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- Bååth, Lars, 1948-, et al.
(författare)
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Ny teknik för avisning av vindkraftsvingar
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This is a pilot study to investigate icing on wings of wind power turbines. In this report we present and discuss various ways and means to either heat water droplets or melt ice when formed on the wings of wind turbines. The situation is different from icing on wings of airplanes in that (1) the wings of wind turbines spend all of their time in the atmosphere where the risk of icing is highest and (2) the speed of wing to air varies over the wing where it is constant for an airplane. The form of the wind turbine wings also varies from tip to centre, to compensate for the varying relative air speed.We have concentrated on icing conditions at temperatures -10°C – 0°C and droplet sizes of 1-10 μm. Icing occurs also at much lower temperatures, but this will probably be because of direct freezing of water vapour to ice. This is presently outside the scope of our pilot project report.We conclude thatThe form of the wing, especially on the contact area may be crucial to the icing problem.Also the nano-metric structure of the wing surface can probably be designed so that the water droplets have a minimized contact area to the wing.Our pilot investigation also suggests the following:Microwaves are much too inefficient to heat water or melt ice. Direct microwave devices should therefore not be developed. Indirect heating with microwaves is possible.Millimeter waves are sufficiently efficient, but the generation is most probably too inefficient to be of any practical use.Infrared waves are very efficient to heat water and melt ice and should be investigated.Heat conduction is also efficient and should be pursued. Using microwaves to heat the wing surface which then conduct heat to the water/ice is a very efficient and robust method.Our pre-study suggests that the solution to avoid icing or de-ice wings of wind turbines most probably is not one single technology. The form and surface structure of the wings play important role for icing conditions. Both variables have to be modified depending on the latitude and atmospheric climate. The surface structure also has to be designed to vary over the wing, both along and across to be optimized for the mean conditions at the site. In addition, heating of the impact area, or at least the possibility to heat this, may be important to avoid loss of energy output due to ice.Further research is required. We strongly suggest investigating the water droplet flow over the wing as function of the cross section form, and the contact with the wing surface as function of the surface structure (e.g. Lotus effect).The present report is the result of a pre-study project. We will now continue with a deeper project which will concentrate on the form and surface structure suggestions which results from our analysis and flow simulations.
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- Löfgren, Hans, 1947
(författare)
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Cooper's Pioneer: Breaking the Chain of Representation
- 2009
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Ingår i: Nordic Journal of English Studies. - 1654-6970. ; 8:3, s. 1-19
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Tidskriftsartikel (refereegranskat)abstract
- In Cooper’s Pioneers, the transition from “national literature” and a realist epistemology of representation toward a Romantic imaginary and increasingly individualized politics is linked to the decline of liberal political philosophy and to the loss of landed property as the political basis of society. While the dominant narrative reconciles two families, healing the breach between colonial and post-revolutionary society, displacing Indian claims, and relegitimizing land ownership, a tragic epilogue—the regressive departure of the pioneer toward a new frontier— opoens up a Romantic subnarrative of desire. A complementary psychosexual narrative and discourse relocates the origin, so deliberately theorized in this novel in terms of natural property rights, in oedipal problematics. It is a regressive move which, paradoxically, also constructs the post-Enlightenment subject.
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- Löfgren, Hans, 1947
(författare)
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Race and Narration in Faulkner's Absalom, Absalom!
- 2006
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Ingår i: Lines and Traces: Papers presented to Lennart Björk on the occasion of his 70th birthday. Ed. Gunilla Florby and Karin Aijmer. Gothenburg Studies in English 93.. - Göteborg : University of Gothenburg. ; , s. 81-89
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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