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  • Numerical Simulation of Multiphase Flows: Level-Set Techniques  Open access

     Balcazar Arciniega, Nestor Vinicio
    Universitat Politècnica de Catalunya
    Theses

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    Ésta tesis se enfoca en el desarrollo de métodos numéricos basados en la aplicación de técnicas level-set para la Simulación Numérica Directa (DNS) de flujos interfaciales y flujos de superficie libre, con el objetivo de ser usados tanto en investigación básica como en aplicaciones industriales.Primero, el método level-set conservativo desarrollado para la captura de interfaces entre dos fluidos, es combinado con un esquema de proyección adaptado para un fluido de densidad variable, con el objetivo de simular flujos de dos fases en mallas no estructuradas. Todas las ecuaciones son discretizadas mediante una aproximación de volúmenes finitos sobre un arreglo de malla colocada. Un esquema de alto orden cuya formulación se basa en el uso de limitadores de flujo, es usado para la discretización de los términos convectivos, mientras que los flujos difusivos son calculados mediante diferencias centradas. Los gradientes son calculados mediante el método de los mínimos cuadrados, en tanto que se asume que las propiedades físicas varían suavemente en una zona estrecha alrededor de la interface con el objetivo de evitar inestabilidades numéricas. La tensión superficial es incorporada mediante el enfoque de la fuerza superficial continua. El método numérico es validado con respecto a los datos experimentales y numéricos reportados en la literatura científica.Segundo, el método level-set conservativo es aplicado en el estudio del flujo de burbujas conducidas por la gravedad. A diferencia de los casos precedentes, se aplica una condición de frontera periódica en la dirección vertical, con el objetivo de simular un canal de longitud infinita. La forma y velocidad terminal de una burbuja ascenciendo en un líquido inicialmente en reposo son calculadas y contrastadas con los resultados reportados en la literatura. Adicionalmente se estudia la interacción hidrodinámica de un par de burbujas para diferentes configuraciones, y finalmente se explora la interacción de un emjambre de burbujas ascendiendo en un canal vertical.En la tercera parte de ésta tesis, se presenta una nueva metodología para la simulación de flujos interfaciales conducidos por la tensión superficial, mediante la combinación de los métodos volume-of-fluid y level-set. La idea principal se basa en usar el método volume-of-fluid para advectar la interface, minimizando las pérdidas de masa, mientras que las propiedades geométricas de la interface se calculan a partir de una función level-set obtenida mediante un algoritmo geométrico iterativo. La propiedades geométricas así calculadas son usadas para el cómputo de la tensión superficial. El método numérico es validado mediante casos bi y tri-dimensionales bien conocidos en la literatura científica. La conservación de la masa es excelente en tanto que la precisión del método es altamente satisfactoria incluso en los casos más complejos.En la cuarta parte de ésta tesis se presenta un nuevo método level-set de múltiples marcadores. Éste método es diseñado para llevar a cabo simulaciones numéricas de partículas de fluido deformables, evitando la coalescencia numérica de las interfaces. Cada partícula de fluido es capturada por una función level-set distinta, así, diferentes interfaces pueden ser resueltas en el mismo volumen de control, evitando la coalescencia artificial y potencialmente no-física de las partículas fluidas. Por lo tanto, las burbujas (o gotas) pueden acercarce y colisionar. El algoritmo es propuesto en el contexto del método level-set conservativo, mientras que la tensión superficial se resuelve mediante una adaptación del enfoque de la fuerza superficial continua. Para su validación, se estudia el impacto conducido por la gravedad de una gota sobre una interface líquido-líquido; luego, se estudia la collisión de dos gotas con salida rebotante, y finalmente el método numérico es aplicado para la simulación de un enjambre de burbujas sin coalescencia numérica.

    This thesis aims at developing numerical methods based on level-set techniques suitable for the direct numerical simulation (DNS) of free surface and interfacial flows, in order to be used on basic research and industrial applications. First, the conservative level-set method for capturing the interface between two fluids is combined with a variable density projection scheme in order to simulate incompressible two-phase flows on unstructured meshes. All equations are discretized by using a finite-volume approximation on a collocated grid arrangement. A high order scheme based on a flux limiter formulation, is adopted for approximating the convective terms, while the diffusive fluxes are centrally differenced. Gradients are computed by the least-squares approach, whereas physical properties are assumed to vary smoothly in a narrow band around the interface to avoid numerical instabilities. Surface tension force is calculated according to the continuous surface force approach. The numerical method is validated against experimental and numerical data reported in the scientific literature. Second, the conservative level-set method is applied to study the gravity-driven bubbly flow. Unlike the cases presented in the first part, a periodic boundary condition is applied in the vertical direction, in order to mimic a channel of infinite length. The shape and terminal velocity of a single bubble which rises in a quiescent liquid are calculated and validated against experimental results reported in the literature. In addition, different initial arrangements of bubble pairs were considered to study its hydrodynamic interaction, and, finally the interaction of multiple bubbles is explored in a periodic vertical duct, allowing their coalescence. In the third part of this thesis, a new methodology is presented for simulation of surface-tension-driven interfacial flows by combining volume-of-fluid with level-set methods. The main idea is to benefit from the advantage of each strategy, which is to minimize mass loss through the volume-of-fluid method, and to keep a fine description of the interface curvature using a level-set function. With the information of the interface given by the volume-of-fluid method, a signed distance function is reconstructed following an iterative geometric algorithm, which is used to compute surface tension force. This numerical method is validated on 2D and 3D test cases well known in the scientific literature. The simulations reveal that numerical schemes afford qualitatively similar results to those obtained by the conservative level-set method. Mass conservation is shown to be excellent, while geometrical accuracy remains satisfactory even for the most complex cases involving topology changes. In the fourth part of the thesis a novel multiple marker level-set method is presented. This method is deployed to perform numerical simulation of deformable fluid particles without numerical coalescence of their interfaces, which is a problem inherent to standard interface tracking methodologies (e.g. level-set and volume of fluid). Each fluid particle is described by a separate level-set function, thus, different interfaces can be solved in the same control volume, avoiding artificial and potentially unphysical coalescence of fluid particles. Therefore, bubbles or droplets are able to approach each other closely, within the size of one grid cell, and can even collide. The proposed algorithm is developed in the context of the conservative levelset method, whereas, surface tension is modeled by the continuous surface force approach. The pressure-velocity coupling is solved by the fractional-step projection method. For validation of the proposed numerical method, the gravity-driven impact of a droplet on a liquid-liquid interface is studied; then, the binary droplet collision with bouncing outcome is examined, and finally, it is applied on simulation of gravity-driven bubbly flow in a vertical column. The study of these cases contributed to shed some light into physics present in bubble and droplet flows.

