Numerical simulations of thermal storage systems : emphasis on latent energy storage using phase change materials (PCM)

The present thesis aims at studying the use of phase change materials (PCM) in thermal energy storage (TES) applications and to develop and implement numerical tools for their evaluation. Numerical analysis is nowadays an indispensable tool for the design, evaluation and optimization of thermal equi...

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Autor: Galione Klot, Pedro Andrés
Tipo de recurso: tesis doctoral
Fecha de publicación:2014
País:España
Institución:Universitat Politècnica de Catalunya (UPC)
Repositorio:UPCommons. Portal del coneixement obert de la UPC
Idioma:inglés
OAI Identifier:oai:upcommons.upc.edu:2117/95565
Acceso en línea:https://hdl.handle.net/2117/95565
https://dx.doi.org/10.5821/dissertation-2117-95565
Access Level:acceso abierto
Palabra clave:Dinàmica de fluids computacional
Calor -- Emmagatzematge
Energia tèrmica solar -- Aprofitament
Àrees temàtiques de la UPC::Enginyeria mecànica
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network_acronym_str ES
network_name_str España
repository_id_str
dc.title.none.fl_str_mv Numerical simulations of thermal storage systems : emphasis on latent energy storage using phase change materials (PCM)
title Numerical simulations of thermal storage systems : emphasis on latent energy storage using phase change materials (PCM)
spellingShingle Numerical simulations of thermal storage systems : emphasis on latent energy storage using phase change materials (PCM)
Galione Klot, Pedro Andrés
Dinàmica de fluids computacional
Calor -- Emmagatzematge
Energia tèrmica solar -- Aprofitament
Àrees temàtiques de la UPC::Enginyeria mecànica
title_short Numerical simulations of thermal storage systems : emphasis on latent energy storage using phase change materials (PCM)
title_full Numerical simulations of thermal storage systems : emphasis on latent energy storage using phase change materials (PCM)
title_fullStr Numerical simulations of thermal storage systems : emphasis on latent energy storage using phase change materials (PCM)
title_full_unstemmed Numerical simulations of thermal storage systems : emphasis on latent energy storage using phase change materials (PCM)
title_sort Numerical simulations of thermal storage systems : emphasis on latent energy storage using phase change materials (PCM)
dc.creator.none.fl_str_mv Galione Klot, Pedro Andrés
author Galione Klot, Pedro Andrés
author_facet Galione Klot, Pedro Andrés
author_role author
dc.contributor.none.fl_str_mv Oliva Llena, Asensio
Rigola Serrano, Joaquim
Lehmkuhl Barba, Oriol
dc.subject.none.fl_str_mv Dinàmica de fluids computacional
Calor -- Emmagatzematge
Energia tèrmica solar -- Aprofitament
Àrees temàtiques de la UPC::Enginyeria mecànica
topic Dinàmica de fluids computacional
Calor -- Emmagatzematge
Energia tèrmica solar -- Aprofitament
Àrees temàtiques de la UPC::Enginyeria mecànica
description The present thesis aims at studying the use of phase change materials (PCM) in thermal energy storage (TES) applications and to develop and implement numerical tools for their evaluation. Numerical analysis is nowadays an indispensable tool for the design, evaluation and optimization of thermal equipment, complementing the experimental techniques. Two levels of analysis are carried out, one in the field of Computational Fluid Dynamics, allowing the accurate simulation of the complex heat transfer and fluid dynamics phenomena present in solid-liquid phase change problems; and another one in which the governing equations are treated assuming several suitable simplifications and integrating empirical correlations, intended for the study of whole thermal storage systems throughout several charge/discharge cycles. Furthermore, the specific application of thermal storage in concentrated solar power (CSP) stations is studied. Different single-tank systems, making use of both sensible and latent energy capacities of the materials, are evaluated and compared against the two-tank molten-salt systems used in current CSP plants. Moreover, a new single-tank TES concept which combines the use of solid and PCM filler materials is proposed, with promising results for its utilization in CSP. In chapters 2 and 3, a numerical fixed-grid enthalpy model for the simulation