Description of the idealized bed roughness effects on tracer transport in water flumes by applying the strange attractor multifractal analysis

River hydrodynamicsTurbulent open channel flow and transport phenomen

Thermal characterisation of a heat exchanger

[Resumen] La optimización y control de los sistemas de calefacción instalados en vehículos de transporte público son fundamentales para garantizar el confort térmico de los pasajeros. Esto es debido a las diversas condiciones de funcionamiento en las que operan, las restricciones impuestas por normativas contra emisiones en los vehículos de combustión y el impacto en la autonomía de los vehículos eléctricos. En este trabajo se presenta la caracterización térmica de un intercambiador de calor compacto de flujo cruzado aire-agua de tubo plano con aletas que forma parte del sistema de climatización de un autobús real. Se propone un modelo de caja gris de parámetros concentrados que se ha ajustado utilizando datos obtenidos de una campaña de ensayos que abarca 226 puntos de trabajo, incluyendo las condiciones nominales del sistema de calefacción real. Este modelo simplificado permitirá el desarrollo e implementación de nuevas estrategias de control de calefacción en estos vehículos.[Abstract] The optimization and control of heating systems installed in public transport vehicles are essential to ensure passenger thermal comfort. This is due to the diverse operating conditions they experience, the emissions regulations imposed on combustion vehicles, and the impact on the range of electric vehicles. This work presents the thermal characterization of a compact crossflow air-water heat exchanger with flat tubes and fins, which is part of a real coach's heating system. A lumped parameter greybox model is proposed and adjusted using data obtained from a test campaign comprising 226 operating points, including the nominal conditions of the actual heating system. This model will enable the development and implementation of new heating control strategies in these vehicles.Junta de Andalucía; P18-TP-2040Ministerio de Ciencia e Innovación;TED2021-130373B-I0

Thermal model of a heating system for public transport vehicles

[Resumen] En este trabajo se describe el modelo térmico de un sistema de calefacción para vehículos de transporte público, en concreto de autobuses. El modelo se compone de varios subsistemas. Por un lado, el habitáculo del vehículo, dividido en dos zonas térmicas (cabina de conductor y zona de pasajeros), así como la unidad de climatización de pasajeros, que han sido ajustados con datos obtenidos en ensayos realizados en autobuses reales. Por otra parte, el subsistema de la unidad de central de climatización de conductor se ha parametrizado con datos extraídos de ensayos realizados en una planta experimental. Este modelo térmico presenta una gran flexibilidad, permitiendo estudiar el comportamiento transitorio y estacionario del sistema de calefacción para diferentes condiciones de trabajo. El modelo contempla diversos parámetros, tales como la irradiancia solar incidente, el número de pasajeros, la temperatura exterior o la temperatura del motor, entre otros. Se muestra la validación del modelo con los datos extraídos de un ensayo en un autobús real.[Abstract] In this work, a thermal model of a heating system for public transport vehicles, specifically coaches, is described. The model is made up of several subsystems. On the one hand, the vehicle interior, which is divided into two thermal zones (driver cabin and passengers area), and the passenger HVAC unit, which have been adjusted with data obtained from tests carried out on a real bus and, on the other hand, the driver HVAC unit, characterized with data collected from tests carried out in an experimental plant for testing coach heating systems. This thermal model presents great flexibility, allowing to study both the transient and stationary behaviours of the heating system for different operating conditions. Several disturbances are considered, such as the incident solar irradiance, the number of passengers, the outside temperature or the engine temperature, among others. The validation of the model with data collected from an experimental test carried out in a real bus is also shown.Los autores agradecen la financiación del proyecto P18-TP-2040, concedida por la Consejería de Transformación Económica, Industria, Conocimiento y Universidades de la Junta de Andalucía y por la empresa Hispacold (grupo Irizar).Junta de Andalucía; P18-TP-204

Improving graph-based detection of singular events for photochemical smog agents

Recently, a set of graph-based tools have been introduced for the identification of singular events of O3, NO2 and temperature time series, as well as description of their dynamics. These are based on the use of the Visibility Graphs (VG). In this work, an improvement of the original approach is proposed, being called Upside-Down Visibility Graph (UDVG). It adds the possibility of investigating the singular lowest episodes, instead of the highest. Results confirm the applicability of the new method for describing the multifractal nature of the underlying O3, NO2, and temperature. Asymmetries in the NO2 degree distribution are observed, possibly due to the interaction with different chemicals. Furthermore, a comparison of VG and UDVG has been performed and the outcomes show that they describe opposite subsets of the time series (low and high values) as expected. The combination of the results from the two networks is proposed and evaluated, with the aim of obtaining all the information at once. It turns out to be a more complete tool for singularity detection in photochemical time series, which could be a valuable asset for future research