- Email: [email protected]
02532 In-situ formation of carbon nanotubes in an alumina-nanotube composite by spray pyrolysis
12 Refractories/ceramids (properties, production, applications) 04102523 Corus Ijmuiden BF No,6 ends successful 15-year campaign den Exter, P. et al. 1SSTech Conference Proceedings, 1st, Indianapolis, IN, United States, 27-30 April, 2003, 1637-1647. Blast furnace No. 6 ended a very successful campaign of 16 years in which 34.3 million tonnes were produced. From the campaign, the following can be concluded. High productivity and high pulverized coal injection/low coke rate operation were mastered. A new philosophy of blast furnace repair strategy was developed to limit the activities during the repair period. The campaign extension programme put in place in 1996 was effective and led to postponement of the repair from 1999 to 2002. The wear of the hearth showed a pronounced elephant foot, but the effectiveness of the safety graphite was shown. The semi-graphite in the bottom fiw: plate cooler rows of the bosh had to be replaced with graphite~ this replacement was not anticipated. No repairs were required in upper bosh, belly, and stack. A fast blow-in and ramp-up were achieved and the first operational results indicate all possibilities for a successfu] new campaign.
04102524 Coupling of steam and dry reforming of methane in catalytic fluidized bed membrane reactors Abashar, M. E. E. International Journal of Itydrogen Energy, 2004, 29, (8), 799-808. A rigorous mathematical model is used for the simulation of steam and CO2 reforming in fluidized bed membrane reactors. A well-mixed catalyst pattern is implemented to couple the reactions. It has been shown that the combined effect of the membrane and reaction coupling provides exciting opportunities to overcome the equilibrium conversion limits and to achieve complete conversion of methane. The results indicate that the complete conversion of methane at low temperature is possible. Optimal conditions are observed to exist and an effective reactor length criterion is used to evaluate the reactor performance. The influence of some key parameters on the optimal conditions and the reactor such as temperature, pressure, steam to carbon ratio and membrane thickness have been investigated.
04102525 Energy penalty associated with fouling in enhanced tubes in chiller-flooded condenser Li, W. Journal of Enhanced Heat Tran~'fer, 2003, 10, (1), 149-158. The article describes the energy penalty associated with long-term cooling tower water fouling data in seven 15.54 mm ID copper, helically ribbed tubes taken at low water velocity (1.07 m/s). The ranges of geometric parameters were number of rib starts (18-45), helix angle (24-45°), and height (0.33-0.55 ram). These geometries provide fouling data on a new class of internal enhancement that is typical of commercially enhanced tubes presently used in water chillers. Significant fouling in the 30-45 start tubes results in a large increase of operating cost at the end of a cooling season. A linear multiple regression correlation of energy penalty as a function of geometric variables and Reynolds numbers was developed.
of this low-temperature methanol synthesis approach is considered in light of the recent advances in CO2 sequestration technologies. A successful development of this technology may also provide an atomeconomical pathway to transport remote natural gas in the form of methanol, a liquid energy-carrier.
04•02528 Isobutene hydration in a countercurrent flow fixed bed reactor Zhang, C. M. et al. Chemical Engineering and Processing, 2004, 43, (4), 533-539. Hydrodynamics, mass transfer and reaction kinetics of isobutene hydration over Amberlyst-15 have been studied in a countercurrent flow fixed bed reactor. The reaction exhibited a pseudo-first-order kinetics with respect to the isobutene partial pressure with an activation energy of 66 kJ reel 1. A modified cell model was used to describe the experimental results.
04•02529 Long-term performance of an industrial water desalination plant A1-Bastaki, N. and Abbas, A. Chemical Engineering and Processing, 2004, 43, (4), 555-558. The long-term performance of a medium-scale industrial spiral wound reverse osmosis ( R e ) water desalination plant was studied. Operational data were analysed for a period of 1500 days as a basis for evaluating the performance variation with time. A theoretical model based on the solution-diffusion mass-transfer theory and concentration polarization was employed to extract the water and salt permeability coefficients. The results indicate that after over 4 years of continuous operation, the water permeability coefficient declined by about 39% and the average salt permeability coefficient increased by about 60%. Periodic membrane cleaning schemes were effective in partially restoring the water and salt permeabilities.