    Ésta tesis se enfoca en el desarrollo de métodos numéricos basados en la aplicación de técnicas level-set para la Simulación Numérica Directa (DNS) de flujos interfaciales y flujos de superficie libre, con el objetivo de ser usados tanto en investigación básica como en aplicaciones industriales. Primero, el método level-set conservativo desarrollado para la captura de interfaces entre dos fluidos, es combinado con un esquema de proyección adaptado para un fluido de densidad variable, con el objetivo de simular flujos de dos fases en mallas no estructuradas. Todas las ecuaciones son discretizadas mediante una aproximación de volúmenes finitos sobre un arreglo de malla colocada. Un esquema de alto orden cuya formulación se basa en el uso de limitadores de flujo, es usado para la discretización de los términos convectivos, mientras que los flujos difusivos son calculados mediante diferencias centradas. Los gradientes son calculados mediante el método de los mínimos cuadrados, en tanto que se asume que las propiedades físicas varían suavemente en una zona estrecha alrededor de la interface con el objetivo de evitar inestabilidades numéricas. La tensión superficial es incorporada mediante el enfoque de la fuerza superficial continua. El método numérico es validado con respecto a los datos experimentales y numéricos reportados en la literatura científica. Segundo, el método level-set conservativo es aplicado en el estudio del flujo de burbujas conducidas por la gravedad. A diferencia de los casos precedentes, se aplica una condición de frontera periódica en la dirección vertical, con el objetivo de simular un canal de longitud infinita. La forma y velocidad terminal de una burbuja ascenciendo en un líquido inicialmente en reposo son calculadas y contrastadas con los resultados reportados en la literatura. Adicionalmente se estudia la interacción hidrodinámica de un par de burbujas para diferentes configuraciones, y finalmente se explora la interacción de un emjambre de burbujas ascendiendo en un canal vertical. En la tercera parte de ésta tesis, se presenta una nueva metodología para la simulación de flujos interfaciales conducidos por la tensión superficial, mediante la combinación de los métodos volume-of-fluid y level-set. La idea principal se basa en usar el método volume-of-fluid para advectar la interface, minimizando las pérdidas de masa, mientras que las propiedades geométricas de la interface se calculan a partir de una función level-set obtenida mediante un algoritmo geométrico iterativo. La propiedades geométricas así calculadas son usadas para el cómputo de la tensión superficial. El método numérico es validado mediante casos bi y tri-dimensionales bien conocidos en la literatura científica. La conservación de la masa es excelente en tanto que la precisión del método es altamente satisfactoria incluso en los casos más complejos. En la cuarta parte de ésta tesis se presenta un nuevo método level-set de múltiples marcadores. Éste método es diseñado para llevar a cabo simulaciones numéricas de partículas de fluido deformables, evitando la coalescencia numérica de las interfaces. Cada partícula de fluido es capturada por una función level-set distinta, así, diferentes interfaces pueden ser resueltas en el mismo volumen de control, evitando la coalescencia artificial y potencialmente no-física de las partículas fluidas. Por lo tanto, las burbujas (o gotas) pueden acercarce y colisionar. El algoritmo es propuesto en el contexto del método level-set conservativo, mientras que la tensión superficial se resuelve mediante una adaptación del enfoque de la fuerza superficial continua. Para su validación, se estudia el impacto conducido por la gravedad de una gota sobre una interface líquido-líquido; luego, se estudia la collisión de dos gotas con salida rebotante, y finalmente el método numérico es aplicado para la simulación de un enjambre de burbujas sin coalescencia numérica.

  • Numerical modeling and experimental validation of encapsulated PCM thermal energy storage tanks for concentrated solar power plants

     Galione Klot, Pedro Andres; Perez Segarra, Carlos David; Rodriguez Pérez, Ivette Maria; Lehmkuhl Barba, Oriol; Rigola Serrano, Joaquim; Oliva Llena, Asensio
    Eurotherm Seminar
    Presentation's date: 2014-05-29
    Presentation of work at congresses

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    A numerical simulation model of thermal energy storage systems with encapsulated PCM is presented. In previous papers (Galione et al., 2011), the performance of cylindrical containers filled with PCM spheres and liquid fluids occupying the rest of the space was studied. Different charging and discharging processes were not only numerically analyzed, but also experimentally tested. Based on these numerical simulation tools for predicting the thermal and fluid dynamic behavior of these systems, new PCM tanks built in different solid filled materials and encapsulated PCMs combined into multi-layer storage with molted salt as heat transfer fluid are here presented. A virtual prototype proposed is numerically analyzed, while performance behavior is presented under different devices (charging and discharging conditions, PCMs temperatures, and multilayer configurations). The efficiency of these new configurations is also compared against conventional thermocline, showing the better option depending on cases and/or plants proposed.

  • Efficient Fan

     Rigola Serrano, Joaquim
    Competitive project

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  • Centre Tecnològic de Transferència de Calor

     Rigola Serrano, Joaquim; Castro Gonzalez, Jesus; Oliet Casasayas, Carles; Rodriguez Pérez, Ivette Maria; Trias Miquel, Francesc Xavier; Colomer Rey, Guillem; Capdevila Paramio, Roser; Ablanque Mejia, Nicolas; Lehmkuhl Barba, Oriol; Carmona Muñoz, Angel; Sadurni Caballol, Alexandre; Kizildag, Deniz; Giraldez Garcia, Hector; Chiva Segura, Jorge; Baez Vidal, Aleix; Lopez Mas, Joan; Farnos Baulenas, Joan; Torras Ortiz, Santiago; Balcazar Arciniega, Nestor Vinicio; Martinez Valdivieso, Daniel; Jofre Cruanyes, Lluís; Calafell Sandiumenge, Joan; Estruch Perez, Olga; Muela Castro, Jordi; Ventosa Molina, Jordi; Aizpurua Udabe, Imanol; Schillaci, Eugenio; Favre, Federico; Zhang, Hao; Aljure Osorio, David E.; Morales Ruiz, Sergio; Borrell Pol, Ricard; Galione Klot, Pedro Andres; Dabbagh, Firas; Oyarzun Altamirano, Guillermo; Gorobets, Andrei; Oliva Llena, Asensio
    Competitive project

