Publication: Conductividades térmicas de sistemas con cambio de fase: nano-fluidos y nano-compuestos
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2018-05-17
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Universidad Complutense de Madrid
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Abstract
Esta Tesis Doctoral presenta, en una primera parte, mediciones experimentales de alta precisión de la conductividad térmica de la serie de alcanos lineales pares e impares (npentadecano, n‐hexadecano, n‐heptadecano, n‐octadecano, n‐nonadecano y n‐eicosano) en función de la temperatura y a presión atmosférica. En todos los casos el rango de temperaturas incluye el punto de fusión, por lo que en algunas mediciones el material está en estado sólido y en otras en estado líquido. Para medir la conductividad térmica se ha utilizado la técnica del hilo caliente transitorio, con un dispositivo experimental específicamente desarrollado en el Departamento de Física Aplicada I (Universidad Complutense) para tal fin. Se incluye una descripción pormenorizada del dispositivo y del método de análisis y reducción de datos, así como un estudio detallado de la reproducibilidad, precisión y fiabilidad de las mediciones realizadas. En este dispositivo la muestra se congela en la celda de medida. Por tanto, en contra de otros trabajos previos, se miden conductividades térmicas en sólido y en líquido sobre la misma muestra, siendo la técnica y el análisis los mismos, independientemente de que la muestra esté en estado sólido o líquido. Los alcanos lineales estudiados están en la base de la formulación de muchos de los llamados Materiales de Cambio de Fase (PCM), que en la actualidad se están incorporando en diversas aplicaciones tecnológicas en el campo de las energías renovables, como el almacenamiento energético y la refrigeración...
This Ph.D. dissertation splits into two parts. In the first one we present high accuracy experimental measurements of the thermal conductivity of even and odd‐numbered n‐alkanes (npentadecane, n‐hexadecane, n‐heptadecane, n‐octadecane, n‐nonadecane and n‐eicosane) as a function of the temperature and at atmospheric pressure. In all cases, the temperature range investigated included the melting point, hence, in some of the measurements the substance was in the solid state and in some other measurements the substance was in the liquid state. To carry out the thermal conductivity measurements, the transient hot‐wire technique was employed, with an experimental setup specifically designed and built in the Applied Physics I Department (Complutense University). We include a detailed description of the experimental setup, of the analysis and data reduction method, as well as a careful estimation of reproducibility, accuracy and reliability of the experimental data obtained. In our setup, the sample crystallizes inside the measurement cell. Hence, in opposition to some previous investigation in the field, the measurements of the thermal conductivity in solid and in liquid state are performed on exactly the same sample, and using the same method and data reduction procedure. The linear alkanes investigated are the basic components of many Phase Change Materials (PCM), which nowadays are being incorporated in various technological applications in the field of renewable energies, for thermal energy storage and thermal cooling...
This Ph.D. dissertation splits into two parts. In the first one we present high accuracy experimental measurements of the thermal conductivity of even and odd‐numbered n‐alkanes (npentadecane, n‐hexadecane, n‐heptadecane, n‐octadecane, n‐nonadecane and n‐eicosane) as a function of the temperature and at atmospheric pressure. In all cases, the temperature range investigated included the melting point, hence, in some of the measurements the substance was in the solid state and in some other measurements the substance was in the liquid state. To carry out the thermal conductivity measurements, the transient hot‐wire technique was employed, with an experimental setup specifically designed and built in the Applied Physics I Department (Complutense University). We include a detailed description of the experimental setup, of the analysis and data reduction method, as well as a careful estimation of reproducibility, accuracy and reliability of the experimental data obtained. In our setup, the sample crystallizes inside the measurement cell. Hence, in opposition to some previous investigation in the field, the measurements of the thermal conductivity in solid and in liquid state are performed on exactly the same sample, and using the same method and data reduction procedure. The linear alkanes investigated are the basic components of many Phase Change Materials (PCM), which nowadays are being incorporated in various technological applications in the field of renewable energies, for thermal energy storage and thermal cooling...
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Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Física Aplicada I, leída el 30-06-2017