| 1. |
- Fiedler, Frank, et al.
(författare)
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Optimisation method for solar heating systems in combination with pellet boilers/stoves
- 2007
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Ingår i: International Journal of Green Energy. - : Informa UK Limited. - 1543-5075 .- 1543-5083. ; 4:3, s. 325-337
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Tidskriftsartikel (refereegranskat)abstract
- In this study an optimisation method for the design of combined solar and pellet heating systems is presented and evaluated. The paper describes the steps of the method by applying it for an example system. The objective of the optimisation was to find the design parameters that give the lowest auxiliary energy (pellet fuel + auxiliary electricity) and carbon monoxide (CO) emissions for a system with a typical load, a single family house in Sweden. Weighting factors have been used for the auxiliary energy use and CO emissions to give a combined objective function. Different weighting factors were tested. The results show that extreme weighting factors lead to their own minima. However, it was possible to find factors that ensure low values for both auxiliary energy and CO emissions, and suitable weighting factors are suggested.
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| 2. |
- Larsson, Mikael, et al.
(författare)
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Comprehensive study regarding greenhouse gas emission from iron ore based production at the integrated steel plant SSAB Tunnplåt AB
- 2006
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Ingår i: International Journal of Green Energy. - : Informa UK Limited. - 1543-5075 .- 1543-5083. ; 3:2, s. 171-183
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Tidskriftsartikel (refereegranskat)abstract
- During the years 2001-2002, a comprehensive study regarding CO2 emissions related to the steel production for the integrated steel making production route, was carried out. The study was financed by SSAB and carried out by a research group with members from SSAB, MEFOS and LTV. The aim was to study the emissions from the existing system and how these could be influenced by process changes and by process modifications. The calculations were made using a global spreadsheet model for calculating the CO2 emissions, developed from an existing energy and process integration model of the same system. The calculated cases included the existing BF/BOF route as well as integration of other processes, e.g., an electric arc furnace, DR processes, COREX and a new future smelting reduction process concept (Sidcomet). All new existing alternative ore based process technologies would increase the specific CO2 emission from the system. A technology transfer to scrap based metallurgy would significantly decrease the emission level, but is not feasible for SSAB, due to the future product mix and the structure of scrap availability. In a 5-20 year perspective, the existing steel making process route with the use of magnetite ore for pellet production has the lowest specific CO2 emission. In a long-term perspective, 20-50 years, alternative process routes, e.g., based on H2 and DRI, could be of interest. Studies on such changes are, however, big projects and should be carried out as joint European and/or international efforts
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| 3. |
- Larsson, Mikael, et al.
(författare)
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Improved energy and material efficiency using new tools for global optimisation of residue material flows
- 2006
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Ingår i: International Journal of Green Energy. - : Informa UK Limited. - 1543-5075 .- 1543-5083. ; 3:2, s. 127-137
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Tidskriftsartikel (refereegranskat)abstract
- Residue materials generated in the metallurgical industry have gained an increasing importance, both from the points of view of energy and material supply. A joint process integration model for the integrated steel plant system is developed and used in this paper. It takes into account both residue materials and energy recirculation for the system. The potential for increased recirculation and the effect on the system from an environmental point of view is presented, and implementations and practical experiences are discussed. The model developed can serve as a benchmark for different steelmaking operations and constitute a basis for the continuous work involved in material, energy, environment or economic analyses for the steel production system.
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| 4. |
- Li, Hailong, et al.
(författare)
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Performance comparison on the evaporative gas turbine cycles combined with different Co2-capture options
- 2009
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Ingår i: International Journal of Green Energy. - : Informa UK Limited. - 1543-5075 .- 1543-5083. ; 6:5, s. 512-526
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Tidskriftsartikel (refereegranskat)abstract
- This article studied the integration of CO2 capture with evaporative gas turbine (EvGT) cycles. Two CO2 capture technologies are involved: MEA-based (monoethanolamine-based) chemical-absorption capture and O-2/CO2 recycle combustion capture. Based on them, three system configurations were analyzed: (1) EvGT cycle without CO2 capture, (2) EvGT cycle with chemical-absorption capture, and (3) EvGT cycle with O-2/CO2 recycle combustion capture. Simulation results show that the EvGT cycle with chemical-absorption capture has a higher electrical efficiency (39.73%) than the EvGT cycle with O-2/CO2 recycle combustion capture (37.45%). Compared with the EvGT cycle without CO2 capture, the penalty on electrical efficiency caused by CO2 capture is 11.91% if EvGT is combined with chemical-absorption capture, and 14.19% if EvGT is combined with O-2/CO2 recycle combustion capture. Moreover compared with combined cycles, EvGT cycles have a smaller gross electricity generation and a lower electrical efficiency no matter if they are combined with CO2 capture or not. Based on the analysis results of this article, several suggestions are also proposed to improve the net electrical efficiency of EvGT cycles with CO2 capture.
