ABSTRACT PATIENT MONITORING VIA MOBILE AD HOC NETWORK - MAXIMIZING RELIABILITY WHILE MINIMIZING POWER USAGE AND DELAYS BY SWETA SNEHA May 22nd, 2008 Committee Chair: Dr. Upkar Varshney Major Department: Computer Information Systems Comprehensive monitoring of patients based on wireless and mobile technologies has been proposed for early detection of anomalies, provision of prompt medical attention, and corresponding reduction in healthcare expenses associated with unnecessary hospitalizations and treatment. However the quality and reliability of patient monitoring applications have not been satisfactory, primarily due to their sole dependence on infrastructure-oriented wireless networks such as wide-area cellular networks and wireless LANs with unpredictable and spotty coverage. The current research is exploratory in nature and seeks to investigate the feasibility of leveraging mobile ad hoc network for extending the coverage of infrastructure oriented networks when the coverage from the latter is limited/non-existent. Although exciting, there are several challenges associated with leveraging mobile ad hoc network in the context of patient monitoring. The current research focuses on power management of the low-powered monitoring devices with the goal to maximize reliability and minimize delays. The PRD protocols leveraging variable-rate transmit power and the PM-PRD scheme are designed to achieve the aforementioned objective. The PRD protocols manage power transmitted by the source and intermediate routing devices in end to end signal transmission with the obejective to maximize end to end reliability. The PM-PRD scheme operationalizes an appropriate PRD protocol in end to end signal transmission for diverse patient monitoring scenarios with the objective to maximize reliability, optimize power usage, and minimize delays in end to end signal transmission. Analytical modeling technique is utilized for modeling diverse monitoring scenarios in terms of the independent variables and assessing the performance of the research artifacts in terms of the dependent variables. The evaluation criterion of the research artifacts is maximization of reliability and minimization of power usage and delays for diverse monitoring scenarios. The performance evaluation of the PRD protocols is based on maximization of end to end reliability in signal transmission. The utility of the PM-PRD scheme is associated with operationalizing an appropriate protocol for a given monitoring scenario. Appropriateness of a protocol for a given scenario is based on the performance of the PRD protocols with respect to the dependent variables (i.e., end to end reliability, end to end power usage, and end to end delays). Hence the performance evaluation of the PRD protocols in terms of the dependent variables is utilized to (a) discover the best protocol and (b) validate the accuracy and utility of the PM-PRD scheme in allocating the best protocol for diverse monitoring scenarios. The results validate the effectiveness of the research artifacts in maximizing reliability while minimizing power usage and delays in end to end signal transmission via a multi-hop mobile ad hoc network. Consequently the research establishes the feasibility of multi-hop mobile ad hoc network in supplementing the spotty network coverage of infrastructure oriented networks thereby enhancing the quality and dependability of the process of signal transmission associated with patient monitoring applications.

For the past four decades, Mars missions have relied on Viking heritage technology for supersonic descent. Extending the use of propulsion, which is required for Mars subsonic deceleration, into the supersonic regime allows the ability to land larger payload masses. Wind tunnel and computational experiments on subscale supersonic retropropulsion models have shown a complex aerodynamic flow field characterized by the interaction of underexpanded jet plumes exhausting from nozzles on the vehicle with the supersonic freestream. Understanding the impact of vehicle and nozzle configuration on this interaction is critical for analyzing the performance of a supersonic retropropulsion system, as deceleration will have components provided by both the aerodynamic drag of the vehicle and thrust from the nozzles. This investigation focuses on the validity of steady state computational approaches to analyze supersonic retropropulsion flowfield structures and their effect on vehicle aerodynamics. Wind tunnel data for a single nozzle and a multiple nozzle configuration are used to validate a steady state, turbulent computational fluid dynamics approach to modeling supersonic retropropulsion. An analytic approximation to determine plume and bow shock structure in the flow field is also developed, enabling rapid assessment of flowfield structure for use in improved grid generation and as a configuration screening tool. Results for both the computational fluid dynamics and analytic approaches show good agreement with the experimental datasets. Potential limitations of the two methods are identified based on the comparisons with available data. Six additional geometries are defined to investigate the extensibility of the analytical model and determine the variation of supersonic retropropulsion performance with configuration. These validation geometries are split into two categories: three geometries with nozzles located on the vehicle forebody at varying nozzle cant angles, and three geometries with nozzles located on the vehicle aftbody at varying nozzle cant angles and number of nozzles. The forebody nozzle configurations show that nozzle cant angle is a significant driver in performance of a vehicle employing supersonic retropropulsion. Aerodynamic drag preservation for a given thrust level increases with increasing cant angle. However, increasing the cant angle reduces the contribution of thrust to deceleration. The tradeoff between these two contributions to the deceleration force is examined, noting that performance improvements are possible with modest nozzle cant angles. Static pitch stability characteristics are investigated for the lowest and highest cant angle configurations. The aftbody nozzle configuration results show that removing the plume flow from the region forward of the vehicle results in less interaction with the bow shock structure. This impacts aerodynamic performance, as the surface pressure remains relatively undisturbed for all thrust values examined. Static pitch stability characteristics for each of the aftbody nozzle configurations are investigated; noting that supersonic retropropulsion for these configurations exhibits a transition point from static stability to instability as a function of this center of mass location along the axis.

