Heat transfer to Newtonian and non-Newtonian fluids in cross-corrugated chevron-type plate heat exchangers: numerical approach

Food fluids are frequently processed in plate heat exchangers (PHEs) and usually behave as non-Newtonian fluids, this behaviour being scarcely considered for PHEs design purposes. Moreover, many food fluids processed in PHEs have a high viscosity and, therefore, data obtained in laminar flow regime is useful to practical applications. The thermal-hydraulic performance of PHEs is strongly dependent on the physical properties of the fluid and on the geometrical properties of the plates namely, on the corrugation angle and on the channel aspect ratio. The mostly widely used PHEs have corrugations of the chevron type with an area enlargement factor defined as the ratio between the effective plate area and projected plate area close to 1.17. In the present work non-isothermal laminar flows of Newtonian and power-law fluids through cross-corrugated chevron-type plate heat exchangers are studied numerically in terms of the geometry of the channels. The plates area enlargement factor was a typical one (1.17), the corrugation angle varied between 30º and 60º and the flow index behaviour, n, between 0.25 and 1. The numerical calculations were performed using the commercial finite element software package POLYFLOW®. The equations solved were the conservation of mass, momentum and energy equations for laminar incompressible flow of Newtonian and power-law fluids. The simulations were performed using channels containing seven consecutive unitary cells, since thermal and hydraulic fully developed flows were achieved in the fifth or sixth consecutive cell, as described in previous works. Coefficient K from the friction curves fRe = K compares very well with experimental and semi-theoretical data for all (seven) values of corrugation angle. Nusselt number reaches a maximum in the interior of the studied corrugation angle range, for a fixed Reynolds, Re, number. Shear thinning effects greatly affect the thermal-hydraulic performance of the plate heat exchanger

Verification and validation of openInjMoldSim, an open-source solver to model the filling stage of thermoplastic injection molding

In the present study, the simulation of the three-dimensional (3D) non-isothermal, non-Newtonian fluid flow of polymer melts is investigated. In particular, the filling stage of thermoplastic injection molding is numerically studied with a solver implemented in the open-source computational library O p e n F O A M ® . The numerical method is based on a compressible two-phase flow model, developed following a cell-centered unstructured finite volume discretization scheme, combined with a volume-of-fluid (VOF) technique for the interface capturing. Additionally, the Cross-WLF (Williams–Landel–Ferry) model is used to characterize the rheological behavior of the polymer melts, and the modified Tait equation is used as the equation of state. To verify the numerical implementation, the code predictions are first compared with analytical solutions, for a Newtonian fluid flowing through a cylindrical channel. Subsequently, the melt filling process of a non-Newtonian fluid (Cross-WLF) in a rectangular cavity with a cylindrical insert and in a tensile test specimen are studied. The predicted melt flow front interface and fields (pressure, velocity, and temperature) contours are found to be in good agreement with the reference solutions, obtained with the proprietary software M o l d e x 3 D ® . Additionally, the computational effort, measured by the elapsed wall-time of the simulations, is analyzed for both the open-source and proprietary software, and both are found to be similar for the same level of accuracy, when the parallelization capabilities of O p e n F O A M ® are employed.This work is funded by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT (Portuguese Foundation for Science and Technology) under the projects UID-B/05256/2020, UID-P/05256/2020, MOLDPRO-Aproximações multi-escala para moldação por injeção de materiais plásticos (POCI-01-0145-FEDER-016665), and FAMEST-Footwear, Advanced Materials, Equipment’s and Software Technologies (POCI-01-0247-FEDER-024529)

On the simulation of the filling stage of thermoplastic injection molding using the open-source solver openInjMoldSim

NORTE-07-0162-FEDER-000086 and the Minho Advanced Computing Center (MACC) for providing HP

Numerical simulation of the injection moulding filling stage using open-source and proprietary software

Injection moulding is one of the most important processing techniques for thermoplastic materials, and, due to the high competition and product requirements, it demands continuous optimization. In industrial practice, aiming to minimize the resources spent on the design and manufacturing activities, it is common to resort to appropriate computational modelling tools. However, mainly due to the typical high cost of proprietary software, the support of computational modelling tools in injection moulding design related tasks is not available to medium and small sized companies. This framework, and the clear perspective of the benefits brought by computational modelling, has been motivating the development of codes based on open-source codes, as happens with OpenFOAM [1] computational library. This work aims to compare the numerical results obtained by an open-source solver with the ones obtained with the proprietary software Moldex3D [2], widely employed in in dustry. The case of study considered is the filling stage of the injection moulding process of a rectangular cavity for a thermoplastic material modeled with a non-isothermal, inelastic and generalized Newtonian constitutive model.This work is funded by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT - Portuguese Foundation for Science and Technology under the projects UID/CTM/50025/2013 and PTDC/EMS-ENE/3362/2014. The authors would like to acknowledge the Minho University cluster under the project Search-ON2: Revitalization of HPC infrastructure of UMinho (NORTE-07-0162-FEDER-000086), co-funded by the North Portugal Regional Operational Programme (ON.2-0 Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF)

