32 research outputs found

    Numerical simulation of heat transfer and fluid flow in a flat plate solar collector with TIM and ventilation channel

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    Flat plate solar collector with plastic transparent insulation materials and ventilation channel as overheating protection system inserted between the absorber and the back insulation has been studied numerically. First, a general object-oriented unsteady model of this solar collector is developed and presented. It allows solving, in parallel way, every component separately and interacting with its neighbors to set the boundary conditions in every time step of the simulation. Every component can be simulated using its own mesh and the number of CPUs necessary (depending on the simulation level needed). Second, the numerical simulations of the fluid flow and heat transfer by natural convection in the bottom part (ventilation channel) and the upper part (air gap + TIM) of the collector are done separately. The simulation has taken into account the different operation modes of the channel (opened at high operation temperatures and closed in normal operations). A three dimensional parallel turbulent CFD model based on Large Eddy Simulation is used in the simulations. The obtained numerical results are validated with experimental and benchmark results found in the literature.Peer ReviewedPostprint (published version

    On the feasibility of affordable high-fidelity CFD simulations for indoor environment design and control

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    Computational fluid dynamics (CFD) is a reliable tool for indoor environmental applications. However, accurate CFD simulations require large computational resources, whereas significant cost reduction can lead to unreliable results. The high cost prevents CFD from becoming the primary tool for indoor environmental simulations. Nonetheless, the growth in computational power and advances in numerical algorithms provide an opportunity to use accurate and yet affordable CFD. The objective of this study is to analyze the feasibility of fast, affordable, and high-fidelity CFD simulations for indoor environment design and control using ordinary office computers. We analyze two representative test cases, which imitate common indoor airflow configurations, on a wide range of different turbulence models and discretizations methods, to meet the requirements for the computational cost, run-time, and accuracy. We consider statistically steady-state simulations for indoor environment design and transient simulations for control. Among studied turbulence models, the no-model and large-eddy simulation with staggered discretizations show the best performance. We conclude that high-fidelity CFD simulations on office computers are too slow to be used as a primary tool for indoor environment design and control. Taking into account different laws of computer growth prediction, we estimate the feasibility of high-fidelity CFD on office computers for these applications for the next decadesThis work is supported by the Ministerio de Econom√≠a y Competitividad, Spain [ENE2017-88697-R]. N. Morozova is supported by the by the Ministerio de Econom√≠a y Competitividad, Spain [FPU16/06333 predoctoral contract]. Part of the calculations was performed on the MareNostrum 4 supercomputer at the Barcelona Supercomputing Center [RES project I-2019-2-0021]. The authors thankfully acknowledge these institutions. The authors would also like to thank our colleague MSc Xavier √Ālvarez Farr√© for the productive discussions.Peer ReviewedPostprint (author's final draft

    MAGICA project: development of a Multi-frequency Automotive GNSS Integrated Cost effective Antenna

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    The present work describes the Multi-frequency Automotive GNSS Integrated Cost-effective Antenna (MAGICA) project and the first results. This is a two years project that started in August 2020 under the sponsorship of the European GNSS Agency (GSA) and within the framework of Fundamental Elements. The main objective of the project is to go beyond the state of the art. For the first time, it will provide a cost-effective high precision positioning antenna providing multi-frequency (L1/E1, L5/E5a/E5b & E6), multi-constellation (Galileo, GPS, BeiDou & GLONASS) characteristics, and phase stability as the most relevant performance features. Moreover, the antenna will be commercially ready to be integrated into a vehicle for Autonomous Driving operation. The proposed antenna will increase the number of frequency bands that are offered to the GNSS receivers of the vehicles today. It will include the E6 band of Galileo, providing, in this manner, not only more accurate but also safer positioning due to the authentication service.Peer ReviewedPostprint (published version

    EXPERIMENTACIO EN ENGINYERIA QUIMICA 1 (Examen 2n Quadr.)

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    A comprehensive simulation tool for adsorption-based solar-cooled buildings. Control strategy based on variable cycle duration

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    Adsorption cooling systems (ACS) may contribute towards a sustainable way of satisfying the increasing cooling demand, as they utilize solar thermal energy and employ non-ozone-depleting substances. Apart from the intrinsic ACS performance, the successfulness of its operation depends on its integration within the entire thermal system (solar collectors, thermal storage and building), which is not straight-forward due to thermal inertia effects and its inherent cyclic operation. Numerical simulations can contribute in understanding the system behavior, its adequate dimensioning and the implementation of optimized control strategies. A computational model was developed, capable of performing conjugate, dynamic simulations of the entire thermal system. The influence of the control criteria is investigated and quantified through three simulation phases, conducted for various solar collectors areas and storage volumes. Higher solar fraction is achieved for lower auxiliary heater activation temperature and lower temperature difference activation of the solar pump. Subsequently, simulations with variable cycle duration were performed, using optimized cycle duration according to the instantaneous operating temperatures. This approach reduces significantly the auxiliary consumption or satifies the demand with less solar collectors. The potential CO2 emissions avoidance is calculated between 28.1-90.7% with respect to four scenarios of electricity-driven systems of different performance and CO2 emission intensity.Peer ReviewedPostprint (author's final draft

    Three dimensional numerical simulations of combined conduction and radiation in transparent insulation material

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    A coupled radiative and conductive three dimensional numerical model of transparent insulation material (TIM) is presented and the simulation results are compared with experimental results found in the literature. Since the studied TIM structure has the form of honeycomb that consists of a cellular array of repetitive nature, we considered a single isolated cell with opaque and adiabatic walls. The combined radiation and conduction heat transfer across the isolated cell is treated by solving the energy equation coupled to the radiative transfer equation (RTE). For the resolution of the RTE, the Finite Volume Method is used. The boundary conditions for the intensity of radiation are considered as diffusely emitting, specularly reflecting opaque surfaces. The detailed simulation of the TIM cells allows to obtain simplified correlations of the heat losses through the TIM that then will be introduced into a general model of flat plate solar collector with TIM.Peer ReviewedPostprint (published version

    Numerical and experimental study of a flat plate solar collector with transparent insulation and overheating protection system

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    In this paper a FPSC with TIM and an overheating protection system is investigated numerically and experimentally. The studied collector has been manufactured using a process similar to that of the conventional FPSC but by inserting a honeycomb TIM glued under the glass cover. The designed overheating protection system consists of a ventilation channel inserted between the absorber and the back insulation and has a thermally actuated door which opens when it reaches a specific temperature and remains closed otherwise. This system is designed to protect the collector when reaching stagnation conditions while preserving good performances during normal operations.Peer Reviewe
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