Este trabalho descreve uma forma prática para planejamento do ciclo de operação de retificação por mergulho, em função da especificação dimensional da peça e da rigidez da máquina. Essa otimização é estendida além do ciclo, envolve produzir lotes de peças com dispersão das dimensões dentro de limites especificados. O tempo de set-up, que normalmente não está incluído no tempo de processo, aqui é incluído e considerado. A primeira atividade de laboratório teve como objetivo confirmar a relação entre a quantidade de material removido em função do tempo de spark-out. A segunda atividade comprovou a existência de uma relação linear entre a velocidade de avanço radial do rebolo e o diâmetro final da peça. A terceira atividade confirmou a existência de uma relação entre a velocidade de avanço radial e o índice de capabilidade especificado para o processo. Ainda, foi sugerida a inclusão deste processo proposto num programa CNC da máquina, de forma a se obter automaticamente o set-up. Concluiu-se que o método aqui apresentado reduziu significativamente o tempo de set-up da máquina conferindo um incremento de produtividade aos processos que fizerem uso deste princípio. / This work shows a practical way to design the cycle of a plunge grinding process as a function of workpiece dimensional specification and the machine stiffness. This optimization is extended beyond the cycle, it\'s included make batch of parts with dispersion within the specification limits. The set-up time, that usually isn\'t in the process time, here it was included and focused. The first activity of laboratory had an objective to confirm the relation of the amount of material removed as a function of spark out time. The second activity has been confirmed the linear relationship between the infeed velocity of the grinding wheel and the final diameter of the workpiece. The third activity has been confirmed the relation of the infeed velocity and the capability of the process. Yet, it was suggested to include this procedure in a CNC set of the machine to allow a faster and automatic set up. So, this work shows a conclusion that the set up time can be reduced a lot, allowing higher productivity for who use this procedure.

Este trabalho descreve uma forma prática para planejamento do ciclo de operação de retificação por mergulho, em função da especificação dimensional da peça e da rigidez da máquina. Essa otimização é estendida além do ciclo, envolve produzir lotes de peças com dispersão das dimensões dentro de limites especificados. O tempo de set-up, que normalmente não está incluído no tempo de processo, aqui é incluído e considerado. A primeira atividade de laboratório teve como objetivo confirmar a relação entre a quantidade de material removido em função do tempo de spark-out. A segunda atividade comprovou a existência de uma relação linear entre a velocidade de avanço radial do rebolo e o diâmetro final da peça. A terceira atividade confirmou a existência de uma relação entre a velocidade de avanço radial e o índice de capabilidade especificado para o processo. Ainda, foi sugerida a inclusão deste processo proposto num programa CNC da máquina, de forma a se obter automaticamente o set-up. Concluiu-se que o método aqui apresentado reduziu significativamente o tempo de set-up da máquina conferindo um incremento de produtividade aos processos que fizerem uso deste princípio. / This work shows a practical way to design the cycle of a plunge grinding process as a function of workpiece dimensional specification and the machine stiffness. This optimization is extended beyond the cycle, it\'s included make batch of parts with dispersion within the specification limits. The set-up time, that usually isn\'t in the process time, here it was included and focused. The first activity of laboratory had an objective to confirm the relation of the amount of material removed as a function of spark out time. The second activity has been confirmed the linear relationship between the infeed velocity of the grinding wheel and the final diameter of the workpiece. The third activity has been confirmed the relation of the infeed velocity and the capability of the process. Yet, it was suggested to include this procedure in a CNC set of the machine to allow a faster and automatic set up. So, this work shows a conclusion that the set up time can be reduced a lot, allowing higher productivity for who use this procedure.