Les tokamaks visent à produire de l'énergie par fusion thermonucléaire en chauffant un plasma d'hydrogène jusqu'à 150 millions K et en le confinant à l’aide d’un champ magnétique intense créé par des aimants transportant d’importants courants. La supraconductivité est un atout précieux ici car permettant de réduire la taille des aimants et leur consommation énergétique en contrepartie d’un refroidissement cryogénique. Cependant, dans les tokamaks, des variations de champ magnétique apparaissent (ex : décharge du solénoïde central) et génèrent des pertes par induction dans les aimants. Si leur température augmente trop, ils peuvent perdre leur état supraconducteur lors d’une transition brutale appelée "quench": afin de les protéger, ils sont déchargés de leur courant entraînant ainsi la perte du plasma. Nous avons concentré notre travail sur la modélisation de ces pertes car leur connaissance est cruciale pour le bon dimensionnement du refroidissement des aimants et la prédiction des limites opérationnelles du tokamak. Afin d'améliorer la compréhension physique de ce phénomène complexe et de proposer des solutions simples mais réalistes, facilement intégrables dans des plateformes multiphysiques déjà fortement sollicitées par la modélisation d'autres effets, nous avons choisi d'adopter une approche analytique. Les câbles présents dans les tokamaks ayant une architecture assez complexe (centaines de brins torsadés ensemble), nous avons mené des études analytiques et expérimentales aux différentes échelles du câble; nous comparons ensuite les résultats de notre approche à ceux d'autres modèles existants (ex : numériques) et, lorsque cela est possible, à l'expérience. / Tokamaks aim at producing energy by thermonuclear fusion heating a hydrogen plasma up to 150 million K and confining it with an intense magnetic field created by magnets carrying important currents. Superconductivity is a very valuable asset in this field since it allows to reduce the size of the magnets and their energy consumption in exchange for cooling them down to cryogenic temperatures. However, in tokamaks, magnetic field variations occur (e.g. due to the central solenoid discharge) and generate induction losses in the magnets. If their temperature increases too much, they lose their superconducting properties in a brutal transition called "quench": to protect their integrity, they are then discharged and the magnetic confinement of the plasma is lost. We have therefore focused on the modeling of these losses - more precisely on the “coupling losses” - since their knowledge is crucial to safely adapt the cryogenic cooling of the magnets and predict the operating limits of the tokamak. In order to both enhance the physical understanding of this complex phenomenon and provide simple but realistic solutions that can easily be integrated in multiphysics platforms already heavily solicited by the modeling of other effects, we have chosen to adopt an analytical approach on this problem. The cables commonly considered for tokamaks presenting a rather complex architecture (several hundreds of strands twisted together in specific patterns), we have carried out analytical and experimental studies at the different scales of the cable; we then compare the results of our approach to other existing ones (e.g. numerical models) and, when possible, to the experiment.

