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01761 The sintering temperature of ash, agglomeration,and defluidisation in a bench scale PFBC
12 Refractories~ceramics (properties, production, applications) differences are due to the differences of the heat transfer characteristics such as thermal conductivity of metal hydride particles and porosity between the assumed and actual ones. It is important to obtain the heat transfer characteristics such as thermal conductivity of metal hydride particles and porosity both during the hydriding and dehydriding to design a metal hydride vessel.
05/01759 Modernisation of existing and new construction of power plants in Germany: results of an optimisation model Schwarz, H.-G. Energy Economics, 2005, 27, (1), 113-137. If the average lifetime of a power plant is assumed, as is commonly accepted, to be 30 to 35 years, then the German power plant inventory is outdated. In light of this, several studies have predicted a comprehensive conversion of the German power-generating industry within the next few years. It is the objective of this paper to verify this finding using an optimization approach. Different policy scenarios are defined. The requirements are calculated for the future modernization of existing and the new construction of conventional power plants in Germany, as well as the share of new and total capacity provided by various energy sources. The optimization approach used considers the modernization of old plants as an investment alternative to the construction of new plants. This fills the gap in existing power station models, which do not consider plant modernization. Estimates, depending on scenario assumptions, show that discrepancies between models that include plant modernization and models that do not include it are considerable.
05/01760 Optimal configuration design for plate heat exchangers Gut, J. A. W. and Pinto, J. M. International Journal of Heat and Mass Transfer, 2004, 47, (22), 4833 4848. A screening method is presented for selecting optimal configurations for plate heat exchangers. The optimization problem is formulated as the minimization of the heat transfer area, subject to constraints on the number of channels, pressure drops, flow velocities and thermal effectiveness, as well as the exchanger thermal and hydraulic models. The configuration is defined by six parameters, which are as follows: number of channels, numbers of passes on each side, fluid locations, feed relative location and type of channel flow. The proposed method relies on a structured search procedure where the constraints are successively applied to eliminate infeasible and sub-optimal solutions. The method can be also used for enumerating the feasible region of the problem; thus any objective function can be used. Examples show that the screening method is able to successfully determine the set of optimal configurations with a very reduced number of exchanger evaluations. Approximately 5% of the pressure drop and velocity calculations and 1% of the thermal simulations are required when compared to an exhaustive enumeration procedure. An optimization example is presented with a detailed sensitivity analysis that illustrates the application and performance of the screening method.
05•01761 The sintering temperature of ash, agglomeration, and defluidisation in a bench scale PFBC A1-Otoom, A. et al. Fuel, 2005, 84, (1), 109 114. Five Australian black coals were studied in a bench scale pressurized fluidized bed combustor (PFBC) to investigate the agglomeration propensity. It was found that coals with higher proportions of calcium aluminosilicate showed higher propensity for agglomeration and defluidization. The pressure-drop sintering technique can predict the agglomeration propensity for coals. Samples with a sintering temperature lower than the operating temperature of the PFBC showed agglomeration. The laboratory ash can be a good representative of the PFBC ash when studying agglomeration and defluidization.
12 REFRACTORIES/ CERAMICS Properties, production, applications 05•01762 Ceramic anode catalyst for dry methane type molten carbonate fuel cell Tagawa, T. et al. Journal of Power Sources, 2004, 126, (1 2), 1 7.
Oxide catalyst materials for methane oxidation were examined in order to develop the anode electrode for molten carbonate type fuel cell (MCFC). As a primary selection, oxides such as lanthanum (La203) and samarium (Sm203) were selected from screening experiments of TPD, TG and tubular reactor. Composite materials of these oxides with titanium fine powder were assembled into a cell unit for MCFC as the anode electrode. Steady-state activities were observed with these anode electrode materials when hydrogen was used as a fuel. When methane was directly charged to anode as a fuel (dry methane operation), a power generation with steady state was observed on both lanthanum and samarium composites after gradual decrease of open circuit electromotive force (OCV) and closed circuit current (CCI). The steady-state activity held as long as 144 h of continuous operation.
05•01763 Determination of effective charge states for point radiation defects in fusion ceramic materials Ryazanov, A. I. et al. Journal of Nuclear Materials, 2004, 329-333, (I), 97-102. Point defects in fusion ceramic materials under irradiation can have an effective charge due to ionization and covalent chemical bonding. The kinetics of charged point defects in these materials is determined by their effective charge and this kinetics is completely different from non-charged point defects in metals. The experimental investigation of point defect charge states in ceramic materials is rather difficult. In this paper, a new method is proposed for the investigation of charge states of point defects in irradiated ceramic materials. This method is based on a new theoretical model and experimental observations of defect cluster formation near permanent sinks, such as grain boundaries. Previous experimental investigations show that a denuded zone is formed in irradiated ceramic materials near free surfaces and grain boundaries. The effect of an applied electric field on the formation of interstitial-type point defect clusters (dislocation loops) near grain boundaries in irradiated ceramic materials is investigated. For this purpose a new theoretical model is suggested, which takes into account the effect of an applied electric field on the denuded zone formation. It is shown that the denuded zone size depends on point defect charge and direction of applied electric field. The obtained theoretical results are compared with experimental data.
