Life cycle costing of thermal energy storage system using CAPEX and OPEX

Ali Akbar,Mohd Amin Bin Abdul Majid,Ainul Akmar Mokhtar 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.7

Electric chillers and thermal energy storage (TES) tanks are important equipment for gas district cooling plants. One feasible way of assessing the critical parameters that define the performance of TES is performing life cycle costing (LCC). First, the LCC model for electrical chillers and TES were developed in this study using the capital and operational expenditures. Random fluctuations in the cost were then introduced to account for the cost and demand changes. The fluctuations were assumed to be increasing with operating years only. The developed model was also validated against the data from the GDC plant of Universiti Teknologi PETRONAS for two scenarios at the GDC plant. Finally, the breakeven analysis was performed. Therefore, for the project to be feasible, the plant should be operated in at least two shifts until economic life is achieved.

Use of Applied Element Method for Structural Analysis

Aliakbar Shakeri,Khosrow Bargi 대한토목학회 2015 KSCE JOURNAL OF CIVIL ENGINEERING Vol.19 No.5

Applied Element Method (AEM) is a numerical analysis used in prediction the behavior of structures. The modeling of objects in AEM has the ability to simulate structural behavior through all stages of loading as well as evaluating seismic behavior of structures. This paper presents the advantages of AEM in comparison with FEM (Finite Element Method). It describes the theory, formulation and algorithm of the method for static and dynamic analysis of structures. The application of AEM is illustrated through the organization of two FORTRAN source codes: AEMST and AEMDN through static and dynamic analysis of frames. The validation results of the programs are also evaluated by some examples. Results show static analysis using AEMST has high accuracy of the program despite simplicity of AEM in theory and formulation. In addition, several selection criteria in order to select the appropriate size of elements and number of connecting springs are proposed for different situations. Besides, dynamic analysis was performed in AEMDN using Newmark-β method directly and WYD (Wilson, Yuan, and Dickens) Ritz vectors. Results show high accuracy of AEM and AEMDN for dynamic analysis. It also illustrated the lowest processing time needed for WYD Ritz vectors as well as its accuracy.

Hopf Bifurcation Index for Large Scale Power Systems

Aliakbar Mohammadi,Hamid Khaloozade,Roya Amjadifard 제어·로봇·시스템학회 2013 International Journal of Control, Automation, and Vol.11 No.3

In this paper, we propose a novel index for the prediction of the Hopf bifurcation (HB) in power systems. The proposed index has strictly less processing load and less computation time in comparison to former HB indices. It also uses modern control properties of the power system such as system matrix and critical eigenvalue. Therefore, stochastic subspace system identification (SSSI) is used as a tool for estimation and prediction of the proposed HB index. Combining beneficial properties of SSSI methods and the processing advantages of the proposed index, we project a new algorithm for power system monitoring. The algorithm is easy and straight-forward. We conduct several test conditions for the proposed materials using 2-area 4-machine system, New England 10-Machine and IEEE 50-machine system. Simulation outcome expresses good performance of proposed index in comparison to former HB indices. The proposed index has fairly linear behavior, without discontinuities with re-spect to increases of system load. It also has less computation load.

Preparation and characterization of Co3O4 nanoparticles by solid state thermal decomposition of cobalt(II) macrocyclic Schiff base complexes

Aliakbar Dehno Khalaji,Raziyeh Rahdari,Fatemeh Gharib,Jesús Sanmartín Matalobos,Debasis Das 한양대학교 세라믹연구소 2015 Journal of Ceramic Processing Research Vol.16 No.5

Nanoparticles of Co3O4 were successfully synthesized by solid state thermal decomposition of the cobalt(II) macrocyclic Schiff base complexes [CoL1] (1) and [CoL2] (2) as novel precursor at 450 o C for 3 hrs without employing toxic solvent or surfactant and complicated equipment. The products were characterized by Fourier transform infrared spectroscopy (FT-IR), UV-Vis spectroscopy (UV-Vis), X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that the Co3O4 products are pure and single phase and have plate-like. The optical spectra of the Co3O4 products indicated two direct band gaps at about 1.4 and 2.5 eV.

Ultra-lightweight Concrete Containing Expanded Poly-lactic Acid as Lightweight Aggregate

Aliakbar Sayadi,Thomas R. Neitzert,G. Charles Clifton,한민철,Karnika De Silva 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.10

The environmental impact of using petroleum products has become a serious issue nowadays. This paper is about the possibility of producing ultra-lightweight concrete by using bio-polymer aggregate as a replacement for petroleum polymer. Expanded poly-lactic acid (EPLA) and Expanded Vermiculite (EV) are used as aggregate in producing biopolymer concrete. In total, five concrete mixtures are designed with varying EPLA and EV contents. The cement content and effective water-cement ratio are kept constant. The EV aggregate was replaced with EPLA aggregate in the ratio of 20%, 40%, 60% and 80%. Three types of curing conditions were used. The mechanical properties, thermal properties, electrical properties of biopolymer concrete were assessed and analysed. The microstructure of concrete was assessed after 28-days and one year. It was found that the properties of EPLA concrete are mainly influenced by the volume of EPLA and curing conditions. The chemical reactivity of EPLA significantly changes the hydration products of concrete and causes concrete carbonation as well as the conversion of hydration products to more calcium carbonate. However, at the long-term investigation (after a year) the more C-S-H gel was found. Furthermore, EPLA aggregates shrunk and lost their strength in the alkaline environment of cement.