Ce travail de thèse est consacré au développement d'un capteur acoustique miniature à transduction capacitive destiné à être intégré dans un système RFID afin de dépasser certaines des limitations actuelles de ce dernier. La configuration originale du capteur acoustique étudié lui offre les avantages d'avoir une bonne performance tout en gardant une forme simple qui peut être aisément réalisée avec les techniques MEMS pour une production à grande échelle. Ce transducteur est constitué d'une membrane circulaire ou carrée et une électrode arrière centrée, de même forme mais de dimensions plus petites, séparées par une très fine couche de fluide, ainsi qu'une petite cavité située à la périphérie de l'électrode, de dimensions extérieures très proches de celles de la membrane. Le comportement de ce capteur est analysé en détail. Cette étude se base sur deux approches mathématiques originales (analytique et numérique), dont les résultats convergent malgré un niveau différent des hypothèses-simplificatrices sur lesquelles reposent ces deux modèles.Finalement, une méthode de réalisation du transducteur en technologie hybride, qui associe le procédé MEMS avec les techniques classiques des circuits imprimé, est présentée. Le prototype développé est aussi caractérisé expérimentalement et les résultats obtenus correspondent bien aux caractéristiques fournies par les modèles théoriques. / This work is devoted to the development of capacitive miniature acoustic sensor to be integrated in an RFID system in order to exceed some of its current limitations.The unusual configuration of the studied sensor offers the benefits of having a significant performance while keeping a simple form that can be easily achieved with standard MEMS techniques and thus successively marketed in perspective. This transducer consists of a circular or square membrane, a centered backing electrode with the same shape, but with smaller dimensions which define a thin fluid layer between them, and a small cavity at the periphery of the backing electrode whose external dimensions are very close to the ones of the membrane. The architecture of the developed sensor is the subject of a deep theoretical study of its behavior. This investigation is based upon two original mathematical approaches (analytical and numerical ones) whose results show a high convergence despite the different-levels of simplifying assumptions on which these models are based.Finally, the transducer is made with the use of a hybrid technology, that includes the MEMS process associated with conventional printed circuit manufacturing techniques, which is presented step by step. The developed prototype is characterized experimentally and the measured results correspond to the ones predicted by theoretical models.

Os processos de negócio desempenham um papel muito importante na indústria, principalmente pela evolução das tecnologias da informação. As plataformas de computação em nuvem, por exemplo, com a alocação de recursos computacionais sob demanda, possibilitam a execução de processos altamente requisitados. Para tanto, é necessário definir o ambiente de execução dos processos de tal modo que os recursos sejam utilizados de forma ótima e seja garantida a correta funcionalidade do processo. Nesse contexto, diferentes métodos já foram propostos para modelar os processos de negócio e analisar suas propriedades quantitativas e qualitativas. Há, contudo, vários desafios que podem restringir a aplicação desses métodos, especialmente para processos com alta demanda (como os workflows de numerosas instâncias) e que dependem de recursos limitados. A análise de desempenho de workflows de numerosas instâncias via modelagem analítica é o objeto de estudo deste trabalho. Geralmente, para a realização desse tipo de análise usa-se modelos matemáticos baseados em técnicas Markovianas (sistemas estocásticos), que sofrem do problema da explosão do espaço de estados. Entretanto, a Teoria do Campo Médio indica que o comportamento de um sistema estocástico, sob certas condições, pode ser aproximado por o de um sistema determinístico, evitando a explosão do espaço de estados. Neste trabalho usamos tal estratégia e, com base na definição formal de aproximação determinística e suas condições de existência, elaboramos um método para representar os workflows, e seus recursos, como equações diferenciais ordinárias, que descrevem um sistema determinístico. Uma vez definida a aproximação determinística, realizamos a análise de desempenho no modelo determinístico, verificando que os resultados obtidos são uma boa aproximação para a solução estocástica. / Business processes play a very important role in the industry, especially by the evolution of information technologies. Cloud computing platforms, for example, with the allocation of on-demand computing resources enable the execution of highly requested processes. Therefore, it is necessary to define the execution environment of the processes in such a way that the resources are used optimally and the correct functionality of the process is guaranteed. In this context, different methods have already been proposed to model business processes and analyze their quantitative and qualitative properties. There are, however, a number of challenges that may restrict the application of these methods, especially for high-demanded processes (such as workflows of numerous instances) and that rely on resources that are limited. The analysis of the performance of workflows of numerous instances through analytical modeling is the object of study of this work. Generally, for the accomplishment of this type of analysis, mathematical models based on Markovian techniques (stochastic systems) are used, which suffer the problem of the state space explosion. However, the Mean Field Theory, indicates that the behavior of a stochastic system, under certain conditions, can be approximated by that of a deterministic system, avoiding the explosion of the state space. In this work we use such a strategy, based on the formal definition of deterministic approximation and its conditions of existence, we elaborate a method to represent the workflows, and their resources, as ordinary differential equations, which describe a deterministic system. Once the deterministic approximation has been defined, we perform the performance analysis in the deterministic model, verifying that the obtained results are a good approximation for the stochastic solution.

