Avanti Publishers
Not a member yet
711 research outputs found
Sort by
Computation of Ancillary Service Requirement Assessment Indices for Load Frequency Control in a Restructured Power System using SMES Unit and SCES Unit
Get PDFTo ensure a quality power supply the power system should not only match the total generation with total load and the associated system losses but also should emphasis better Ancillary Services. Even small disturbances to the power system can result in wide deviation in system frequency and quick restoration process are of prime importance not only based on the time of restoration and also should ensure stability limits. This paper proposes various design procedures for computing Power System Ancillary Service Requirement Assessment Indices (PSASRAI) for a Two-Area Thermal Reheat Interconnected Power System (TATRIPS) in a restructured environment. As simple conventional Proportional plus Integral (PI) controllers are still popular in power industry for frequency regulation as in case of any change in system operating conditions new gain values can be computed easily even for multi-area power systems, this paper focus on the computation of various PSASRAI for Two Area Thermal Reheat Interconnected Power System in restructured environment based on the settling time and peak undershoot concepts of control input deviations of each area. Energy storage is an attractive option to augment demand side management implementation, so storage devices like Super Capacitor Energy Storage (SCES) and Superconducting Magnetic Energy Storage (SMES) unit can be efficiently utilized to meet the peak demand. So the design of the Proportional plus Integral (PI) controller gains for the restructured power system without and with the storage units are carried out using Bacterial Foraging Optimization (BFO) algorithm. These controllers are implemented to achieve a faster restoration time in the output responses of the system when the system experiences with various step load perturbations. In this paper the PSASRAI are calculated for different types of possible transactions and the necessary remedial measures to be adopted are also suggested. If PSARAI based on settling time lies between 1 to 1.5 and if PSARAI based on peak undershoot is less than 0.2 distributed generation has to be incorporated and if the limit exceeds then the system becomes vulnerable and may result to black outs
A New Model for Accurate Prediction of Pressure Drop in Gas Well
Get PDFThe analytical model for predicting the pressure at any point in a flow string from the bottom hole to the well head is essential in determining optimum production string dimension and in the design of gas-lift installations.A variety of models for predicting pressure transience in flowing wells have been reported in the literatures. Most of the early models were based on steady state fluid flow equation that did not consider time factor which results in inaccurate at early production time. Hence, there is the need for developing a model capable of estimating pressure transverse accurately at all times in flowing well bore.This study presents equation for pressure drop in flowing vertical well without neglecting any term in the momentum equation by the inclusion of accumulation and kinetic term. The analytical solution of the resulting differential equation gives functional relationship between flow rates and pressure at any point in flowing well at any given time. The results show improvement over previous studies as the assumptions previously neglected were all considered
Black Box Modelling of Gasoil Hydrotreating by Artificial Neural Networks
Get PDFHydrotreating of gasoil is one of the most important processes in petroleum refining; it helps to improve the characteristics of diesel fuel to make it meet the required specifications and pollution standards. Modelling of this process would, among other things, allow to predict the product quality as a function of different process variables (temperature, pressure, space velocity). There are several modelling techniques, among them the Black Box type modelling by Artificial Neural Networks (ANNs), which is used to model the hydrotreating process at pilot scale. The approach used in this work is an artificial intelligence approach. The model developed is a neural network Multi Layer Perceptron (MLP) type. Network learning (NL) is carried out according to the Backpropagation Gradient algorithm with momentum; The Early Stopping (ES) technique has been used to prevent the effect of overfitting and thereby ensure a good generalization of the model. Experimental and predicted results show good agreement with an error not exceeding 4%
Contact Photothermal Techniques for Thermal Characterization of Liquids
Get PDFTwo contact photothermal (PT) techniques, the well-known photopyroelectric (PPE) calorimetry, and a recently introduced photothermoelectric (PTE) one, are proposed for thermal inspection of some liquid samples. The paper contains a summary of the recent results and a comparison of the investigations performed with the previously mentioned techniques for the measurement of the dynamic thermal parameters (thermal diffusivity and effusivity) of some liquids of interest: magnetic nanofluids with transformer oil as carrier liquid and various concentrations of magnetite (Fe3O4) nanoparticles. For both techniques, the same detection configurations have been used: (i) the front detection configuration, together with the thermal-wave resonator cavity (TWRC) method as scanning procedure, was used to measure the value of thermal effusivity; (ii) the back configuration, together with the same TWRC technique, leads to the direct measurement of thermal diffusivity. The main theoretical aspects of the particular detection cases for both techniques are described and the performances (advantages and limitations) of the methods are analyzed. Concerning the nanofluid under investigation, small increases of thermal diffusivity (9.33 m2s-1 – 10.33 m2s-1) and effusivity (450 Ws1/2 m-2K-1 – 530 Ws1/2 m-2K-1) with increasing nanoparticles' concentration (0.156 mg(Fe3O4)/ml fluid - 0.623 mg(Fe3O4)/ml fluid) are observed
