Volume 9 Issue 1

Title Page

MHD's impact on entropy production and natural convection in a particular shape of a cavity filled with a nanofluid Al2O3 - water

Saadi Bougoul, Imene Rahmoune

Abstract: An analysis of the impact of the magnetic field on the flow of the Al2O3-water nanofluid which results from the natural convection that occurs inside a cavity having a non-regular shape was investigated. For this study the monophasic model is applied. Analytical solution of the transport equations is difficult; therefore, the use of Ansys-Fluent software appears essential. An analysis of the impacts of Rayleigh numbers (7.68.104, 1.5.105 and 3.072.105) and Hartmann (0 to 75) as well as the concentration of nanoparticles expressed as a percentage (0 to 5%) on heat transmission and entropy production was exposed. Numerical results are expressed in form of streamlines, isotherms and Nusselt number. Mean Nusselt number and entropy production vary proportionally with the Rayleigh number and the volume fractions of the particles and they are inversely proportional to the Hartmann number. For volume fractions of the chosen Al2O3 nanoparticles, heat transfer is improved. After analysis of obtained results, correlations for Nusselt number expressed as an expression of two variables which are Hartmann and volumes fractions of nanoparticles have been proposed to predict the rate of heat transmission inside the enclosure. These laws are rarely presented in this kind of study.


Keywords: Magneto-hydrodynamic, free convection, nanofluid, enclosure, entropy production.


Estimation of Cross-Flow Heat Exchanger Fouling in Phosphoric Acid Concentration Plant using Artificial Neural Networks

Rania Jradi, Christophe Marvillet, Mohamed Razak Jeday

Abstract: One of the most frequently encountered problems in industrial heat exchangers is fouling, which degrades the thermal and hydraulic performances of these equipment, leading thus to failure if undetected. And it occurs due to the accumulation of undesired material on the heat transfer surface. So, it is necessary to know about the heat exchanger fouling dynamics to plan mitigation strategies, ensuring a sustainable and safe operation. This paper proposes an Artificial Neural Network (ANN) approach to estimate the fouling resistance in a cross-flow heat exchanger by the collection of the operating data of the phosphoric acid concentration loop. The operating data of 361 was used to validate the proposed model. The ANN attains AARD (Absolute Average Relative Deviation) = 0.048%, MSE (Mean Squared Error) = 1.811x10-11, RMSE (Root Mean Square Error) = 4.256x 10-6 and r2 (correlation coefficient) =99.5% of accuracy which confirms that it is credible and valuable approach for industrialists and technologists who are faced with the drawbacks of fouling in heat exchangers.

Keywords: Heat exchanger, estimation, fouling, artificial neural networks, Phosphoric acid concentration loop, fouling resistance.



Computation and Analysis of the Extremely Low Frequency Magnetic Fields Generated by High Voltage Overhead Transmission Lines

Salah-Eddine Houicher, Rabah Djekidel, Sid-Ahmed Bessedik

Abstract: Such systems should be structured according to the high magnetic fields when designing high voltage power transmission lines. This paper proposes a method for computing and illustrating the magnetic field profile along a three-phase high voltage overhead power line; It proposes to take the aspects of the issues caused by that restriction to the owner of those appears to be working: Calculate the magnetic field intensities in order to know their calculation and measurement. Many spirits asked about this possible physiological action of the magnetic fields. In order to understand this probability, the intensity of the fields produced by transport energy works must be retained; In this work, a method for the evaluation of 50Hz magnetic fields produced by overhead power lines is presented. In the magnetic field calculation, the non -uniform trajectory character described by the conductors between towers, Catenary drawing is known. Using this method, a program for calculation the magnetic field intensity was produced. It can handle any power line geometry. This paper presents a simulation methodology for analyze the distribution of the magnetic field generated by high voltage under three phase overhead transmission line. The effect of sag due to the weight of the line on the values of the magnetic field on ground level has also been discussed. We also give examples of application of the method and program. The analytical results of the calculation of 275kV three-phase transmission line based on image method and obtained by MATLAB numerical software which makes it possible to better analyze and to represent the transverse profile of the magnetic field intensity under and in the vicinity of high voltage overhead electric power transmission lines.

Key words: Magnetic field, energy, extremely low frequency, high voltage, overhead transmission line, 2D computation.


Artificial Neural Networks and Response Surface Methodology for Predicting of Cross-Flow Heat Exchanger Fouling in Phosphoric Acid Concentration Plant

Rania Jradi, Christophe Marvillet, Mohamed Razak Jeday

Abstract: Among the most frequently encountered issues that are occurred in industrial heat exchangers is fouling which results in reducing the performance of heat exchangers while increasing energy losses and damaging the apparatus. This study aims to investigate the comparative suitability of response surface methodology (RSM) and artificial neural networks (ANN) in predicting the thermal resistance of fouling in cross-flow heat exchanger. The employed structure for both techniques is composed by six input variables as time, acid inlet and outlet temperatures, steam temperature, acid density and acid volume flow, and output variable as thermal resistance of fouling. The results show that the model predicted values in both techniques were in close agreement with corresponding experimental values. The results of different accuracy parameters in terms of correlation coefficient, absolute average relative deviation, mean squared error and root mean squared error indicate the functionality of both modeling approaches for fouling resistance prediction. However, RSM model yield better accuracy in simulating the fouling resistance than ANN model.

Keywords: Heat exchanger, artificial neural networks, response surface methodology, fouling resistance, prediction.


Compressive strength behavior of earth blocks stabilized with quarry waste aggregates

Amel Soukaina Cherif, Taoufik Achour, Sadok Ben Jabrallah

Abstract: Starting from the fact that the exploitation of quarries has serious environmental impacts through their emission of dust and fine sands which are dispersed in nature, and in an ecological and sustainable approach, in this article, we propose a study allowing their recycling and valorization, in the manufacture of earth blocks reconstituted for a possible use in the constructions. The produced samples have been made according to the proportion’s addition of (0%, 10%, 20%, 30%, 40% and 50%) with quarries waste aggregates. They were hardened and tested in order to study the influence of these additions on the behavior of the compressive strength. Another formula seeking an optimized mixture according to the compressible packing model where highest resistance was also tested. The results showed that for a substitution greater than the optimized formulation, the compressive strength decreases.

Keywords: Earth block, Crushing sand substitution, Compressive strength, Experimental approach, Compressible stacking model


All rights Reserved. Made by SMDI