Measurement errors and uncertainty estimation of an experimental set up using a 2D PIV technique

The study of the flow interaction and the heat transfer between air jets and a surface is of paramount importance in industrial processes that apply multiple air jet impingement. To ensure a good performance of the process, high heat transfer rates and uniformization of the flow over the target plate are required. To perform this analysis, a PIV technique was implemented for the measurement of the velocity fields of the flow. However, as any real experiment, the values recorded by the PIV method are subjected to several errors that compromise the reliability and accuracy of the measurements. These errors can have different sources, from the installation and alignment to the particles seeding and calibration procedure. To determine an interval that contains the measurement error, the uncertainty quantification is crucial. In that sense, this paper focus on the identification of measurement errors and uncertainty quantification of an experimental set up specially built for the analysis of the interaction between a non-isothermal jets and non-flat surfaces moving perpendicularly to the jet axis. To ensure the reliability of the results, preliminary tests were performed to guarantee a uniform and stable flow and to determine the range and conditions of operation. In addition, this work presents an analysis of the system, and the source of errors are identified, quantified and, when possible, corrected. The particle seeding, which consists of olive oil droplets, is characterized and its efficiency for the flow tracking is analysed. The test facility was tested to fully characterize the flow field in terms of mean velocity profile and turbulence intensity over a wide range of Reynolds numbers and temperature. Several velocity fields are then measured until convergence of the flow quantities is reached. The combination of these measurements with high spatial resolution and low measurement errors allow to obtain accurate and precise measurement values.Portuguese Foundation for Science and Technology (FCT) through the Research Grant PD/BD/128216/2016. This work has been supported by FCT within the Project Scope UID/CEC/00319/2019 (ALGORITMI) and Project Scope UID/EMS/04077/2019 (METRICS)

Screening of thermotolerant yeast strains for more sustainable, eco-efficient and competitive industrial fermentations

Financial support is aknowledged to Project ERA-IB “YeastTempTation” (ERA-IB -2-6/0001/2014), and FCT for the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684), RECI/BBB-EBI/0179/2012 (FCOMP -01-0124-FEDER-027462) and BioTecNorte operation (NORTE-01-0145-FEDER-000004). Lallemand Ibéria, SA and Unicer Bebidas, SA are acknowledged for the supply of yeast strainsinfo:eu-repo/semantics/publishedVersio

Assessment of the sustainability of fibre-reinforced concrete by considering both environmental and mechanical properties

The environmental consequences of human activities, e.g., the depletion of non-renewable fuel resources, consumption of natural raw materials, and release of huge amounts of CO2 into the atmosphere, resulted in new challenges in materials engineering. Based on these challenges, building materials must fulfil not only mechanical performance criteria, but also produce the least environmental impact accompanied by their production. In the present study, the possibility of employing scrap tire recycled steel fibres (RSF) as a substitution to industrial steel fibres (ISF) for developing more sustainable fibre-reinforced concretes was explored by adopting a life-cycle approach, integrated both environmental and mechanical properties. Four different fibre-reinforced self-compacting concretes–FRSCCs–were tailored by means of replacing the ISFs partially/totally (i.e., 0%, 50%, 67%, 100% by mass of) with the recycled ones. The effect of applying various dosages of RSFs on mechanical behavior of FRSCC–namely compressive, flexural, and splitting tensile responses–were evaluated experimentally. The environmental impacts associated with the production of each FRSCC were also assessed through life-cycle analysis. The potentiality of the RSFs to be used as concrete reinforcement with a comparable mechanical performance to that of ISF-reinforced concrete and lower environmental footprint was evaluated through a consolidated environmental and mechanical index (EM). In this study, using RSFs instead of industrial fibres for developing FRSCC has provided up to 37% higher EM index. The results confirmed the promising prospects for the application of RSFs in developing more eco-efficient and sustainable reinforced concrete.FOATIDE, reference POCI-01-0145-FEDER-028112, co-financed by the European Regional Development Fund (ERDF), through the Operational Programme for Competitiveness and Internationalization (COMPETE 2020), under Portugal 2020, and by the Fundação para a Ciência e a Tecnologia—FCT (National Agency for Science and Technology). The first author also acknowledges the Scientific Employment funding, No. CEECIND/01627/2017, provided by FCT. The financial support provided by FCT under the project UIDB/04033/2020 is kindly acknowledged by the last author

An exploratory study on the influence of socio-demographic characteristics on water end uses inside buildings

