Berge Djebedjian

Water supply and demand and a desalination option for Sinai, Egypt☆

The development of non-conventional water resources in Egypt is a must in order to respond to the continuously increasing demand. The present paper presents the results of an investigation undertaken in order to evaluate technically and economically the installed desalination units in Sinai. The available water resources were evaluated. Forecast study was undertaken in order to evaluate the expected shortage. The future need for desalination units was identified. The main objective of this work is to identify the potential sites for desalination project implementation.

Theoretical investigation on the performance prediction of solar still

A theoretical investigation on the performance prediction of solar still is presented in this paper. A solar still of conventional type is considered. The mathematical model is based on time-averaged Navier-Stokes equations. The effect of the variable fluid properties is taken into consideration by using a mixture of air and vapour in the still. A steady state two-dimensional approach with constant temperature boundaries is considered. A discretization schema with finite-difference technique is adapted. The SIMPLER (Semi-Implicit Method for Pressure-Linked Equations Revised) methodology is used. The grid size independence solution is checked for convergence. The numerical results show clearly different zones of circulation with reverse velocity on the inside still glass cover. The numerical results prove the necessity to undertake a numerical investigation before the sizing of solar still. The objective of the present investigation is to present a mathematical model in order to improve the still design, also the obtained results prove to be a good tool for performance prediction according to a given geometry.

A New Adaptive Penalty Method for Constrained Genetic Algorithm and Its Application to Water Distribution Systems

This paper presents a new adaptive penalty method for genetic algorithms (GA). External penalty functions have been used to convert a constrained optimization problem into an unconstrained problem for GA-based optimization. The success of the genetic algorithm application to the design of water distribution systems depends on the choice of the penalty function. The optimal design of water distribution systems is a constrained non-linear optimization problem. Constraints (for example, the minimum pressure requirements at the nodes) are generally handled within genetic algorithm optimization by introducing a penalty cost function. The optimal solution is found when the pressures at some nodes are close to the minimum required pressure. The goal of an adaptive penalty function is to change the value of the penalty draw-down coefficient during the search allowing exploration of infeasible regions to find optimal building blocks, while preserving the feasibility of the final solution. In this study, a new penalty coefficient strategy is assumed to increase with the total cost at each generation and inversely with the total number of nodes. The application of the computer program to case studies shows that it finds the least cost in a favorable number of function evaluations if not less than that in previous studies and it is computationally much faster when compared with other studies.Copyright

Modeling and Optimization of Potable Water Network

A potable water network hydraulic analysis is presented in this paper. A mathematical model was developed, the model treats looped network. A computer program is developed in order to facilitate water distribution system design, which satisfies all constraints including pipe diameter and nodal pressure. An optimization technique is developed in order to evaluate the optimum network configuration and cost, the parameters are pipe diameter, flow rate, corresponding pressure and hydraulic losses. A non-linear technique was adopted in the solution. The model uses the sequential unconstrained minimization technique (SUMT) of Fiacco and McCormick (1964) to solve the optimal design of network. The adopted optimization technique decreases the required number of design iterations which for example may reach 1.48 billion iterations for a network with 8 pipes and a set of 14 available commercial pipes. The initially assumed pipe diameters are successively adjusted to suit the existing standard commercial pipe diameters. The technique was applied on a simple case study of gravity-fed network. The objective of the present investigation is to present a practical tool to help in the optimization of water distribution system, design and operation.

Advances in Desalination Technologies: Solar Desalination

Availability of freshwater is the prime mover of the human life activities. The advances in desalination technologies clearly show that desalinated water can be used as a substitute for freshwater to be used as potable water. A breakthrough in reverse osmosis costs has been reached, particularly in decreasing energy consumption. The introduction of nanotechnology in the membrane manufacture has resulted in reducing the volume of rejected brine which in turn alleviates the brine disposal issue. Several recent studies show that desalinated water for development of isolated areas is economically competitive to transportation of freshwater by pipeline. The introduction of solar energy to power desalination process has given a new dimension to the expansion of desalination technology. Several studies show the importance of solar desalination in countries suffering from freshwater shortage, particularly in isolated areas. This chapter presents an overview of desalination technologies with emphasis on solar energy-driven units. Some case studies are highlighted. The chapter concludes with a discussion of future avenues in solar desalination.