04/02530 The use of chemical recuperation of heat in a power plant Verkhivker, G. and Kravchenko, V. Energy, 2004, 29, (3), 379-388. Chemical recuperation of heat is the most considerable method of increasing the efficiency of combined-cycle plants, but plants with chemical recuperation are not in application yet. In this paper, the causes of this phenomenon have been examined and the thermodynamic basis of using chemical recuperation of heat has been given. The energy efficiency of a combined cycle plant with chemical recuperation has reached 80-90% and more and it increases with lower reforming pressure. Additionally, chemical recuperation has raised the amount of gas fuel used in energy and chemical industries and has decreased the amount of waste carbon dioxide ejected into the environment by nearly 20%. The energy efficiency of a power plant with chemical recuperation must be calculated with registration of the methane which does not undergo a reaction in the reformer.
04102525 Fluidized bed carbonization system for method of production of carbonaceous materials Toyota, S, et al. Jpn. Kokai Tokkyo Koho JP 2003 213,270 (C1. Cl10B49/22), 30 Jul 2003, Appl. 2002/18,253. (In Japanese) The system includes a carbonization chamber having a fluidization medium for pyrolysis of the first raw material (e.g. waste wood) by heating to produce carbonaceous material, a heating chamber for receiving fluidization medium and portion of the first law material from the carbonization chamber to form fluidized bed in the heating chamber for combustion and heating the fluidization medium, a passage for recycling heated medium back to the carbonization chamber, and a separator for separating the carbonaceous material and the medium discharged from the carbonization chamber, to improve yield of carbonaceous material with formation of hot spot.
04•02527 integrating low-temperature methanol synthesis and CO2 sequestration technologies: application to IGCC plants Mahajan, D. and Goland, A. N. Catalysis Today, 2003, 84, (I-2), 7181. Coupling a low-temperature once-through methanol synthesis process with CO2 separation technology would provide an option for integrated gasification combined cycle (IGCC) power plants to address the C O , mitigation issue and also create the capability to utilize methanol as a peak-shaving fuel. Data are presented that show that several nickel complexes activated by alkoxide bases catalyse facile synthesis of methanol from synthesis gas (primarily a mixture of CO and H2) in homogeneous liquid phase under mild conditions of temperature (<150°C) and pressure (<5 MPa). Under these mild conditions, batchmode productivity of up to 20 g reel MeOH/1 cat. h is achieved and more importantly, per pass gas conversion and methanol selectivity exceed 90 and 95%, respectively. The overall synthesis gas to methanol process has built-in waste-minimization and minimum by-product formation features and thus achieves CO2 mitigation, The potential
12
REFRACTORIES/ CERAMICS Properties, production, applications
04102531 High precision (1 part in 104) reflectivity measurement for the study of reflective materials used in solar collectors Chen, Y. T. et al. Solar Energy Materials and Solar Cells', 2003, 80, (3), 305-314. A new method of reflectivity measurement for the study of reflective materials in solar energy technology is reported in this paper. The method employs a fast rotating reference mirror and certain geometry configuration to alternatively deliver the light via a sample mirror or by passin~ it to a photo detector. It has been proved to reach a precision of 10 4 . With a good repeatability of the method, outdoor exposure tests of sample mirrors have been carried out in a relatively short period (1 month) and significant specular reflectance losses due to an aging process have been observed.
04•02532 In-situ formation of carbon nanotubes in an alumina-nanotube composite by spray pyrolysis Kamalakaran, R. et al. Carbon, 2003, 41, (14), 2737-2741.
Fuel and Energy Abstracts September 2004 353
13 Space heating and cooling Alumina (AleO3)-earbon nanotube composite materials were synthesized by spraying a slurry of ferrocene (Fe(C5Hs)z) and alumina in xylene, at 1000~50°C, using argon (_<1.5 bar) as carrier gas. The asprepared materials were formed in large flakes (ca. 2 era) and consist of nanotubes intricately matted in a glassy alumina matrix. Based on the structural and microstructural investigations done by scanning electron microscopy and high-resolution transmission electron microscopy, a possible growth mechanism has been suggested.
04/02533 window
Modeling and simulation of a simple glass
Ismail, K. A. R. and Henrfquez, J. R. Solar Energy Materials and Solar Cells, 2003, 80, (3), 355-374. This paper presents a mathematical model with numerical simulations of the heat transfer across a simple glass window. The model is twodimensional, transient based upon the energy equation with a source term to account for the solar radiation absorbed through the glass sheet. Variable incident solar radiation and external ambient temperature are considered in the numerical simulations. The governing equations and the associated boundary conditions are discretized by the finite difference approach and the ADI scheme. Numerical simulations are realized for the cases of clear and absorbing glass to show the effect of the glass thickness on the total heat gain, the solar heat gain and the shading coefficient.
