Narayan S.,Lambton College
International Journal of Energy, Environment and Economics | Year: 2011
When the pressure losses occuring in the Brayton cycle are accounted for, the cycle efficiency depends on the ratio of specific heats of the working fluid. The lower the ratio of specific heats, the higher the cycle efficiency. When tetrafluoromethane (CF 4 or Refrigerant-14), a non-toxic, non-flammable, thermally stable, fairly inert gas having a specific heat ratio of 1.1 - 1.14, is used as the working fluid in a closed cycle gas turbine, a 22% increase in the thermal efficiency can be obtained than when air is the working fluid. Other organic gases too could be used in the proposed Closed Organic Brayton (COB) cycle which can achieve a thermal efficiency of about 21 % with a heat source temperature of only 540°C (~1000 deg F). Its capital and operating costs will be competitive with existing small Rankine cycle steam power plants that burn biomass, and have typical gas turbine advantages like small plant footprint and quick startup. © 2012 Nova Science Publishers, Inc.
Zheng J.,University of Western Ontario |
Choo K.,University of Western Ontario |
Choo K.,Lambton College |
Bradt C.,GreenField Specialty Alcohols Inc. |
And 2 more authors.
Biotechnology Reports | Year: 2014
A modified twin-screw extruder incorporated with a filtration device was used as a liquid/solid separator for xylose removal from steam exploded corncobs. A face centered central composite design was used to study the combined effects of various enzymatic hydrolysis process variables (enzyme loading, surfactant addition, and hydrolysis time) with two differently extruded corncobs (7% xylose removal, 80% xylose removal) on glucose conversion. The results showed that the extrusion process led to an increase in cellulose crystallinity, while structural changes could also be observed via SEM. A quadratic polynomial model was developed for predicting the glucose conversion and the fitted model provided an adequate approximation of the true response as verified by the analysis of variance (ANOVA). © 2014 The Authors.
Karimi S.,Lambton College
ECS Transactions | Year: 2013
An electrochemical method based on pulse current electrodeposition (PCE) utilizing different waveforms was developed and used for fabricating membrane-electrode assemblies (MEAs) with low catalyst loading for use in proton exchange membrane (PEM) fuel cells. It was found that both peak deposition current density and duty cycle control the nucleation rate and the growth of platinum crystallites. Based on the combination of parameters used in this study, the optimum conditions for PCE were found to be a peak deposition current density of 400 mA cm-2, a duty cycle of 4%, and a pulse generated and delivered in the microsecond range utilizing a ramp-down waveform. MEAs prepared by PCE using the ramp-down waveform show performance comparable with commercial MEAs that employ several times the loading of platinum catalyst. © The Electrochemical Society.
Karimi S.,Lambton College |
Karimi S.,University of Toronto |
Foulkes F.R.,University of Toronto
Electrochemistry Communications | Year: 2012
The effects of waveform and other associated parameters on the pulse current electrodeposition of platinum electrocatalysts for use in polymer electrolyte membrane fuel cells were investigated. Using microsecond pulses with ramp-down waveforms yielded well dispersed, high surface area nanoparticles of 2-3 nm diameter, which, when incorporated into fuel cell membrane-electrode assemblies (MEAs), resulted in fuel cell performance comparable with commercial MEAs that employed ten times as much platinum loading. © 2012 Elsevier B.V. All rights reserved.
Trifkovic M.,University of Western Ontario |
Sheikhzadeh M.,LANXESS Corporation |
Choo K.,Lambton College |
Rohani S.,University of Western Ontario
Polymer Engineering and Science | Year: 2010
Multi-input multi-output (MIMO) models of a twinscrew co-rotating extruder for thermoplastic vulcanizate (TPV) are developed using the process identification techniques. The process inputs are screw speed (SS) and barrel temperature (WT). The three outputs are motor load (ML), melt temperature (MT), and melt pressure (MP). Two appropriate rubbers for TPV applications with different physical and mechanical properties are used for the experimentation. The process model is obtained from the experimental input-output data using various identification techniques such as least squares and prediction error. Recursive online model identification is performed on the process to update the model parameters in real time. To perform the identification studies, the process data was transferred via OPC server from the local PLC (Programmable Logic Controller) to the Advanced Control and Identification toolbox in MATLAB software. The effect of rubber properties and two curative agents (Peroxide and Phenolic) in the TPV experiment are studied on the final identified models. This comprehensive model identification study provided sufficient accurate models for further model based process analysis and control for TPV applications. © 2009 Society of Plastics Engineers.