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Descripción
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| Low temperature geothermal energy is considered as one of the most efficient and promising renewable energy sources, especially when harvested for the HVAC (heating, ventilation, and air conditioning) system of a building. When correctly designed and sized, these geothermal HVAC systems can provide significant monetary savings and a clean and efficient way of cooling and heating buildings. A geothermal HVAC system is typically conformed by a water?to?water heat pump connected to geothermal heat exchanger composed of multiple vertical boreholes equipped with, normally, U?shaped pipes. Through these pipes a heat carrying liquid flows and exchanges heat with the surrounding ground. A well designed geothermal heat exchanger avoids an excessive drift in the operating temperatures of the heat carrying liquid that otherwise would negatively affect the energy efficiency of the heat pump, and consequently of the whole HVAC system. Sometimes the buildings require higher heating and cooling needs than usual, for example during the hottest or coldest weeks of the year. These so?called peak loads determine the maximum and minimum operating temperatures of the geothermal HVAC system. During these transitory regimes the ground temperature perturbations reach distances from the borehole that are comparable to the borehole diameter. Thanks to the extreme slenderness of geothermal boreholes, the resulting heat transfer problem can be analyzed using a two?dimensional model, relegating the vertical coordinate of the borehole to the status of a parameter that connects the multiple temperature planes, which are obtained individually. The formulated heat transfer problem is then solved by means of Fourier expansions for the harmonic case and the Laplace transform for the transitory case, where both of these methods involve a very similar solution procedure. Given the linearity of the equations, the solution of the model considers the presence of an infinite number of heat sources and poles in each of the pipes, which in fact are the eigenfunctions of the problem. These are typically called multipoles in the literature. The numerous effects of all these multipoles are superposed to obtain the overall temperature field in the borehole and the surrounding ground. This approach is closely related to the work done by Claesson and Hellström (2011), who developed the use of multipoles for the steady state case of the problem and were able to obtain solutions with outstanding accuracies. By analyzing the harmonic and transitory regimes, the present work expands their analysis to all relevant time regimes of the problem. | |
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Internacional
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Si |
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Nombre congreso
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First Colloquium of the Spanish Theoretical and Applied Mechanics Society |
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Tipo de participación
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970 |
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Lugar del congreso
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Madrid, España |
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Revisores
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Si |
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ISBN o ISSN
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DOI
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Fecha inicio congreso
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28/03/2019 |
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Fecha fin congreso
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29/03/2019 |
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Desde la página
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57 |
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Hasta la página
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57 |
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Título de las actas
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First Colloquium of the Spanish Theoretical and Applied Mechanics Society: PROGRAMME |