The Analytical Strip Method (ASM) for the analysis of thin cylindrical shells is presented in this dissertation. The system of three governing differential equations for the cylindrical shell are reduced to a single eighth order partial differential equation (PDE) in terms of a potential function. The PDE is solved as a single series form of the potential function, from which the displacement and force quantities are determined. The solution is applicable to isotropic, generally orthotropic, and laminated shells. Cylinders may have simply supported edges, clamped edges, free edges, or edges supported by isotropic beams. The cylindrical shell can be stiffened with isotropic beams in the circumferential direction placed anywhere along the length of the cylinder. The solution method can handle any combination of point loads, uniform loads, hydrostatic loads, sinusoidal loads, patch loads, and line loads applied in the radial direction. The results of the ASM are compared to results from existing analytical solutions and numerical solutions for several examples; the results for each of the methods were in good agreement. The ASM overcomes limitations of existing analytical solutions and provides an alternative to approximate numerical and semi-numerical methods.

La densification extrême des cartes électroniques, couplée à une compacité toujours plus accrue entraîne des contraintes thermiques exacerbées, ceci constitue un verrou technologique à l’évolution des systèmes électroniques.Ce document traite de la modélisation thermique des composants électroniques, et de leur interaction avec des systèmes électroniques en général.Dans une première partie, le concept de modèles compacts, qui est une représentation partielle d’un composant électronique qui s’affranchit de sa géométrie, est abordé. Les différents concepts de modèles numériques sont expliqués et comparés en fonction de leur niveau de précision par rapport à une représentation détaillée d’un composant électronique.Dans une deuxième partie, la modélisation analytique des composants électroniques est développée, pour les composants mono-puces puis multi-puces. Le modèle analytique établi est basé sur la résolution 3-D de l’équation de la chaleur par les séries de Fourier dans un domaine multi-couche et avec des sources de chaleur volumique. Le modèle analytique est également comparé à une modélisation numérique dans le but de quantifier l’avantage de ce type de modélisation.Le concept de modèles compacts temporels est validé expérimentalement dans la troisième partie de ce document. Les modèles compacts explicités dans la première partie sont confrontés à des essais expérimentaux en régime transitoire. Ces essais démontrent que les modèles compacts temporels permettent d’obtenir un écart de température inférieur à 10%, ceci quelle que soit la configuration des véhicules de test thermique.Une quatrième partie s’attache sur un nouveau concept de modèles simplifiés dans le cas où la géométrie des composants électroniques n’est pas connue. Ce type de modélisation se base sur le modèle analytique de la seconde partie. Il est démontré que celui permet d’obtenir un écart inférieur à 10% avec le modèle numérique détaillé, quel que soit le niveau de complexité du composant.Enfin, la dernière partie aborde la potentielle utilisation des modèles compacts développés pour améliorer la conception d’une carte électronique industrielle. Pour cela, la modélisation compacte de cartes électroniques avec composants enterrés a été explorée. Cette approche s’appuie sur le développement analytique effectuée dans la seconde partie des travaux exposés avec pour objectif d’accentuer la capacité à modéliser les cartes possédant de multiples couches. Une méthode intelligente de calcul des diverses couches d’une la carte électronique a été établie. Celle-ci offre la possibilité d’explorer rapidement diverses options d’une conception tout en préservant un niveau de précision important. / The extreme densification of electronic boards, coupled with their size reduction leads to critical thermal stress, resulting in technology barriers to the evolution of electronic systems.This document is about the thermal modelling of electronic components, and their interaction with electronic systems in general.In the first chapter, the concept of compact models, which is a partial representation of an electronic component without its geometry complexity, is addressed. The different types of compact models are explained and discussed in function of their accuracy towards detailed models of electronic components.In a second chapter, the analytical modelling of electronic components is developed, for mono and multi chips packages. The analytical model is based on the resolution of 3-D heat equation by the use of Fourier series for multi-layer domain and volumetric heat sources. The analytical model is therefore compared to numerical models with the goal to quantify the cons and pros of this representation.The concept of dynamical compact models is validated experimentally in a third chapter. The compact models of first chapter are confronted to experimental data in dynamic state. This comparison shows that the developed dynamical compact models have a deviation lower than 10% with experimental results, whatever the configuration of the thermal test vehicles.A fourth chapter introduces a new concept of simplified models, in the case of a lack of information about the geometry of electronic components. This new modelling concept is based on the analytical development of second chapter. It is shown that a discrepancy of less than 10% with detailed numerical models can be achieved, whatever the complexity level of electronic components.Finally, the last chapter deals with a potential way to exploit the developed thermal models for performing industrial board design. Thus, the compact modelling of electronic multilayer boards with buried components in its core layers is investigated.This approach is based on the analytical model of second chapter in order to deal with thin multi-layer electronic boards. A concept of a smart decomposition of the board layers is introduced, which allows a fast design exploration while preserving a high accuracy level.