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| 5. |
- Li, Hailong, et al.
(författare)
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Simulation And Optimization Of Evaporative Gas Turbine With Chemical Absorption For Carbon Dioxide Capture
- 2009
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Ingår i: International Journal of Green Energy. - : Informa UK Limited. - 1543-5075 .- 1543-5083. ; 6:5, s. 527-539
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Tidskriftsartikel (refereegranskat)abstract
- This article studied the integration of an evaporative gas turbine (EvGT) cycle with chemical absorption for CO2 capture. Two systems of EvGT cycle without CO2 capture and EvGT cycle with CO2 capture were simulated and optimized. The impacts of key parameters such as the water/air ratio (W/A), the stripper pressure, and the flue-gas condensing temperature were studied regarding the electrical efficiency and CO2 reduction. Simulation results show that (1) there always exists an optimum point of W/A for both EvGT and EvGT combined with CCS; (2) although lowering the stripper pressure would lower the heat quality requirement of reboiler, it increases the quantity more obviously. Therefore increasing the operating pressure of stripper would help to increase the total electrical efficiency; but the efficiency improvement becomes smaller if stripper pressure is high; (3) adding a flue-gas condenser to condense out the excessive water is another method to increase the total electrical efficiency. There is also an optimum point of condensing temperature considering the concentration of mono ethanol amine (MEA) and inlet temperature of stripper; and (4) comparatively the combined cycle has a higher gross electricity generation and electrical efficiency than the EvGT cycle no matter if combined with CO2 capture or not.
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| 6. |
- Mahmoudi, Jafar, et al.
(författare)
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An Experimental Study on Productivity and Quality Improvement of Horizontal Continuous Casting Process
- 2006
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Ingår i: International Journal of Green Energy. - : Informa UK Limited. - 1543-5075 .- 1543-5083. ; 3:2, s. 185-199
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the current work is to provide information on how to improve the productivity and quality in the Horizontal Continuous Casting process (HCC). After a first numerical 2D/3D survey about the solidification in the HCC, an experimental investigation has been carried out to validate numerical results. Some casting parameters have been measured and collected: inlet and outlet temperatures, flow rate, heat flux and casting temperature. The study results lead to a correlation between these casting parameters and the casting quality. To obtain the best quality for each alloy, a set of operating parameters has been proposed. There is a very good agreement between the current results and earlier numerical results. Also based on the results, one can gain an insight on the productions of each casting machine and the grades of its quality.
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| 7. |
- Mahmoudi, Jafar
(författare)
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Modeling of flow field and heat transfer in a copper-base automotive radiator application
- 2006
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Ingår i: International Journal of Green Energy. - : Informa UK Limited. - 1543-5075 .- 1543-5083. ; 3:1, s. 25-41
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a methodology used for designing louvered fins. Louvered fins are commonly used in many compact heat exchangers to increase the surface area and initiate new boundary layer growth. Detailed measurements can be accomplished with computational models of these louvered fins to gain a better understanding of the flow field and heat distribution. The particular louver geometry studies for this work have a louver angle of 23° and fin count of 17 fpi. The flow and he at transfer characteristics for three-dimensional mixed convection flows in a radiator flat tube with louvered fins are analyzed numerically. A three-dimensional model is developed to investigate flow and conjugate heat transfer in the copper-based car radiator. The model was produced with the commercial program FLUENT. The theoretical model has been developed and validated by comparing the predictions of the model with available experimental data. The thermal performance and temperature distribution for the louvered fins were analyzed and a procedure for optimizing the geometrical design parameter is presented. One fin specification among the various flat tube exchangers is recommended by first considering the heat transfer and pressure drop. The effects of variation of coolant flow conditions and external air conditions on the flow and the thermal characteristics for the selected radiator are investigated also. The results will be used as fundamental data for tube design by suggesting specifications for car radiator tubes.
