Performance analysis of an industrial waste heat‐based trigeneration system

The thermodynamic performance of an industrial waste heat recovery‐based trigeneration system is studied through energy and exergy efficiency parameters. The effects of exhaust gas inlet temperature, process heat pressure, and ambient temperature on both energy and exergy efficiencies, and electrical to thermal energy ratio of the system are investigated. The energy efficiency increases while electrical to thermal energy ratio and exergy efficiency decrease with increasing exhaust gas inlet temperature. On the other hand, with the increase in process heat pressure, energy efficiency decreases but exergy efficiency and electrical to thermal energy ratio increase. The effect of ambient temperature is also observed due to the fact that with an increase in ambient temperature, energy and exergy efficiencies, and electrical to thermal energy ratio decrease slightly. These results clearly show that performance evaluation of trigeneration system based on energy analysis is not adequate and hence more meaningful evaluation must include exergy analysis. The present analysis contributes to further information on the role of exhaust gas inlet temperature, process heat pressure, ambient temperature influence on the performance of waste heat recovery‐based trigeneration from a thermodynamic point of view. Copyright © 2009 John Wiley & Sons, Ltd.     

Sonochemical synthesis of crystalline nanoporous zinc oxide spheres and their application in dye-sensitized solar cells

A composite material made of zinc oxide and polyvinyl alcohol was prepared by a sonochemical method. Annealing of the composite under air removed the polymer, leaving porous spheres of ZnO. This change was accompanied by a change of the surface area from 2 m²/g to 34 m²/g. The porous ZnO particles were used as the electrode material for dye-sensitized solar cells (DSSCs). It was tested by forming a film of the doped porous ZnO on a conductive glass support. The performance of the solar cell is reported.     

Electric and dielectric study of cobalt substituted MgMn nanoferrites synthesized by solution combustion technique

Cobalt substituted Mg–Mn nanoferrites with formulae Mg_0.9Mn_0.1Co_xFe_2?xO₄, x=0.0, 0.1, 0.2 and 0.3, have been synthesized for the first time by the solution combustion technique. The effects of Co²⁺ ions on the dc resistivity, dielectric constant and dielectric loss tangent of Mg–Mn nanoferrites at room temperature are presented in this paper. X-ray diffraction confirmed the formation of a single phase spinel structure. Particle size was found to increase, 20.9–23.9 nm, with increasing Co²⁺ concentration. The dc resistivity was increased by two order of magnitude with substitution of Co²⁺ ions while the dielectric constant was found to be decreasing with the increasing concentration of cobalt ions. The value of dc resistivity obtained for Mg_0.9Mn_0.1Fe₂O₄ nanoferrite in our work is greater than the value obtained for the same composition prepared by the conventional ceramic technique. Further, the dielectric constant and dielectric loss tangent were observed to be decreasing with the increase in frequency.     

An evaluation of fuelwood properties of some Aravally mountain tree and shrub species of Western India

The study analyses the fuelwood characteristics of 26 trees including shrub species from the dry deciduous forest in Aravally region, Rajasthan, Western India was carried out to explore trees with potential for fuelwood production. Fuelwood value index (FVI) based on the properties of calorific value, wood density and ash. Calorific value was ranged between 18.54 ± 0.04 and 27.44 ± 0.09 KJ g⁻¹ in Jatropha curcus and Wrightia tinctoria respectively. Wood density varied from 0.538 ± 0.01 to 0.966 ± 0.07 g/cm³ in J. curcus and Acacia nilotica. Same way ash and moisture content was highest in J. curcus (3.38 ± 0.19%) and Sterculia urens (70.28 ± 7.52%) and lowest in Miliusa tomentosa (0.85 ± 0.06%) and Azadirachta indica (30.7 ± 10.02%) respectively. On the basis, of the 26 species analyzed, M. tomentosa has the highest FVI, followed by Lannea coromandelica, Acacia leucophloea, Madhuca indica, A. nilotica, W. tinctoria, Butea monosperma, Zizyphus nummularia, S. urens, Boswellia serrata, A. indica, Grewia tenax, Syzygium cuminii, Tectona grandis and Dalbergia sissoo were shown to have promising fuelwood production.     