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  • Large eddy simulation model assessment of the turbulent flow through dynamic compressor valves

     Estruch Perez, Olga; Lehmkuhl Barba, Oriol; Rigola Serrano, Joaquim; Oliva Llena, Asensio; Perez Segarra, Carlos David
    International Conference on Compressors and Coolants
    Presentation's date: 2013-09-03
    Presentation of work at congresses

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    The present paper attempts the dynamic simulation of the fluid flow through the valve reed taking into account valve movement due to piston displacement. This work widens previous studies based on numerical experiments with static geometry and constant boundary conditions. Hence, in this work attends the newly in-house implemented CFD and moving mesh coupled code TermoFluids. The CFD solver consists of a three-dimensional explicit finite volume fractional-step algorithm formulated in a second-order, conservative and collocated unstructured grid arrangement. Large eddy simulation is performed to solve the turbulent flow, using the subgrid scale WALE model. A radial basis function interpolation procedure is used to dynamically move the mesh according with the displacement of the valve. A simplified geometry of an axial hole plus a radial diffuser with a piston based inlet condition is considered. The valve dynamics is assumed to be given by a law according modal analysis of valve reed.

  • A new thermocline-PCM thermal storage concept for CSP plants. Numerical analysis and perspectives

     Galione Klot, Pedro Andres; Perez Segarra, Carlos David; Rodriguez Pérez, Ivette Maria; Lehmkuhl Barba, Oriol; Rigola Serrano, Joaquim
    Solar Power and Chemical Energy Systems Conference
    Presentation's date: 2013-09
    Presentation of work at congresses

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    Thermocline storage concept has been considered for more than a decade as a possible solution to reduce the huge cost of the storage system in CSP plants. However, one of the drawbacks of this concept is the decrease in its performance throughout the time. The objective of this paper is to present a new thermocline-PCM storage concept which aims at circumventing this issue. The concept proposed is built of different solid filler materials and encapsulated PCMs combined into a multi-layer storage tank with molten salt as heat transfer fluid. The performance evaluation of each of the prototypes proposed is virtually tested by means of a detailed numerical methodology which considers the heat transfer and fluid dynamics phenomena present in these devices. The virtual tests carried out are designed so as to take into account several charging and discharging cycles until equilibrium is achieved, i.e. the same amount of energy stored in the charging phase is delivered in the discharge. As a result, the dependence of the storage capacity on the PCMs temperatures, the total energy stored/released, as well as the efficiencies of the storing process have been compared for the different thermocline, PCM-only and multi-layered thermocline-PCM configurations. Based on this analysis the selection of the best option for a given case/plant is proposed.

  • A parallel object oriented code framework for numerical simulation of reciprocating compressors - introduction of solid parts modeling

     Lopez Mas, Joan; Rigola Serrano, Joaquim; Lehmkuhl Barba, Oriol; Oliva Llena, Asensio
    International Conference on Compressors and Their Systems
    p. 731-738
    Presentation's date: 2013-09-09
    Presentation of work at congresses

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    A partitioned coupled approach is employed to modeling a reciprocating compressor in a modular way. The approach allows the implementation of an object oriented parallel code framework for simulation of multiphysics systems in general and hermetic reciprocating compressors in particular. Several works in compressor modeling have been presented before. Those works already addressed the resolution of the fluid flow by using this code framework. Now, a new model for simulation of solid components has been developed. In this way the thermal effect of the solid parts on the working fluid can be considered as well. Some numerical results are presented to show first achievements in this research line. © The author(s) and/or their employer(s), 2013.

  • Transient and dynamic numerical simulation of the fluid flow through valves based on large eddy simulation models

     Estruch Perez, Olga; Lehmkuhl Barba, Oriol; Rigola Serrano, Joaquim; Oliva Llena, Asensio; Perez Segarra, Carlos David
    International Conference on Compressors and Their Systems
    p. 577-587
    Presentation's date: 2013-09-09
    Presentation of work at congresses

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    The present paper attempts the dynamic simulation of the fluid flow through valve reed using the in-house implemented CFD and moving mesh coupled code TermoFluids. The CFD solver is based on a parallel, second-order, conservative and unstructured finite volume discretization. Large eddy simulation is performed to solve the turbulent flow, using the subgrid scale WALE model. The moving mesh technique uses RBF interpolation. As a preliminary approach, a simplified geometry of an axial hole plus a radial diffuser with a piston based inlet condition is considered. The valve dynamics is modelled by a specific law according modal analysis of valve reed. © The author(s) and/or their employer(s), 2013.

  • REtrofitting Solutions and Services for the enhancement of Energy Efficiency in Public Edification

     Oliva Llena, Asensio; Oliet Casasayas, Carles; Kizildag, Deniz; Ablanque Mejia, Nicolas; Rigola Serrano, Joaquim
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  • Modelling and experimental validation of the heat accumulator in a Low Trust Cryogenic Propulsion (LTCP) system¿¿e,

     Castro Gonzalez, Jesus; Torras Ortiz, Santiago; Rigola Serrano, Joaquim; Morales, Sergio; Riccius, Jorg; Leiner, Johannes
    European Conference for Aerospace Sciences
    Presentation's date: 2013-07-02
    Presentation of work at congresses

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    The study of one of the components, the heat accumulator, of Low Thrust Cryogenic Propulsion systems (LTCP), is of scientific interest in the framework of ISP-1 project [1]. This device stores thermal energy from the fuel cell that provides electrical energy to the whole system. This thermal energy is employed for the pressurization of the propellant tanks. A numerical model is being developed [2] in order to predict the thermal behaviour of the heat accumulator and having a tool for its design in the next future. The numerical model is validated with experimental results of ISP-1 partners (DLR) [3], [4].