Reliability-Based Water Network Optimization for Steady State Flow and Water Hammer

The paper presents the reliability-based water network optimization by selecting the optimal pipe diameters for steady state flow and water hammer under hydraulic reliability. Hydraulic reliability is the probability that a water distribution system can supply consumers’ demands over a specified time interval under specified conditions. Thus, hydraulic reliability refers to the basic function of a water distribution system; conveyance of desired water quantities at desired pressures to desired locations at desired times. The evaluation of the hydraulic reliability of a network is achieved through stochastic simulation. In this study, the Monte Carlo simulation is used. The optimization method used in this study is the Genetic Algorithm (GA) which is a popular optimization choice for solving problems that are difficult for traditional deterministic optimization methods. The main advantage of GA is its ability to find the global optimum by using function values only. The GA is integrated with a hydraulic analysis solver, a Monte Carlo simulation program and a transient analysis program to improve the search for the optimal diameters under certain constraints. These include the minimum allowable pressure head constraints at the nodes for the steady state flow and the minimum and maximum allowable pressure head constraints for the water hammer. The approach was applied on a network and the transient flow is introduced to the water system by the pump power failure. The application of GA optimization tool to the case study demonstrates the capability of the Monte Carlo method and the genetic algorithm to find the optimal pipe. The technique of the optimal pipe diameter selection is very economical as the network design can be achieved without using hydraulic devices for water hammer control. This technique is not only crucial for the design and performance of water networks, but also effective in minimizing costs.Copyright

Numerical Investigation on Vortex Shedding Flow Behind a Wedge

The present work is concerned with a numerical investigation of the unsteady two-dimensional incompressible turbulent flow around a 45° wedge inclined at an angle of attack of 45°. The incompressible time-dependent Navier-Stokes equations written in a finite volume formulation with an upwind discretization scheme were used in this study. The numerical solutions of the elliptic partial differential equations have been obtained using the standard k-e turbulence model. The numerical results are compared with available experimental data. The comparison includes the Strouhal number and the distribution of velocities and vorticity in the wake flow. The comparison shows that the Strouhal number, time-averaged streamlines and vorticity pattern agree well with experiments. However, the agreement with the experimental data is less satisfactory for the time-averaged normal velocity profile and root mean square values of fluctuating velocity components.Copyright

Urban Water Management Challenges in Developing Countries: The Middle East and North Africa (MENA)

Accelerated growing population and migration to urban areas in developing countries have resulted in a vital need for the establishment of protected source water and modern, well-maintained drinking-water treatment plants to disseminate potable water to residents. While the challenge in the developed world is mainly to prevent existing infrastructure from decay and to initiate a transition from the disposal-oriented regimes toward more sustainable approaches with a focus on reuse options, the situation is more complex in developing countries. Developing countries suffer from economic problems and are often struggling with insufficient infrastructure and low water supply and sanitation coverage, particularly in rapidly growing urban slum settlements, with significant consequences, especially regarding public health. In this chapter, we discuss the urban water cycle and water consumption, the challenges facing urban water management in developing countries including climate change, the concept of integrated water resources management, and the framework for integrated urban water management in the Middle East and North Africa (MENA) region, including the salient socioeconomic and environmental stresses and trends that will drive and condition water supply and demands over the coming decades. It is concluded that approaches for advanced international and intersectoral cooperation and for identifying and strengthening intellectual and technical resources, tools, lessons, and best practices should be shared, applied, or adapted across the region. Finally, recommendations are made for improved management of water resources in MENA countries.