Optimierung kontinuierlich betriebener Durchlauföfen mit Hilfe von Teilbilanzen

Bei der energetischen Optimierung von Durchlauföfen ist insbesondere die Frage zu beantworten, in welcher Weise der Gesamtprozeß von seinen Teilprozessen - wie z. B. Vorwärmung des Gutes in der Vorwärmzone, Erwärmung des Gutes im beheizten Ofenteil und Luftvorwärmung im Rekuperator - beeinflußt wird. Dazu ist es zweckmäßig, außer einer Gesamtbilanz Teilbilanzen für die einzelnen Prozeßstufen aufzustellen. Die Verknüpfungen zwischen den Wirkungsgraden der Teilprozesse mit den entsprechenden Wirkungsgraden für den Gesamtprozeß liefern dann die gesuchten Beziehungen. Dabei zeigt sich, daß es aus energetischen Gründen gleichgültig ist, ob eine Wärmerückgewinnung durch Vorwärmung des Wärmgutes oder durch Vorwärmung der Verbrennungsluft erreicht wird. Es hängt aber von der Art des Brennstoffes ab, in welchem Maße eine Luftvorwärmung möglich ist. Insbesondere bei Öfen mit Schwachgasbeheizung (Gichtgas) ist eine relativ hohe Gutvorwärmung erforderlich, was bekanntlich zu Bauformen mit langer Vorwärmzone führt. Zur Bestimmung der im einzelnen benötigten Ofenlängen sind die maßgebenden Gleichungen für die Wärmeübertragung und gegebenenfalls für den Ausbrandverlauf hinzuzuziehen.     

Simulation of the pressure distribution under a two-dimensional heap of polygonal particles

Granular heaps in two dimensions are studied using the molecular dynamics method with convex polygons. The angle of repose shows a dependence on the size dispersion of the particles. There is a pressure minimum under the apex of the heap which depends strongly on the way the heap is built. The results and the comparisons with the experiments suggest that there is not such a thing as a generic pressure distribution for granular heaps.     

A new high detectivity room temperature linear thermopile array with a D* greater than 2 × 109 cmHz1/2/W based on organic membranes

We present a newly designed high-detectivity thermoelectric linear array, based on an organic membrane for use in the room temperature range. The sensor array has 64 individual readable channels and was designed and developed for IR spectroscopy. This detector may be used to infer the condition of lubricants and coolants within a mechanical system, so that they can be replaced when needs be, e.g. determining the age of technical oils of wind power plants in real time. Thus valuable resources can be saved and costly damage to equipment avoided. In order to achieve a D* greater than 2 × 10⁹ cmHz^1/2/W, the sensor was designed and optimized to be operated under vacuum conditions. To minimize the thermal cross talk between individual pixels, the pixels are separated from each other by a 50 μm slit in the self-supporting organic membrane made of SU-8.     

Dynamic relations for sparsely sampled Gaussian processes

In longitudinal studies, it is common to observe repeated measurements data from a sample of subjects where noisy measurements are made at irregular times, with a random number of measurements per subject. Often a reasonable assumption is that the data are generated by the trajectories of a smooth underlying stochastic process. In some cases, one observes multivariate time courses generated by a multivariate stochastic process. To understand the nature of the underlying processes, it is then of interest to relate the values of a process at one time with the value it assumes at another time, and also to relate the values assumed by different components of a multivariate trajectory at the same time or at specific times selected for each trajectory. In addition, an assessment of these relationships will allow to predict future values of an individual’s trajectories.     

A new way to reduce the edge drop

Two new ways to reduce the edge drop are being investigated both theoretically and in rolling trials. The edge drop control cooling system (EDC cooling) produces a crown shape with the aid of three cooling beams arranged on stand-exit side that, on the one hand, feature a very fine spray pattern distribution in the strip edge area and, on the other hand, are applied with differently tempered cooling medium, allowing the edge drop to be reduced. The EDC rolls are more flexible in the strip edge area than in the remaining part of the barrel. The thus created heavier flattening is, on the one hand, sufficiently large and, on the other hand, also excellently suited by its characteristic property to compensate the edge drop. The effects of both systems were evidenced during comprehensive rolling trials in the first stand of a 2-stand DCR cold tandem mill. For these trials 52 coils of annealed tin plate were used. With the aid of the EDC system, the strip thickness in the immediate strip edge area could be increased by up to 4% of the nominal thickness.     

Zerkleinerung von Abfällen mittels Rotorscheren,Rotorreißern und Schraubenreißern

Starting from the properties of the materials constituting waste, approaches suitable for size reduction of tough materials are considered. The rotary shears, rotary shredders, and screw shredders that have recently come into use for preliminary, coarse, and medium-level size reduction of bulky household waste, scrap wood, used tyres, biological waste, old documents are now widespread. The forces exerted by these machines and their design and important design parameters are examined. A necessary detailed comparison of the three basic types of machine depending upon the nature of the material handled (systematic size-reduction studies) has yet to be performed.