International Journal of Energetica
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The relationship between the compressive strength and ultrasonic pulse velocity concrete with fibers exposed to high temperatures
Get PDFThe paper analyses the effects of high temperatures on the concrete residual strength using ultrasonic velocity (UPV). An experimental investigation was conducted to study the relationship between UPV residual data and compressive strength of concrete with different mixture proportions, cubic specimens with water-cement ratio of 0.35. They were heated in an electric furnace at temperatures ranging from 200°C to 600°C. In this experiment a comparison was made between the four groups which include two types of fibers steel 0,19%, 0,25% and 0,5%, polypropylene: 0,05%, 0,11% 0,16 % by volume. Cube specimens were tested in order to determine ultrasonic velocity. The compressive strength was tested too. According to the results, relations were established between ultrasonic velocity in the specimens and the compressive strength at different temperature and the range of the velocity of the waves were also determined for this kind of concrete. Result of the test showed that UPV test can be successfully used in order to verify the consistency of structures damaged by fire
Economic Evaluation Analysis of Nano-silica Ultrafiltration Membrane Production from Sand
Get PDFThe purpose of this research was to analyze the production method of a membrane of silica nanoparticles from an economic perspective. Silica nanoparticles are synthesized using a coprecipitation method. Briefly, the process consists of immersion, heating, precipitation, washing and drying, and packaging. The parameters used for economic analysis are gross profit margin (GPM), internal rate return (IRR), payback period (PBP), cumulative net present value (CNPV), break-even point (BEP), and profitability index (PI). The production of this ultrafiltration nano-silica membrane can be done by varying the amount of initial sand from 6 to 14 kg. The production of ultrafiltration nano-silica membranes can be produced in both domestic and micro-scale industries. To get a very good profit, economic analysis shows the minimum amount of sand used should be more than six kg. This study is very important because the production of ultrafiltration nano-silica membranes have a high potential in the field of economics and will encourage further investigation for the possibility of industrial production of these ultrafiltration nano silica membranes
Proposed Algorithm MPPT for Photovoltaic System
Get PDFA proposed algorithm MPPT (Maximum Power Point Tracking) is proposed in this paper. When the insolation change rapidly, the P&O (Perturb and Observe) algorithm is used to adjust the operating point of the PV (Photovoltaic) array close to the MPP (Maximum Power Point) for fast tracking; also, the INC (Incremental Conductance) algorithm and the fuzzy controller skip drawbacks of the P&O algorithm by decreasing oscillations around the MPP and the underestimated. In addition, to improve the control precision, the effectiveness of proposed algorithm is validated by simulation using Matlab/Simulink, the simulation results show that the proposed algorithm tracks the MPP quickly, reduces the oscillation around the MPP effectively and improves the energy conversion efficiency of the PV panel
Structural, electronic and thermoelectric properties of the intermetallic materials based on Mg2X (X= Si, Ge, Sn): DFT calculations
Get PDFThe scope of this work is the investigation of the physical properties of chalcopyrite materials using ab-initio methods in order to simulate a new structure of thin-films photovoltaic cells with high conversion efficiency. In the first framework, we obtained the results of calculations based on Density Functional Theory (DFT) using the full-potential linearized augmented plane wave method (FP-LAPW) as involved in the WIEN2K computational package. For the exchange-correlation potential, the local density approximation (LDA) was used to calculate the lattice parameters, Bulk modulus and its first derivative as well as the densities of states of the intermetallic semiconductors materials based on Mg2X (X=Si, Ge and Sn). The semi-local Becke-Johnson (mBJ) potential and its modified form proposed by Tran and Blaha (TB-mBJ) were also used for studying the electronic and thermoelectric properties; (merit factor, Seebeck coefficient, electronic conductivity). The achieved results were compared to computational works and other data acquired experimentally
A parabolic trough solar collector as a solar system for heating water: a study based on numerical simulation
Get PDFThis paper is an optical and thermal study of a small model of a parabolic trough solar collector (CTP), which will be used to heat tap water in the winter at Guemar, El-Oued province, Algeria. A mathematical model drawn from the energy balance equation applied to the absorber tube, this model was solved by the finite difference method. A computer program was developed to solve our problem. MATLAB was used as a tool for numerical simulation where it is used to calculate dynamic shifts at the level of the absorbent tube. The results are very honorable and encouraging, where the thermal efficiency of the concentrator had passed 61%, and the fluid temperature had passed 343 K
