Wyniki wyszukiwania - BazTech

1

Performance assessment and leakage analysis of feed water pre-heaters in natural gas-fired steam power plants

Shabani G. A. S., Ameri M., Akbari O., Seifi A.

Journal of Power Technologies

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2018

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Vol. 98, nr 4

352--364

EN

The performance of feed water pre-heaters (FWH) at a steam power plant with a capacity of 200 MW is evaluated in this paper. The main objective of this study is to investigate the behavior of these FWHs in various cases. The effect of leakage of condensates on the condenser was also studied in detail. To do this, each FWH was studied separately and also in groups (LP, HP and both groups). While some of the results are exclusive to the studied power plant, others can be generalized to similar power plants. The results show that although LPH-1 and LPH-2 have the lowest exergy efficiency, they have the greatest effect on the efficiency of the cycle. Whereas HPH-6 and LPH-4 have the highest heat exchange (31.3 and 21.73 MW), LPH-2 and LPH-1 deliver the greatest positive effect on energy efficiency (0.81% and 0.61/0%). Moreover, the results show the particular importance of preventing any leakage of heater condensate. In the event of leakage along the route to the condensate of heaters, the most negative effect will be due to the HP heaters: 20 kg/s leakage in the HPHs line will cause an increase in CO2 production p.a. of roughly 10150 metric tons. Furthermore, energy efficiency and power produced will fall by 0.374% and 5.1 MW. In terms of the impact of leakages on the cooling tower, the study showed that LPH-1 and LPH-2 have the greatest effect. The effects of LP and HP FWHs on the energy efficiency of the cycle were 2.53% and 0.82%.

2

Structural, Mechanical and Thermodynamic Properties Under Pressure Effect of Rubidium Telluride: First Principle Calculations

Bidai K., Ameri M., Ameri I., Bensaid D, Slamani A., Zaoui A., Al-Douri Y.

Archives of Metallurgy and Materials

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2017

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Vol. 62, iss. 2A

865--871

EN

First-principles density functional theory calculations have been performed to investigate the structural, elastic and thermodynamic properties of rubidium telluride in cubic anti-fluorite (anti-CaF2-type) structure. The calculated ground-state properties of Rb2Te compound such as equilibrium lattice parameter and bulk moduli are investigated by generalized gradient approximation (GGA-PBE) that are based on the optimization of total energy. The elastic constants, Young’s and shear modulus, Poisson ratio, have also been calculated. Our results are in reasonable agreement with the available theoretical and experimental data. The pressure dependence of elastic constant and thermodynamic quantities under high pressure are also calculated and discussed.

3

Predictive study of structural, electronic, magnetic and thermodynamic properties of XFeO3 (X = Ag, Zr and Ru) multiferroic materials in cubic perovskite structure: first-principles calculations

Moulay N., Ameri M., Azaz Y., Zenati A., Al-Douri Y., Ameri I.

Materials Science Poland

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2015

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Vol. 33, No. 2

402--413

EN

The full potential linear-muffin-tin-orbital method within the spin local density approximation has been used to study the structural, electronic, magnetic and thermodynamic properties of three multiferroic compounds of XFeO3 type. Large values of bulk modulus for these compounds have been obtained, which demonstrates their hardness. The calculated total and partial density of states of these compounds shows a complex of strong hybridized 3d and 4d states at Fermi level. The two degenerate levels e(g) and t(2g) clearly demonstrate the origin of this complex. We have also investigated the effect of pressure, from 0 GPa to 55 GPa, on the magnetic moment per atom and the exchange of magnetic energy between the ferromagnetic and antiferromagnetic states. For more detailed knowledge, we have calculated the thermodynamic properties, and determined heat capacity, Debye temperature, bulk modulus and enthropy at different temperatures and pressures for the three multiferroic compounds. This is the first predictive calculation of all these properties.

4

Investigations of structural, elastic, electronic and thermodynamic properties of lutetium filled skutterudite LuFe4P12 under pressure effect: FP-LMTO method

Boudia K., Ameri M., Al-Douri Y., Ameri I., Bouafia H.