04•02534
Natural convection at an indoor glazing surface
Cuevas, C. and Fissore, A. Building and Environment, 2004, 39, (9), 1049-1053. An experimental study was made to determine correlations that allow the calculation of heat transferred by convection through the window. Three configurations were studied: a hot plate; a cold plate and a window with a single-step frame placed on the wall of a room. A correlation was obtained that could be used to calculate the convection heat transfer through the window. The new correlation in the hot plate configuration differed by 14.5% from the A S H R A E correlation for laminar-free convection on a vertical surface, is 27.5% from the cold plate and is 12% from the single step-frame.
04/02535 Peculiarities of boiling heat transfer on capillaryporous coverings Poniewski, M. E. International Journal of Thermal Sciences, 2004, 43, (5), 431-442. The paper discussed specific features of boiling heat transfer on developed industrial micro-surfaces and surfaces with capillary porous coverings obtained with various techniques. Boiling on such surfaces is characterized by the occurrence of a few physically disparate hysteresis phenomena, as well as by the different course of nucleate boiling crisis as compared with smooth surfaces. Attempts at modelling the nucleation hysteresis and that of the I-kind and also nucleate boiling crisis for various surfaces with capillary-porous covering were presented. Apart from the discussion of other researchers' investigation results, the physical interpretation of lI-kind hysteresis phenomenon was given. A theoretical model congruent with experimental data for metal fibrous coverings was also provided. The properties of three hydrodynamic models of nucleate boiling crisis were discussed as well. The statistical concept of the maximum point process was employed for the sake of intra-layer boiling crisis modelling; the result obtained was consistent with the experiment.
04/02536 Protonic ceramic fuel cells for high-efficiency operation with methane Coors, W. G. Journal of Power Sources, 2003, 118, (1-2), 150 156. A new class of fuel cells is being developed, based on ceramic electrolyte materials that exhibit high protonic conductivity at elevated temperatures. The protonic ceramic fuel cell (PCFC) is fundamentally different and unique among fuel cell types currently being developed because it relies on conduction of protons through the electrolyte at much higher temperatures than is possible with other protonconducting fuel cells. Operating at 750°C, the PCFC is ideal for use with hydrocarbon fuels, such as natural gas. Proton conduction implies that water vapour is produced at the cathode, where it is swept away by air, rather than at the anode (as in a solid oxide fuel cell), where it dilutes the fuel. Since carbon dioxide is the only exhaust gas produced, higher fuel utilization is possible. Ambipolar steam permeation from the cathode to the anode provides the steam for direct reforming of hydrocarbons, so external steam injection is not required. Therefore, high thermodynamic efficiency is achieved and coking is not a problem. All of these features make it possible to construct a fuel cell of unprecedented electrical efficiency when operated on hydrocarbon fuels. The principles of operation and the current status of single-cell testing on methane at Protonetics will be described.
354
Fuel and Energy Abstracts
September 2004
04/02537 Silica antireflective films on glass produced by the sol-gel method Bautista, M. C. and Morales, A. Solar Energy Materials and Solar Cells, 2003, 80, (2), 217-225. Up to now antireflective silica thin films deposited on glass do not have enough strength and display poor adhesion to the substrate. Three methods to obtain silica antireflective films on glass were surveyed to identify the best way to produce the antireflective effect on glass by introducing a certain degree of porosity. Porous silica layers, obtained from the polymeric and colloidal methods, permit a considerable reduction of these light reflections compared with uncoated glasses in all the cases studied, but the degree of reduction as well as the adhesive properties is different depending on the method used to achieve the precursor solution. The AM1.5 solar transmittance increased from 0.915 for the bare slide up to 0.970 for the best-made sample corresponding to the Triton-doped silica.