  • Hot run test results of a validation optimized water-ice phase change heat accumulator and comparison to numerical analysis¿X¿¿c

     Riccius, Jorg; Leiner, Johannes; Castro Gonzalez, Jesus; Rigola Serrano, Joaquim
    European Conference for Aerospace Sciences
    Presentation's date: 2013-07-02
    Presentation of work at congresses

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    Phase change heat accumulators are essential devices for the thermal management of multiple ignition, electric pump driven in-space propulsion systems such as the Low Cost Cryogenic Propulsion (LCCP) system [1], [2]. For Low Temperature Accumulators (LTAs), water/ice is of special interest as phase change material because of its high heat capacity and high latent heat. Therefore, an analysis of the phase change behaviour of both, this heat storage material and an heat transfer medium were performed in the framework of the ISP1 project [2], [3]. In the experiments shown in the current paper, gaseous nitrogen at 80°C is injected to the inlet of the heat transfer tube. By passing through the heat transfer tube, it causes the heat storage medium ice to melt and the hot nitrogen is cooled down. The phase change behaviour of the phase change material ice and the heat transfer process from nitrogen to the ice were analysed experimentally in a qualitative and a quantitative way. Finally, the obtained experimental results are compared to the analysis results of theoretical phase-change models carried out by the ISP-1 partner institution UPC [7], [8], [9].

  • Experimental studies of fin-and-tube evaporators for household no-frost refrigerators

     Oliet Casasayas, Carles; Rigola Serrano, Joaquim; Perez Segarra, Carlos David; Sadurní, Alexandre
    World Conference on Experimental Heat Transfer, Fluid Mechanics, and Thermodynamics
    Presentation's date: 2013-06-17
    Presentation of work at congresses

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  • Numerical simulation and experimental validation of sensible heat accumulators oriented to zero energy buildings

     Oliet Casasayas, Carles; Torras Ortiz, Santiago; Lehmkuhl Barba, Oriol; Rigola Serrano, Joaquim
    REHVA World Congress
    Presentation's date: 2013-06
    Presentation of work at congresses

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    The sensible heat accumulation is an efficient and low-cost way of storing thermal energy for its direct or indirect reutilization in typical building processes as space heating and sanitary hot water generation. The authors are developing both numerical and experimental tools for the study and optimisation of this kind of systems, focusing on the analysis of a specific sensible heat accumulator based on a cylindrical tank with an internal coiled pipe. The numerical simulation has been performed using a high-level platform that links two codes to solve the system. The fluid inside the tank is solved with a CFD&HT (Computational Fluid Dynamics & Heat Transfer) software called TermoFluids and the fluid flow inside the pipe is solved considering a quasi-homogenous fully-implicit one-dimensional model, where the governing equations are discretized along the whole tube domain. The resolution of the pipe wall in a detailed way couples both fluid solvers. On the other hand, an experimental infrastructure has been developed for the analysis of the system, which has been instrumented to provide detailed information of its heat storage capacity and temperature map. Several temperature sensors are incorporated in the heat accumulator at different heights and radius inside the tank. For the internal flow, the mass flow rate is measured, as well as the inlet and outlet temperatures. Different internal flow rates and operational temperatures have been studied both numerically and experimentally. From the results obtained it can be said that the device shows interesting heat storage capacities, while the numerical platform shows promising comparison results against the experiments.

  • Numerical simulation tools for energy efficiency in buildings. HAM transfer in facades coupled with CFD models for air distribution

     Mohan Damle, Rashmin; Lehmkuhl Barba, Oriol; Rigola Serrano, Joaquim; Oliva Llena, Asensio
    REHVA World Congress
    Presentation's date: 2013-06
    Presentation of work at congresses

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    Buildings represent a major part of the world energy requirement. The simulation of combined heat, air and moisture (HAM) and pollutant transfer in this context is important to predict the indoor air quality, along with the thermal comfort. Moreover, it is important to have appropriate levels of indoor humidity along with the room temperature as movement of water vapor through the building envelope causes a lot of harm to the building structure and reduces the quality of its thermal insulation leading to higher energy demand. The knowledge of the peak loads, temperatures, humidity levels can help to optimize the building design and therefore results in energy efficient buildings. In this work a modular object-oriented building simulation tool (NEST), capable of coupling different levels of simulation models, allowing the simulation of heat, air, moisture distribution (multizone model, envelope model, room analysis and HVAC system) is presented. The modular approach gives flexibility of choosing a model for each element and to have different levels of modeling for different elements in the system. Special attention has been focused on: the large eddy simulation turbulence models used for the room air dynamics and pollutants distribution transport and high performance parallel software. Parallelization of the building simulation is necessary if some critical processes/zones need to be modeled with more detail for reducing computational time. The main focus of this article is to couple the HAM models for the building envelope with CFD HT models with heat, moisture and pollutant transfer models for room airflow.

  • Máquina de absorción refrigerada por aire

     Oliva Llena, Asensio; Perez Segarra, Carlos David; Rigola Serrano, Joaquim; Castro Gonzalez, Jesus; Oliet Casasayas, Carles; Rodriguez Pérez, Ivette Maria; Lehmkuhl Barba, Oriol; Trias Miquel, Francesc Xavier; Capdevila Paramio, Roser; Alba Queipo, Ramiro; Ordoño Martinez, Manuel Miguel; Farnos Baulenas, Joan
    Date of request: 2013-06-14
    Invention patent

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  • Acumulador de energía térmica en base a materiales de cambio de fase sólido-líquido y método de fabricación de la unidad

     Oliva Llena, Asensio; Perez Segarra, Carlos David; Rigola Serrano, Joaquim; Castro Gonzalez, Jesus; Oliet Casasayas, Carles; Rodriguez Pérez, Ivette Maria; Lehmkuhl Barba, Oriol; Trias Miquel, Francesc Xavier; Capdevila Paramio, Roser; Alba Queipo, Ramiro; Ordoño Martinez, Manuel Miguel; Morales Ruiz, Sergio
    Date of request: 2013-03-01
    Invention patent

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  • Q-00036

     Rigola Serrano, Joaquim
    Competitive project

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  • Q-00035

     Rigola Serrano, Joaquim
    Competitive project

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  • Sistema de almacenamiento de energía térmica combinando material sólido de calor sensible y material de cambio de fase

     Oliva Llena, Asensio; Perez Segarra, Carlos David; Rigola Serrano, Joaquim; Castro Gonzalez, Jesus; Oliet Casasayas, Carles; Rodriguez Pérez, Ivette Maria; Lehmkuhl Barba, Oriol; Trias Miquel, Francesc Xavier; Capdevila Paramio, Roser; Galione Klot, Pedro Andres
    Date of request: 2012-12-27
    Invention patent

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    Un sistema para el almacenamiento y recuperación de energía térmica empleando como medio al menos un material de cambio de fase (sólido-líquido) y un material sólido de calor sensible que se encargan de almacenar/recuperar el calor obtenido desde una fuente externa en forma de calor sensible y calor latente de cambio de fase. Dichos materiales están debidamente contenidos en un único tanque, en cuyo interior existen al menos dos zonas, cada una conteniendo un material diferente, y diferenciadas por el rango de temperaturas a las que son sometidas. La configuración más usada consiste en tres diferentes zonas configuradas al interior del tanque: zona caliente, en la parte superior del tanque, donde un material de cambio de fase encapsulado caracterizado por una temperatura de fusión alta está encerrado; zona fría, ubicada en la parte inferior, donde un material de cambio de fase con baja temperatura de fusión está colocado; y una zona media, que contiene un material sólido de calor sensible.