Materials Science Poland

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2015

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Vol. 33, No. 4

867--878

EN

Structural, elastic, electronic and thermodynamic properties of ternary cubic filled skutterudite compound were calculated. We have computed the elastic modulus and its pressure dependence. From the elastic parameter behavior, it is inferred that this compound is elastically stable and ductile in nature. Through the quasi-harmonic Debye model, in which phononic effects are considered, the effect of pressure P (0 to 50 GPa) and temperature T (0 to 3000 degrees C) on the lattice constant, elastic parameters, bulk modulus B, heat capacity, thermal expansion coefficient alpha, internal energy U, entropy S, Debye temperature theta(D), Helmholtz free energy A, and Gibbs free energy G are investigated.

5

FP-LAPW investigation of mechanical and thermodynamic properties of Na2X (X = S and Se) under pressure and temperature effects

Bidai K., Ameri M., Bensaid D, Moulay N. E., Al-Douri Y., Ameri I.

Materials Science Poland

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2015

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Vol. 33, No. 3

649--659

EN

Structural, elastic and thermodynamic properties of sodium chalcogenides (Na2X, X = S, Se) have been calculated using FP-APW+lo method. The ground state lattice parameter, bulk moduli have been obtained. The Zener anisotropy factor, Poisson’s ratio, shear modulus, Young’s modulus, have also been calculated. The calculated structural and elastic constants are in good agreement with the available data. We also determined the thermodynamic properties, such as heat capacities Cv and Cp, thermal expansion α, entropy S, and Debye temperature ΘD, at various pressures and temperatures for Na2X compounds. The elastic constants under high pressure and temperature are also calculated and elaborated.

6

Ab initio calculations of structural, elastic, electronic and thermodynamic properties of the cerium filled skutterudite CeRu4P12 under the effect of pressure

Berrahal M., Ameri M., Al-Douri Y., Hashim U., Varshney D., Ameri I., Boubchir M., Abderrahim B.

Materials Science Poland

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2015

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Vol. 33, No. 4

699--708

EN

The paper presents an investigation on crystalline, elastic and electronic structure in addition to the thermodynamic properties for a CeRu4P12 filled skutterudite device by using the full-potential linear muffin-tin orbital (FP-LMTO) method within the generalized gradient approximations (GGA) in the frame of density functional theory (DFT). For this purpose, the structural properties, such as the equilibrium lattice parameter, bulk modulus and pressure derivatives of the bulk modulus, were computed. By using the total energy variation as a function of strain we have determined the independent elastic constants and their pressure dependence. Additionally, the effect of pressure P and temperature T on the lattice parameters, bulk modulus, thermal expansion coefficient, Debye temperature and the heat capacity for CeRu4P12 compound were investigated taking into consideration the quasi-harmonic Debye model.

7

Structural and elastic properties of TiN and AlN compounds: first-principles study

Fodil M, Mounir A, Ameri M., Baltache H, Bouhafs B, Al-Douri Y, Ameri I

Materials Science Poland

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2014

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Vol. 32, No. 2

220--227

EN

First-principles calculations of the lattice constants, bulk modulus, pressure derivatives of the bulk modulus and elastic constants of AlN and TiN compounds in rock-salt (B1) and wurtzite (B4) structures are presented. We have used the fullpotential linearized augmented plane wave (FP-LAPW) method within the density functional theory (DFT) in the generalized gradient approximation (GGA) for the exchange-correlation functional. Moreover, the elastic properties of cubic TiN and hexagonal AlN, including elastic constants, bulk and shear moduli are determined and compared with previous experimental and theoretical data. Our results show that the structural transition at 0 K from wurtzite to rock-salt phase occurs at 10 GPa and -26 GPa for AlN and TiN, respectively. These results are consistent with those of other studies found in the literature.

8

FP-LMTO study of structural, electronic, thermodynamic and optical properties of Mg x Cd1−x Se alloys

Bensaid D, Ameri M, El Hanani M D, Azaz Y, Bendouma D, Al-Douri Y, Ameri I

Materials Science Poland

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2014

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Vol. 32, No. 4

719--728

EN

Structural, electronic and optical properties of MgxCd1−xSe (0 6 x 6 1) are calculated for the first time using density functional theory. Our results show that these properties are strongly dependent on molar fraction of particular components – x. The bond between Cd and Se is partially covalent and the covalent nature of the bond decreases as the concentration of Mg increases from 0 % to 100 %. It is found that MgxCd1−xSe has a direct band gap in the entire range of x and the band gap of the alloy increases from 0.43 to 2.46 eV with the increase in Mg concentration. Frequency dependent dielectric constants ε1(ω),ε2(ω) refractive index n(ω) are also calculated and discussed in detail. The peak value of refractive indices shifts to higher energy regions with the increase in Mg. The larger value of the extraordinary refractive index confirms that the material is a positive birefringence crystal. The present comprehensive theoretical study of the optoelectronic properties of the material predicts that it can be effectively used in optoelectronic applications in the wide range of spectra: IR, visible and UV. In addition, we have also predicted the heat capacities (CV ), the entropy (S), the internal energy (U) and the Helmholtz free energy (F) of MgxCd1−xSe ternary alloys.

