Design of calibrators for extruded profiles. Part I: modelling the thermal interchanges

The parameters influencing the calibration/cooling stage of profile extrusion are discussed, and a numerical finite-volume method code to model the heat transfer is described and validated. For this purpose, the numerical predictions are compared with the analytical solution of a simple problem, with results available in the literature and with those produced by a commercial software. The routines developed are then used to identify the main process parameters and boundary conditions and to estimate their relative importance. The investigation clearly shows the advantages of using several calibrators separated by annealing zones, relative to a single calibrator of the same total length, and the large impact of the contact resistance between extrudate and cooling unit while showing negligible impact of other boundary conditions. A decrease of the extrudate velocity is seen to be also an effective control parameter, but it decreases the production rates

Effect of polymer melt wall slip on the flow balance of profile extrusion dies

This work describes the implementation of the wall slip boundary condition in an in-house developed 3D numerical code based on the Finite Volume Method. For this purpose, several phenomenological models relating the velocity and the shear stress at the wall were implemented. This new feature is verified using a simple case study, by comparing the numerical results with those obtained through the corresponding analytical solution. Then, the potentialities of the new code are illustrated performing flow simulations of a polymer melt in a complex flow channel. The results obtained show that the slip at the wall influences the flow distribution at the die flow channel outlet. Therefore, and to assess the relevance of slippage in the optimal die geometry, the automatic optimization of a die flow channel, required for the production of a specific thermoplastic profile, is performed using both the no-slip and slip boundary conditions, together with two alternative optimization strategies. It is shown that slip favors the flow balance of the dies and also other issues of its performance.The authors gratefully acknowledge funding from Fundação para a Ciência e Tecnologia, FCT (COMPETE Program) under the projects FCOMP-01-0124 - FEDER-010190 (Ref. PTDC / EME - MFE/102729/2008) and FCOMP-01-0124-FEDER-015126 (Refª. FCT PTDC/EME-MFE/113988/2009), and FEDER, via FCT, under the PEst-C/CTM/LA0025/2011 (Strategic Project - LA 25 - 2011-2012)

Neuropsicologia e desnutrição: um estudo com crianças de 7 a 10 anos de idade, em uma comunidade carente

OBJECTIVES: to compare the neuropsychological profile of eutrophic, stunted and chronically malnourished children, and to analyse the role of socio-economic factors on the cognitive development. METHODS: seven to 10 year-old girls and boys from a poor community in São Paulo were evaluated: 27 eutrophyc, 31 stunted and 15 chronically malnourished. Neuropsychological evaluation involved cognitive functions not fully assessed in this population, such as working, declarative and non-declarative memories, attention and executive functions. Socio-economic indicators, maternal mental health and the children's behaviour at school were also evaluated. RESULTS: malnourished children had a lower score on the vocabulary test than the eutrophic and stunted groups (p s<0.05), performed worse in the visuospatial working memory task (p = 0.01), were more anxious than the stunted (p = 0.006), and despite having lower average birth weight than eutrophic children (p = 0.01), only two children as had prenatal malnutrition. Stunted children exhibited no impairment. No differences in socio-economic variables were found among groups. CONCLUSIONS: chronic malnutrition was associated to impairment of expressive speech, visual-spatial short-term memory and increased anxiety. No effects were observed in intellectual abilities, executive functions, verbal working memory, long-term memory, nor in visuoconstructive function. Preservation of the latter cognitive functions can be attributed to adequate environmental conditions and the lack of overall prenatal malnutrition.OBJETIVOS: comparar o perfil neuropsicológico de crianças eutróficas, desnutridas pregressas e crônicas, em idade escolar, e analisar o papel de fatores, socioeconômicas, no seu desenvolvimento cognitivo. MÉTODOS: foram avaliadas crianças de ambos os sexos, 27 eutróficas, 31 desnutridas pregressas e 15 desnutridas crônicas, de 7 a 10 anos de idade, de uma comunidade carente da cidade de São Paulo. A avaliação incluiu funções cognitivas pouco investigadas nessa população; memória operacional, memória declarativa e não-declarativa, atenção e funções executivas. Foram analisados também condições socioeconômicas, saúde mental materna e comportamento na escola. RESULTADOS: as crianças desnutridas crônicas tiveram pior desempenho do que as eutróficas no teste de vocabulário (p s < 0,05) e no teste de memória operacional vísuo-espacial (p = 0,01), mostraram-se mais ansiosas (p = 0,006), somente dois indivíduos tinham desnutrição pré-natal. As crianças desnutridas pregressas não mostraram prejuízos. Nas variáveis socioeconômicas não houve diferenças. CONCLUSÕES: a desnutrição crônica foi relacionada a prejuízo de linguagem expressiva, memória operacional vísuo-espacial e maior ansiedade. Não houve prejuízo de nível intelectual, funções executivas, memória de longo prazo e função vísuo-construtiva. A preservação da maioria das funções cognitivas pode ser atribuída à ausência de desnutrição intra-uterina, e/ou ao fato de que, as crianças vivem em adequado ambiente socio-econômico.Universidade Federal de São Paulo (UNIFESP) Departamento de PsicobiologiaUNIFESP, Depto. de PsicobiologiaSciEL