Ground source heat pumps (GSHP) are efficient alternatives to air source heat pumps to provide heating and cooling for conditioned buildings. GSHPs are widely deployed in the midwest and eastern regions of the United States but less so in Texas and the southwest regions whose climates are described as being semi-arid. In these semi-arid regions, building loads are typically cooling dominated so the unbalance in energy loads to the ground, coupled with less conductive soil, cause the ground temperature to increase over time if the ground loop is not properly sized. To address this ground heating problem especially in commercial building applications, GSHPs are coupled with supplemental heat recovery/rejection (SHR) systems that remove heat from the water before it is circulated back into the ground loops. These hybrid ground source heat pump systems are designed to reduce ground heating and to lower the initial costs by requiring less number of or shallower boreholes to be drilled. This thesis provides detailed analyses of different SHR systems coupled to GSHPs specifically for residential buildings. The systems are analyzed and sized for a 2100 ft2 residential house, using Austin, Texas weather data and ground conditions. The SHR systems investigated are described by two heat rejection strategies: 1) reject heat directly from the water before it enters the ground loops and 2) reject heat from the refrigerant loop of the vapor compression cycle (VCC) of the heat pump so less heat is transferred to the water loop at the condenser of the VCC. The SHR systems analyzed in this thesis are cooling towers, optimized VCC, expanded desuperheaters and thermosyphons. The cooling towers focus on the direct heat rejection from the water loop. The VCC, desuperheater, and thermosyphon systems focus on minimizing the amount of heat rejected by the VCC refrigerant to the water loop. In each case, a detailed description of the model is presented, a parametric analysis is provided to determine the amounts of heat that can be rejected from the water loop for various cases of operation, and the practical feasibility of implementation is discussed. An economic analysis is also provided to determine the cost effectiveness of each method. / text

A computer program, called &ldquo / Cogeneration Design&quot / is developed using Visual Basic 6.0, for conceptually designing cogeneration power plants. Design is focused on power plants to be built in university campuses, where there is mainly heating, hot water, electricity and sometimes cooling demands. Middle East Technical University campus is considered as the primary working area. Before the conceptual design study, detailed information regarding description of the campus, infrastructure, annual electric, water and heat demand covering last 10 years, properties of existing heat plant including natural gas expenses and specifications of the steam distribution pipes and electricity grid are collected and examined in detail. Throughout the thesis, eight different natural gas fired cogeneration power plant designs are developed regarding different gas turbine and steam turbine configurations, for METU Campus, considering the Campus&#039 / properties described above, by using the &quot / Cogeneration Design&quot / program. Then, by means of a thermoeconomic optimization process, cost summary reports are prepared and the feasibility of the designed cogeneration power plants are discussed.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniversitet, 2004. / Härtill 4 uppsatser.

This thesis will investigate the possibility of leasing as a 'greener' form of business transaction. With leasing, the customer pays for the service obtained form the product, but does not own the physical asset; ownership remains with the lessor. This has been claimed to increase resource productivity and close material loops. Numerous complications exist, however, such as tax regulations limiting operating leases to terms of 75% of the total product's life. In addition, no clear pattern has emerged in leasing practices, and in most cases manufacturers approach leasing on an ad hoc basis. Research has found that usage-phase impacts play a major role in determining the advantages realized by leasing. Products such as vehicles or refrigerators that continually consume energy negatively impact the environment much more during their use than during manufacturing or transportation. Because most lease agreements contain maintenance contracts, the opportunity to upgrade and increase product efficiency during this use-phase is paramount to reducing negative impacts. Remanufacturing also shows potential to further reduce resource requirements. However, if product efficiency is not improving significantly, remanufacturing alone does not make a significant impact. In some cases, such as carpets, remanufacturing is not practical, but recycling can be utilized. However, tax regulations require leased terms to be less than that of a product's designed life, hastening replacement. This has the potential to offset any advantages seen with a lease agreement. Academic work in this area remains very limited and product-specific. Case study analyses performed in this thesis found that increased product turnover can actually be environmentally beneficial when product technology is improving. These gains can be further improved with remanufacturing and optimized product replacement moderated by lease agreements. If usage energy is significantly less than manufacturing energy, leasing has little value for reducing impacts. Also leasing may motivate closed material loops, without improving product efficiencies there is no advantage to optimizing life cycles with lease contracts.