of the solid-liquid phase change is developed. This technique is implemented using the Finite Volume Method in a collocated unstructured domain discretization and using explicit time integration schemes. Issues regarding the form of the energy equation, the treatment of the pressure equation as well as the momentum source-term coefficient introduced by the enthalpy-porosity method, are described in detail in the first chapter. In the second, the possibility of taking into account the variation of the different thermo-physical properties with the temperature is dealt with. Thermal expansion and contraction associated to the phase change are taken into account in the conservation equations and different strategies for the numerical treatment of the energy equation are discussed in detail. Furthermore, simulations of an interesting case of melting of an encapsulated PCM are carried out using two and three-dimensional meshes, and the results are compared against experimental results from the literature. In the next two chapters, the issue of numerically simulating whole single-tank TES systems is developed. These systems are composed of a single tank filled with solid and/or PCM materials, forming a packed bed through which a heat transfer fluid flows. Thermal stratification separates the fluid layers at different temperatures. The zone in which a steep temperature gradient is produced is called "thermocline", and it is desirable to maintain it as narrow as possible in order to keep a high stored exergy. Different designs of single-tank TES systems ¿classified according to the filler material/s used¿ are evaluated for CSP plants. The analysis is performed evaluating different aspects, as the energy effectively stored/released and the efficiency in the use of the theoretical capacity after several charge/discharge cycles, obtaining results independent of the initial thermal state. The operating time is not fixed, but depends on the temperature of the fluid coming out of the tank, limited by the restrictions of the receiving equipment (solar field and power block). Degradation of the stratification is observed to occur after several cycles, due to the temperature restrictions. In this context, a new concept of single-tank TES is presented, which consists of the combination of different layers of solid and PCM filler materials in a suitable manner, resulting in a lower degradation of the thermocline and increasing the use of the theoretical capacity. This concept, called Multi-Layered Solid PCM (MLSPCM), is demonstrated as a promising alternative for its use in CSP plants.
publishDate 2014
dc.date.none.fl_str_mv 2014
2014-12-23
2015
2015-01-12
dc.type.none.fl_str_mv doctoral thesis
http://purl.org/coar/resource_type/c_db06
VoR
http://purl.org/coar/version/c_970fb48d4fbd8a85
dc.type.openaire.fl_str_mv info:eu-repo/semantics/doctoralThesis
format doctoralThesis
dc.identifier.none.fl_str_mv https://hdl.handle.net/2117/95565
https://dx.doi.org/10.5821/dissertation-2117-95565
url https://hdl.handle.net/2117/95565
https://dx.doi.org/10.5821/dissertation-2117-95565
dc.language.none.fl_str_mv Inglés
eng
language_invalid_str_mv Inglés
language eng
dc.rights.none.fl_str_mv open access
http://purl.org/coar/access_right/c_abf2

http://creativecommons.org/licenses/by/3.0/es/
dc.rights.openaire.fl_str_mv info:eu-repo/semantics/openAccess
rights_invalid_str_mv open access
http://purl.org/coar/access_right/c_abf2

http://creativecommons.org/licenses/by/3.0/es/
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv application/pdf
dc.publisher.none.fl_str_mv Universitat Politècnica de Catalunya
publisher.none.fl_str_mv Universitat Politècnica de Catalunya
dc.source.none.fl_str_mv reponame:UPCommons. Portal del coneixement obert de la UPC
instname:Universitat Politècnica de Catalunya (UPC)
instname_str Universitat Politècnica de Catalunya (UPC)
reponame_str UPCommons. Portal del coneixement obert de la UPC
collection UPCommons. Portal del coneixement obert de la UPC