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| 8. |
- Mahmoudi, Jafar
(författare)
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Modeling of fluid flow and heat transfer in a copper based heat sink application
- 2006
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Ingår i: International Journal of Green Energy. - : Informa UK Limited. - 1543-5075 .- 1543-5083. ; 3:3, s. 219-237
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Tidskriftsartikel (refereegranskat)abstract
- With the trend towards increasing the speed of processors in smaller sized of computers, there has been considerable interest in heat sink technologies with higher levels of performance and further miniaturization. This work addresses the fundamental heat transfer augmentation question of how to design a copper-based heat sink, when the overall dimensions of the bottom plate or fan are specified. A three-dimensional finite-volume model has been developed and applied to investigate flow and conjugate heat transfer in the copper-based heat sink. The model was produced with the commercial program FLUENT, which allows this nonlinear, highly turbulent problem to be simulated using the k-ε turbulence model. The theoretical model developed is validated by comparing the model predictions with available experimental data. The thermal performance and temperature distribution for the heat sink were analyzed and a procedure for optimizing the geometrical design parameters based on less space occupation and more efficient heat transfer coefficient is presented. Several design examples with different types of cooling methods and manufacturing processes have been analyzed. The reliability and effectiveness in heat spreading of those has been compared. It has been shown that the copper-based heat sink with louvered fins (case No.3) has an optimum design configuration.
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| 9. |
- Sand, Ulf, et al.
(författare)
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Two-phase transport model for the pyrolysis process of a vertical dry wood cylinder, including the surrounding flow field
- 2006
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Ingår i: International Journal of Green Energy. - : Informa UK Limited. - 1543-5075 .- 1543-5083. ; 3:1, s. 63-78
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a mathematical model for the pyrolysis of a small dry pine wood cylinder. The computational domain is axisymmetric and involves the heating chamber, with the wood cylinder vertically situated in the centre of the chamber. The model simulates the laminar flow around the particle and the laminar flow inside the wood/char matrix by applying a two-phase transport model where the solid wood/char matrix acts as one phase and the various gases produced from the pyrolysis process is assembled in the other phase.Convective, conductive and thermal radiation transfer modes are included in the model. A two-step pyrolysis reaction scheme is used for the modelling of the conversion from wood to tar and gas. Both the thermal conductivity and the permeability of the wood/char matrix are modelled anisotropically in order to capture the directional differences in heat and mass transport, existing in real wood.Results from simulations are compared with measurements from literature for the centre core solid temperature and the conversion from wood to char, tar and pyrolysis gas in the particle during heating. The results show very good agreement with the measured temperature profile. The simulated conversion profile shows an overall good agreement with the measurements, however with discrepancies in the early stage of the process. Besides the successful validation with the experimental data, it provides us with all the details of the distribution of the migrating pyrolysis gas and tar, the temperature, the velocity flow field and pressure in the wood/char cylinder.
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| 10. |
- Sandberg, Jan, et al.
(författare)
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Measurements, theories and simulations of particle deposits on super-heater tubes in a CFB biomass boiler
- 2006
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Ingår i: International Journal of Green Energy. - : Informa UK Limited. - 1543-5075 .- 1543-5083. ; 3:1, s. 43-61
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Tidskriftsartikel (refereegranskat)abstract
- The present investigation involves theories, simulations and experiments on deposit layers on super-heater tubes in a circulating fluidised bed in Vdsteras in Sweden. Simulation of particle trajectories in the vicinity of two super-heater tubes is conducted in a Eulerian-Lagrangian mode for the flue gas and the ash particles from the combustion process. Particle impingements on the tubes are investigated for different particle sizes. Measurements of the buildup of deposit layers in the super-heater environment are conducted using a deposit probe. Deposit layer growth and growth rate is analysed for different probe temperatures, as well as the aspect of sintering on the probe ring surface. Analysis of the probe deposit material and deposits from the super-heaters and from textile filters are chemically analysed. The temperature dependence of the deposit materials viscosity is predicted from the chemical analysis of the samples. A model is included to simulate the effect of the deposit layer thickness on the tube heat exchange. The results from the particle trajectory simulations show that particle larger than 10 mu m will mainly impinge on the front of the first tube and that smaller particles are more dispersed due to turbulence and thermophorectic forces, enabling a more even impingement on the whole surface of the tubes. The probe deposit layer growth measurements show significant temperature dependence. The deposit material sintering and distribution is proven to be dependent on; temperature, particle size and exposure time. The stickiness of the deposit material is shown to be dependent on the SiO2 and alkali relation in the samples, estimated through a viscosity model.
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