The objective of reservoir management is to maximize a key performance indicator (net present value in this study) at a minimum cost. A typical approach includes engineering analysis, followed by the economic value of the technical study. In general, operators are inclined to spend more effort on the engineering side to the detriment of the economic area, leading to unbalanced and occasionally suboptimal results. Moreover, most of the optimization methods used for production scheduling focus on a given recovery phase, or medium-term strategy, as opposed to an integrated solution that allocates resources from discovery to field abandonment. This thesis addresses the optimization of a reservoir under both technical and economic constraints. In particular, the method presented introduces a life cycle maximization approach to establish the best exploitation strategy throughout the life of the project. Deterministic studies are combined with stochastic modeling and risk analysis to assess decision making under uncertainty. To demonstrate the validity of the model, this document offers two case studies and the optimal times associated with each recovery phase. In contrast with traditional depletion strategies, where the optimization is done myopically by maximizing the net present value at each recovery phase, our results suggest that time is dramatically reduced when the net present value is optimized globally by maximizing the NPV for the life of the project. Furthermore, the sensitivity analysis proves that the original oil in place and non-engineering parameters such as the price of oil are the most influential variables. The case studies clearly show the greater economic efficiency of this life cycle approach, confirming the potential of this optimization technique for practical reservoir management. / text

Il y a peu, j’ai pu lire « qu’on pouvait considérer que les ponts romains de l’Antiquité, pouvaient être considérés comme inefficaces, au regard des standards actuels : ils utilisaient trop de pierre et énormément de travail était nécessaire à leur construction. Au fil des années, pour répondre à une problématique équivalente, nous avons appris à utiliser moins de matériaux et à réduire la charge de travail ». Ces problématiques nous les retrouvons aussi en conception mécanique où l’on essaye en continu de proposer des systèmes de plus en plus performants mais devant être conçus en moins de temps, étant moins cher à produire et fournissant des prestations au moins équivalentes à ce qui a déjà été conçu.Au cours d'un processus de conception classique, les concepteurs définissent une géométrie ne présentant aucun défaut puis, étant donné que les moyens de production ne permettent pas d’obtenir de telles pièces finales, ils spécifient les schémas de cotation définissant les écarts acceptables garantissant le bon fonctionnement du système. Seulement, cela est fait après avoir produit les dessins détaillés, c'est à dire trop tard. Pour répondre à cette problématique, je présenterai l’intégration, très tôt dans le cycle de vie de conception, d’un processus de validation optimisé, basé sur une maquette numérique directement en lien avec sa représentation fonctionnelle (maquette fonctionnelle), et permettant de valider des schémas de cotation 3D standardisés.Je décrirai d'abord ce que l’on entend par « maquette fonctionnelle » et surtout ce que cette nouvelle définition apporte en plus de la définition numérique. Une fois ce point abordé, je détaillerai les liens qui permettent d’avoir une unicité de l’information au sein de l’environnement de travail, tout comme les processus qui permettent de lier les représentations fonctionnelles et numériques.Ensuite, je détaillerai les processus basés sur ces concepts, et qui ont pour but de valider les choix qui sont effectués en avance de phase au niveau des schémas de cotation. Pour ce faire, je commencerai par présenter l’analyse au pire des cas (utilisant les modèles de domaines écarts notamment), permettant de garantir le bon fonctionnement de l’ensemble mécanique, dans le cas ou touts les écarts se retrouvent à l’intérieur des zones respectives (définies par les tolérances).Enfin, je finirai par introduire ce qu’une couche statistique, couplée à l’analyse au pire des cas utilisant les enveloppes convexes, peut amener dans le contexte industriel et notamment sous la contrainte temporelle. / Some time ago, I read "According to our current standards, we could consider Roman bridges of ancient times as ineffective: they used too much stone and hard work during construction. Over the years, in order to respond to similar problems, we learned how to use fewer materials and reduce the workload. These issues can also be found in the mechanical design field, where we continuously try to offer more efficient systems, but which have to be designed in less time, be cheaper to produce and provide benefits at least equivalent to what has already been designed.During a conventional design process, designers define the ideal geometries and - given that the machining tools cannot produce mechanical parts without any geometrical defects - specify the associated tolerancing schemes. These tolerancing schemes define acceptable geometrical deviations, thus providing a well-functioning system. Unfortunately this is done after having designed detailed parts and thus, too late.In order to address this problem, I will begin by introducing the integration, in the first design stages, of a new optimized validation process based on a Digital Mock-Up, directly linked to its functional representation (Functional Mock-Up), in order to validate 3D standardized tolerancing schemes. I'll first describe what is meant by "Functional Mock-Up" (FMU) and specify which information is added to the Digital Mock-Up (DMU). Once that is done, I will detail the relationship that leads to the uniqueness of the information and the processes linking the Functional and Digital representations.Then, I'll detail the processes based on these concepts, which aim to validate the tolerancing schemes, during the early design stages. To do this, I'll begin by introducing the worst case analysis (using the deviation domain model), which ensures the proper functioning of the mechanical system. Finally, I will end this by introducing the benefits that can be brought, by coupling a statistical layer to the worst case analysis (using the convex hull).