Viscosity measurements of compressed ionic liquid EMIM OTf

1ª edição do CQE Days, organizada pelo Centro de Química Estrutural, realizada na Academia das Ciências de Lisboa, de 30-31 de maio de 2019 - https://cqe.tecnico.ulisboa.pt/cqedaysIonic liquids have attracted considerable interest in recent years, as they can be used for multiple aims, namely, as antistatic agents, electrolytes, solvents, lubricants, and CO2 absorbents [1]. The use of ionic liquids in industrial processes require their thermophysical properties, in particular, the viscosity and the thermal conductivity. However, transport properties are scarce due to the difficulty of the measurements, particularly at pressures higher than the atmospheric pressure. Our group has developed a programme of measurements aiming at obtaining rigorous results for the viscosity of ionic liquids using the vibrating wire method. This technique, although very accurate for molecular, non-conducting liquids, could have some difficulties with ionic liquids due to their electrical conductivity [2]. As we were planning to use the vibrating wire method in the forced mode of oscillation, the method requires the acquisition of the frequency response of the wire in a range of frequencies containing the velocity resonance for the transverse oscillations of the wire. Therefore, it is important to verify if the ionic liquid sample is a good electrolytic conductor in the range of frequencies that matter for the measurement of viscosity. The problematic of measuring the viscosity of ionic liquids both in general and in particular, using the vibrating wire technique was studied [3]. Pardal et al. [4] have used 1-ethyl-3-methylimidazolium trifluoromethanesulfonate (EMIMOTf) mixed with water as the electrolyte to successfully reduce CO2 at high pressure. The objective of this work is to contribute with viscosity data in the pressure and temperature range of the work performed by those authors. Therefore, we present new ionic viscosity results for temperatures between 298 K and 347 K and pressures up to 50 MPa.N/

Studying the PEG family

1ª edição do CQE Days, organizada pelo Centro de Química Estrutural, realizada na Academia das Ciências de Lisboa, de 30-31 de maio de 2019 - https://cqe.tecnico.ulisboa.pt/cqedaysThe main goal of this line of research is the realisation of experimental measurements of thermophysical properties of a homologous series of ethylene and polyethylene glycols [H(OCH2CH2)nOH], and the development of correlation methods, with an accuracy adequate for the applications. Ethylene glycols and poly (ethylene) glycols (PEG) are widely used in many industrial applications as green solvents and as components of important sustainable processes as they are considered environmentally acceptable compounds [1,2]. Liquid Poly(ethyleneglycols) [PEGs] are in general considered as green solvents. They are non-volatile; their toxicity is very low, such that they are being used as food additives [3]. PEGs have been found to be biodegradable by bacteria in soil or sewage, but the ability of bacteria to biodegrade PEG decreases with increasing molecular weight [3]. The study of this series of compounds is important in many respects, not only because it is aimed at the study of PEGs which have innumerable practical applications but also because this study can be useful to monitor the degree of polymerization in the production of PEGs, themselves. In the present work, the viscosity of three ethylene glycols, namely diethylene, triethylene and tetraethylene glycols [4] and PEG 400 were measured with high accuracy using the vibrating wire technique at moderately high pressures. Complementary experimental density, surface tension and rheological behavior were obtained for the same liquids. One of the aims of the work is to analyse the relation of the present results with those obtained before for CO2 saturated PEG400 mixturesProject UID/QUI/00100/2013 and Project UID/QUI/00100/2019 funded by Fundação para a Ciência e a Tecnologia (FCT), Portugal.N/

Exploratory study on the viscosity of Poly(ethyleneglycols) and their mixtures with CO2

Encontro realizado em Erlangen, a 31 de agosto de 2019.Project UID/QUI/00100/2013 and Project UID/QUI/00100/2019 funded by Fundação para a Ciência e a Tecnologia (FCT), Portugal.N/

Viscosity and density measurements on compressed liquid n-Tetradecane

Comunicação apresentada na "University of Technology", em Graz, Áustria de 3-8 de setembro de 2017FCT - Fundação para a Ciência e Tecnologiainfo:eu-repo/semantics/publishedVersio

Quest for a reference standard for viscosity at high temperatures and high pressures

This communication is dedicated to give notice of the present situation concerning the proposal of tris(2-ethylhexyl) trimellitate (TOTM) to be a reference standard fluid for viscosity at high temperatures and high pressures. This proposal stems from an internal project of the International Association for Transport Properties (IATP). A general overview of the efforts carried out so far by the scientific community towards that objective will be made. This will be complemented by a description of its main characteristics that support its proposal. In particular, the present work is concerned with the determination of the shear dependence of the viscosity of TOTM. Moreover, new results for the density of TOTM at moderately high temperatures and pressures up to 70 MPa are presented.This work was supported by the Strategic Project PEstOE/QUI/UI0100/2013 funded by Fundação para a Ciência e a Tecnologia (FCT, Portugal).N/

On the viscosity and other properties of poly(Ethylene Glycol) 600

Poster da conferência realizada na "University of Technology", em Graz, Áustria de 3-8 de setembro de 2017info:eu-repo/semantics/publishedVersio