Lígia Maria Ribeiro

The dynamic behaviour of liquid-liquid agitated dispersions—I. The hydrodynamics

Abstract This paper develops a new numerical algorithm for the hydrodynamics of liquid-liquid systems with simultaneous coalescence and break-up. The algorithm is precise and fast in the computation of the transient behaviour of single continuous or batch stirred vessels, requiring computing times compatible with its use in control applications. The Coulaloglou-Tavlarides drop interaction model is used, and the predictions obtained for the asymptotic steady state are compared with those obtained for the same conditions by Guimaraes, both by moment-generating functions and by a Monte-Carlo (Bastenaires point) technique, with an agreement better than 0.2%; those two previous algorithms, however, are not applicable to dynamic conditions. Although in the two case studies discussed herein the Coulaloglou-Tavlarides interaction model is used, the new algorithm accommodates virtually any other models or equations describing drop interaction. The algorithm has also been extended to the simulation of mass transfer, thus being the first potentially able to predict the full trivariate behaviour of liquid-liquid dispersions in transient, dynamic, conditions, within reasonably short computation times.

The dynamic behaviour of liquid-liquid agitated dispersions—II. Coupled hydrodynamics and mass transfer

This paper extends the algorithm previously developed by the authors (Ribeiro et al., Comp. Chem. Engng 19, 333, 1995b) to the simulation of the full trivariate (drop volume, age and solute concentration) unsteady-state behaviour of interacting liquid-liquid dispersions, in continuous or batch stirred vessels. The algorithm uses Coulaloglou and Tavlarides (1977) drop interaction model, but it may easily accommodate any alternative models. Both rigid and oscillating drop mass transfer behaviour have been tested. The procedure enables to simulate in detail all relevant aspects of the dynamics of interacting dispersions in mass transfer conditions, namely the gradual approach to steady-state and the response to pulse and step changes in the main process variables. The algorithms speed is high, allowing to envisage its future application in the control of mass transfer contacting equipment, with only modest computer resources.

Numerical modelling of a gravity settler in dynamic conditions

An iterative numerical technique has been developed to simulate in detail the dynamics of a shallow-layer gravity settler. Currently acknowledged models apply only to specific equipments at steady-state and laboratory scale [Jeelani SAK, Hartland S. The continuous separation of liquid/liquid dispersions. Chem Eng Sci 1993;48(2):239-54]. To our knowledge, no study has ever addressed the dynamic simulation of a gravity settler. In this paper a direct numerical technique is presented for computing the thickness and drop-size composition of the dispersion band formed in a shallow-layer settler under steady-state and transient conditions. This technique is an extension for the settler of the one used on the stirred vessel by Ribeiro [Ribeiro LM. Simulacao Dinamica de Sistemas Liquido-Liquido, Um novo Algoritmo com Potencialidades de Aplicacao em Controlo. PhD thesis, Universidade do Minho, Portugal; 1995].

Numerical simulation of liquid-liquid agitated dispersions on the VAX 6520/VP

Abstract This work began as a study of the implementation of a liquid-liquid hydrodynamic and mass transfer simulation algorithm on the VAX 6000 model 520 vector processor. A scalar code developed by Riberio et al. 3 has proved adequate and accurate to describe the transient and the limiting hydrodynamic steady-state, either of a continuous or of a batch liquid-liquid contactor; it also may be extended to predict the mass transfer performance of this type of system. Using this pre-existing FORTRAN code, we describe some techniques for modifying it in order to take advantage of the VAX 6000 vector architecture. The main thrust of this investigation is to identify the characteristics of the VAX vector processor that affect performance, and to show how that performance information can be used to build optimized algorithms. The nature of the modifications made to the algorithm and their effect on the overall computation time are reported for two types of changes: scalar optimization and vectorization.

How the FEUP Removal to the New Premises Was Facilitated by the Internal Information System