  • Numerical simulation of incompressible two phase flows by conservative level set method

     Balcazar Arciniega, Nestor Vinicio; Jofre Cruanyes, Lluís; Lehmkuhl Barba, Oriol; Rigola Serrano, Joaquim; Castro Gonzalez, Jesus
    Conference on Modelling Fluid Flow
    p. 665-673
    Presentation's date: 2012-09-04
    Presentation of work at congresses

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  • Solid-liquid phase change with turbulent flow

     Galione Klot, Pedro Andres; Rigola Serrano, Joaquim; Castro Gonzalez, Jesus; Rodriguez Pérez, Ivette Maria
    International Symposium on Turbulence, Heat and Mass Transfer
    p. 871-874
    Presentation's date: 2012-09-26
    Presentation of work at congresses

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    The present paper describes a numerical simulation of the solid-liquid phase change Computational Fluid Dynamics and Heat Transfer (CFD&HT) model developed in order to account for natural convection inside Phase Change Materials (PCMs) taking into account turbulent effects.

  • Numerical Analysis and Experimental Studies of Vapour Compression Refrigerating Systems. Special Emphasis on Different Cycle Configurations  Open access

     Sadurni Caballol, Alexandre
    Department of Heat Engines, Universitat Politècnica de Catalunya
    Theses

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    The aim of this work is to study the thermal behavior and fluid-dynamic systems, vapor compression refrigeration and its components (heat exchangers, expansion devices, compressors, connecting pipes, pumps and pressure vessels). Topics discussed throughout this thesis arise from the growing interest in refrigerants friendly environment as well as different types of cooling systems for vapor compression has motivated the research group of the CTTC (Centre for Heat Transfer Technology ) to carry out major research efforts as well as participate in several projects with national and European institutions. The information contained in this thesis represents a summary of work performed by the author in recent years but also includes many of the contributions made by other members of CTTC. This thesis has led to the publication of several articles in international conferences. The main achievement of this thesis was the development of a numerical tool based on several subroutines flexibility to study different cooling Systemas vapor compression. The entire digital infrastructure has been the result of attaching specific numerical resolutions of each element of the cycle with the overall resolution algorithm. The simulations have been oriented to the study of thermodynamic cycle as well as to study some relevant aspects of the elements. In addition to the numerical results has been carried out important experimental work in the CTTC facilities in order to validate numerical models. The author has been fully involved in the process of data acquisition and has collaborated in the development of the units. The thesis is structured into five chapters plus a final conclusions and future actions. The first chapter, the introduction puts the reader in regard to the problematic situation, the history of cooling and objectives. The second presents the mathematical formulation and numerical methodology used in the simulation of the different elements and all cooling systems. The third study presents the numerical code verification. The fourth focuses on the validation of models with experimental results. And finally the fifth presents a suite of parametric studies and analysis. The numerical simulation code implemented has proven to be a flexible tool as various aspects of the steam compression systems have been successfully simulated and studied. It has also proven a reliable and good level of accuracy as the numerical results have been simulated properly the various experimental data compared.

  • Numerical simulation of wrap scroll temperature for refrigeration and air conditioning compressors

     Rovira Casals, Jordi; Rigola Serrano, Joaquim; Perez Segarra, Carlos David; Oliva Llena, Asensio
    International Compressor Engineering Conference
    p. 1380, 1-1380, 8
    Presentation's date: 2012-07-16
    Presentation of work at congresses

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    Being part of a model which simulates the whole consecutive overall compression process in a scroll compressor by solving equations of mass, momentum and energy balance for fluid refrigerant (Rovira et al. ,2006), an updated version is presented. In this new model, an energy balance over the scroll wraps is implemented; where temperatures and heat fluxes are obtain ed dividing the wall into 36 parts (slices) each turn. The scroll wrap is divided into different solid slices; energy balance is carried out, taking into account: i) conduction along the scroll wrap; ii) convection heat transfer between each slice and each fluid chamber, with special attention on solid slice - fluid chamber contact at each time step. The numerical model shows the one dimensional and transient temperature, pressure and mass flow rate, at each fluid chamber along the scroll compressor, among detailed solid wrap temperature distribution. The whole numerical model has been experimentally validated against experimental data from technical literature (Halm,1997)(Chen et al.,2004a)(Chen et al.,2004b), comparing mass flow rate, discharge temperature, compression work and power consumption. Finally, the influence of wall temperatures and wall heat fluxes on the compressor performance and other output variables is analyzed.

  • Numerical simulation of the turbulent fluid flow through valves based on low mach models

     Rigola Serrano, Joaquim; Lehmkuhl Barba, Oriol; Ventosa Molina, Jordi; Perez Segarra, Carlos David; Oliva Llena, Asensio
    International Compressor Engineering Conference
    p. 1375, 1-1375, 8
    Presentation's date: 2012-07-19
    Presentation of work at congresses

