José Rui Camargo

Optimization of a Thermoelectric Air Conditioning Systems

This paper studies the optimization of a thermoelectric cooling system of air. Based on both results obtained experimentally and from a mathematical model, we evaluated the available features of thermoelectric modules and parameters subject to optimization. In the thermoelectric cooling air process based on the effect discovered by Jean Peltier Charles Athanase in 1834, when an electrical current is conducted through a semiconductor junction between two materials with different properties, heat is absorbed and dissipated. Thermoelectric modules are made of semiconductor materials and sealed between two plates. According to the shape of the plate, the current flow cools the one hand and the other is heated. The most important parameters to evaluate the efficiency of the thermoelectric cooling is the coefficient of performance, the rate of heat transfer and temperature difference between the maximum possible to the cold and hot sides of the thermoelectric module. In this evaluation were used thermoelectric modules and heat sinks, commercially available temperature sensors and a software for obtaining, storing and comparing the data. The prototype auxiliary allows the surface temperatures of thermoelectric modules of the hot and cold sides, the air inlet and outlet temperatures of the heat sink sides of the hot and cold air flow, the voltage and the electrical current to be applied to the modules. A simulation is performed using two air flows at a speed controlled for the hot and cold sides of the module and a set of tests for various modules, i.e. one, two, three and four coupled in parallel. Using this system, the performance data is analyzed making it possible to check the power, voltage and electrical current to maximize the coefficient of performance of the system.

Principles of Direct Thermoelectric Conversion

The aim of this chapter is to present some fundamental aspects of the direct thermoelectric conversion. Thermoelectric systems are solid-state heat devices that either convert heat directly into electricity or transform electric power into thermal power for heating or cooling. Such devices are based on thermoelectric effects involving interactions between the flow of heat and electricity through solid bodies. These phenomena, called Seebek effect and Peltier effect, can be used to generate electric power and heating or cooling. The Seebeck effect was first observed by the physician Thomas Johann Seebeck, in 1821, when he was studying thermoelectric phenomenon. It consists in the production of an electric power between two semiconductors when submitted to a temperature difference. Heat is pumped into one side of the couples and rejected from the opposite side. An electrical current is produced, proportional to the temperature gradient between the hot and cold sides. The temperature differential across the converter produces direct current to a load producing a terminal voltage and a terminal current. There is no intermediate energy conversion process. For this reason, thermoelectric power generation is classified as direct power conversion. On the other hand, a thermoelectric cooling system is based on an effect discovered by Jean Charles Peltier Athanasius in 1834. When an electric current passes through a junction of two semiconductor materials with different properties, the heat is dissipated and absorbed. This chapter consists in eight topics. The first part presents some general considerations about thermoelectric devices. The second part shows the characteristics of the physical phenomena, which is the Seebeck and Peltier effects. The thirth part presents the physical configurations of the systems and the next part presents the mathematical modelling of the equations for evaluating the performance of the cooling system and for the power generation system. The parameters that are interesting to evaluate the performance of a cooling thermoelectric system are the coefficient of performance (COP), the heat pumping rate and the maximum temperature difference that the device will produce. It shows these parameters and also the current that maximizes the coefficient of performance, the resultant value of the applied voltage which maximizes the coefficient of performance and the current that maximizes the heat pumping rate. To evaluate the power generator performance it is presented the equations to calculate the efficiency and the power output, as well as the operating design that maximizes the efficiency, the optimum load and the load resistance that maximizes the power output. The last part of the chapter presents the selection of the proper module for a specific application. It requires an evaluation of the total system in

Notes on Steady Natural Convection Heat Transfer by Double Diffusion From a Heated Cylinder Buried in a Saturated Porous Media

This paper aims to present numerical solutions for the problem of steady natural convection heat transfer by double diffusion from a heated cylinder buried in a saturated porous media exposed to constant uniform temperature and concentration in the cylinder and in the media surface. A square finite domain 3 x 3 and acceptance criterion converged solution with an absolute error under 1 x 10(-3) were considered to obtain results presented. The Patankars power law for approaching of variables calculated T, C, and phi also was adopted. In order of method validation, an investigation of mesh points number as function of Ra, Le, and N was done. A finite volume scheme has been used to predict the flow, temperature, and concentration distributions at any space from a heat cylinder buried into a fluid-saturated porous medium for a bipolar coordinates system. Examples presented show that the differences in the flow distribution caused not only when Rayleigh number range is considered but also when Lewis number range is considered. Further, increase in the Rayleigh number has a significant influence in the flow distribution when the concentration distribution is considered. Steady natural convection heat transfer by double diffusion from a heated cylinder buried in a saturated porous medium is studied numerically using the finite volume method. To model fluid flow inside the porous medium, the Darcy equation is used. Numerical results are obtained in the form of streamlines, isotherms, and isoconcentrations. The Rayleigh number values range from 0 to 1000, the Lewis number values range from 0 to 100, and the buoyancy ratio number is equal to zero. Calculated values of average heat transfer rates agree reasonably well with values reported in the literature.