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spelling Numerical simulations of thermal storage systems : emphasis on latent energy storage using phase change materials (PCM)Galione Klot, Pedro AndrésDinàmica de fluids computacionalCalor -- EmmagatzematgeEnergia tèrmica solar -- AprofitamentÀrees temàtiques de la UPC::Enginyeria mecànicaThe present thesis aims at studying the use of phase change materials (PCM) in thermal energy storage (TES) applications and to develop and implement numerical tools for their evaluation. Numerical analysis is nowadays an indispensable tool for the design, evaluation and optimization of thermal equipment, complementing the experimental techniques. Two levels of analysis are carried out, one in the field of Computational Fluid Dynamics, allowing the accurate simulation of the complex heat transfer and fluid dynamics phenomena present in solid-liquid phase change problems; and another one in which the governing equations are treated assuming several suitable simplifications and integrating empirical correlations, intended for the study of whole thermal storage systems throughout several charge/discharge cycles. Furthermore, the specific application of thermal storage in concentrated solar power (CSP) stations is studied. Different single-tank systems, making use of both sensible and latent energy capacities of the materials, are evaluated and compared against the two-tank molten-salt systems used in current CSP plants. Moreover, a new single-tank TES concept which combines the use of solid and PCM filler materials is proposed, with promising results for its utilization in CSP. In chapters 2 and 3, a numerical fixed-grid enthalpy model for the simulation of the solid-liquid phase change is developed. This technique is implemented using the Finite Volume Method in a collocated unstructured domain discretization and using explicit time integration schemes. Issues regarding the form of the energy equation, the treatment of the pressure equation as well as the momentum source-term coefficient introduced by the enthalpy-porosity method, are described in detail in the first chapter. In the second, the possibility of taking into account the variation of the different thermo-physical properties with the temperature is dealt with. Thermal expansion and contraction associated to the phase change are taken into account in the conservation equations and different strategies for the numerical treatment of the energy equation are discussed in detail. Furthermore, simulations of an interesting case of melting of an encapsulated PCM are carried out using two and three-dimensional meshes, and the results are compared against experimental results from the literature. In the next two chapters, the issue of numerically simulating whole single-tank TES systems is developed. These systems are composed of a single tank filled with solid and/or PCM materials, forming a packed bed through which a heat transfer fluid flows. Thermal stratification separates the fluid layers at different temperatures. The zone in which a steep temperature gradient is produced is called "thermocline", and it is desirable to maintain it as narrow as possible in order to keep a high stored exergy. Different designs of single-tank TES systems ¿classified according to the filler material/s used¿ are evaluated for CSP plants. The analysis is performed evaluating different aspects, as the energy effectively stored/released and the efficiency in the use of the theoretical capacity after several charge/discharge cycles, obtaining results independent of the initial thermal state. The operating time is not fixed, but depends on the temperature of the fluid coming out of the tank, limited by the restrictions of the receiving equipment (solar field and power block). Degradation of the stratification is observed to occur after several cycles, due to the temperature restrictions. In this context, a new concept of single-tank TES is presented, which consists of the combination of different layers of solid and PCM filler materials in a suitable manner, resulting in a lower degradation of the thermocline and increasing the use of the theoretical capacity. This concept, called Multi-Layered Solid PCM (MLSPCM), is demonstrated as a promising alternative for its use in CSP plants.Esta tesis se centra en el estudio del uso de materiales de cambio de fase (PCM) en el almacenamiento de energía térmica (TES) y en el desarrollo de herramientas numéricas para su evaluación. El análisis numérico es hoy en día una herramienta indispensable para el diseño, evaluación y optimización de equipos térmicos, complementando las técnicas