Since 1996 that FEUP possesses an information system (SiFEUP) that was developed mainly to record the information on the school’s activity concerning teaching and learning, research and development as well as for school management. The system has been built in-house and has nowadays more than 30 integrated modules that are enabling the modernization of many processes and services providing simultaneously decision support facilities. In this work we will show how this system was a key tool to organise the logistics of the Faculty removal to new premises, namely its importance for minimizing the impact on the users resulting from the change to completely new infrastructures. 1 Presentation of the Engineering Faculty and its environment Descending from the Polytechnic Academy, created in 1837, the Faculty of Engineering of the University of Porto (FEUP) is presently a prestigious public institution concerning the teaching and research of Engineering. The Engineering Faculty is the biggest of all the faculties that belong to the Porto University. It has almost six thousand students, four hundred professors, more than a half with a PhD, and two hundred staff. The University of Porto, is itself the biggest in Portugal, with approximately 25 000 students. FEUP presents a departmental structure, composed of six areas, Civil Engineering, Chemical Engineering, Electrical Engineering and Computers, Mechanical Engineering and Industrial Management, Mining Engineering, Metallurgical Engineering and Materials. To support the activities of these departments and of the Faculty as a whole there are several central services, including the Computer Centre, the Library, the Academic and Staff, the Economic and Financial, the Continuous Education and Development, the Public Relations and Image and the Technical and Maintenance Support services. FEUP offers eight undergraduate courses, 23 MSc degree courses and 8 areas for PhD studies, as well as other specialized post-graduate courses. Besides teaching the FEUP is currently involved in more than a hundred research projects, many of these on an international basis and in co-operation with industry. Since the year 1937 until September 2000, the Engineering Faculty occupied a location in the centre of the Porto city, with around 30 000 m, where several adapted buildings housed the departments, services and R&D institutes. Figure 1. SiFEUP: information about the Faculty map On September 2000, the Faculty moved to a new location, in the city periphery. This new location almost triplicates the available area. The different departments and services occupy 12 main buildings, as shown in Figure 1. The covered area is now about 90.000 m, where lecture rooms and offices occupy each 17.000 m and laboratories 41.300 m. This was probably the biggest and most complex move that occurred in town for many years. One of the many aspects of the move that has been particularly demanding was the maintenance of the users connectivity to the network and computing services. Since 1988 the Engineering Faculty possesses a local data network. It has been built as a shared 10Mbps Ethernet network and upgraded to a switched 10Mbps Ethernet technology in 1995. Just before the removal to the new premises the number of nodes connected to this infrastructure was around 2 500. In the new location, the local area network is a completely different infrastructure incorporating ATM OC-12/OC-3 technology, respectively in the core and in the backbone, and offering switched 100BASE-TX to the users, at the access level. If necessary, it can also offer ATM to designated users. The number of active access points is this infrastructure is 6000 and about 3500 nodes are presently connected. These nodes comprise central clusters of UNIX/Linux and NT servers, plus several departmental NT and Linux servers, and more than 500 microcomputers in 30 general computer labs. The library has also about 100 desktop computers for the students and many others are available at the departmental laboratories. The ratio student/computer is better than 5. The FEUP LAN, that we call FEUPNet, is connected to the national scientific communication network (RCTS) by a 2Mbps link. The Faculty always promoted the use of the computing environment. All the students are allowed to use the network and computing resources since the first year of their undergraduate programmes. They also have full access to the Internet, as well as all the other elements of the academic community. Almost every professor, technician or administrative staffs has a personal computer connected to the FEUPNet. FEUP offers teleworking facilities and presently near 2000 students and staff use traditional analogue telephone lines and ISDN to connect to the FEUP Access Server and access the resources available to do remote work. As the network and its computing and information resources are used on a daily basis, it was necessary to guarantee the users connectivity to the main services during the removal period and no more than a 24h interruption was acceptable. Because the removal of the Faculty was scheduled to occur in less than two months, the connectivity to the network and access to the servers should be available to the users that were already at the new premises as well as to the users that were waiting to move, at the old buildings. We will show in this work that the internal Information System (SiFEUP) has been a key factor to make the removal of the whole Faculty feasible in an especially short interval. It helped on minimizing the impact on the users and permitted the new academic year to start normally, with just two weeks of delay. The initiative of creating an integrated campus wide information system belonged to the faculty direction board, in 1996 [1]. Its strong commitment with the project was essential to make it possible, as the different departments and R&D units within FEUP have large freedom in managing their resources and thus a high level influence is necessary to push towards the development of such a system. The main goal of the SiFEUP has been to enable faster access and dissemination of scholar, scientific, technical and other info-resources, stimulating a stronger collaboration among members of our academic community. A second, but equally important goal, has been the possibility to increase the connection and the interaction with other higher education institutions and with industries, especially in the northern region of Portugal. Before the removal, the information system already included about 30 modules covering aspects ranging from the school infrastructures and the academic and staff records, to the course plans, scientific productivity or the external assessment processes [2, 3]. 2 Planning the removal

A Parallel Algorithm for the Simulation of the Dynamic Behaviour of Liquid-Liquid Agitated Columns

Simulation of the dynamic behaviour of liquid-liquid systems is of prominent importance in many industrial fields. Algorithms for fast and reliable simulation of single stirred vessels and extraction columns have already been published by some of the present authors. In this work, we propose a methodology to develop a parallel version of a previously validated sequential algorithm, for the simulation of a liquid-liquid Kuhni column. We also discuss the algorithm implementation in a distributed memory parallel-computing environment, using MPI. Despite the difficulties encountered to preserve efficiency in the case of a heterogeneous cluster, the results demonstrate performance improvements that clearly indicate that the approach followed may be successfully extended to allow real-time plant control applications.

Lab4Act: Laboratories for Active Learning Spaces

Having recognized the need for a national digital asset management infrastructure, SRCE – University of Zagreb University Computing Centre in assoc

The U.Porto e-learning café: Learning spaces and the path of self education

In the European Higher Education Area “learning” is a key word as well as individual responsibility and engagement with self education. Universities are facing demanding challenges mainly due to the rising of life-long-learning needs, to significant cuts on public budgets and to strong pressures to achieve increasing levels of excellence both in education and research. In a globalized society where information and communication technologies (ICT) play a major role, employers require that college graduates be excellent in communication and in the use of information, be able to think creatively, innovate, cooperate and compete across borders. At the University of Porto (U.Porto) we believe that the spatial configuration of learning spaces and the facilities and initiatives they accommodate may be rather important to provide effective environments for learning and mingling, motivating students to become more knowledgeable and equipped with the interdisciplinary and high level skills the 21st century society requires. In these contexts information technologies are important tools for creating and promoting innovative students environments.