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| 2. |
- Ellegård, Anders, 1952, et al.
(författare)
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Solar service is rural infrastructure
- 2003
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Ingår i: Renewable Energy for Development. - 1101-8267. ; 16:1, s. 7-8
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Solar Photovoltaics (PV) provide basic lighting requirements and opportunities for education, entertainment, information and business improvement in many rural areas around the world. But solar PV technology provided for free, or heavily subsidized, has proven not to be sustainable. An alternative is to look at solar technology as a consumer commodity, for which rural consumers should bear the full cost. There is, however, an intermediate solution in which solar PV Energy Service Companies provide solar PV services. We argue that this solar power provision should be acknowledged as a part of rural infrastructure and not only as a consumer product. It should not be given away for free, but neither is it fair to demand the poorest people to pay the full price up front for a service that the urban middle class gets at a subsidy.
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| 3. |
- Gustavsson, Mattias, 1977
(författare)
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Changing the game, maintaining the passion
- 2003
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Ingår i: Bättre produktivitet : tidning för regionalföreningar inom SPRF och PLAN : med plan-nytt. - 1402-1145. ; :7, s. 11-
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 4. |
- Gustavsson, Mattias, 1972
(författare)
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Fluidized Bed Operating Parameters and Eulerian Erosion Models
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A numerical two-fluid code, Gemini 2D, was adapted to study gas-solid fluidization in arbitrary 2D domains. The code was also used to study fluid dynamic mechanisms of dense particle flow that cause ductile and brittle erosion of solids. Simulations of the in-bed fluid dynamics of a small-scale pressurized fluidized bed were made with and without internals. The inflow and outflow system of a small-scale bed was studied, where the air-feed system - incorporating an air inflow system, plenum chamber and distributor plate - was modelled. It was found that the simulated large-scale fluid dynamics was significantly improved when a model was included for the air feed system of the bed. In particular, at atmospheric operating conditions, it was found that regular pressure fluctuations occurred at a constant frequency, in good agreement with experimental observations for a slugging bed behaviour. These pressure fluctuations correlate well with a strong temporal variation in the total inflow of air. Animated sequences of the slugging bed behaviour resemble that of a piston-like motion of the major part of the bed mass. Previous modelling of the same bed when a constant influx of air through the distributor plate is assumed resulted in large discrepancies between simulated and experimental bed behaviour. It is concluded that it is necessary to include complementary operating parameters to describe the present fluidized bed system, as the standard operating parameters such as fluidization velocity and operating pressure are not sufficient. A simple erosion model was used to study erosion of cooling tubes for a bed containing two tubes. This model, the monolayer kinetic energy dissipation erosion model, was used to study erosion mechanisms when bubbles pass a tube. In accordance with experimental observations, the impact of bubble wakes results in high instantaneous simulated erosion rates. Time-averaged local erosion rates around tubes were also modelled. This simple Eulerian erosion model was further developed to enable erosion modelling of real engineering metals subject to dense flow impacts of hard particles. The irreversible processes in the simulated flow field in the vicinity of a solid eroding surface can be divided into two fundamental components that can be associated with cutting and deformation wear, respectively. Ductile and brittle erosion were simulated for stationary jet streams of particles impacting a tilted plate. The influence of particle diameter, particle concentration, jet velocity and jet diameter was investigated. The literature has a great many reports of erosion models that can be applied in the case of dilute flows and in studies of single particle impacts. However, these models - generally Lagrangian - are here argued to be difficult to implement successfully for dense flows causing erosion. Examples of such cases are sandblasting or erosion caused by a large collection of particles, which is common in bubbling fluidized beds.
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| 5. |
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| 6. |
- Gustavsson, Mattias, et al.
(författare)
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Numerical simulation of fluid dynamics in fluidized beds with horizontal heat exchanger tubes
- 2000
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Ingår i: Chemical Engineering Science. - 0009-2509. ; 55:4, s. 857-866
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Tidskriftsartikel (refereegranskat)abstract
- A numerical code, Gemini, based on the implicit multifield method (IMF) of Harlow and Amsden for Eulerian two-fluid modelling, is used to simulate the fluid dynamics of bubbling fluidized beds, assuming no turbulence in the gas or solid phase. The paper gives a formulation of the equations of motion and empirical closure laws in general curvilinear coordinates for calculation of the fluid dynamics in beds with complex internal geometries. A special discretization method for general curvilinear structured grids with multiblock connectivity is implemented, and two-dimensional non-stationary calculations are performed for a bed with a cross-sectional width of 0.3 m, containing two horizontal heat exchanger tubes. The local visible bubble flow and the gas and particle motion around the tubes are briefly discussed and compared with experimental fluid dynamic results at different pressure levels.
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| 7. |
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| 8. |
- Gustavsson, Mattias, et al.
(författare)
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Two-fluid modelling of cooling-tube erosion in a fluidized bed
- 2000
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Ingår i: Chemical Engineering Science. - 0009-2509. ; 55:4, s. 867-879
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Tidskriftsartikel (refereegranskat)abstract
- The fluid dynamics of a bubbling fluidized bed is simulated in general curvilinear co-ordinates using an Eulerian two-fluid model. Computations are performed at different pressure levels for a bed with a cross-sectional width of 0.3 m in which two heat exchanger tubes were inserted. A monolayer kinetic energy dissipation model is implemented to simulate the erosion of cooling tube surfaces. The local visible bubble flow and particle motion close to the tubes are correlated with the modelled instantaneous erosion rate. Experiments were conducted in order to validate the erosion simulations, and fair qualitative agreement between experimental and numerical results was obtained.
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