Defense University Center

Naval Academy, Spain

Defense University Center

Naval Academy, Spain
Time filter
Source Type

Valenca J.,University of Lisbon | Jalio E.,University of Lisbon | Puente I.,Defense University Center | Gonzalez-Jorge H.,University of Vigo
IABSE Congress Stockholm, 2016: Challenges in Design and Construction of an Innovative and Sustainable Built Environment | Year: 2016

Assessing and monitoring the structural behaviour of concrete bridges is fundamental to define maintenance strategies and to decide interventions. Therefore, crack identification and characterization plays an extremely important role. However, current evaluation techniques are work-intensive and prone to human error. In this context, the development of automatic methods based on image processing and laser scanning, for assessing and monitoring cracks in concrete bridges, shows important benefits. Besides the aforementioned limitations, current methods also require the use of extremely expensive inspection platforms, such as underbridge trucks. In this paper, a new method, herein named 'MCrack-TLS', is proposed, for automatically detecting and monitoring cracks in concrete bridges, based on image processing and laser scanning. The application of MCrack-TLS to a real structure, performed in the scope of the validation phase, is also included, the latter being a concrete viaduct of the IC2 road in Rio Maior, Portugal. Results prove the viability of MCrack-TLS and its advantages compared to traditional methods, such as increased productivity and reduced exposure of bridge inspectors to risky situations.

Cacabelos A.,Defense University Center | Eguia P.,University of Vigo | Febrero L.,University of Vigo | Granada E.,University of Vigo
Energy and Buildings | Year: 2017

Calibration of a Building Energy Model (BEM) is necessary to reduce the discrepancies between the simulation results and real data. This research work proposes a novel ground-breaking calibration methodology that divides the entire building into different sub-models and calibrates them separately to obtain an accurate model. To validate this new procedure, a public library Heating, Ventilation and Air Conditioning (HVAC) system with a Ground-Source Heat Pump (GSHP) and a Radiant Floor (RF) was simulated and calibrated using TRNSYS and GenOpt. The results demonstrated that this new multi-stage procedure met the ASHRAE standards and achieved better results than those obtained with a global calibration. The Mean Bias Error (MBE) and the Coefficient of Variation of the Root Mean Square Error (CV(RMSE)) of the hourly temperature data were reduced below −3.74% and 6.03% respectively, involving an improvement of approximately 50% over typical global calibration methods. © 2017 Elsevier B.V.

Ulloa C.,Defense University Center | Arce M.E.,Defense University Center | Rey G.,Defense University Center | Miguez J.L.,University of Vigo | Hernandez J.,Armada Espanola
Energies | Year: 2017

It is thought that there are 14 million standardised sea containers out of order, equal to 23.3 million twenty-foot equivalent unit (TEU), which could be devoted for other purposes. The COR-TEN® steel containers are the best, due to the features of the materials, to be used in applications intended for the accommodation of people. One of the uses is framed in the area of humanitarian help, as service modules in areas of social emergency. Moreover, the deployment of these kinds of modules is quite simple, as the Army is generally able to transport containers in its units. In this project we have selected three typologies of service modules and we have designed modules based on sea containers which can fit into these typologies. The container chosen to be recycled is the 1 TEU, to which the closings and divisions are defined, which must reflect the different typologies of the service modules chosen. Afterwards, a study of thermal charges is carried out on three different settings of service modules located in five locations spread in different climate areas. Throughout a thermal simulation in Trnsys® (V17, Thermal Energy System Specialists, LLC, Madison, WI, USA), the consumption and maximum demand of heat and cold are analysed. Based on these results, the best equipment to cover the energy demand of the modules analysed in this study could be chosen. Moreover, the results can be used to estimate the operational costs of the deployment of the modules. © 2017 by the authors. Licensee MDPI.