9

Exergy and exergo-economic based analysis of a gas turbine power generation system

Mousafarash A., Ameri M.

Journal of Power Technologies

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2013

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Vol. 93, nr 1

44--51

EN

In this research study, energy, exergy and exergo-economic analysis of Montazer Ghaem gas turbine power plant which is located near Tehran, capital city of Iran is carried out. The results of this study reveal that the highest exergy destruction occurs in the combustion chamber (CC) where the large temperature difference is the major source of the irreversibility and also gas turbine and compressor are the other components followed by the combustion chamber. In addition, the effects of the gas turbine load variations and ambient temperature are conducted to see how system performance changes since the gas turbine is significantly affected by the ambient temperature which leads to a decrease in the net power output. The results of the load variation of the gas turbine show that a reduction in the gas turbine load, results a decrease in the exergy efficiency of the cycle as well as all the components. As it was expected, the effect of an increase in ambient temperature has a negative effect on the exergy efficiency of the cycle so this reason could be enhanced by using the gas turbine air inlet cooling methods. In addition, an exergo-economic analysis is conducted to determine the cost of exergy destruction in each component and to determine the cost of fuel. The results show that combustion chamber has the largest cost of exergy destruction like exergy analysis.

10

Thermodynamic modeling and second law based performance analysis of a gas turbine power plant (exergy and exergoeconomic analysis)

Ameri M., Enadi N.

Journal of Power Technologies

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2012

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Vol. 92, nr 3

183--191

EN

It this research paper, a complete thermodynamic modeling of one of the gas turbine power plants in Iran is performed based on thermodynamic relations. Moreover, a complete computer code is developed for the simulation purposes using the Matlab software. To assess the system performance, exergy and exergo-economic analysis are conducted to determine the exergy destruction of each component and cost of each flow line of the system. A complete parametric study is also carried out to study the effect of some design parameters such as exergy efficiency and total cost of exergy destruction on the system performance variation. The exergy analysis results have revealed that combustion chamber (CC) is the most exergy destructor component compared to other cycle components. Also, its exergy efficiency is less than other components which is due to the high temperature difference between working fluid and burner temperature. In addition, it was found that by an increase in the TIT (gas turbine inlet temperature), the exergy destruction of this component can be reduced. On the other hand, the cost of exergy destruction, which is a direct function of exergy destruction, is high for combustion chamber. The effects of design parameters on exergy efficiency have shown that an increase in the air compressor pressure ratio and TIT increases the total exergy efficiency of the cycle. Furthermore, the results have revealed that by an increase in the TIT for about 350 K the cost of exergy destruction can be decreased for about 22%. Therefore, TIT is the best option to improve the cycle losses.

11

Comparison of a dual-fuel internal combustion engine performance for CNG and gasoline fuels

Ameri M., Kiaahmadi F., Khanaki M. M.

Journal of Power Technologies

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2012

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Vol. 92, nr 4

214--226

EN

In this paper, comparison of a dual-fuel internal combustion engine performance for CNG and gasoline fuels is evaluated at the steady-state condition by application of energy and exergy analysis using the experimental test results. The energy and exergy balances are calculated at different engine speeds. The results show that the energy and exergy of the heat rejection for gasoline and CNG fuels increases with increasing engine speed and the exergy efficiencies are slightly higher than the corresponding energy efficiencies. Moreover, the results show that the exergy efficiency for gas-fuel is higher than the gasoline-fuel exergy efficiency at all engine speeds. The results show that due to volumetric efficiency drop, power and torque of the gas-fuel engine is lower than gasoline-fuel one. Furthermore, the specific fuel consumption of the gas-fuel engine is lower than gasoline-fuel one. The results of this study have revealed that the most important source of the system inefficiency is the destruction of exergy by irreversible processes, mostly by the combustion. Moreover, it should be noted that liquid fuels like gasoline have many important advantages like much greater volumetric energy density, ease of transport and storage, which have made them as the preferred fuels for IC engines.