05•01764 Effects of atmospheric powder on microstructure and piezoelectric properties of PMZN-PZT quaternary ceramics Hou, Y.-D. et al. Journal of the European Ceramic Society, 2004, 24, (15-16), 3731 3737. The effects of atmospheric powder on microstructure and piezoelectric properties of Pb(Mnl/3Nbz/3)O3-Pb(Znx/3Nb2/3)O3-PbZrO3-PbTiO3 (PMZN-PZT) quaternary ceramics were investigated. Specimens with various contents of Pb(Mnl/3Nb2/3)O3 from 0 to 20 tool% were prepared by columbite two-stage process with and without atmospheric powder of PbZrO3. The results revealed that the atmospheric powder is favored to the liquid-state sintering process in PbO vapour pressure equilibrium. The specimen sintered with atmospheric powder is homogenous and the fracture is intergranular. However, the specimen sintered without atmospheric powder is less homogenous and the fracture is essentially transgranular. On the other hand, the pyrochlore phase was formed along with the perovskite phase for the specimens sintered without atmospheric powder and the second phase was seriously detrimental to the electromechanical properties. The superior piezoelectric properties were observed for the specimens sintered with atmospheric powder. By optimizing the specimen composition, excellent piezoelectric, and dielectric properties (Qm=2528, Kp = 0.55, tan 6 = 0.003) were obtained at 10 tool% Pb(Mnl/3Nb2/3)O3.
05/01765 Experimental investigation of performance of a multi-purpose PV-slat window Khedari, J. et al. Solar Energy Materials and Solar Cells, 2004, 82, (3), 431-445. This paper reports on experimental investigation of performance of a new type of PV-slat window (PV-SW). The main functions of this PVSW are as follows: to admit sufficient daylight, to act as a shading device for decreasing direct heat gain through window glazing and to ensure indoor air movement, which improves resident's thermal comfort. To assess the performance of this PV-SW, two test rooms of l x l x l . 5 m 3 (H.'W.'L) volume were built using plywood and gypsum boards. At the first, the PV-SW of 0.5x0.6 m surface area was located at the south-facing wall whereas the other room was equipped with a commercial transparent slat window of the same size. The PV-SW consists of six PV slats. The photovoltaic cells were connected in series giving a maximum electrical power output of 36 W (12 Vx3 A). The circuit was connected to a direct current axial fan, located inside the room, that requires a maximum power of 43 W. The analysis of performance of this PV-SW was investigated based on power output, daylight factor and temperature difference between indoor and ambient. The experimental results showed that this multi-purpose PV-SW is extremely interesting as it can produce power up to 15 W,
Fuel and Energy Abstracts
July 2005 259
05/01759 Modernisation of existing and new construction of power plants in Germany: results of an optimisation model Schwarz, H.-G. Energy Economics, 2005, 27, (1), 113-137. If the average lifetime of a power plant is assumed, as is commonly accepted, to be 30 to 35 years, then the German power plant inventory is outdated. In light of this, several studies have predicted a comprehensive conversion of the German power-generating industry within the next few years. It is the objective of this paper to verify this finding using an optimization approach. Different policy scenarios are defined. The requirements are calculated for the future modernization of existing and the new construction of conventional power plants in Germany, as well as the share of new and total capacity provided by various energy sources. The optimization approach used considers the modernization of old plants as an investment alternative to the construction of new plants. This fills the gap in existing power station models, which do not consider plant modernization. Estimates, depending on scenario assumptions, show that discrepancies between models that include plant modernization and models that do not include it are considerable.
05/01760 Optimal configuration design for plate heat exchangers Gut, J. A. W. and Pinto, J. M. International Journal of Heat and Mass Transfer, 2004, 47, (22), 4833 4848. A screening method is presented for selecting optimal configurations for plate heat exchangers. The optimization problem is formulated as the minimization of the heat transfer area, subject to constraints on the number of channels, pressure drops, flow velocities and thermal effectiveness, as well as the exchanger thermal and hydraulic models. The configuration is defined by six parameters, which are as follows: number of channels, numbers of passes on each side, fluid locations, feed relative location and type of channel flow. The proposed method relies on a structured search procedure where the constraints are successively applied to eliminate infeasible and sub-optimal solutions. The method can be also used for enumerating the feasible region of the problem; thus any objective function can be used. Examples show that the screening method is able to successfully determine the set of optimal configurations with a very reduced number of exchanger evaluations. Approximately 5% of the pressure drop and velocity calculations and 1% of the thermal simulations are required when compared to an exhaustive enumeration procedure. An optimization example is presented with a detailed sensitivity analysis that illustrates the application and performance of the screening method.
05•01761 The sintering temperature of ash, agglomeration, and defluidisation in a bench scale PFBC A1-Otoom, A. et al. Fuel, 2005, 84, (1), 109 114. Five Australian black coals were studied in a bench scale pressurized fluidized bed combustor (PFBC) to investigate the agglomeration propensity. It was found that coals with higher proportions of calcium aluminosilicate showed higher propensity for agglomeration and defluidization. The pressure-drop sintering technique can predict the agglomeration propensity for coals. Samples with a sintering temperature lower than the operating temperature of the PFBC showed agglomeration. The laboratory ash can be a good representative of the PFBC ash when studying agglomeration and defluidization.