Rey G.,Defense University Center | Ulloa C.,Defense University Center | Miguez J.L.,University of Vigo | Cacabelos A.,Defense University Center
Energies | Year: 2016

Tri-generation plants will have an important role in the near future in the residential sector where heating and cooling demands come into play throughout the year. Depending on the building's location, the characteristics of its enclosure and its use, the thermal loads and demands will be different. This article analyses and compares a combined cooling, heating and power (CCHP) system tested in the laboratory and a single household located in Spain. The cooling capacity is obtained using a reversible heat pump where the compressor is driven directly by a gas engine with internal combustion engine (ICE) technology. The tests were carried out in a work bench at three different operating speeds. A variable-speed model is developed in the TRNSYS simulation environment with an operating strategy following the thermal load (FTL). Once the micro-CCHP system was modeled with experimental data and validated, it was dynamically simulated to analyze its performance in different climatic zones defined in the Spanish "Código Técnico de la Edificación" (CTE). This study reveals that the micro-CCHP system is suitable in mild weathers during the summer season. © 2016 by the authors; licensee MDPI.

Porteiro J.,University of Vigo | Miguez J.L.,University of Vigo | Crespo B.,University of Vigo | De Lara J.,Technical University of Madrid | Pousada J.M.,Defense University Center
Materials | Year: 2016

Advantages, such as thermal storage improvement, are found when using PCMs (Phase Change Materials) in storage tanks. The inclusion of three different types of materials in a 60 ℓ test tank is studied. Two test methodologies were developed, and four tests were performed following each methodology. A thermal analysis is performed to check the thermal properties of each PCM. The distributions of the water temperatures inside the test tanks are evaluated by installing four Pt-100 sensors at different heights. A temperature recovery is observed after exposing the test tank to an energy demand. An energetic analysis that takes into account the energy due to the water temperature, the energy due to the PCM and the thermal loss to the ambient environment is also presented. The percentage of each PCM that remains in the liquid state after the energy demand is obtained. © 2016 by the authors.

Rey G.,Defense University Center | Ulloa C.,Defense University Center | Miguez J.L.,University of Vigo | Arce E.,Defense University Center
Energies | Year: 2016

Micro combined heating and power (micro-CHP) systems are becoming more than important, and even essential, if we pretend to take full advantage of available energy. The efficiency of this kind of systems reaches 90% and important savings in energy transport processes can occur. In this research, an internal combustion engine (ICE)-based micro-CHP system was developed and tested under specific constraints. The system uses a two cylinder Otto engine as prime mover, coupled to an electrical alternator, and it uses exhaust gases and engine cooling circuit heat. The micro-CHP system was developed to match the electrical power of a typical Stirling engine (SE)-based micro-CHP unit, in order to later compare both systems' performance under similar circumstances. Different operating modes were tested under different engine speeds, in order to find the optimum operating point. A stand-alone portable application of this system was performed using recreational sailing boats as mobile homes. Specific considerations had to be taken, related to boundary conditions with sea water, and a transient simulation was performed, considering the boat under three different European climates. Results were compared for the different locations and the performance of the equipment shown. A comparative study with the SE-based micro-CHP system performance was done, and a sensitivity analysis of the influence of the battery size was carried out under the same conditions. The SE and ICE-based proposed micro-CHP system have similar behavior, except for the differences found due to the electric/thermal power ratios in both systems. Battery bank size sensitivity analysis reflects a limit in performance improvement. This limit is caused by the uniform distribution of electrical demand profile. © 2016 by the authors.