We numerically analyze three mechanics problems described below. For each problem, the developed computational model is verified by comparing computed results for example problems with those available in the literature. Effective utilization of single wall carbon nanotubes (SWCNTs) and single layer graphene sheets (SLGSs) as reinforcements in nanocomposites requires their strong binding with the surrounding matrix. An effective technique to enhance this binding is to functionalize SWCNTs and SLGSs by covalent attachment of appropriate chemical groups. However, this damages their pristine structures that may degrade their mechanical properties. Here, we delineate using molecular mechanics simulations effects of covalent functionalization on elastic moduli of these nanomaterials. It is found that Young's modulus and the shear modulus of an SWCNT (SLGS), respectively, decrease by about 34% (73%) and 43% (42%) when 20% (10%) of carbon atoms are functionalized for each of the four functional groups of different polarities studied. A shell theory that gives results close to the solution of the corresponding 3-dimensional problem depends upon the shell geometry, applied loads, and initial and boundary conditions. Here, by using a third order shear and normal deformable theory and the finite element method (FEM), we delineate for a doubly curved shell deformed statically with general tractions and subjected to different boundary conditions effects of geometric parameters on in-plane and transverse stretching and bending deformations. These results should help designers decide when to consider effects of these deformation modes for doubly curved shells. Composite laminates are usually fabricated by curing resin pre-impregnated fiber layers in an autoclave under prescribed temperature and pressure cycles. A challenge is to reduce residual stresses developed during this process and simultaneously minimize the cure cycle time. Here, we use the FEM and a genetic algorithm to find the optimal cycle parameters. It is found that in comparison to the manufacturer's recommended cycle, for a laminate with the span/thickness of 12.5, one optimal cycle reduces residual stresses by 47% and the total cure time from 5 to 4 hours, and another reduces the total cure time to 2 hours and residual stresses by 8%. / Ph. D. / We analyze using computational techniques three mechanics problems described below. In the last three decades, two carbon nanomaterials (i.e., allotropes of carbon having length-scale of 10^-9 m), namely, single wall carbon nanotubes (SWCNTs) and single layer graphene sheets (SLGSs) have evolved as revolutionary materials with exceptional properties per unit weight that are superior to conventional engineering materials. A composite (i.e., a material made by combining two or more materials to attain desired properties which cannot be achieved by any of its constituents alone) made by using either of these carbon nanomaterials as reinforcements in a polymer could be a potential candidate for applications requiring high strength and light weight. However, the effective utilization of these composites for an application requires the strong binding between their constituents. An effective technique to enhance this binding is to modify the surface properties of SWCNTs and SLGSs by covalently bonding to them suitable chemical group that is usually called covalent functionalization. However, this damages their pristine structures that may degrade their mechanical properties. Here, it is found that the functionalization reduces elastic moduli of carbon nanomaterials, the reduction increases with an increase in the amount of functionalization and is essentially independent of the functionalizing chemical group. This study should help engineers interested in utilizing these materials to design novel nanocomposites. Composite laminates, made by stacking and binding together layers of fiber-reinforced composites, are widely used in aircraft, aerospace, marine, automobile, power generation, chemical and ballistic applications due to their high strength and stiffness per unit weight compared to that of conventional metallic materials. Shell theories are widely used to analyze deformations of composite laminates which reduces a 3-dimensional (3-D) problem to an equivalent 2-D problem by making certain assumptions related to the deformations of the laminate. This approach requires less computational effort to find a numerical solution (i.e., an approximate solution obtained using a computational technique) of the problem as compared to that needed for solving the full 3-D problem. However, the accuracy of the results predicted by a shell theory depends on the problem being studied, i.e., the shell geometry, applied loads, initial conditions (i.e., the motion of the laminate at the start of application of the load) and boundary conditions (i.e., constraints imposed on the deformations of the edges of the laminate). Here, we analyze effects of geometric parameters of the laminated shells on their deformations for different types of applied loads and various boundary conditions specified on the edges. The results should help designers find an optimal geometry of the composite laminates for a given mechanical application. Fiber-reinforced composite laminates are usually fabricated by curing (which involves heating and cooling in a prescribed manner under application of the pressure) resin preimpregnated fiber layers under prescribed temperature and pressure cycles. However, during this cure process the laminate deforms and the final product is not stress-free. Here, we find optimal parameters of the cure cycle that minimize stresses developed during the cure process as well as the time required to cure the laminate. It is found that for a laminate studied these optimal parameters reduce the stresses by 47% and the cure time from 5 to 4 hours in comparison to the standard cure cycle recommended by the laminate manufacturer. This study will provide manufacturing engineers with an approach to fabricate composite laminates of desired quality.