Design of Biogas Pipeline Energy and Sanitation

The study aimed at developing a methodology for the design and appropriate use of materials in the pipes for the collection and distribution of biogas. The increasing use of biogas for distributed generation in agro-industries, sewage treatment effluent and anaerobic landfills, and the absence of a specific standard for biogas pipes led to the development of the work. Because there is no standard for design and delivery of pipes for the collection and distribution of biogas, the main eco-efficient energy projects implemented in the country, units digester / bike generator 50 kVA to 200 kVA, were used duct poly vinyl chloride (PVC) that permeable to gases, suffers from contamination of biogas network to air, leaks, reduce the efficiency of filter retention of H2S and reduced life of the motor generator. The methane in biogas reacts with PVC and decomposition occurs, dissolution, swelling and loss of ductility of the tube. Since polyethylene is the material world-known and most suitable for transportation of gas fuels, and the fact that its raw material, ethylene in the chain of thermoplastics derived from petroleum, polyethylene comes before the PVC, which makes it more economical and safe.

Trajectories generation for a robotic manipulator

The inverse kinematics determines the joint angles that result in the desired position of the manipulators end-effector with regard to the reference coordinated system. The inverse kinematics solution is difficult a time that the mapping between the Cartesian space and the joint space is nonlinear and involves equations that can have multiple solutions. This work presents the application of a neural network with radial basis function (RBF) for the inverse kinematics solution of a robotic manipulator with three degrees of freedom. For a good learning generalization in the training phase of RBF network, some initial and final points had been initially generated inside of the manipulators work volume. In order to prevent extreme angular oscillations, the angles for each one of the n generated points, they had been optimized by genetic algorithms. In accordance with the cartesian coordinate (x, y) supplied, the RBF neural network implemented in this work supplied angles that it had presented very next to the desired values.

Modeling the Mechanical Behaviour of a Subsea Guide Base Subject to Installation and Operations Loads

Historically, the guide cable system for installation of subsea oil production equipment has proven its efficiency. These cables extend from the rig to the wellhead, which are fixed to the guide base posts and will be subject to loads during the installation and operation of the production equipment. The majority of guide base designs have been calculated by analytical methods, although they allow obtaining exact answers in all infinite points of a structure, they are not applicable to all cases. This motivated the application of finite element analysis method (FEA) in this work, which from the development of approximate procedures can be applied regardless of the structure shape and loading conditions. This paper consists of a structural analysis of the guide base frame model, generated in Autodesk Inventor® software and analyzed in ANSYS® Workbench. The study brings a diagnostic research using a quantitative and exploratory approach. Different mathematical models were generated to obtain the results at the most critical points of the structure in order to determine its resistance to the loads applied during installation and operation, taking into account the criteria laid down in DNV 2.7-3, API 17D 1st Ed and von-Mises equivalent stress.

Rational Use of Residential Digesters for Sewage Treatment with Carbon Credits

The present work aims at decentralization of sewage treatment and eco-efficient way of enabling the deployment of residential digesters to treat only the water with high organic load without overloading the system, avoiding the drag of sludge and effluent untreated into the urban network of collection. For this purpose we developed a low-cost technology that treats sewage in the house of the citizen, thus avoiding that large stations aerobic treatment of sewage and its result regarding the large demands for energy and area: the generation and disposal of biogas smelly collection networks in urban, high production and disposal costs aerobic sludge, the disposal of sewage in fresh water bodies causing eutrophication of waters and spread of diseases hydro transmitted. The system proposed digester residential removes about 80% of the organic load of sewage without the use of any electromechanical element, and also allows to collect the biogas produced subsequently be used for energy or simply be burned to hygiene and / or crediting of carbon . Basically, the system comprises three anaerobic digesters in upflow sludge bed, arranged in series forming cascade phase separator with solid-liquid gas-shaped coil. Used to treat wastewater with high organic load coming from the toilet and the kitchen sink. Then the waters with low organic load coming from the baths, sinks and laundry, are used to dilute and improve the quality end of the anaerobically treated effluent in a sustainable manner. Social and environmental technology developed aligns with the guidelines of the National Water Agency and the Kyoto Protocol, whose goal is to reduce greenhouse gases.

Direct Thermoelectric Microgeneration Using Residual Heat of Photovoltaic System

All photovoltaic panel heats up when exposed to sunlight and this heating reduces the electrical power output of the same. This work presents the use of this unwanted waste heat, converting it into thermal energy directly by means of the Seebeck effect, which is the direct conversion of thermal energy into electrical energy by means of an arrangement of semiconductor materials that when exposed to temperature gradients generate electric current. In this work emphasis was placed on the influence of temperature on generation processes involved. Thus, the theoretical evaluation, it presents the mathematical models of thermoelectric and photovoltaic systems by raising the curves of voltage, current and electric power generated, and analyses the influence of temperature in each model. To obtain the simulation curves it uses MATLAB ® 5.3, taking into account the parameters of thermoelectric modules and real photovoltaic cells. In practical evaluation, a prototype was assembled containing thermoelectric module attached to the bottom of a photovoltaic panel in order to use the heat energy absorbed by the panel. The data were stored and analyzed, where we observed the influence of temperature in both systems, validating the mathematical modeling. It is the applicability of the mathematical model given the results obtained with the prototype system.