Aref Y. Maalej

Experimental validation of the distillation module of a desalination station using the SMCEC principle

This paper presents the simulation and the experimental validation of the distillation module of a desalination unit, currently operating in Sfax, Tunisia. The desalination process is based on the Solar Multiple Condensation Evaporation Cycle (SMCEC) principle.

A methodology to design and predict operation of a solar collector for a solar-powered desalination unit using the SMCEC principle☆

A methodology is proposed to design and predict operation of a solar collector for the desalination unit using the SMCEC principle. The corresponding dynamic model developed from the thermal energy and mass balances is based in the double infinite temperature hypothesis for the fluid and the absorber. This model represents an extension of the one-temperature model presented in a previous paper [1]. Two numerical methods are used for solving the corresponding model. The first method uses the well-known finite difference method, while the second solves the equations by using the functional approximation method. Experimental validation is carried out on the solar collector and the whole desalination unit to determine which of the two methods is most suited for theses studies. The good results confirm that the new theoretical model resolved with the orthogonal collocation method represents better the real behavior of the system and can be used to investigate the effect of various parameters on the performance of the collector and the production of the desalination unit.

The cellular manufacturing paradox: a critical review of simulation studies

Purpose – A number of simulation studies have been conducted previously by several researchers, in order to compare the performance of cellular and functional layouts. The purpose of this paper is to highlight the lack of objectivity of a number of these studies, in order to explain the origin of their conflicting conclusions.Design/methodology/approach – A taxonomy of the main experimental factors and performance measure used in the main simulation comparative studies is followed by a critical assessment of ten of these studies. The analysis is focused on the objectivity of the layout comparison methodologies. Then, the determined shortcomings are categorized and some of them are illustrated by way of simulation.Findings – The revealed shortcomings are most likely responsible for the conflicting conclusions of the studies and may well explain what is called in the literature the “cellular paradox.”Originality/value – This work sets up the basis for an objective comparison methodology between the two manu...

A study of a water desalination station using the SMCEC technique: production optimisation

Following the detailed study of the three modules of the Solar Multiple Condensation Evaporation Cycle (SMCEC)-based desalination unit located in Sfax, Tunisia, it was found necessary to couple the three modules, to simulate the desalination unit operation in an environment close to that of the real process and to develop a regulation scheme that would optimise the desalination production. The developed models were then reduced using the orthogonal collocation method. Based on the reduced models, several cases of numerical simulation of the unit operation have been conducted to monitor the evolution of the unit operation as a function of its command parameters and external perturbations. In this study and for the sake of optimising the desalination unit operation, a global model is developed based on which a regulation algorithm is designed.

Study of a water desalination station using the SMCEC technique: dynamic modelling and simulation

The dynamic modelling and simulation of the three sections of a water desalination facility using the Solar Multiple Condensation Evaporation Cycle (SMCEC) technique are presented. The models are obtained using thermal energy and mass balances of the different sections of the unit. The resulting distributed parametric systems of equations are transformed into a system of ordinary differential equations using the orthogonal collocation method. The parametric study in the dynamic mode and the numerical simulation allow to predict the behaviour of output of each of the three unit sections following variations in the internal signals and external perturbations.

Labor and machine sizing through a Simulation-Expert-System-based Approach

This work presents the development of an enhanced version of the Simulation-Expert-System-based Approach (SESA) previously used to solve the manufacturing system (MS) machine sizing problem. The SESA is improved by considering operator sizing along with machine sizing. The proposed approach consists in coupling an expert system (ES) with a simulation tool. The main performance measures considered in this work are related to the manufacturing orders due dates. Accordingly, labor resources are now implemented in the MS simulation model and ES reasoning mechanism is adjusted in order to optimise both machine and operator quantities. Finally, an illustrative example showed the potential benefits of the approach enhancements through the enrichment of both simulation model and the expert system reasoning mechanism.

Analysis of cellular manufacturing systems in the presence of machine breakdowns

Purpose – The aim of this paper is to illustrate a solution that can be used to reduce the severity of breakdowns and improve performances in the cellular manufacturing (CM) system with unreliable machines.Design/methodology/approach – The performance of CM system is conditioned by disruptive events, such as the failure of machines, which randomly occurs and penalizes the performance of the cells, seriously disturbing the smooth working of the factory. To overcome the problem caused by the breakdowns, the authors develop a solution, based on the principle of virtual cell and the notion of intercellular transfer that can improve the availability of the system. In this context, the use an analytical method based on Markov chains to model the availability of the cell. The results are validated using simulation.Findings – The proposed solution in this paper confirmed that it is possible to reduce the severity of breakdowns in the CM system and improve the availability of the cells through an intercellular tra...

A simulation‐expert‐system‐based approach for machine sizing of production systems

Purpose – The purpose of this research is to focus on the solution of the resource sizing problem for production systems (PSs), defined as the specification of the number of each type of resources to be used in a production process for a given time period.Design/methodology/approach – The resource sizing problem is tackled by a simulation‐expert‐system‐based approach, coupling an expert system (ES) with a simulation tool. Hence, a number of “simulation – ES optimization” cycles are realized until obtaining non‐improvable levels of performance. The main performance measures considered in this work are related to the manufacturing orders due dates (DD).Findings – Through the approach proposed in this work, it is possible to size machines in order to optimize DD related performance measures for a PS belonging to a specific application domain. PSs of this domain are characterized by a functional layout and feature no labor constraints. In addition, machines belonging to a same department are considered to be ...

Domain knowledge versioning and aggregation mechanisms in product design processes

In the context of concurrent engineering and routine design, this study consists in the first step of structuring knowledge models. In the second step, it deals with the development of a method that puts in emergence the collaboration of actors involved in a design process. This aims to dynamically build a project library that traces the history of engineering process and capitalizes knowledge related to the product. The crucial part of this article studies domain knowledge versioning and aggregation mechanisms after modifications made by actors during the design process. We propose, to mitigate these problems, a mechanism that allows expressing and managing knowledge version’s evolution strategies. The validation of the suggested approach was through its application on the design of car air-conditioners and the development of a prototype of knowledge processing tool named ‘DISKOVER’.

Comparing functional and cellular layouts using simulation and Taguchi method

Purpose – A number of simulation studies were conducted by several researchers in order to compare performances of cellular and functional layouts. The methodologies used by these studies either present several objectivity lacks or are highly time‐consuming. The purpose of this paper is to propose a novel and objective methodology, based on the coupling of simulation and the Taguchi method.Design/methodology/approach – Simulation models for both layouts are first developed. Simulations are then conducted following a standard Taguchi orthogonal array. Subsequently, the obtained results are analyzed using the analysis of variance technique. Finally, a mathematical model is built, and validated by the confirmation test.Findings – The proposed comparison method permitted to obtain a valid mathematical model used to predict the superiority rank of the two layouts within the scope of the paper.Originality/value – This paper presents a novel objective methodology for comparing functional and cellular layouts.