Application Of Additives' Drag Reducing Technology In District Heating System

This paper firstly introduced the practical application experiment of the surfactant drag-reducing technology in a district heating system in Qingdao. The experiment has confirmed the surfactant drag-reducing technology's drag-reducing effect and energy conservation effect. Simultaneously, some problems which were found in the practical application have also been proposed, such as, the shortness of the effective surfactant drag-reducing duration; the unstablility of the drag reduction; and the reducing agent's corrosiveness.In view of the effective drag reducing time's shortness, the paper researched the surfactant drag reduction solution's drag reduction effect in fully developed straight pipe in the laboratory. And the factors influencing the drag reducing effect, which contains the density and temperature of the surfactant solution and the Reynolds number of the surfactant solution flow, were also analyzed. The experimental result indicated: in fully developed straight pipe whose diameter is 26mm, there is varying degree drag-reducing instabilization while the CTAC/ NaSal drag-reducing solution concentration is 200~600 mg/L, and there is as high as 81% high and stable effection when the solution concentration C=800mg/L and the solution temperature T < 60℃, the solution flowing Reynolds number Re<105.At the same time, this paper has analysised some partial fitting's drag reduction effect through the laboratory experimental study. The results indicated that the drag-reducing effect is very bad in the partial fitting, and the factors influencing their drag reducing effect include: Local resistance coefficient values, own structures, as well as all factors influencing drag reducing solution's drag-reducing effect in straight pipe.If"the diameter effect"and the pipeline's adsorption to the surfactant in the actual DHC system were also considered, the possible effective drag-reducing density is 1500mg/L in the actual system, and we may get 56% drag reduction for at lest 1 year.The laboratory also analyzed the surfactant solution's heat transfer and flow properties in a radiator. The experimental result had indicated: when surfactant solution flow through the raditor, the heat transfer and the drag-reducing performance was suppressed at varying degree under the turbulent condition, and the high wall-shearing stress in the internal flowing can effectively enhance the heat transfer ability; but the flow drag and heat transfer effect were increased under laminar condition.Finally the paper designed a method used to strengthen the surfactant solution's heat transfer performance in a tube-in-tube heat exchanger heat transfer. In view of surfactant solution's strong entrance effect and sensitive characteristic to the high shearing stress, we put some box-type boards to connect the tubes in the tube-in-tube heat exchanger as to enhance its heat transfer performance. However, presently, this method's heat-transfer-strengthening effect was only obtained in water flow through the FLUNENT software's simulation, and the computed result is good and helpful to the further development of this method.