04/02538 Thick-film nickel-metal-hydride battery based on porous ceramic substrates Do, J.-S. et al. Journal of Power Sources, 2003, 117, (1-2), 203-211. Nickel-metal-hydride (Ni-MH) batteries are prepared with thick-film and thin-film technologies based on porous ceramic substrates. The porosity and the mean pore diameter of BP ceramic substrates prepared from the argils increases from 19.81% and 0.0432 pm to 29.81% and 0.224 ~tm, respectively, upon increasing the ethyl cellulose content in the BP argil from 0 to 0.79%. The pore diameter of A1203 substrates prepared from A1203 powder is mainly distributed in the range 0.01-0.5 gin. The distribution of the pore diameters of BP ceramic substrates ties in two ranges, namely: 0.04-2 gm and 10-300 gm. Using BP ceramic plates and A1203 plates as substrates to fabricate thick-film N i - M H batteries, the optimal electroactive material utilization in the batteries is 77.0 and 71.1%, respectively. On increasing the screen-printing number for preparing the cathode (Ni(OH)z) from 1 to 3, the discharge capacity of the thick-film battery increases from 0.2917 to 0.7875 mAh, and the utilization in the battery decreases from 71.0 to 53.0%.
13
SPACE HEATING A N D COOLING
04/02539 Total solar energy transmittance of glass double fa(;ades with free convection Manz, H. Energy and Buildings, 2004, 36, (2), 127-136. Double facades made of glass layers with a ventilated mid-pane shading device are often used in commercial buildings. The solar-collector-like construction leads to high temperatures in the facade cavities during summertime and the possible overheating of the building. Of key significance for the cooling load of the building and thermal comfort of its occupants is the total solar energy transmittance to the interior. A procedure for modelling such facades - comprising a spectral optical and a computational fluid dynamic (CFD) model-is described and simulation results are compared with data derived from an experimental investigation of a single-story glass double facade with free convection, incorporated in an outdoor test facility. The influence of the layer sequence and ventilation properties on the thermal behaviour is discussed. It is shown that, for a given set of layers, total solar energy transmittance can easily vary by a factor greater than five. Hence, for reliable prediction of the total solar energy transmittance of a designed facade, models are needed that factor in all the relevant parameters. A spectral optical model combined with a CFD model that includes convection, conduction and radiation, is therefore recommended for analysing and optimizing glass double facades.
04/02540 A four-bed mass recovery adsorption refrigeration cycle driven by low temperature waste/ renewable heat source Alam, K. C. A. et al. Renewable Energy, 2004, 29, (9), I461-1475. The study deals with an advanced four-bed mass recovery adsorption refrigeration cycle driven by low temperature heat source. The proposed cycle consists of two basic adsorption refrigeration cycle. The heat source rejected by one cycle is used to power the second cycle. Due to the cascading use of heat and cooling source, all major components of the system maintain different pressure levels. The proposed cycle utilize those pressure levels to enhance the refrigeration mass circulation that leads the system to perform better performances. The performance of the proposed cycle evaluated by the mathematical model at equilibrium condition and compared with the performance of the basic two-bed adsorption refrigeration cycle. It is seen that the cooling effect as well as COP of the proposed cycle is superior to those of the basic cycle. The performances of the cycle are
04102524 Coupling of steam and dry reforming of methane in catalytic fluidized bed membrane reactors Abashar, M. E. E. International Journal of Itydrogen Energy, 2004, 29, (8), 799-808. A rigorous mathematical model is used for the simulation of steam and CO2 reforming in fluidized bed membrane reactors. A well-mixed catalyst pattern is implemented to couple the reactions. It has been shown that the combined effect of the membrane and reaction coupling provides exciting opportunities to overcome the equilibrium conversion limits and to achieve complete conversion of methane. The results indicate that the complete conversion of methane at low temperature is possible. Optimal conditions are observed to exist and an effective reactor length criterion is used to evaluate the reactor performance. The influence of some key parameters on the optimal conditions and the reactor such as temperature, pressure, steam to carbon ratio and membrane thickness have been investigated.
04102525 Energy penalty associated with fouling in enhanced tubes in chiller-flooded condenser Li, W. Journal of Enhanced Heat Tran~'fer, 2003, 10, (1), 149-158. The article describes the energy penalty associated with long-term cooling tower water fouling data in seven 15.54 mm ID copper, helically ribbed tubes taken at low water velocity (1.07 m/s). The ranges of geometric parameters were number of rib starts (18-45), helix angle (24-45°), and height (0.33-0.55 ram). These geometries provide fouling data on a new class of internal enhancement that is typical of commercially enhanced tubes presently used in water chillers. Significant fouling in the 30-45 start tubes results in a large increase of operating cost at the end of a cooling season. A linear multiple regression correlation of energy penalty as a function of geometric variables and Reynolds numbers was developed.
of this low-temperature methanol synthesis approach is considered in light of the recent advances in CO2 sequestration technologies. A successful development of this technology may also provide an atomeconomical pathway to transport remote natural gas in the form of methanol, a liquid energy-carrier.