Medial dorsal cutaneous nerve entrapment following inversion ankle sprain

The medial dorsal cutaneous nerve is one of the terminal branches of the superficial peroneal nerve that provides sensory innervation to the dorsum of the foot. It may be prone to injury by direct blow, iatrogenic surgical lesion or in rare situations secondary to ankle sprains. The authors report a case of persistent ankle pain in a female patient caused by a post- traumatic compressive neuropathy of the medial dorsal cutaneous nerve secondary to an ankle sprain which was successfully surgically treated with complete resolution of the symptoms

Viscosity measurements of compressed liquid refrigerant blend R-507A, using a vibrating-wire technique

The refrigerant blend R-507A (50 wt % HFC-143a, 50 wt % HFC-125) is an azeotropic mixture of hydrofluorocarbon refrigerants, 1,1,1-trifluoroethane (HFC-143a) and pentafluoroethane (HFC-125). The paper reports viscosity measurements, performed with a vibrating-wire viscometer, of the refrigerant blend R-507A,at five temperatures in the range (253 to 293) K. The measurements were carried out at pressures from slightly above saturation up to 10 MPa, except for the isotherms at 253.26 K where the maximum pressure was 7.52 MPa and at 263.23 K where the maximum pressure was 7.09 MPa. The overall uncertainty of these measurements is estimated to be ( 1.0 %. The data obtained were correlated by means of a modified hard-sphere based correlation technique. The root-mean-square deviation, rmsd, of the experimental results from the correlation equations is 0.23 %, and their bias is not significant. This correlation method has also been used to interpolate and extrapolate the present results to enable comparisons with measurements performed by other authors of the viscosity of liquid R-507A at different temperatures and pressures

The electroencephalogram in the parkinsonian syndrome

The electroencephalograms of 50 parkinsonian patients with no convulsive antecedents were studied. EEG abnormalities were found in 20 patients (40% of the cases). The incidence of abnormal records was larger in the bilateral parkinsonian syndrome than in the unilateral one (52% and 25%, respectively). Paroxysmal abnormalities characterized mainly by bursts of theta waves were the most frequent ones (65% of the cases). Sharp activity found in the EEG patterns of three patients is emphasized. Alterations of the base rhythm were recorded in 30% of the abnormal EEG cases. The patient's age doesn't seem to have an important role in the genesis of the electroencephalographic abnormalities.Foram estudados os eletrencefalogramas de 50 pacientes parkinsonianos livres de qualquer antecedente convulsivo, sendo registrados traçados anormais em 40% dos casos. A incidência de traçados anormais foi maior na síndrome parkinsoniana bilateral do que na unilateral (52% e 25%, respectivamente). Entre as anormalidades assinaladas foram as paroxísticas as mais freqüentes (65% dos casos), caracterizando-se predominantemente por surtos de ondas teta. O registro de anormalidades paroxísticas do tipo irritativo encontrado em três casos é salientado. Alterações da atividade de base foram assinaladas em 35% dos pacientes. A idade dos pacientes não parece ter tido importante papel na gênese das anormalidades eletrencefalográficas.Escola Paulista de Medicina Departamento de Neurologia e NeurocirurgiaUNIFESP, EPM, Depto. de Neurologia e NeurocirurgiaSciEL

Production of electroactive filaments by coextrusion

The development of new products for i-textiles (interactive textiles) or e-textiles (electronic textiles) applications shows a significant growth in the most recent years due to their huge potential. Although much scientific work has been published in the last years, actual practical applications are still limited. This is due, on one hand, to unsatisfactory state of development of the technology and, on the other, to difficulties on the integration of technologies and methods of the textile and electronic areas. Products for e/i-textiles very often involve the use of sensors, preferably in the form of films, filaments or fibres, due to the inherent easy insertion in the product. For this purpose, electroactive filaments, that benefit from the piezoelectric properties of poly(vinylidene fluoride), PVDF, can be an interesting choice. There aresome works published in the literature related to the development of films with piezoelectric properties [1], that employ PVDF as the electroactive material. However, despite its importance, the manufacture methodologies employed are very difficult to use in industrial scale production. In this work a novel methodology for the production of electroactive filaments, by coextrusion of PVDF and an electrical conductive polymer composite, is proposed and tested. The developed methodology involves a conventional coextrusion line, and can be easily scaled up for industrial massive production. It is shown that The PVDF filament with a conductive PP/carbon black composite core crystallizes in the crystalline phase related just to the temperatures and stretch ratio conditions, independently of the existence of the conductive core: for 80ºC the material crystallizes in the -phase and undergoes increasing to phase transformation for increasing stretch ratios from 1 to 5.FCT- Portuguese Foundation for Science and Technology through the projects PTDC/CTM/69316/2006, NANO/NMed-SD/0156/2007 and PTDC/CTM/108801/2008 and FEDER via FCT, Fundação para a Ciência e Tecnologia, under the POCI 2010 and Pluriannual programs. A.F., P.C. and V. S. thank the FCT grants SFRH/BD/69796/2010, SFRH/BD/64267/2009 and SFRH/BPD/63148/200