12 REFRACTORIES/ CERAMICS Properties, production, applications 05•01762 Ceramic anode catalyst for dry methane type molten carbonate fuel cell Tagawa, T. et al. Journal of Power Sources, 2004, 126, (1 2), 1 7.
Oxide catalyst materials for methane oxidation were examined in order to develop the anode electrode for molten carbonate type fuel cell (MCFC). As a primary selection, oxides such as lanthanum (La203) and samarium (Sm203) were selected from screening experiments of TPD, TG and tubular reactor. Composite materials of these oxides with titanium fine powder were assembled into a cell unit for MCFC as the anode electrode. Steady-state activities were observed with these anode electrode materials when hydrogen was used as a fuel. When methane was directly charged to anode as a fuel (dry methane operation), a power generation with steady state was observed on both lanthanum and samarium composites after gradual decrease of open circuit electromotive force (OCV) and closed circuit current (CCI). The steady-state activity held as long as 144 h of continuous operation.
05•01763 Determination of effective charge states for point radiation defects in fusion ceramic materials Ryazanov, A. I. et al. Journal of Nuclear Materials, 2004, 329-333, (I), 97-102. Point defects in fusion ceramic materials under irradiation can have an effective charge due to ionization and covalent chemical bonding. The kinetics of charged point defects in these materials is determined by their effective charge and this kinetics is completely different from non-charged point defects in metals. The experimental investigation of point defect charge states in ceramic materials is rather difficult. In this paper, a new method is proposed for the investigation of charge states of point defects in irradiated ceramic materials. This method is based on a new theoretical model and experimental observations of defect cluster formation near permanent sinks, such as grain boundaries. Previous experimental investigations show that a denuded zone is formed in irradiated ceramic materials near free surfaces and grain boundaries. The effect of an applied electric field on the formation of interstitial-type point defect clusters (dislocation loops) near grain boundaries in irradiated ceramic materials is investigated. For this purpose a new theoretical model is suggested, which takes into account the effect of an applied electric field on the denuded zone formation. It is shown that the denuded zone size depends on point defect charge and direction of applied electric field. The obtained theoretical results are compared with experimental data.
05•01764 Effects of atmospheric powder on microstructure and piezoelectric properties of PMZN-PZT quaternary ceramics Hou, Y.-D. et al. Journal of the European Ceramic Society, 2004, 24, (15-16), 3731 3737. The effects of atmospheric powder on microstructure and piezoelectric properties of Pb(Mnl/3Nbz/3)O3-Pb(Znx/3Nb2/3)O3-PbZrO3-PbTiO3 (PMZN-PZT) quaternary ceramics were investigated. Specimens with various contents of Pb(Mnl/3Nb2/3)O3 from 0 to 20 tool% were prepared by columbite two-stage process with and without atmospheric powder of PbZrO3. The results revealed that the atmospheric powder is favored to the liquid-state sintering process in PbO vapour pressure equilibrium. The specimen sintered with atmospheric powder is homogenous and the fracture is intergranular. However, the specimen sintered without atmospheric powder is less homogenous and the fracture is essentially transgranular. On the other hand, the pyrochlore phase was formed along with the perovskite phase for the specimens sintered without atmospheric powder and the second phase was seriously detrimental to the electromechanical properties. The superior piezoelectric properties were observed for the specimens sintered with atmospheric powder. By optimizing the specimen composition, excellent piezoelectric, and dielectric properties (Qm=2528, Kp = 0.55, tan 6 = 0.003) were obtained at 10 tool% Pb(Mnl/3Nb2/3)O3.
05/01765 Experimental investigation of performance of a multi-purpose PV-slat window Khedari, J. et al. Solar Energy Materials and Solar Cells, 2004, 82, (3), 431-445. This paper reports on experimental investigation of performance of a new type of PV-slat window (PV-SW). The main functions of this PVSW are as follows: to admit sufficient daylight, to act as a shading device for decreasing direct heat gain through window glazing and to ensure indoor air movement, which improves resident's thermal comfort. To assess the performance of this PV-SW, two test rooms of l x l x l . 5 m 3 (H.'W.'L) volume were built using plywood and gypsum boards. At the first, the PV-SW of 0.5x0.6 m surface area was located at the south-facing wall whereas the other room was equipped with a commercial transparent slat window of the same size. The PV-SW consists of six PV slats. The photovoltaic cells were connected in series giving a maximum electrical power output of 36 W (12 Vx3 A). The circuit was connected to a direct current axial fan, located inside the room, that requires a maximum power of 43 W. The analysis of performance of this PV-SW was investigated based on power output, daylight factor and temperature difference between indoor and ambient. The experimental results showed that this multi-purpose PV-SW is extremely interesting as it can produce power up to 15 W,
Fuel and Energy Abstracts
July 2005 259