Investigation on the Collapse Behavior of Diagonal Stiffened Composite Plate Girders Subjected to Shear Loading

Aliakbar Hayatdavoodi,Mohammad Nazari,Alireza Javadi Pordesari 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.2

In this study, a new analytical method is presented to estimate the shear capacity of diagonally stiffened steel–concrete composite plate girders. This method is formulated based on tension field action in steel girder web and failure mechanism of concrete slab deck. To validate the accuracy of the proposed method, the obtained results are compared with three-dimensional finite element analysis of composite plate girders with different configuration of stiffeners. The results of analytical and numerical investigations indicate that the proposed method can accurately estimate the ultimate shear capacity of composite plate girders. In addition, it is shown that the diagonal stiffeners on one hand can reduce the buckling effects of shear panel of girders and on the other hand can increase the strength of elastic shear buckling and ultimate shear capacity of girders well in comparison with the unstiffened thin steel plate girders.

Failure analysis of a heat-resistant stainless steel ring in a gas turbine burner

Aliakbar Fallah Sheykhlari,Saeed Khani Moghanaki,Meisam Khodabakhshi 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.4

Hot gas path components in gas turbines are damaged by several mechanisms due to aggressive environments. In this research, the cracking of an insert ring, which is composed of Nb-stabilized heat-resistant stainless steel, after 8000 operation hours, is investigated. The microstructure of the ring is examined by optical and scanning electron microscopes equipped with energy-dispersive X-ray spectroscopy. The generated stress and strain within the ring during a complete operation cycle (startup to shutdown) of gas turbine are simulated by finite element simulation software. The microstructural investigations indicate the formation of some precipitates that mainly contain nitrogen atoms. The development of tensile loads within the ring during shutdown and brittle N-contained precipitates leads to cracking. The indicators of both types of hot corrosion are also observed.

Energy Analysis of Hydraulic Fracturing

Aliakbar Golshani,Thanh Tran-Cong 대한토목학회 2009 KSCE Journal of Civil Engineering Vol.13 No.4

In this paper, numerical simulations of circular boreholes under internal hydraulic pressure are carried out to investigate the energy transferred to the surrounding rock and the breakdown pressure. The simulation results suggest that the borehole breakdown pressure and the energy transferred to the surrounding rock are dependent on the mechanical properties of the rock and borehole size. Although the energy transferred to the surrounding rock increases with increasing borehole size, the borehole breakdown pressure decreases. In this paper, numerical simulations of circular boreholes under internal hydraulic pressure are carried out to investigate the energy transferred to the surrounding rock and the breakdown pressure. The simulation results suggest that the borehole breakdown pressure and the energy transferred to the surrounding rock are dependent on the mechanical properties of the rock and borehole size. Although the energy transferred to the surrounding rock increases with increasing borehole size, the borehole breakdown pressure decreases.

Volumetric properties of supercritical carbon dioxide from volume-translated and modified Peng-Robinson equations of state

Aliakbar Roosta,Javad Hekayati,Jafar Javanmardi 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.11

Following three well-established approaches, different modifications have been proposed that significantly improve the Peng-Robinson EOS’s predictions of the volumetric properties of carbon dioxide in the supercritical region. By making use of 5301 experimental PVT data points of supercritical carbon dioxide (SC-CO2), three models have been developed based on the volume-translation concept, modification of the alpha function of the attractive term of the Peng-Robinson EOS and the addition of a third translation parameter to the EOS. The experimental data considered encompass a wide temperature and pressure range of 304.35-1,273.15 K and 7.38-800.00MPa, respectively. According to the results from several graphical and statistical analyses, the proposed models can reliably be employed for prediction and representation of the volumetric properties of SC-CO2 with AARDs below 1.3%. Comparisons have also been made with the modified Redlich-Kwong EOS as well as the standard reference multiparameter EOS developed by Span and Wagner, demonstrating the comparable accuracy of the proposed models, while offering notably simpler mathematical formulation.

Reverse Micellar Extraction of Fungal Glucoamylase Produced in Solid-State Fermentation Culture

( Aliakbar Paraj ),( Morteza Khanahmadi ),( Keikhosro Karimi ),( Mohammad J. Taherzadeh ) 한국미생물 · 생명공학회 2014 Journal of microbiology and biotechnology Vol.24 No.12

Partial purification of glucoamylase from solid-state fermentation culture was, firstly, investigated by reverse micellar extraction (RME). To avoid back extraction problems, the glucoamylase was kept in the original aqueous phase, while the other undesired proteins/ enzymes were moved to the reverse micellar organic phase. The individual and interaction effects of main factors (i.e., pH and NaCl concentration in the aqueous phase, and concentration of sodium bis-2-ethyl-hexyl-sulfosuccinate (AOT) in the organic phase) were studied using response surface methodology. The optimum conditions for the maximum recovery of the enzyme were pH 2.75, 100 mM NaCl, and 200 mM AOT. Furthermore, the optimum organic to aqueous volume ratio (Vorg/Vaq) and appropriate number of sequential extraction stages were 2 and 3, respectively. Finally, 60% of the undesired enzymes including proteases and xylanases were removed from the aqueous phase, while 140% of glucoamylase activity was recovered in the aqueous phase and the purification factor of glucoamylase was found to be 3.0-fold.