Kamal El-Nahhas | Mansoura University (original) (raw)

Papers by Kamal El-Nahhas

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One of the most important practical problems in non-Newtonian fluids flowing in pipes is the reli... more One of the most important practical problems in non-Newtonian fluids flowing in pipes is the reliable prediction of the pressure drop accompanying the flow. For laminar flow, this problem is well established as the relation between the pressure drop and mean velocity can be derived by integration of the representative rheological model. However, the prediction of the pressure losses in the turbulent regime is still requiring more theoretical and practical analysis. The analysis in this paper has been focused on the observed phenomena that the turbulent flow behaviour appears unrelated to the laminar rheological characteristics and it could be found similar to Newtonian turbulent flow behaviour. The aim of study in this paper is to find a theoretical approach that could match the experimentally investigated turbulent flow behavior of non-Newtonian slurries flowing in pipes. The suggested approach is based on the similarity of non-Newtonian turbulent flow behaviour with that of Newtonian one. Dependence of turbulent flow behaviour on the laminar rheological characteristics and also will be discussed. So, the experimental measurements of kaolin slurries at different concentrations have been analyzed and compared with the suggested approach.

The properties of slurries mainly depend on the tendency of the particles to settle out from the ... more The properties of slurries mainly depend on the tendency of the particles to settle out from the carrying liquid. The motion of particles under the influence of gravity is characterized by initial acceleration after which descent continues at the free-fall or terminal velocity. The extent to which the particles will be free to settle in horizontal flow depends on the terminal velocity, the turbulence within the liquid tending to support the particles and particle-particle interaction. The aim of study is experimentally investigate the flow behaviour of coarse-particle settling slurries with an attention to energy consumption analysis.

Optimizing water treatment plant operation is a concept should be applied to all plants because s... more Optimizing water treatment plant operation is a concept should be applied to all plants because some operational improvements can always be made. Optimization at a water treatment plant can be considered achieved when certain goals are being met to attain the most efficient use of the water treatment plant facilities. The most important goals are to reduce the water wastes, manage the energy consumption and achieve the chemical cost performance that means the chemical cost for obtaining an aimed treatment effect. Understanding and control of the physicochemical nature of water and colloidal suspensions play an important rule to obtain several goals for optimization. One of these optimization goals for the plant operation is the colloids removal improvement with economic coagulant dosing. This could be achieved by studying all parameters affecting particle-to-particle interaction. Taking these parameters into consideration can help to optimize the coagulant dosing required to remove ...

Separation of suspended and colloidal materials from water and wastewater by settlement is one of... more Separation of suspended and colloidal materials from water and wastewater by settlement is one of the most widely used process in water and wastewater treatment. Hydraulic retention time is a main parameter for design and optimization of any water treatment tank or reactor. Determination of the retention time distribution at all different locations within the tank gives information about the possibility of presence of dead zones or and short circuits. The presence of dead zones decrease the effective volume of the tanks that may almost result in a short circuit between the inlet and outlet of the tank. some part of the flow exits the tank without spending the retention time required for settling. On the other hand, it also induces high turbulence intensity in other regions, which not only decreases the possibility of particle aggregation and deposition, but may also causes solids re-stabilization. A uniform flow field is essential to increase the efficient performance of settling ta...

A drinking water treatment plant produces large quantities of residuals as a result of treatment ... more A drinking water treatment plant produces large quantities of residuals as a result of treatment processes such as clarification, filtration and powdered activated carbon adsorption. Generated residuals mainly include suspended solids removed from raw water, chemical precipitates created by the treatment process and carrier water. Recently, more stringent regulatory changes have caused dramatic changes in the handling of residuals from water treatment plants. Limitations have been placed on the ability of drinking water treatment plants to discharge residuals to sanitary sewers or natural waterways. So, the impact of regulations has placed a greater careful consideration on the on-site treatment of these residuals. The treatment, transportation and disposal of the sludge make up a major fraction of the total water treatment costs. The purpose of sludge treatment is to receive and concentrate these residuals and dispose of them. Residuals in liquid form may be pumped through pipeline...

Natural surface water contains a wide range of impurities, mostly arising from weathering and hum... more Natural surface water contains a wide range of impurities, mostly arising from weathering and human activities. The availability of safe water, and in particular safe drinking water, is one of the most important determinants of our general health. The removal of suspended matter from water is one of the major goals of drinking water treatment. Effective clarification is really necessary for completely reliable disinfection because microorganisms are shielded by particles in the water. Coagulation, flocculation and clarification, followed by rapid gravity sand filtration, are the main steps in conventional water treatment systems. Colloidal particles and other finely divided matter are brought together and agglomerated to form larger size particles that can subsequently be removed in a more efficient fashion. The increase in the contact mass increases the probability that collisions will take place inside the flocculator resulting in a more efficient flocculation. Therefore, the intentional introduction of preformed floc or sludge into the mixing and flocculation stage is a feature of most proprietary water treatment equipment. The aim of study is to explore the wealth of literature to present the new trends of the conventional drinking water treatment that is continuously evolving, especially clarification enhancement and acceleration by solids contact increase. The study will experimentally demonstrate the possibility of turbidity removal enhancement, by increasing the contact mass with adding a sludge dosage during flocculation process. The raw water turbidity removal was investigated under conditions that the destabilized colloids and sludge dosage are mixed during flocculation process. This will simulate the actual condition in which the performed sludge is recycled from the clarifier bottom to the flocculation zone by submersible pumps mainly for sludge blanket establishment.

