Objectif Preliminary tests on a laboratory scale proved that the drag-depending pressure loss in pipe flows can noticeably be reduced by applying hydrous tenside solutions. The maximum reduction in pressure loss achievable for a turbulent flow in straight pipe sections is about 90 %. The drag reducing effect can be used in existing district heating systems for saving pump current or for increasing supply capacity. When planning new district heating systems, investment costs can be saved by the application of drag reducing additives since, in this case, system elements (pipes, fittings, measuring sensors, etc.) of smaller nominal diameters can be installed.In the period from September to October 1988, the drag reducing additive "dobone" was applied in a 1.2 km long pipe section between the combined heating and power station Fenne and the central station Volklingen. The pipe had a diameter which is typical for transport systems, i. e. DN 450. The applied drag reducing additive showed a marked influence on the pressure loss in the pipeline. However, its drag reducing effect was available exclusively in the temperature range between 90 and 140 deg. C, so that the pressure loss could only be reduced in the flow pipe of the district heating system.A second drag reducing additive, i. e. an additive consisting of the substances dobone G and sodium salicylate, has been developed in cooperation with HOECHST AG. In laboratory tests this additive has a drag reducing effect within a temperature range of 55-140 deg. C which is relevant for district heating systems.In the period from September to October 1990, this additive was again applied inthe pipe section between the combined heating and power station Fenne and the central station Luisenthal. During this test an average pressure loss reduction of 50 % was observed; the pressure loss reduction for straight pipe sections even amounted to 75 % - 90 %. The drag reducing additive was effective both in the flow and in the reflux transport pipe.After the applied concentrations of dobone G and sodium salicylate (NaSal) had been varied, the following concentration values were stipulated for future tenside dosings: dobone G = 1,500 wppm sodium salicylate = 720 wppmGiven the above-mentioned concentrations of substances, there will nearly be a techno-economic optimum between the drag-reducing effect and the operating expenses for purchasing drag reducing additives.During this demonstration test it could further be shown that the additives have nearly no influence on the characteristic curves and efficiencies of the feed pumps. However, the drag reducing additives exercised a significant influence on the heat transmission behaviour of heat exchangers and on the measuring accuracy of heat quantity counters. Comprehensive and detailed tests to this effect are carried out in the demonstration project "Tensides II".In 1988 and in 1990 two field tests were carried out in a transport pipe of the district heating system of the Saar region. In both large-scale tests, it was checked by specified test programmes whether the laboratory tests could be transferred to real site conditions (scale of approx. 1:20) and individual system elements were tested, such as heat exchangers, pumps, pipe bends and flow meters. Within the framework of these tests, volume flow rates, temperatures and concentrations of drag reducing additives were varied in order to determine the optimum application range and the optimum tenside efficiency. Programme(s) ENG-ENDEMO C - Programme (EEC) of demonstration projects and industrial pilot projects (EEC) in the energy field, 1985-1989 Thème(s) 2.2 - HEAT Appel à propositions Data not available Régime de financement DEM - Demonstration contracts Coordinateur FERNWAERME-VERBUNG SAAR GMBH Contribution de l’UE Aucune donnée Adresse BISMARCKSTRABE 11 6620 VÖLKLINGEN Allemagne Voir sur la carte Coût total Aucune donnée