<p>In the heating, ventilation, air conditioning and refrigeration (HVAC&R) industry, bonding and joining play an important role in the manufacturing and assembly process, which is critical to the cost, safety, reliability, and design freedom of systems. The goal of this thesis is to understand and evaluate the usage of adhesive bonds in the manufacture of HVAC&R systems, specifically in regards to leakage/reliability characterization and stress analysis under loading.</p> <p>The bonding performance under static loading is first studied using a commercial epoxy adhesive product. In addition to the traditional surface preparation methods of mechanical and chemical etching, a novel laser-interference surface structuring preparation technique was utilized to improve bonding performance. Laser interference structuring uses a ND:YAG laser beam that is split into two beams that are re-directed to overlap on the same area of a copper alloy. A structuring pattern near the interference structuring limits is achieved due to the phase shift between the beams that is imparted as they are re-directed. Two different laser structuring methods were tested: spot-by-spot and laser raster. Different structuring parameters were varied including the laser spot size and pulses per spot (2, 4, 6, 8, 10, 12 pulses/spot) for the spot-by-spot method, and raster speed (2, 4, 6, 8, 10, 12 mm/s) for laser raster method. The microstructure morphology and surface profile after processing were characterized using the scanning electron microscopy (SEM) and profilometry for all surfaces. It was found that the laser-interference structuring removed the surface contaminants efficiently and formed dot- or net-shaped structures on the surface. This indicates that melting, vaporization, and solidification of the metal happened differently. Due to the much higher speed of the laser raster method, considering practical industrial applications, it is selected for additional investigation for shear strength improvement. The shear strength is measured by a single lap shear test which pulls apart adhesively bonded single lap joint specimen under shear loading using a mechanical tester.</p> <p>Based on the surface profiles, three different laser raster speeds of 2 mm/s, 6 mm/s and 12 mm/s were selected for the manufacture of single lap joint specimens for comparison with the traditional surface preparation methods. The shear lap strength and displacement at maximum load were obtained for the specimens. The laser raster at 6 mm/s increased these values by approximately 11.0% and 25.1%, respectively, while the 12 mm/s condition had an increase of 16.8% and 43.8%, compared with the baseline traditional surface preparation method. It is concluded that laser structuring can enhance the single lap shear joint bonding performance. Within the tested laser processing parameters, a higher laser raster speed results in a larger enhancement. </p> <p>In addition to the static loading test with epoxy adhesive, different adhesive formulations are investigated and developed by the collaborating adhesive manufacturer to determine their suitability for use under the temperature and pressure conditions in HVAC&R systems. Reliability, especially fatigue failure, is another major concern because the strength of the adhesive joints is sufficient for HVAC&R applications. Two primary types of fatigue may happen in practical applications: thermal fatigue and vibration fatigue. Two test facilities were designed and built to test the adhesive performance and understand the failure mechanisms. For the thermal fatigue testing, a novel pressure and temperature cyclic (PTC) test stand was designed to simulate the pressure and temperature changes that may occur in HVAC&R systems. The test stand was designed to switch between hot high-pressure gas and cold low-pressure gas by using a compressor with hot gas bypass setup. For the vibration testing, a standard industrial shaker was used to provide the required vibration at a given displacement and frequency with a specially designed fixture for the tested joints. In both tests, adhesive joints were tested in parallel with brazed joints, undergoing extreme thermal and vibration loading conditions. All the samples were leak-checked before and after the testing, which were found to be leak-free after the testing, indicating that they pass the required qualification test according to available standards. It is confirmed that adhesive joints can be a potential alternative when dealing with thermal and vibration fatigue in the common working conditions of HVAC&R systems.</p> <p>The qualification testing is specific to the required loading conditions, such as pressure and temperature variations, and limited to certain tube sizes. An analytical model is developed to allow for design and evaluation across various operating conditions. The model aims to predict the adhesive stress and strain fields of in tube-to-tube joints based on the geometric parameters, material properties, and the loading conditions. In particular, the model uniquely considers the influence of thermal expansion and contraction in the joint, which is necessary for the periodically changing temperatures in HVAC&R systems. It is numerically solved using Mathematica and validated against the published data in the literature. The exact same solutions are achieved using the reported data in the literature, under simplified conditions without any temperature change involved. The validated model is then used in parametric studies to investigate the influence of geometric sizes