1,721,499 research outputs found
Microdissipatore polimerico, in particolare per il condizionamento termico di dispositivi meccanici ed elettronici
No full textMetodo e apparato per lo stampaggio a caldo di prodotti in materiale termoplastico
No full textThe present invention relates to a method and apparatus for the moulding of products in thermoplastic material, particularly for the cooling of products obtained by hot injection of plastic materials into moulds.
The production of products by the injection of thermoplastic materials into suitably shaped metal moulds is known in many sectors of the art. The moulds are mainly shaped by elements and contra-elements that, when united to close the mould, define a hollow space that reproduces the shape of the object that it is desired to obtain. The materials used, initially available in solid phase, usually as granules, are liquefied by increasing the temperature above their relative melting point and anjected by one ormore nozzles into the hollow space inside the closed mould. Subsequently, the mould is cooled to solidify the injected material and then to extract the finished product.
With this system it is possible to produce parts, components, objects, etc., having complex shapes even for the most varied applications, e.g. for the production of objects in the auto, electrical appliance, electronic, aerospace and biomedical apparatus industries, etc
Boiling of R134a inside a glass minichannel. A new statistical approach of flow pattern characterization based on flow visualization
No full textA test rig to study R134a flow boiling inside mini and micro-channels has been constructed. The test section is made up of a glass tube and several ITO conductive layers as heaters. A novel image processing technique has been developed for the study of R134a flow boiling regimes. The software routine extracts the bubble contours, measures geometrical features of each frame and collects the data analytically and statistically. The results refer to mass flux between 20 and 122 kg/m2 s and the heat flux between 200 and 45,000 W/m2, at the saturation temperatures of 20–25 °C. The tube inner diameter is 4 mm and the heated length was globally of 320 mm, distributed in eight shorter heaters of 40 mm each. The main goals are the development of a method that, starting from the analysis of several parameters, is able to identify the flow pattern inside the tube, as well as the study of the effects of coalescence on the flow pattern development along the tube.
The flow patterns have been identified from a statistical point of view and the “transition zone” has been quantitatively characterized. Part of the analysis is then devoted to the flow pattern variation along the test section. The experiments demonstrated that coalescence is a phenomenon that can be analyzed also in terms of a statistical approach and that the flow pattern variations are not only a function of the mass flux and the quality, but along the tube bubble coalescence and gravity effects have a role in the flow patterns appearance
Trnsys integrated modeling support tool for a fast building-plant system design
Full text linkThe present thesis stems from the benefits of the application of energy analysis in any stage of building-plant system design. The research highlights the barriers that prevent this integration and finally proposes the development of a dynamic modeling support tool able to simulate, with a reasonable workload, a very large number of integrated building-plant systems with different scales and resolutions, in order to have a guided design support for architects and HVAC designers/engineers, reducing their modeling effort and errors. The starting point is represented by a flexible and detailed model created with the calculation engine TRNSYS, which allow for the dynamic and integrated simulation of the building envelope, all the heating plant subsystems, and all the plant components related to the production of domestic hot water.
The research explores then strategies and simplifications that can considerably reduce the number of necessary inputs for the simulations, thus minimizing the modeling, implementation and simulation runtime of the model, while still maintaining an acceptable degree of accuracy with respect to the computational results and real energy consumptions. Those results are achieved by defining a methodology, which consists in developing a sizing protocol and a simplification protocol and applying them to real life, complex case studies, first modeling detailed models and progressively enhancing the level of simplification. At each progressive simplification step, the comparison with the detailed model results is given in terms of building energy needs, power curves, efficiencies, modeling and simulation workloads. In particular results show that the accuracy of the most simplified model is always below the 16% with respect to the most detailed model, with a 90% modeling and simulation workload reductions, able to make the tool easy to be adopted at every stage of building-plant system design
Boiling of the R134a inside a glass minichannel : a new approach of flow pattern characterization based on flow visualization
Full text linkPulsating heat pipes. Numerical Modelling and Experimental Assessment
Full text linkThe present thesis is the result of a three year research study on the developing and experimental validation of a numerical model for the thermal-hydraulic simulation of Closed Loop Pulsating Heat Pipes. The project has been carried out in the framework of the PRIN-2009 and put the basis for a fruitful collaboration between the University of Bergamo and the Indian Institute of Technology Kanpur (IITK, India).
The first two years were mainly devoted to improve the theoretical model and to the subsequent implementation of new subroutines. During this first stage the model has been validated by means of experimental data available from the literature. In the last year an actual CLPHP test-rig has been designed, built and tested. The outcome of the proprietor experimental apparatus provided new data on the heat transfer capability of two phase flows in mini-channels and allowed to perform a more accurate quantitative comparison with the simulation results.
Although the final version of the numerical model is able to satisfactorily reproduce many trends of actual PHP devices, further work is needed in order to understand some open issues related to the physics and to release a reliable software tool for the PHP design
L'edificio energeticamente sostenibile : verifiche energetiche, strategie per la raccolta dati e tecniche d'intervento per edifici esistenti
Full text linkRefrigerant R134a two-phase ?ow automatic ?ow pattern identi?cation based on a probabilistic criterion related to the bubbles diameter
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Design of pulsating heat pipes. A novel non-equilibrium lumped parameter model for transient gravity levels
Full text linkAs relatively new and promising members of the wickless heat pipe family, Pulsating Heat Pipes (PHPs), with high effective thermal conductivity and construction simplicity, may answer to the present industrial demand of efficient thermal control, flexibility and low costs. In the last twenty years, many experimental and numerical works focused on PHPs, but despite the great efforts, their non linear, two-phase, internal flow remains essentially an unknown and, thus, none of the existing models is actually able to simulate it.
One of the most important unsolved questions regards the influence that gravity may have on the device thermal-hydraulic behavior. Literature, indeed, reports very poor and contradictory data, even if modified gravity conditions arise in various applications from automotive to aerospace, from chemistry to material synthesis. This work aims to fill this serious lack of knowledge. Thus, a capillary, closed loop PHP made of a copper tube bended into 32 parallel channels and filled with FC-72 has been investigated both on the ESA ESTEC Large Diameter Centrifuge (ESA Educational project Spin Your Thesis! 2013), and on board of the ESA-NoveSpace Airbus A300 Zero-G flying parabolic trajectories (58th and 59th ESA Parabolic Flight Campaigns). For the first time, a planar PHP with circular cross section channels, equipped with 14 thermocouples and a pressure transducer has been fully, thermally characterized in several operative conditions from 0.01g to 20g.
In addition, in order to provide a numerical tool able to help and support the experimental research in enlarging the present knowhow and spreading PHPs industrial application, the results of these experimental campaigns have been used to develop and validate a novel lumped parameters model. It uses an advanced numerical technique to allow fast simulations, extending sensitivity analysis and device designs. Lumped parameter models are not a novelty for PHPs per se: however, for the first time this kind of numerical tools has been applied to simulate transient operative conditions removing physical simplified assumptions and embedding directly phase changes processes. The resulting code showed very good prediction capability, being able to reproduce with high accuracy the experimental recorded data both in steady and transient conditions
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