experimentales. Se realizan dos niveles de análisis, uno en el campo de la dinámica de fluidos computacional, permitiendo la simulación precisa de fenómenos complejos de transferencia de calor y dinámica de fluidos presentes en los problemas de cambio de fase sólido-líquido; y otro en la que las ecuaciones gobernantes son tratadas mediante simplificaciones razonables e integrando correlaciones empíricas, destinado al estudio de sistemas TES en varios ciclos de carga/descarga. Por otra parte, se estudia el almacenamiento térmico para plantas de generación termosolar (CSP). Se evalúan diferentes sistemas de un solo tanque, utilizando tanto las capacidades de energía sensible como latente de los materiales, y se comparan con los sistemas de sales fundidas de doble tanque utilizados actualmente. Además, se propone un concepto novedoso de TES de un único tanque que combina el uso de materiales de relleno sólidos y PCM, con resultados prometedores para su utilización en CSP. En los capítulos 2 y 3, se desarrolla un modelo de entalpía de malla fija para la simulación de la fusión y solidificación. Se utiliza una discretización por volúmenes finitos en mallas no estructuradas en un esquema colocado, y esquemas de integración temporal explícitos. En el primer capítulo, se discuten cuestiones relativas a la forma de la ecuación de energía, el tratamiento de la ecuación de presión, así como el coeficiente de término fuente en la ecuación de momentum introducido por el método de entalpía-porosidad. En el segundo, se trata la posibilidad de tener en cuenta la variación de las propiedades termofísicas con la temperatura. La expansión/contracción térmica asociada al cambio de fase se tiene en cuenta en las ecuaciones de conservación y se tratan en detalle diferentes estrategias para el tratamiento numérico de la ecuación de la energía. Además, se realizan simulaciones de un caso interesante de fusión de un PCM encapsulado, utilizando mallas bi y tridimensionales, y los resultados se comparan con otros de la literatura. En los dos capítulos siguientes, se desarrolla el tema de la simulación numérica de sistemas TES de un único tanque. Estos sistemas están compuestos de un tanque relleno de materiales sólidos y/o PCM, formando un lecho poroso a través del cual circula un fluido de transferencia de calor. La estratificación térmica separa las capas de fluido a diferentes temperaturas. La zona en donde se da el mayor gradiente de temperaturas vertical se conoce generalmente como "termoclina", la cual es deseable mantenerla lo más angosta posible, con el fin de mantener una mayor exergía almacenada. Diferentes diseños de sistemas de un solo tanque -clasificados de acuerdo con el/los material/es de relleno utilizado/s- se evalúan para plantas de CSP. El análisis se realiza evaluando diferentes aspectos, como la energía efectivamente almacenada/liberada y la eficiencia en el uso de la capacidad teórica luego de varios ciclos de carga/descarga, obteniendo resultados independientes del estado térmico inicial. El tiempo de operación no es fijo, sino que depende de la temperatura del fluido de salida, limitada por las restricciones de los equipos que lo reciben (campo solar y bloque de potencia). Se observa una degradación de la estratificación a lo largo de los ciclos debido a las restricciones de temperatura. En este contexto, se presenta concepto de TES novedoso, combinando de diferentes capas de materiales de relleno sólidos y PCM de una manera adecuada. Este concepto, llamado "multi-layered solid-PCM" (MLSPCM) resulta ser una alternativa prometedora para su uso en plantas de CSPUniversitat Politècnica de CatalunyaOliva Llena, AsensioRigola Serrano, JoaquimLehmkuhl Barba, Oriol20142014-12-2320152015-01-12doctoral thesishttp://purl.org/coar/resource_type/c_db06VoRhttp://purl.org/coar/version/c_970fb48d4fbd8a85info:eu-repo/semantics/doctoralThesisapplication/pdfhttps://hdl.handle.net/2117/95565https://dx.doi.org/10.5821/dissertation-2117-95565reponame:UPCommons. Portal del coneixement obert de la UPCinstname:Universitat Politècnica de Catalunya (UPC)Inglésengopen accesshttp://purl.org/coar/access_right/c_abf2http://creativecommons.org/licenses/by/3.0/es/info:eu-repo/semantics/openAccessoai:upcommons.upc.edu:2117/955652026-05-27T15:37:01Z
score 15,301603

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