Gomez M.A.,Defense University Center | Porteiro J.,University of Vigo | de la Cuesta D.,University of Vigo | Patino D.,University of Vigo | Miguez J.L.,University of Vigo
Fuel | Year: 2016

This paper presents a transient model for the simulation of biomass combustion in a fixed bed boiler fed through particle drop. The method combines classical CFD techniques, which are used to simulate the gas phase, with a set of Eulerian variables defined to model the solid phase and Lagrangian trajectories that model the particle drop. Several submodels are implemented to simulate the numerous processes that occur during the combustion of the solid phase. These submodels include the thermal conversion of biomass, heat and mass transfer, particle shrinkage and bed compaction as well as the interaction of the DPM (Discrete Phase Model) trajectories and the bed variables. The predictions are contrasted with various experimental tests, which provide reasonably good results and demonstrate the overall good behavior of the models. The simulation facilitates an understanding of the heat transfer inside the boiler and the instability of the emission measurements. © 2015 Elsevier Ltd

Gomez M.A.,Defense University Center | Porteiro J.,University of Vigo | Patino D.,University of Vigo | Miguez J.L.,University of Vigo
Energy Conversion and Management | Year: 2015

This paper describes a transient model for biomass combustion in a fixed bed boiler. This method implements several submodels which address a variety of conversion processes and interactions between solid and gas phases. A set of Eulerian variables will be defined representing the solid phase state as well as the governing equation model for both the evolution and the thermal conversion of the bed. The solid phase components including the ash content is divided into solid and volatile elements. The fuel feeding is modelled by an advective flux term in the transport equations of the solid phase variables. The advective flux term includes a treatment that prevents the numerical diffusion beyond the bed's surface. This method also includes heat and mass transfer models between phases, particle and bed shrinkage, porous media and gas reactions. Several experimental tests have been simulated to contrast model behaviour. The primary variable profiles of the solid phase in the bed and gas phase in the furnace have been analysed. The results show reasonably good predictions for the exchanged heat and the flue gas concentrations. © 2015 Elsevier Ltd. All rights reserved.

Suarez-Garcia A.,Defense University Center | Alfonsin V.,Defense University Center | Urrejola S.,Defense University Center | Sanchez A.,University of Vigo
Journal of Power Sources | Year: 2015

This paper describes the mathematical parametrization of an electrodynamical battery model using different model selection criteria. A good modeling technique is needed by the battery management units in order to increase battery lifetime. The elements of battery models can be mathematically parametrized to enhance their implementation in simulation environments. In this work, the best mathematical parametrizations are selected using three model selection criteria: the coefficient of determination (R2), the Akaike Information Criterion (AIC) and the Bayes Information Criterion (BIC). The R2 criterion only takes into account the error of the mathematical parametrizations, whereas AIC and BIC consider complexity. A commercial 40 Ah lithium iron phosphate (LiFePO4) battery is modeled and then simulated for contrasting. The OpenModelica open-source modeling and simulation environment is used for doing the battery simulations. The mean percent error of the simulations is 0.0985% for the models parametrized with R2, 0.2300% for the AIC ones, and 0.3756% for the BIC ones. As expected, the R2 selected the most precise, complex and slowest mathematical parametrizations. The AIC criterion chose parametrizations with similar accuracy, but simpler and faster than the R2 ones. © 2015 Elsevier B.V.

Prego F.J.,University of Vigo | Solla M.,Defense University Center | Nunez-Nieto X.,Defense University Center | Arias P.,University of Vigo
Journal of Construction Engineering and Management | Year: 2016

Ground-penetrating radar (GPR) has proved to be a valuable method for tunneling quality management and evaluation. The research literature includes many successful works addressing the use of this technique with the aim to detect the existence of internal pathologies and anomalies. However, most of them have been carried out on tunnels in operation. In these situations, the identification of inner elements and possible damage has been severely limited due to a shallower rebar mesh that complicates the radar data interpretation process. Therefore, this paper presents the evaluation of an excavated high-speed railway tunnel during the early stages of construction instead of considering a finished one. The purpose of the study was to demonstrate the potential of this method when applied during these first critical phases. The results provided noteworthy information: namely, thickness of the gunite layer, lining voids and delamination, moisture problems, and the presence of reinforcing in the tunnel lining. All this information may be useful for civil engineers when they must make a decision on maintenance and prevention tasks. © 2015 American Society of Civil Engineers.

Loading Defense University Center collaborators
Loading Defense University Center collaborators