and temperature change. Several conclusions are made about the trend of stress changes as well as the maximum stress, which provide insight from a perspective of general design guidance. Adhesive bonding length should be selected such that the maximum stress is smaller than the allowed material strength for both normal and shear stress. Adhesive thickness has less impact in the parametric range considered and is nevertheless usually dictated by the manufacture recommendation in view of other practical considerations. In regard to the thermal stresses, it is found that in practical HVAC&R working environment, the temperature-induced thermal stress dominates the stress fields and leads to significant change in the stress distribution across the adhesive layer. If a temperature change is present, the combination of all possible loading and temperature change should be analyzed to find the most extreme loading condition. This work demonstrates the first stress and strain analysis of tube-to-tube adhesive joints considering the working conditions of HVAC&R applications involving temperature cycling. All of these results provide a detailed guidance for use of adhesive joints across different application or locations in HVAC&R systems. The model can be also used as a framework to evaluate and compare the performance of different adhesives, as long as the adhesive properties are available.</p> <p>Lastly, it is also essential to demonstrate the application of these joints in real HVAC&R systems. A proof-of-concept test was done to demonstrate that the use of adhesive joints in a real system would cause no change in operation or leakage. A commercial heat pump dryer system was used to perform the testing at the Ray W. Herrick Laboratories. Two adhesive joints were installed to replace the brazing joints at the compressor inlet and outlet, where the most extreme temperature and pressure conditions are present. Results show that the system operates without any change in performance and experience no obvious leakage after more than 50 hours of testing over 6 months. </p> <p>This work explores the feasibility and reliability of adhesive bonding of copper for HVAC&R applications. The bonding strength of adhesive was studied and tested with both traditional surface preparation and advanced laser-interference structuring technique. The results show that for the tested structural epoxy adhesive, the bonding strength is large enough considering the internal pressure in the tube and the laser structure technique can increase the shear strength. </p> <p>The long-term reliability with respect to thermal, stress and vibration fatigue are then experimentally investigated and the adhesive joints pass the qualifications tests required by the standard. Further modeling work for predicting the stress distribution in adhesively bonded joints is developed to understand the influence on geometric parameters and temperature change. The adhesive length can influence the stress distribution significantly and temperature-induced stress dominates the stress distribution under the HVAC&R loading conditions. Further material characterization is needed for crack propagation or detailed fatigue analysis, which is highly dependent on the adhesive formula, working environment and loading conditions, which can be performed with a more specific targeted application. The experimental and modeling work in this thesis provides a foundation for adhesives to be applied in HVAC&R applications and a framework to further develop, optimize, and utilize adhesive joining in HVAC&R applications. </p>

The significant increase in energy requirements across the world, provides several opportunities for innovative methods to be developed to facilitate the storage and utilization of energy. The major energy demand is in the form of electrical energy for domestic as well as industrial sectors, a large part of which are the heating and cooling requirements. Appropriate utilization of thermal energy storage can effectively aid in reducing the electrical demand by storage and release of this thermal energy during peak hours. Thermal Energy Storage using Phase Change Materials (PCMs) is an attractive method of energy storage, with a wide variety of potential applications. Several configurations have been tested by researchers to develop energy storage devices with PCMs. The cycling of melting and solidification of PCMs results in storage and release of heat at a relatively small temperature difference. Design and deployment of these storage systems have certain challenges and considerations associated to them for instance, when used in buildings, PCMs should be non-toxic, non-corrosive, and others. In this thesis, we aim to provide models for designing Latent Thermal Energy Storage (LTES) devices with PCMs, based on their operating conditions, thermophysical properties of materials, and geometric parameters. The models are developed considering fluid dynamics and heat transfer involved in melting and solidification of PCMs. Parameters like inlet temperature and velocity, and volume of storage container are varied to determine the time taken for melting or solidification. For sizing and predicting performance of the storage devices we aim at presenting an analytical correlation, with time taken for melting as the variable defining the ‘charging/discharging time’ of storage device. Along with this, a transient model is developed to predict amount of PCM melted/solidified, along with rate of latent energy storage in defined time period intervals.

No description available.