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    The aim of the present paper is to carry out a group of numerical experiments over the fluid flow through the valve reed, using the CFD&HT code TermoFluids, an unstructure d and parallel object-oriented CFD code for accurate and reliable solving of industrial flows (Lehmkuhl, O. et al. 2007 ) with special attention on incompressible hypothesis against low Mach compressible flow modeling, as a critic al numerical aspect depending on Reynolds number and gap thickness conditions. In all studied cases a multi-dimensional explicit finite volume fractional-step based algorithm extended to simulate low Mach fluxes using a Runge-Kutta/Crank-Nicholson time integration scheme, with a symmetry preserving discretization has been used. When turbulence modeling is needed, an extension of the WALE (Wall Adapting Local Eddy-viscosity) (Nicoud, F. and Ducros, F., 1999) model to non-structured meshes is applied. The pressure equation is solved by means of parallel Fourier Schur decomposition solver which is an efficient direct solver for loosely coupled PC clusters (Borrell, R. et al. 2011). In a two dimensional periodic way the fluid flow is approach ed by two parallel phenomena (an entrance flow through a channel and a free jet through a surface). In that sense, the present paper is focused on the numeri cal simulation model of the fluid flow through the valve reeds, considering a simplified geometry of an axial hole plus a radial diffuser. The numerical results presented are based on a specific geome try – valve diameter D is 3 times orifice diameter d, while s/d ratio is 0.6 – considering high Reynolds number at the entrance as boundary condition. The studied cases show the influence from laminar to turbulent flow from incompressible assumption to lower subsonic conditions and/or chocked flow.

  • Parallelization of the coupling between CFD models for airflow and building energy simulation with an object-oriented infrastructure

     Damle, Rashmin; Lehmkuhl Barba, Oriol; Rigola Serrano, Joaquim; Lopez Mas, Joan; Oliva Llena, Asensio
    International High Performance Buildings Conference
    p. 3379, 1-3379, 8
    Presentation's date: 2012-07-18
    Presentation of work at congresses

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    Integrating CFD & HT models with the general building program raises the computational time of building simulations as these simulations are usually performed over a period of one year. Within this context, our aim is to couple a object-oriented modular building program with CFD & HT for airflow and parallelize the simulation with numerous processors for reducing computational time. Also the modular nature of the code will allow to resolve selective critical zones with CFD & HT models while employing simple models for airflow in less critical zones. Thus, there are different levels of modelling different rooms/elements of the building system depending on the requirements of a specific case.

  • Combined heat and moisture transfer in buildings systems

     Damle, Rashmin; Lehmkuhl Barba, Oriol; Rigola Serrano, Joaquim; Oliva Llena, Asensio
    International High Performance Buildings Conference
    p. 3378, 1-3378, 8
    Presentation's date: 2012-07-18
    Presentation of work at congresses

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    Temperature and humidity are the two main parameters indicating the comfort level of the building occupants. Although the effect of temperature is taken into account in thermal simulation of buildings, the moisture transfer through the rooms and porous building walls is sometimes neglected. The level of humidity can give different sensations of thermal comfort. It is necessary to take into account both heat and moisture transport in and around buildings to predict the hygrothermal behavior of rooms and building walls so as to calculate the energy demands correctly. In this work some benchmark exercises are worked out to see the performance of the heat and moisture transfer model implemented for rooms and porous walls. Finally, numerical results are compared with the measured data for a room exposed to varying outdoor conditions.

  • Use of a Low-Mach model on a CFD&HT solver for the elements of an object oriented program to numerically simulate hermetic refrigeration compressors

     Lehmkuhl Barba, Oriol; Rigola Serrano, Joaquim; Lopez Mas, Joan; Perez Segarra, Carlos David
    International Compressor Engineering Conference
    p. 1385, 1-1385, 8
    Presentation's date: 2012-07-19
    Presentation of work at congresses

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    A powerful object oriented approach for the simulation of generic thermal systems (Damle et al., 2008) is used as a framework to numerically simulate the thermal and fluid behavior of hermetic reciprocating compressors. A physical abstraction of the compressor system provides a vertex-edge graph, defining the elements and the neighborhood relations of the system to be solved. Each one of these resulting elements is modeled in order to be solved by itself by giving their respective boundary conditions. Since each element provides its own solver tool, the coupled system can be solved in an integrated form. Into previous works, an unstructured and parallel object oriented Computational Fluid Dynamics and Heat Transfer code (from now on CFD&HT) for accurate and reliable solving of turbulent industrial flow, called TermoFluids (Lehmkuhl et al., 2007), was used to provide with CFD&HT capability the system elements (López et al., 2010). In this work, a Low-Mach based CFD&HT module (Chiva et al., 2011) implemented within the TermoFluids software has been used solve the fluid domain existing inside the shell of a reciprocating compressor, which is identified as one of the compressor elements in the abstraction stage. This improvement allows us to numerically simulate the recirculation flow inside the shell of a reciprocating compressor, providing detailed information about suction area of the compressor and allowing study of new geometric configurations of such part. Furthermore, in comparison with previously tested CFD&HT modules, the Low-Mach model allows better treatment of the compressibility effects generated at the inner elements of the compressor such as chambers, tubes and undoubtedly the compression chamber.

  • Modular simulation of vapour compression systems with an object oriented tool

     Ablanque Mejia, Nicolas; Oliet Casasayas, Carles; Rigola Serrano, Joaquim; Lehmkuhl Barba, Oriol; Perez Segarra, Carlos David
    International Referigeration and Air Conditioning
    p. 2377, 1-2377, 8
    Presentation's date: 2012-07-16
    Presentation of work at congresses

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    The objective of this work is to simulate vapour compression refrigeration systems through a modular approach by means of an object - oriented numerical tool called NEST. For this purpose, the global system is modeled as a collection of different elements which are linked between them. Each element represents a specific part of the system (e.g. heat exchanger, compressor, expansion device, tube, cavity, wall, etc.) and can be independently solved for given boundary conditions. The global resolution procedure is carried out by solving all the elements iteratively, transferring information between them, until a converged solution is reached. The system is easily modified by adding, subtracting or substituting any of its elements. This feature gives great flexibility to the model, not only because the configuration of the system can be clearly altered, but also because the numerical model of any element can be easily replaced allowing different levels of simulation. In this work the object - oriented methodology together with the elements description and their resolution procedures are presented. The model is validated against experimental data obtained from a refrigeration cycle working with isobutane. In addition to this, an illustrative case is presented in order to show the system capabilities.

