Vattenfall

About: Vattenfall is a company organization based out in Stockholm, Sweden. It is known for research contribution in the topics: Wind power & Combustion. The organization has 685 authors who have published 857 publications receiving 18912 citations. The organization is also known as: Vattenfall AB & Kungliga Vattenfallstyrelsen.

Steam blowing assembly for nuclear power plants

Abstract: The invention relates to a steam blowing tube for nuclear power plants of the kind which has a lower end immersed in a water pool, the purpose of tube being to permit, if required, the blow down of steam into the water of the pool with the purpose of condensing the same so as to counteract the build-up of damaging steam overpressure in the containment of the reactor. A number of through holes are recessed in the wall (11) of the individual blow down tube (10) which each one is delimited by upper and lower edges (13, 14) of which at least one constitutes part of a portion (15) bent in relation to the tube wall (14). The lower hole edge (14) forms a steam flow cutting edge which, when the steam rushes down through the tube, divides a part flow from the main steam flow and brings said part flow out into the surrounding water of the pool before the main flow reaches the bottom opening (12) of the tube.

Thermally induced convective movements in a standard experimental model for characterization of lesions prior to radiofrequency functional neurosurgery.

Abstract: Experimental exploration of equipment for stereotactic functional neurosurgery based on heating induced by radio-frequency current is most often carried out prior to surgery in order to secure a correct function of the equipment. The experiments are normally conducted in all experimental model including an albumin solution in which the treatment electrode is submerged, followed by a heating session during which a protein clot is generated around the electrode tip. The clot is believed to reflect the lesion generated in the brain during treatment. It is thereby presupposed that both the thermal and electric properties of the model are similar to brain tissue. This study investigates the presence of convective movements in the albumin solution using laser Doppler velocimetry. The result clearly shows that convective movements that depend on the time dependent heating characteristics of the equipment arise in the solution upon heating. The convective movements detected show a clear discrepancy compared with the in vivo situation that the experimental model tries to mimic; both the velocity (maximum velocity of about 5 mm/s) and mass flux are greater in this experimental setting. Furthermore the flow geometry is completely different since only a small fraction of the tissue surrounding the electrode in vivo consists of moving blood, whereas the entire surrounding given by the albumin solution in the experimental model is moving. Earlier investigations by our group (Eriksson et al., 1999, Med. Biol. Eng. Comput. 37, pp. 737-741; Wren, 2001, Ph.D. thesis; and Wren et al., 2001, Med. Biol. Eng. Commit. 39, pp. 255-262) indicate that the heat flux is an essential parameter for the lesion growth and filial size, and that presence of convective movements in the model might substantially increase the heat flux. Thus, convective movements of the magnitude presented here will very likely underestimate the size of the brain lesion, a finding that definitely should be taken into consideration when using the model prior to patient treatment.

Are Fundamentals Enough? Explaining Price Variations in the German Day-Ahead and Intraday Power Market

Abstract: European electricity market participants are encouraged to balance intraday deviations from their day-ahead schedules via trades in the intraday market. Together with the increasing production of variable renewable energy sources (RES), the intraday market is gaining importance. We investigate the explanatory power of a fundamental modeling approach explicitly accounting for must-run operations of combined heat and power plants (CHP) and intraday peculiarities such as a shortened intraday supply stack. The fundamental equilibria between every hour's supply stack and aggregated demand in 2012 and 2013 are modeled to yield hourly price estimates. The major benefits of a fundamental modeling approach are the ability to account for non-linearities in the supply stack and the ability to combine time-varying information consistently. The empirical results show that fundamental modeling explains a considerable share of spot price variance. However, differences between the fundamental and actual prices persist and are explored using regression models. The main differences can be attributed to (avoided) start up-costs, market states and trading behavior.