature at the liquid-solid interface. The IR thermography technique was also used to characterize temperature gradients at the droplet impact zone. The results and effects of droplet frequency, fluid flow rate, and fluid temperature on heat flux are also presented.

For a number of years spray cooling has shown to be a viable alternative for thermal management of high-density electronics. Nevertheless, the key fundamental physical processes are to a large degree poorly understood due mostly to the complicated fluid dynamics resulting from nucleate boiling coupled with spray drop impingement. In this combined experimental and modeling effort, a representative configuration consisting of a liquid film resting on a solid silicon-based substrate with an imposed constant heat flux and an impinging train of droplets has been studied. This configuration mimics to a great degree the physics of spray cooling, while simultaneously simplifying the experimental and computational analysis to a manageable level. It is shown that a number of statistically quasi-stationary states are possible by carefully coordinating the heat flux and drop impingement rates. Studies were both performed for water and FC-72. Due in part to its lower surface tension, the quasi-stationary states for FC-72 were instantaneously much more chaotic than the corresponding water cases. The OpenFoam (open source computational fluid dynamics) code has been supplemented with an energy equation within the existing Volume-of-Fluid infrastructure. This was used to analyze the dynamics in the impingement region. It is shown that the temperature in this region is approximately equal to the temperature of incident droplets. For all water and FC-72 films, it was found that each droplet impact penetrated the entire thickness of the film bringing a significant cooling effect on the heated substrate. This was the case even for film thickness-to-impact droplet diameter ratios far exceeding one.

ABSTRACT In the last decade, microencapsulated phase change material (MPCM) slurries have been proposed and studied as novel coolants for heat transfer applications. Such applications include electronics cooling, and secondary coolants in air conditioning systems among others. Experiments have shown that MPCM’s increase the overall thermal capacity of thermal systems by taking advantage of the phase change material’s latent heat of fusion. However, research has also shown that the overall heat transfer coefficient is diminished due to a reduction in the effective thermal conductivity and increased viscosity of the slurry. For this reason, there is an urgent need to modify the content of microcapsules containing phase change material to increase their effective thermal conductivity and the overall heat transport process. Our solution consists of increasing the thermal conductivity of MPCM by adding carbon nanotubes to the shell and core of the microcapsules. Carbon nanotubes have shown to increase the thermal conductivity of liquids by 40% or more in recent experiments. In this paper, MPCM slurry containing octadecane as phase change material and multi-wall carbon nanotubes (MWCNTs) embedded in the capsule material and core are compared with pure water as heat transfer fluid. Thermal and physical properties of MPCM slurry containing carbon nanotubes were determined using a differential scanning calorimeter and concentric viscometer, respectively. Experimental convective heat transfer coefficient data for MWCNT aqueous suspensions under laminar flow and constant heat flux were determined using a bench-top heat transfer loop. Experimental heat transfer results are presented.