Cold Flow Simulation in Underground Coal Gasification (UCG) Cavities
Get PDFUnderground coal gasification (UCG), in the recent years, have gathered a significant amount of interest from the researchers because of its advantages over conventional mining and utilization techniques. It is one of the most promising and innovative technology where coal is gasified in-situ by injection of a suitable oxidant for the production of synthetic gas. The simultaneous occurrence of several phenomena such as complex flow patterns, chemical reactions, water influx, thermo-mechanical failure of the coal seam etc. make the mathematical modeling of the entire UCG process very abstruse and computationally challenging. The reaction between the oxidant and the coal in the deep underground seams leads to the formation of combustible gas and subsequently results in a cavity. As the gasification proceeds the cavity grows three dimensionally in a non-linear fashion. The cavity size strongly depends on several parameters like position and orientation of the inlet nozzle, coal properties etc. A comprehensive three-dimensional numerical study is conducted to understand the hydrodynamics within a given cavity size which would give us a relatively quick but reliable insights into the process. Five different cavity sizes are considered inside which the complete turbulent transport is simulated. Apart from the usual vertical and horizontal injection, the effect of inclined injection on the hydrodynamics is also reported here for the first time
Production and Purification of Fungal Milk Clotting Enzyme from Aspergillus candidus
Get PDFThe search for rennet substitutes such as microbial rennet has increased fold due to increase in the demand for cheese products. Microbial rennet covers about one-third of the cheese consumption worldwide. Hence it is important to develop commercially viable and cost efficient method for purification of rennet from microbial sources. Hence the present work was focused on the production and purification of microbial rennet from Aspergillus candidus. The rennet was purified using a two step purification process involving solvent precipitation and chromatographic separation. The purity of the milk clotting enzyme was increased by 7.43 fold by solvent precipitation using equal mixture of 150% (v/v) ethanol-acetone. Then the enzyme was further purified using Diethylaminoethyl (DEAE) cellulose chromatography and 10.45 fold increase in enzyme activity was obtained after purification. The temperature of 35°C and substrate concentration of 0.25 mg/ml were found as optimum for maximum enzyme activity. The kinetics of the purified enzyme was studied and the Michaelis-Menten parameters such as rate constant (Km) and the maximum reaction rate (Vmax) were found as 0.059 mg/ml and 8.59 x 10-3 mmol/ml/sec respectively
Volatile Terpenoids from Water Pepper (Polygonum punctatum) Against Pseudomonas aeruginosa and Staphylococcus aureus Virulence Strategies
Get PDFPolygonum punctatum Elliot (water pepper) is a pungent herb ancestrally employed as a disinfectant in traditional medicine by Toba Indians of the north-eastern region of Argentina and also commonly used as spice in Japanese cuisine. GC-MS of whole diethyl ether extract (EE) from aerial parts allowed to identify 14 volatile terpenoids such as sesquiterpenes: α-bisabolol (3.4 %), polygodial and isotadeonal (34.0%); various methylated phenol like α-tocopherol or vitamin E (3.6 %), and phytosterols: stigmasterol (2.1%) and β-sitosterol (29.9 %). Thus, water pepper is a promising source of drimane sesquiterpenes and phytoestrogens with important bioactivities.
Following a taste- guided fractionation by CC and HPLC, drimane-type sesquiterpenes, polygodial (1) and its stereoisomer isotadeonal (2) were isolated as main compounds from the EE. The antipathogenic effects on the bacterial growth, biofilm formation, and elastase activity of both pure compounds and EE were evaluated against two Staphylococcus aureus and two Pseudomonas aeruginosa strains at 10 and 100 µg/mL.
The highest effects were observed for the non pungent drimane isotadeonal (2) which was able to reduce about 75 % the bacterial growth of all tested microorganisms and to inhibit Gram-positive biofilm formation (85 % mean) at 100 µg/mL. In addition, elastase activity of P. aeruginosa, another virulence strategy, was attenuated more than 50 % at 100 µg/mL by 2.
These results provide evidence that support the antimicrobial use of P. punctatum against P. aeruginosa and S. aureus, as well as, demonstrating that isotadeonal (2), despite it has been suggested to lack biological properties, is a bioactive compound able to control biofilm formation and bacterial growth of both human pathogens
Mass Transfer Resistances at the Boundary of a Fractured Porous Medium
Get PDFThe aim of this paper is the study of the mass transfer resistance effects at the boundary of a fractured porous media. The boundary between the porous media adjacent to the fluid considers the transient effects. The numerical experiments show that the α parameter has an influence that facilitates the mass transfer of the porous region to the fluid region. The α parameter expresses the relation of the mass transfer resistances between the porous media and the homogeneous fluid; in the present work it is considered as a parameter which facilities mass transfer of the porous region to the fluid region