  • Analysis of refrigerating cycles working with isobutane under transient conditions

     Ablanque Mejia, Nicolas; Rigola Serrano, Joaquim; Oliet Casasayas, Carles; Perez Segarra, Carlos David
    IIR-Gustav Lorentzen Conference on Natural Working Fluids
    p. 1 (928)-8 (935)
    Presentation's date: 2012-06-26
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  • Numerical simulations of energy storage with encapsulated phase change materials. Special emphasis on solid-liquid phase change CFD modelling

     Galione Klot, Pedro Andres; Lehmkuhl Barba, Oriol; Rigola Serrano, Joaquim; Oliva Llena, Asensio; Rodriguez Pérez, Ivette Maria
    International Conference on Energy Storage
    p. 188-189
    Presentation's date: 2012-05-17
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  • A parallel and object-oriented general purpose code for simulation of multiphysics and multiscale systems

     Lehmkuhl Barba, Oriol; Damle, Rashmin; Lopez Mas, Joan; Rigola Serrano, Joaquim
    International Conference on Parallel Computational Fluid Dynamics
    p. 58-59
    Presentation's date: 2012-05-22
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  • Numerical modelling of the phase change material heat accumulator under fast transient gasification conditions in a low thrust cryogenic propulsion (LTCP) system

     Castro Gonzalez, Jesus; Galione Klot, Pedro Andres; Morales Ruiz, Juan José; Lehmkuhl Barba, Oriol; Rigola Serrano, Joaquim; Perez Segarra, Carlos David; Oliva Llena, Asensio
    International Conference on Space Propulsion
    Presentation's date: 2012-05-09
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  • SEILA E2.1.4 Modelo de simulación sistema alternativo

     Rigola Serrano, Joaquim; Oliet Casasayas, Carles; Torras Ortiz, Santiago; Morales Ruiz, Sergio; Galione Klot, Pedro Andres; Sadurni Caballol, Alexandre; Oliva Llena, Asensio
    Date: 2012
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  • SEILA E2.1.5 Resultados estudio del comportamiento térmico

     Rigola Serrano, Joaquim; Oliet Casasayas, Carles; Torras Ortiz, Santiago; Morales Ruiz, Sergio; Galione Klot, Pedro Andres; Sadurni Caballol, Alexandre; Oliva Llena, Asensio
    Date: 2012
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  • SEILA E2.1.6 Resultados de evaluación del sistema de recuperación de energía

     Rigola Serrano, Joaquim; Oliet Casasayas, Carles; Torras Ortiz, Santiago; Morales Ruiz, Sergio; Galione Klot, Pedro Andres; Sadurni Caballol, Alexandre; Oliva Llena, Asensio
    Date: 2012
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  • SEILA E2.1.8 Informe de evaluación de las mejoras en el diseño

     Rigola Serrano, Joaquim; Oliet Casasayas, Carles; Torras Ortiz, Santiago; Morales Ruiz, Sergio; Galione Klot, Pedro Andres; Sadurni Caballol, Alexandre; Oliva Llena, Asensio
    Date: 2012
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  • SIMULACION NUMERICA Y VALIDACION EXPERIMETNAL DE FENOMENOS DE CAMBIO DE FASE LIQUIDO-VAPOR

     Castro Gonzalez, Jesus; Lopez Mas, Joan; Ablanque Mejia, Nicolas; Oliet Casasayas, Carles; Rigola Serrano, Joaquim
    Competitive project

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  • SEILA E2.1.7 Resultados de evaluación del sistema no convencional

     Rigola Serrano, Joaquim; Oliet Casasayas, Carles; Torras Ortiz, Santiago; Morales Ruiz, Sergio; Galione Klot, Pedro Andres; Sadurni Caballol, Alexandre; Oliva Llena, Asensio
    Date: 2012
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  • ISP-1 Deliverable 5.2.3 Modelling optimization

     Castro Gonzalez, Jesus; Perez Segarra, Carlos David; Rigola Serrano, Joaquim; Morales Ruiz, Sergio; Torras Ortiz, Santiago; Rodriguez Pérez, Ivette Maria; Oliva Llena, Asensio
    Date: 2012
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  • Numerical modeling of simultaneous heat and moisture transfer under complex geometry for refrigeration purposes

     Hou, Xiaofei; Rigola Serrano, Joaquim; Lehmkuhl Barba, Oriol; Oliet Casasayas, Carles; Perez Segarra, Carlos David
    European Thermal Sciences Conference
    p. 1-9
    DOI: 10.1088/1742-6596/395/1/012178
    Presentation's date: 2012
    Presentation of work at congresses

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    The aim of the paper is to gain a better insight into heat and moisture transfer in refrigerator and to do fundamental study for water evaporation and condensation in refrigeration application. The governing transport equations (continuity, momentum, energy and concentration equations) in 3D Cartesian coordinates are firstly introduced. As the mixed convection is simulated in the paper, buoyancy forces caused by both temperature and concentration gradient are considered and are also included in momentum equation. Numerical results are carried out by using Termofluids code. The pressure-velocity linkage is solved by means of an explicit finite volume fractional step procedure. In order to validate the code, a humid air flowing in a horizontal 3D rectangular duct case is carried out and compared with the published numerical and experimental results. The contour of temperature and vapor density of air at a cross section is provided and analyzed. Finally, the heat and mass transfer process during the moist air flow through complicated geometry is simulated and temperature and humidity distributions are obtained.

  • Numerical simulation of heat storage for domestic applications

     Lehmkuhl Barba, Oriol; Torras Ortiz, Santiago; Rigola Serrano, Joaquim; Oliva Llena, Asensio
    IIR International Congress of Refrigeration
    p. 1-8
    Presentation's date: 2011-08-21
    Presentation of work at congresses

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    The aim of this work is to perform a high-level numerical simulation platform for heat storage systems with or without phase change materials (PCM). The simulation allows to predict the thermal behavior of the aforementioned systems and to carry out parametric studies in order to find the most appropriate geometry and materials for different operating conditions. The studied storage system here presented is composed by a cylindrical tank and a pipe tube inside the tank. The proposed methodology is based on the numerical simulation of the storage system by means of Computational Fluid Dynamics & Heat Transfer (CFD&HT) software, called TermoFluids, which is used in this work for solving the heat transfer in the fluid flow inside tank. In the case of fluid flow inside pipe, it is solved considering a quasi-homogenous fully-implicit one-dimensional (1D) model, where the governing equations are discretized along the whole tube domain.