04•02528 Isobutene hydration in a countercurrent flow fixed bed reactor Zhang, C. M. et al. Chemical Engineering and Processing, 2004, 43, (4), 533-539. Hydrodynamics, mass transfer and reaction kinetics of isobutene hydration over Amberlyst-15 have been studied in a countercurrent flow fixed bed reactor. The reaction exhibited a pseudo-first-order kinetics with respect to the isobutene partial pressure with an activation energy of 66 kJ reel 1. A modified cell model was used to describe the experimental results.
04•02529 Long-term performance of an industrial water desalination plant A1-Bastaki, N. and Abbas, A. Chemical Engineering and Processing, 2004, 43, (4), 555-558. The long-term performance of a medium-scale industrial spiral wound reverse osmosis ( R e ) water desalination plant was studied. Operational data were analysed for a period of 1500 days as a basis for evaluating the performance variation with time. A theoretical model based on the solution-diffusion mass-transfer theory and concentration polarization was employed to extract the water and salt permeability coefficients. The results indicate that after over 4 years of continuous operation, the water permeability coefficient declined by about 39% and the average salt permeability coefficient increased by about 60%. Periodic membrane cleaning schemes were effective in partially restoring the water and salt permeabilities.
04/02530 The use of chemical recuperation of heat in a power plant Verkhivker, G. and Kravchenko, V. Energy, 2004, 29, (3), 379-388. Chemical recuperation of heat is the most considerable method of increasing the efficiency of combined-cycle plants, but plants with chemical recuperation are not in application yet. In this paper, the causes of this phenomenon have been examined and the thermodynamic basis of using chemical recuperation of heat has been given. The energy efficiency of a combined cycle plant with chemical recuperation has reached 80-90% and more and it increases with lower reforming pressure. Additionally, chemical recuperation has raised the amount of gas fuel used in energy and chemical industries and has decreased the amount of waste carbon dioxide ejected into the environment by nearly 20%. The energy efficiency of a power plant with chemical recuperation must be calculated with registration of the methane which does not undergo a reaction in the reformer.
04102525 Fluidized bed carbonization system for method of production of carbonaceous materials Toyota, S, et al. Jpn. Kokai Tokkyo Koho JP 2003 213,270 (C1. Cl10B49/22), 30 Jul 2003, Appl. 2002/18,253. (In Japanese) The system includes a carbonization chamber having a fluidization medium for pyrolysis of the first raw material (e.g. waste wood) by heating to produce carbonaceous material, a heating chamber for receiving fluidization medium and portion of the first law material from the carbonization chamber to form fluidized bed in the heating chamber for combustion and heating the fluidization medium, a passage for recycling heated medium back to the carbonization chamber, and a separator for separating the carbonaceous material and the medium discharged from the carbonization chamber, to improve yield of carbonaceous material with formation of hot spot.
04•02527 integrating low-temperature methanol synthesis and CO2 sequestration technologies: application to IGCC plants Mahajan, D. and Goland, A. N. Catalysis Today, 2003, 84, (I-2), 7181. Coupling a low-temperature once-through methanol synthesis process with CO2 separation technology would provide an option for integrated gasification combined cycle (IGCC) power plants to address the C O , mitigation issue and also create the capability to utilize methanol as a peak-shaving fuel. Data are presented that show that several nickel complexes activated by alkoxide bases catalyse facile synthesis of methanol from synthesis gas (primarily a mixture of CO and H2) in homogeneous liquid phase under mild conditions of temperature (<150°C) and pressure (<5 MPa). Under these mild conditions, batchmode productivity of up to 20 g reel MeOH/1 cat. h is achieved and more importantly, per pass gas conversion and methanol selectivity exceed 90 and 95%, respectively. The overall synthesis gas to methanol process has built-in waste-minimization and minimum by-product formation features and thus achieves CO2 mitigation, The potential
12
REFRACTORIES/ CERAMICS Properties, production, applications
04102531 High precision (1 part in 104) reflectivity measurement for the study of reflective materials used in solar collectors Chen, Y. T. et al. Solar Energy Materials and Solar Cells', 2003, 80, (3), 305-314. A new method of reflectivity measurement for the study of reflective materials in solar energy technology is reported in this paper. The method employs a fast rotating reference mirror and certain geometry configuration to alternatively deliver the light via a sample mirror or by passin~ it to a photo detector. It has been proved to reach a precision of 10 4 . With a good repeatability of the method, outdoor exposure tests of sample mirrors have been carried out in a relatively short period (1 month) and significant specular reflectance losses due to an aging process have been observed.
