DRAG REDUCTION AND HEAT TRANSFER AUGMENTATION OF SURFACTANT ADDITIVES IN TWO- DIMENSIONAL CHANNEL FLOW

摘要

An experimental test is conducted to attempt heat transfer augmentation in the channel flow, which shows drag reduction. As is generally known, the small addition of certain polymers or surfactants in liquid flow can considerably reduce the turbulent frictional drag. Many investigations have been carried out for the application of this effect to the pipeline or other transportation systems to minimize pumping costs. Some researches relative to the heat transfer in such flow have focused on application to the district heating and cooling system, but these researches have confirmed that heat transfer was reduced simultaneous to drag reduction. To recover this reduction, in the two-dimensional channel, several turbulence promoters were used: a two-dimensional fence, saw-toothed plates and a porous plate. Both friction factor and heat transfer coefficient have been measured to evaluate the performance of heat exchange under the condition of constant pumping power in the channel flow with a cationic surfactant Cetyltrimethyl ammonium chloride (CTAC) solution. Upon installation of the promoters, large heat transfer reduction that had been seen in the case of the plane channel was improved. But a large pressure drop was brought out and their effect restricted near the promoter; therefore, most of their efficiency for the whole heat transfer area had not exceeded that of water flow in the plane channel. But under certain conditions, saw-toothed plates promoted heat transfer without substantial increase in the frictional drag, and its efficiency exceeded the result of a plane channel, and maintained reduced drag (Figure A-1,2).