Habib Ben Bacha

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.

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.

Contributing to the improvement of the production of solar still

Abstract Solar still can be considered as a promising desalination system to produce distilled water with quality good enough for drinking and irrigation in remote areas due to its simplified design, low maintenance, extended life time, and low capital cost. In addition, among the nonconventional methods to disinfect the polluted water, the solar distillation is considered as one of the most prominent methods. The productivity of the solar still is determined basically by the temperature of water in the basin and the glass temperature. Various active methods have been tested to increase the temperature of the basin, so as to improve the productivity of solar still. In this work, an energy storing material is used in the basin, a flat plate solar collector and a separate condenser are coupled with the solar still to increase the daily productivity by increasing the temperature of the water during the day and to store the hot water excess that would extend water desalination beyond sunset. The models of the...

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...

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’.

Design and analysis of an original multi-bed dehumidifier used for air-conditioning prototype powered by solar energy

This work deals with the mass and heat transfer of water/silica gel in both adsorption and desorption modes. An original dehumidifier system, based on a circular repetition of several silica gel beds, is proposed as a feasible alternative to the classical dehumidifier systems. Thanks to an appropriate working order ensuring an optimal synchronization between different beds, the proposed design permits regularization of the air humidity ratio and air temperature in the outlet of the dehumidifier system. The simulation of adsorption and desorption modes are carried out for one typical bed. Combined mass and energy differential equations are numerically implemented using the finite-volume method in order to simulate the effect of operating conditions on the temporal behavior of both silica gel moisture content, adsorbent temperature, and air humidity ratio. The obtained results are then presented and interpreted. The rise of humid air temperature (in adsorption mode) and its drop (in desorption mode), in return for each 1 g (0.0022 lbm) of adsorbed water vapor and desrobed water, are quantified. The specific heat gained (in adsorption mode) and lost (in desorption mode) by humid air is also evaluated.

Can C-K theory apply to Knowledge-Based Engineering systems?

The aim of this study is to provide a framework for the development of an interactive system for assistance to collaborative design. This framework provides to designers a tool to formalise design knowledge in order to share and reuse the active resources of the design. The study of domain knowledge models was based on a new theory of design known as C-K theory (Hatchuel and Weil, 2002). This theory is based on the distinction between the concept space and the knowledge space in integrated design. It stipulates that design oscillates from one space to another by co-building the product and knowledge which supports it. In this paper, we implement DeSIgn with KnOwledge VERsioning (DISKOVER) knowledge models as an application of the C-K theory operators. Those models are based on three knowledge levels, which are split into a product models (concepts) and design process models, otherwise knowledge that describe the product. The impact of versioning on the instantiation of DISKOVER knowledge models to C-K design theory was also studied in this research.

The Performance of an AGMD Unit Coupled with a Water Solar Collector the Experimental Validation for Desalination of Seawater

Our work consists in presenting the results of an invention for a membrane distillation system coupled to an efficient and robust water solar collector which produces potable water with high quality and a small percentage of brackish discharge independent of salinity of the water source. The air gap membrane distillation (AGMD) model for the modules has been developed. This model is based on mathematical equations that describe the heat and mass transfer mechanisms of a single-stage AGMD process. It can simulate AGMD modules in regimes. The theoretical model was validated using in AGMD under different operating conditions and parameters. The predicted water vapor flux was compared to the flux measured at five different feed water temperatures, two different feed water salinities. The model was then used to study and analyze the parameters that have significant effect on scaling-up the AGMD process such as the effect of increasing the membrane length, and feed and coolant flow rates. The model was also used to analyze the maximum thermal efficiency of the AGMD process

Maintenance policy selection for cellular manufacturing: a simulation study

This paper describes the development of a simulation study to reduce the effect of failure in cellular manufacturing with the use of a maintenance policy. It analyses the effects of corrective, preventive and opportunistic maintenance policies on the performance of a manufacturing cell. We consider the productivity of the cell as performance criteria, and we study the cell performance under different times between failure distributions and different operational conditions. A simulation model was established in Arena simulation software. The results are compared to determine the best policy for a given system.