La pompe à chaleur industrielle très haute température (PAC THT) à compression mécanique de vapeur, fonctionnant à l'électricité, figure parmi l'une des technologies innovantes les plus efficaces permettant de valoriser les rejets thermiques industriels à basse et moyenne température (<90 °C). Néanmoins, compte tenu des besoins industriels actuels de chaleur, les niveaux de température cible atteignable par les PACs restent trop faibles et freinent fortement son implantation. Les procédés de séchage, dans leur grande majorité, rejettent des buées ou de la vapeur d'eau à moyenne température (50 °C-90 °C) et ont des besoins de chaleur à très haute température (110 °C-150 °C). Le grand écart de température entre la source et le besoin de chaleur ainsi que le niveau de température du besoin, font qu'aujourd'hui envisager l'intégration d'une PAC dans ce type de procédés relève d'un défi énergétique et technologique particulièrement intéressant, dont l'enjeu économique est considérable. Les présents travaux de recherche envisagent à l'aide d'une méthodologie générique d'optimisation de cycles thermodynamiques basée sur la minimisation de la production d'entropie dans les échangeurs de chaleur de déceler les architectures de PACs les plus efficaces d'un point de vue énergétique. L'analyse théorique a permis de déceler la haute efficacité énergétique des architectures transcritiques de PACs dans des conditions de grands glissements de température entre l'entrée et la sortie du besoin de chaleur. Le développement d'un démonstrateur de PAC transcritique très haute température fonctionnant au R32 (PAC T-THT R32) a permis d'une part de démontrer la faisabilité technique d'une PAC, pouvant atteindre la température cible de 120 °C en partant de 60 °C avec une source de chaleur disponible à 50 °C, et d'autres part de démontrer sa haute efficacité énergétique (COP = 4). / The mechanical vapour compression high temperature heat pump for industry using electricity is one of the most effective innovative technologies to recover the industrial waste heat at low and medium temperature (<90°C). However, given the current industrial heat needs, the heat pump target temperature levels remain too low and slow strongly its implantation. Overwhelmingly, the drying processes reject saturated moist air at middle temperature (50°C-90°C) and have heat needs at very high temperature (110°C-150°C). The large temperature difference between the source and the heat need and the level off temperature that is needed, today, makes the heat pump integration in such processes an interesting energy and technological challenge, whose economic stake is considerable. The present works tackle, with a generic methodology of thermodynamic optimisation cycles based on the entropy minimization in the heat exchangers, to identify the most efficiency heat pump architectures from an energy point of view. The theoretical analysis allowed to detect the transcritical heat pump architecture, in conditions of high temperature glides between the inlet and the outlet of the heat need. The development of a transcritical high temperature heat pump demonstrator using the R32 as working fluid allowed to demonstrate the technical feasibility of a heat pump that can reach the target temperature of 120°C from 60°C with an available heat source at 50°C, and to demonstrate its high energy efficiency (COP = 4).