04•02532 In-situ formation of carbon nanotubes in an alumina-nanotube composite by spray pyrolysis Kamalakaran, R. et al. Carbon, 2003, 41, (14), 2737-2741.
Fuel and Energy Abstracts September 2004 353
13 Space heating and cooling Alumina (AleO3)-earbon nanotube composite materials were synthesized by spraying a slurry of ferrocene (Fe(C5Hs)z) and alumina in xylene, at 1000~50°C, using argon (_<1.5 bar) as carrier gas. The asprepared materials were formed in large flakes (ca. 2 era) and consist of nanotubes intricately matted in a glassy alumina matrix. Based on the structural and microstructural investigations done by scanning electron microscopy and high-resolution transmission electron microscopy, a possible growth mechanism has been suggested.
04/02533 window
Modeling and simulation of a simple glass
Ismail, K. A. R. and Henrfquez, J. R. Solar Energy Materials and Solar Cells, 2003, 80, (3), 355-374. This paper presents a mathematical model with numerical simulations of the heat transfer across a simple glass window. The model is twodimensional, transient based upon the energy equation with a source term to account for the solar radiation absorbed through the glass sheet. Variable incident solar radiation and external ambient temperature are considered in the numerical simulations. The governing equations and the associated boundary conditions are discretized by the finite difference approach and the ADI scheme. Numerical simulations are realized for the cases of clear and absorbing glass to show the effect of the glass thickness on the total heat gain, the solar heat gain and the shading coefficient.
04•02534
Natural convection at an indoor glazing surface
Cuevas, C. and Fissore, A. Building and Environment, 2004, 39, (9), 1049-1053. An experimental study was made to determine correlations that allow the calculation of heat transferred by convection through the window. Three configurations were studied: a hot plate; a cold plate and a window with a single-step frame placed on the wall of a room. A correlation was obtained that could be used to calculate the convection heat transfer through the window. The new correlation in the hot plate configuration differed by 14.5% from the A S H R A E correlation for laminar-free convection on a vertical surface, is 27.5% from the cold plate and is 12% from the single step-frame.
04/02535 Peculiarities of boiling heat transfer on capillaryporous coverings Poniewski, M. E. International Journal of Thermal Sciences, 2004, 43, (5), 431-442. The paper discussed specific features of boiling heat transfer on developed industrial micro-surfaces and surfaces with capillary porous coverings obtained with various techniques. Boiling on such surfaces is characterized by the occurrence of a few physically disparate hysteresis phenomena, as well as by the different course of nucleate boiling crisis as compared with smooth surfaces. Attempts at modelling the nucleation hysteresis and that of the I-kind and also nucleate boiling crisis for various surfaces with capillary-porous covering were presented. Apart from the discussion of other researchers' investigation results, the physical interpretation of lI-kind hysteresis phenomenon was given. A theoretical model congruent with experimental data for metal fibrous coverings was also provided. The properties of three hydrodynamic models of nucleate boiling crisis were discussed as well. The statistical concept of the maximum point process was employed for the sake of intra-layer boiling crisis modelling; the result obtained was consistent with the experiment.
04/02536 Protonic ceramic fuel cells for high-efficiency operation with methane Coors, W. G. Journal of Power Sources, 2003, 118, (1-2), 150 156. A new class of fuel cells is being developed, based on ceramic electrolyte materials that exhibit high protonic conductivity at elevated temperatures. The protonic ceramic fuel cell (PCFC) is fundamentally different and unique among fuel cell types currently being developed because it relies on conduction of protons through the electrolyte at much higher temperatures than is possible with other protonconducting fuel cells. Operating at 750°C, the PCFC is ideal for use with hydrocarbon fuels, such as natural gas. Proton conduction implies that water vapour is produced at the cathode, where it is swept away by air, rather than at the anode (as in a solid oxide fuel cell), where it dilutes the fuel. Since carbon dioxide is the only exhaust gas produced, higher fuel utilization is possible. Ambipolar steam permeation from the cathode to the anode provides the steam for direct reforming of hydrocarbons, so external steam injection is not required. Therefore, high thermodynamic efficiency is achieved and coking is not a problem. All of these features make it possible to construct a fuel cell of unprecedented electrical efficiency when operated on hydrocarbon fuels. The principles of operation and the current status of single-cell testing on methane at Protonetics will be described.