* Ph.D., Suez Canal Authority, Egypt, E-mail: k_elnahhas@yahoo.com ** Professor, Faculty of Engin... more * Ph.D., Suez Canal Authority, Egypt, E-mail: k_elnahhas@yahoo.com ** Professor, Faculty of Engineering, Mansoura University, Egypt E-mail: mrayan@mans.edu.eg *** Professor, Faculty of Engineering, Suez Canal University, Port Said, Egypt E-mail: iaelsawf@hotmail.com

The effective design, control and safe operation of a slurry hydraulic transport system require t... more The effective design, control and safe operation of a slurry hydraulic transport system require the successful prediction of slurry flow behavior in the pipeline. Slurry flow behavior is not only dependent on the properties of both solids and carrier, but also it is strongly affected by mutual particle-particle and particle liquid interaction. To decrease specific power consumption and increase overall the transport system efficiency, the carrying capacity should be increased. Particle size distribution plays an important rule to obtain higher concentrated slurries and higher carrying capacity. Therefore, economic advantage can be gained by adjusting particle size distribution. The aim of study is experimentally investigate the effect of solids size distribution on the flow behavior and pressure frictional losses of settling slurries flowing in pipes. Measurements of three different sorts of sand solids (ρs = 2650, d50 = 0.2, 0.7 and 1.4 mm) at different concentration (Cv � 4 to 33%...

The present work are a theoretical and an experimental investigation based on the influence of th... more The present work are a theoretical and an experimental investigation based on the influence of the main operation parameters on the performance of the RO elements. The theoretical work is experiment is performed in order to measure the total dissolved salts, PH and conductivity of the permeate water when different temperatures and concentrations values for the Feed water. Combined between RO desalination system and heater system would improve the performance of the system as the results which is clarified under the temperature limits to prevent scaling and fouling deposition. Temperature of the feed water is the most noticeable environmental condition affecting the performance of RO systems. The general rule of thumb is to estimate productivity change at 3% per degree Celsius, °C change from the standard of 25 °C. There are equations to provide a more exact estimate of productivity. Pressure is approximated by direct proportionality to productivity. Temperature correction is an expo...

Hydraulic transport of fine-grained suspensions through pipelines has been a progressive technolo... more Hydraulic transport of fine-grained suspensions through pipelines has been a progressive technology. Higher solids throughputs for economical considerations necessitate an increase in the solids concentration of the suspensions flowing in the pipelines. When increasing the solids concentration, the fine-grained suspensions could have non-Newtonian characteristics implying more complicated rheological behaviour. The suspension rheological behaviour is affected not only by the physical properties of its individual components but also by physical/chemical forces acting in slurry. One possibility for reducing the frictional losses in slurry pipe flow, and hence power requirement reduction, is based on change of physical-chemical behaviour of the slurry. The aim of study is experimentally investigate the possibility of energy and water requirement reduction for the suspension transport by pipes. The physical/chemical environment of slurry could be changed by a peptizing process. Kaolin slurries of different concentrations were tested in a pipeline test loop comprising laminar and turbulent regimes. Modified suspensions produced by changing the physical/chemical characteristics of kaolin slurries by the addition of a peptizing agent with different amounts were also tested. The study showed that the peptizing process results an ability to obtain higher concentration slurries with a significant decrease in apparent viscosity and yield stress. Non-Newtonian behaviour of the slurry is depressed and the laminar/turbulent transition region is reached at lower flow velocity.

Non-Newtonian flow behaviour in the laminar region is related to the rheological characteristics ... more Non-Newtonian flow behaviour in the laminar region is related to the rheological characteristics and the pressure losses could be predicted by integration of the constitutive rheological model. For turbulent flow, the prediction of the pressure losses stills one of the difficult theoretical and practical problems. The aim of the paper is experimentally investigate the flow behaviour of the non-Newtonian clay slurries. Kaolin and peptized kaolin slurries of different concentrations were tested by a pipeline test loop in both laminar and turbulent regimes. Predictive models were applied to fit the experimental data. The similarity of non-Newtonian turbulent flow behaviour with that of Newtonian one has been confirmed.

In this paper,a computational fluid dynamics simulation technique (CFD) is introduced to obtain t... more In this paper,a computational fluid dynamics simulation technique (CFD) is introduced to obtain the numerical solution of sand–water slurry flowand to have better insight about the complexity of slurry flow in pipelines. The model is utilized to predict the concentration profile, velocity profile and their effect on pressure drop, taking the effect of particle size into consideration. At first a twodimensional model has been developed, then, a three-dimensional model has been generated in order to complete the understanding and visualization of slurry flow behavior. The two-fluid model based on the Eulerian-Eulerian approach along with a standard k-ε turbulence model with mixture properties was used. The Eulerian model is the most complex and computationally intensive among the multiphase models. In particular, it solves a set of momentum and continuity equations for each phase.The computational model was mapped onto the(CFD) solver FLUENT 6.3. The experimental data comprised water-...

The particles tendency to settle in horizontal flow depends upon gravitational settling velocity,... more The particles tendency to settle in horizontal flow depends upon gravitational settling velocity, the turbulence within the liquid, carrier properties and particle- particle interaction. When water is used, as a carrier, for the transportation of coarse particles, it is necessary to operate at velocities that remain the turbulent flow condition is in order to avoid the risk of blockage. The pressure drops may be too high and solids attrition and wear in pipes fittings and pumps can present serious problems. Flocculated suspensions of colloidal particles generally exhibit shear-thinning non-Newtonian characteristics and offer several advantages for the transport of coarse solids. The aim of study is experimentally investigate the flow behaviour of settling slurries that contain colloidal particles studying the effect of carrier properties. Two sorts of the sand (ρs = 2650 kg/m 3 ) were used for the experiments; medium (d50 = 0.7 mm) and coarse (d50 = 1.4 mm). Kaolin (d50 = 2.8 µm, ρk...

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