Any strategy of water demand management needs the collaboration of the population involved and so it is important to know how characteristics as residence area, number of residents, presence/absence of children/elders, income level, and educational level, among others, may influence the use of water. Empirical studies that quantify relationship between socio-demographic factors and the water end use patterns inside buildings are still largely lacking. To help to fill this gap this paper gathers information about the characterization of water end use per domestic device in three regions of north of Portugal with different socio-demographic characteristics. The main research goal was to establish indoor water end use patterns per domestic device and to evaluate possible relations between these patterns with the socio-demographic characteristics of the area where the household is, namely the number of residents, the presence/absence of children/elders, the income level and educational level. The washbasin is in average the domestic device with more number of uses in a day (responsible for 34% of the total use), close followed by the kitchen sink (32%), the toilet flush (23%), the bathtub (6%) and finally the dishwasher (3%) and the washing machine (2%). The results found might reflect differences in rural and urban lifestyles once that, with the exception of the kitchen sink, Valpaços is the city that registers the lowest number of uses in the appliances monitored. Significant correlations were found in the following cases: between the residence area and the number of uses in washbasin and in the toilet flush; between the presence of children in the household and the use in the dishwasher; between the income level and the number of uses in the washbasin, in the bathtub, in the washing machine and in the dishwasher

Thermohydrodynamic modelling of journal bearings under varying load angle and negative groove flow rate

The performance of hydrodynamic journal bearings is affected by the conditions under which the lubricant is fed to the bearing gap. Axial grooves are often used and, depending on their location relatively to the load line, they might substantially interfere with the hydrodynamic pressure generation and the thermal behaviour of the bearing. However, many of the existing tools for predicting bearing performance are not able to suitably predict bearing behaviour under varying load angle given the oversimplified way under which they treat lubricant feeding conditions. The present work proposes a detailed Thermohydrodynamic approach which realistically incorporates these conditions into the bearing analysis. Special care is put on the mass and energy-conserving models of the ruptured film region and on a detailed treatment of lubricant mixing within the vicinity of grooves. This includes the first full modelling of the effect of negative flow rate in a groove, a phenomenon originally described experimentally in detail by the authors in previous publications, and which happens for a broad range of load/groove angles. An extensive investigation on the influence of loading direction on the performance of twin groove journal bearings has been performed. This parameter is found to affect deeply all major performance parameters due to the interference of groove regions in the hydrodynamic pressure generation and in the flow rates at each groove.Fundação para a Ciência e a Tecnologia (FCT

Influence des conditions d’alimentation sur l’amélioration des performances et la réduction du frottement dans les paliers

The performance of hydrodynamic journal bearings is significantly affected by the conditions under which the lubricant is fed to the bearing. However, many conventional analyses are not prepared to suitably incorporate these parameters and their effect on bearing performance, due to the over-simplified way they treat them. A thermohydrodynamic analysis suitable for conveniently deal with lubricant feeding conditions is now presented. It couples the numerical solution of the generalized Reynolds equation, the energy equations within the lubricant film and the heat transfer within the bush body. Special attention has been given to the treatment of the phenomena taking place within the grooves and in their vicinity, as well as to the ruptured film region. The effect that lubricant feed pressure and temperature, groove length ratio, groove width ratio and groove number (single / twin) have on bearing performance has been analyzed for a broad range of conditions. The results were found to be in good agreement with experimental published results and the robustness of the model to suitably treat these phenomena has been confirmed. It was found that a careful tuning of the feeding conditions may indeed improve bearing performance.Les performances des paliers lisses hydrodynamiques sont significativement affectées par les conditions dans lesquelles le lubrifiant est introduit dans le palier. Cependant, de nombreuses analyses classiques ne sont pas prêtes à intégrer convenablement ces paramètres et leurs effets sur les performances des paliers, en raison de la façon trop simplifiée avec laquelle ils les traitent. Une analyse thermohydrodynamique appropriée pour traiter convenablement les conditions d'alimentation de lubrifiant est maintenant présenté. Elle intègre la solution numérique simultanée des équations de Reynolds généralisée, de l'énergie dans le film lubrifiant et de la de chaleur dans le coussinet. Une attention particulière a été portée pour le traitement des phénomènes se produisant dans les rainures et dans leur voisinage, ainsi que dans la région de rupture du film. L'influence de la pression et de la température d'alimentation en lubrifiant, de la longueur et largeur de la rainure et du nombre de rainures (simple ou double) sur les performances du palier a été analysée pour un large éventail de conditions. Les résultats numériques obtenus sont en bon accord avec ceux issus de la littérature expérimentale et la robustesse du modèle à traiter convenablement ces phénomènes a pu être confirmée. Il a été constaté qu'un réglage minutieux des conditions d'alimentation peut effectivement améliorer les performances.FCT - POCTI/EME/39202/2001 & Postdoctoral grant SFRH/BPD/89553/201

On the occurrence of negative groove flow rate in twin groove hydrodynamic journal bearings

This paper describes the phenomenon of negative flow rate (hot oil reflux) occurring in one of the grooves of twin axial groove hydrodynamic journal bearings. This rarely described phenomenon, which can occur under severe operating conditions, increases the risk of bearing seizure. Existing codes for predicting bearing behaviour do not seem to be suitably incorporating this phenomenon into the analysis. The present work reports some experimental observations of the phenomenon and the way it can be taken into account in theoretical modelling.FCT - POCTI/39202/EME/2001 & PhD grant SFRH/BD/22278/200