354
Fuel and Energy Abstracts
September 2004
04/02537 Silica antireflective films on glass produced by the sol-gel method Bautista, M. C. and Morales, A. Solar Energy Materials and Solar Cells, 2003, 80, (2), 217-225. Up to now antireflective silica thin films deposited on glass do not have enough strength and display poor adhesion to the substrate. Three methods to obtain silica antireflective films on glass were surveyed to identify the best way to produce the antireflective effect on glass by introducing a certain degree of porosity. Porous silica layers, obtained from the polymeric and colloidal methods, permit a considerable reduction of these light reflections compared with uncoated glasses in all the cases studied, but the degree of reduction as well as the adhesive properties is different depending on the method used to achieve the precursor solution. The AM1.5 solar transmittance increased from 0.915 for the bare slide up to 0.970 for the best-made sample corresponding to the Triton-doped silica.
04/02538 Thick-film nickel-metal-hydride battery based on porous ceramic substrates Do, J.-S. et al. Journal of Power Sources, 2003, 117, (1-2), 203-211. Nickel-metal-hydride (Ni-MH) batteries are prepared with thick-film and thin-film technologies based on porous ceramic substrates. The porosity and the mean pore diameter of BP ceramic substrates prepared from the argils increases from 19.81% and 0.0432 pm to 29.81% and 0.224 ~tm, respectively, upon increasing the ethyl cellulose content in the BP argil from 0 to 0.79%. The pore diameter of A1203 substrates prepared from A1203 powder is mainly distributed in the range 0.01-0.5 gin. The distribution of the pore diameters of BP ceramic substrates ties in two ranges, namely: 0.04-2 gm and 10-300 gm. Using BP ceramic plates and A1203 plates as substrates to fabricate thick-film N i - M H batteries, the optimal electroactive material utilization in the batteries is 77.0 and 71.1%, respectively. On increasing the screen-printing number for preparing the cathode (Ni(OH)z) from 1 to 3, the discharge capacity of the thick-film battery increases from 0.2917 to 0.7875 mAh, and the utilization in the battery decreases from 71.0 to 53.0%.
13
SPACE HEATING A N D COOLING
04/02539 Total solar energy transmittance of glass double fa(;ades with free convection Manz, H. Energy and Buildings, 2004, 36, (2), 127-136. Double facades made of glass layers with a ventilated mid-pane shading device are often used in commercial buildings. The solar-collector-like construction leads to high temperatures in the facade cavities during summertime and the possible overheating of the building. Of key significance for the cooling load of the building and thermal comfort of its occupants is the total solar energy transmittance to the interior. A procedure for modelling such facades - comprising a spectral optical and a computational fluid dynamic (CFD) model-is described and simulation results are compared with data derived from an experimental investigation of a single-story glass double facade with free convection, incorporated in an outdoor test facility. The influence of the layer sequence and ventilation properties on the thermal behaviour is discussed. It is shown that, for a given set of layers, total solar energy transmittance can easily vary by a factor greater than five. Hence, for reliable prediction of the total solar energy transmittance of a designed facade, models are needed that factor in all the relevant parameters. A spectral optical model combined with a CFD model that includes convection, conduction and radiation, is therefore recommended for analysing and optimizing glass double facades.
04/02540 A four-bed mass recovery adsorption refrigeration cycle driven by low temperature waste/ renewable heat source Alam, K. C. A. et al. Renewable Energy, 2004, 29, (9), I461-1475. The study deals with an advanced four-bed mass recovery adsorption refrigeration cycle driven by low temperature heat source. The proposed cycle consists of two basic adsorption refrigeration cycle. The heat source rejected by one cycle is used to power the second cycle. Due to the cascading use of heat and cooling source, all major components of the system maintain different pressure levels. The proposed cycle utilize those pressure levels to enhance the refrigeration mass circulation that leads the system to perform better performances. The performance of the proposed cycle evaluated by the mathematical model at equilibrium condition and compared with the performance of the basic two-bed adsorption refrigeration cycle. It is seen that the cooling effect as well as COP of the proposed cycle is superior to those of the basic cycle. The performances of the cycle are