  • Transient response in small capacity vapour compression systems. Experimental data and numerical approach

     Ablanque Mejia, Nicolas; Rigola Serrano, Joaquim; Oliet Casasayas, Carles; Perez Segarra, Carlos David
    IIR International Congress of Refrigeration
    p. 1-8
    Presentation's date: 2011-08-21
    Presentation of work at congresses

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    The aim of this work is to introduce a numerical approach to study the transient response of vapour compression refrigerating systems. The emphasis is put on small capacity systems working with R600a (power consumption lower than 1 kW). The proposed method consists in linking all the specific sub-models of the cycle main components (compressor, heat exchangers and expansion device) and transferring adequate information from one to each other until convergence is reached. The model allows to simulate both steadystate and transient conditions. In order to validate the numerical scheme, an experimental facility (specially designed to analyze domestic refrigerators) has been built and used to collect relevant measurements. The work is focused on a specific case considering domestic refrigerating conditions at both steady-state and transient conditions. The numerical steady-state conditions are compared against experimental data, while a detailed transient process is numerically studied.

  • Numerical analysis of no-frost domestic refrigerator evaporators

     Oliet Casasayas, Carles; Perez Segarra, Carlos David; Oliva Llena, Asensio; Rigola Serrano, Joaquim
    IIR International Congress of Refrigeration
    p. 1-8
    Presentation's date: 2011-08-21
    Presentation of work at congresses

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    The air-to-refrigerant evaporator placed in no-frost refrigerators is a critical component because of its simultaneous treatment of both cooler and freezer air streams, which implies a strong drying process on the cooler air flow, and the corresponding intense and non-uniform frost formation process. This paper presents a numerical model developed to analyse fin-and-tube heat exchangers in general and this kind of evaporators in particular. This is a distributed model which gives a very detailed picture of the nonuniform heat exchanger behaviour in terms of heat and mass transfer, considering local effects (frost formation, fin density, in-flow state, etc.). The mathematical formulation and the numerical methodology are presented, showing the model capabilities and level of analysis. Afterwards, illustrative computational results show the potential of the model as a design tool for this application. Validation studies are included in an accompanying paper.

  • Access to the full text
    Numerical simulations of thermal energy storage systems with phase cahnge materials  Open access

     Galione Klot, Pedro Andres; Lehmkuhl Barba, Oriol; Rigola Serrano, Joaquim; Oliva Llena, Asensio; Rodriguez Pérez, Ivette Maria
    ISES Solar World Congress
    p. 1-12
    Presentation's date: 2011-08-29
    Presentation of work at congresses

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    This paper deals with the numerical simulation of thermal energy storage systems with PCM. Numerical simulations are a powerful tool for predicting the thermal behaviour of thermal systems, as well as for optimizing their design. The system under study is a cylindrical container, filled with spheres containing paraffin wax (PCM) and water occupying the space left between the spheres. Two different processes are studied: charging and discharging. In charging mode, hot water coming from the solar field passes through the container, delivering energy to the PCM spheres. In the discharging mode, cold water from supply comes through, extracting the energy previously stored in the PCM and leaving the tank at a higher temperature.

    Postprint (author’s final draft)

  • Analysis of vapour-compression refrigerating systems

     Sadurni Caballol, Alexandre; Oliet Casasayas, Carles; Rigola Serrano, Joaquim; Perez Segarra, Carlos David
    IIR International Congress of Refrigeration
    p. 1-8
    Presentation's date: 2011-08-21
    Presentation of work at congresses

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    The aim of this paper is to show the authors proposal for steady state numerical simulation of Vapour-Compression Refrigerating Systems (dry expansion, liquid overfeed systems, ...). The developed tool allows using different levels of simulation for some elements (compressors, pipes, etc.) as well as the possibility of use different kind of expansion devices. A verification study for a steady state regime is presented analysing also influence of mesh density and of the numerical accuracy. A validation study for steady state regime is shown. Some computational results for steady state regime are also presented to provide an overview of the level of detail given by the model. A set of parametric studies is finally given to evaluate the influence of some boundary conditions (environmental temperature, secondary inlet temperatures, etc.).

  • Numerical resolution in a PCM accumulator in cryogenic conditions

     Morales Ruiz, Sergio; Rigola Serrano, Joaquim; Castro Gonzalez, Jesus; Oliva Llena, Asensio
    IIR International Congress of Refrigeration
    p. 1-8
    Presentation's date: 2011-08-21
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  • Experimental analysis of no-frost domestic refrigerator evaporators

     Oliet Casasayas, Carles; Perez Segarra, Carlos David; Oliva Llena, Asensio; Rigola Serrano, Joaquim
    IIR International Congress of Refrigeration
    p. 1-8
    Presentation's date: 2011-08-21
    Presentation of work at congresses

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    The air-to-refrigerant evaporator placed in no-frost refrigerators is a critical component because of its simultaneous treatment of both cooler and freezer air streams, which implies a strong drying process on the cooler air flow, and the corresponding intense and non-uniform frost formation process. This paper presents a numerical model developed to analyse fin-and-tube heat exchangers in general and this kind of evaporators in particular. This is a distributed model which gives a very detailed picture of the nonuniform heat exchanger behaviour in terms of heat and mass transfer, considering local effects (frost formation, fin density, in-flow state, etc.). The mathematical formulation and the numerical methodology are presented, showing the model capabilities and level of analysis. Afterwards, illustrative computational results show the potential of the model as a design tool for this application. Validation studies are included in an accompanying paper.

  • Numerical resolution of the heat accumulator in a Low Cost Cryogenic Propulsion (LCCP) system

     Morales Ruiz, Sergio; Castro Gonzalez, Jesus; Rigola Serrano, Joaquim; Perez Segarra, Carlos David; Oliva Llena, Asensio
    European Conference for Aerospace Sciences
    p. 1-8
    Presentation's date: 2011-07-08
    Presentation of work at congresses

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  • SEILA E2.1.1 Especificaciones de diseño

     Rigola Serrano, Joaquim; Oliet Casasayas, Carles; Torras Ortiz, Santiago; Morales Ruiz, Sergio; Galione Klot, Pedro Andres; Sadurni Caballol, Alexandre; Oliva Llena, Asensio
    Date: 2011
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  • SEILA E2.1.2 Modelo dinámico

     Rigola Serrano, Joaquim; Oliet Casasayas, Carles; Torras Ortiz, Santiago; Morales Ruiz, Sergio; Galione Klot, Pedro Andres; Sadurni Caballol, Alexandre; Oliva Llena, Asensio
    Date: 2011
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