Poly(3-hexylthiophene) and hexafluoro-2-propanol-substituted polysiloxane based OFETs as a sensor for explosive vapor detection

The organic field effect transistors (OFETs) with regioregular poly 3-hexylthiophene (rr-P3HT) and hexafluoro-2-propanol-substituted polysiloxane (SXFA) as an organic layer, have been used for detection of explosive vapors with excellent sensitivity of less than 70 ppt for 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) and less than 100 ppt for 2,4,6-trinitrotoluene (TNT). The sensor response (% change in saturation current) was found to be 125 ± 10% for TNT and 90 ± 10% for RDX. It was also observed that the incorporation of Cu^II tetraphenylporphyrin (CuTPP) into rr-P3HT/SXFA matrix resulted in an improved selectivity for the vapors of nitro based analytes (TNT, RDX and DNB) as compared to the vapors of non explosive oxidizing agents such as nitrobenzene (NB), benzoquinone (BQ) and benzophenone (BP). This is attributed to the increased binding of the vapors containing nitro compound to the thin films due to the presence of CuTTP. Spin coated thin films were further characterized by Atomic Force Microscopy (AFM) and Electrostatic Force Microscopy (EFM).     

Deformation Behavior of Metastable Austenitic Steel at Low and Moderate Temperatures

Metal Science and Heat Treatment - The TRIP effect and deformation behavior of metastable austenitic steel were studied under tension in the temperatures range from –120 to +200°C. The...     

Effect of Retrogression and Re-Aging on Tensile Mechanical Properties in Transverse Direction of Extruded Rods from Aluminum Alloy AA7049

Metal Science and Heat Treatment - The effect retrogression and re-aging (RRA treatment) on the tensile properties in the transverse direction of extruded rods from aluminum alloy AA7049 is...     

Modeling the drain current and its equation parameters for lightly doped symmetrical double-gate MOSFETs

A 2D model for the potential distribution in silicon film is derived for a symmetrical double gate MOSFET in weak inversion. This 2D potential distribution model is used to analytically derive an expression for the subthreshold slope and threshold voltage. A drain current model for lightly doped symmetrical DG MOSFETs is then presented by considering weak and strong inversion regions including short channel effects, series source to drain resistance and channel length modulation parameters. These derived models are compared with the simulation results of the SILVACO (Atlas) tool for different channel lengths and silicon film thicknesses. Lastly, the effect of the fixed oxide charge on the drain current model has been studied through simulation. It is observed that the obtained analytical models of symmetrical double gate MOSFETs are in good agreement with the simulated results for a channel length to silicon film thickness ratio greater than or equal to 2.     

Propagation delay and power dissipation for different aspect ratio of single-walled carbon nanotube bundled TSV

Through-silicon vias (TSVs) have provided an attractive solution for three-dimensional (3D) integrated devices and circuit technologies with reduced parasitic losses and power dissipation, higher input-output (I/O) density and improved system performance. This paper investigates the propagation delay and average power dissipation of single-walled carbon nanotube bundled TSVs having different via radius and height. Depending on the physical configuration, a comprehensive and accurate analytical model of CNT bundled TSV is employed to represent the via (vertical interconnect access) line of a driver-TSV-load (DTL) system. The via radius and height are used to estimate the bundle aspect ratio (AR) and the cross-sectional area. For a fixed via height, the delay and the power dissipation are reduced up to 96.2% using a SWCNT bundled TSV with AR = 300 : 1 in comparison to AR = 6 : 1.     

Study of Temperature Dependence of Electrode–Glass Ceramic Interface Using Impedance Spectroscopy

The electrical behavior of strontium titanate borosilicate glass ceramics (SrO.TiO₂- 2SiO₂.B₂O₃) with additives K₂O, La₂O₃, CoO and Nb₂O₅ was studied by using Impedance Spectroscopy as a function of temperature and composition. An equivalent circuit model having three parallel RC's connected in series with a capacitor C₄ could represent the data well. By comparing the complex modulus plots with simulated ones and looking at the values of the time constants these RC's were attributed to represent crystalline, glassy and glass-crystal interface regions of the glass- ceramic whereas C₄ represented the glass-ceramic sample and contact electrode interface. When the glass ceramic sample contained only SrTiO₃ crystalline phase and the remaining glassy matrix, the interface capacitance showed an Arrhenius type of nature with an activation energy (0.11 ± 0.04) eV and when the glass- ceramic sample contained number of crystalline phases no clear cut trend appeared. These findings are useful in selecting suitable electrodes for applications as well as in deciding upon experimental techniques for measurement of dielectric constants of materials.