Piezometric variation of the water table in the the Municipality of El-Oued, south-east Algeria
Get PDFMunicipality of El-Oued has been confronted with the phenomenon of the upwelling of water for several years and without almost any cease to become more extensive each year. This phenomenon took very alarming dimensions the last twenty years. The use of the deep layers water (the Continental intercalary and the Final Complex) in an excessive way considerably increased the volume of the water input, as well as the absence of a natural discharge system for the rejections of wastewater, are the principal causes of this ecological imbalance. Contributing to the deterioration of the palm trees, the inundation of (Ghouts) causes mortal consequences at the level of environment, agriculture, the economy and the health of Municipality of El-Oued.The piezometric variation of the water table has shown that in the areas of upwelling groundwater; correspond to piezometric depressions which has favored the accumulation and especially of the waste water
Direct Torque Control of a Doubly Fed Induction Generator
Get PDFIn this paper a direct torque control system is proposed and is applied to doubly fed induction generator (DFIG) based wind power generation systems. In this control system the rotor flux and the electromagnetic torque are estimated based on the rotor voltage and currents measurements. The validity and effectiveness of this control is demonstrated by some simulation results
Seasonal effect on solar distillation in the El-Oued region of south-east Algeria
Get PDFIn the present purely experimental work, we tested a solar distiller with a simple slope in the region of El-Oued located in the south-east of Algeria, during the winter then the summer seasons at the same place. Dimensions of the studied device are (1000 x 500 mm), while the depth of the water to be distilled is 1 cm, the glazing thickness is 4 mm, and the tilt angle with respect to the horizontal is 10 °.The aim of this work is to compare distillation between winter (January) and summer (May) to show that weather factors such as solar radiation, ambient temperature and humidity are influential on the distiller productivity. The amount of distilled water in winter was about 119 ml per day. However, that in summer was 1127 ml per day in total, so it is an increase of more than 9 times the production of distilled water
Numerical Study of the Combustion of CH4-C3H8/ Air: Application to a Combustion Chamber with Two Coaxial Jets
Get PDFIn this study, we studied numerically the non-premixed combustion provided by two coaxial methane-propane/air jets in a 3D cylindrical combustion chamber. To study this kind of phenomenon we used a special treatment of the mathematical model and we chose two models of computation PDF and LES. In order to find the aero-thermo-chemical characteristics in the burner, namely: axial velocity, temperature and mass fraction of carbon monoxide CO. Using commercial calculation software CFD Fluent The objective of this work is to research the fuel that reduces the emission of carbon monoxide CO, which is considered a gas toxic to the environment, by comparing the two fuels CH4 and C3H8. The results give methane fuel reduces carbon monoxide as a pollutant chemical species in combustion products compared to propane fuel.
Fuzzy Logic Control of Wind Turbine Storage System Connected to the Grid Using Multilevel Inverter
Get PDFThis paper aimed to evaluate the use of wind turbine storage systems to provide electricity in the electrical grid through a five-level inverter. The proposed system is composed of four wind turbine generators based on permanent magnet synchronous generator (PMSG), four battery storage systems connected to each capacitor of the DC link and a five level diode clamped inverter connected to the grid by three phase transformer. The control algorithm proposed is based on fuzzy logic to tracks and extract the maximum wind power by controlling the rotational speed of wind turbine, which is most appropriate when there is a lack of information on the characteristic Cp (λ,β) of the turbine. The system operator controls the power production of the four wind turbine generators by sending out reference power signals to each input side regulation unit, the input side regulation units regulate the voltage of each capacitor of the DC link, regulate the voltage and the state of charge of each battery storage system. The inverter is controlled by simplified space vector modulation which allows us to reduce the computational time and reduce the algorithm complexity compared to the conventional five levels space vector modulation, the grid side control level regulate the power and the current injected to the grid