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Department of Chemical Engineering, University of Kuwait, P.O.Box: 5969, Safat, 13060, Kuwait

ABSTRACT

Polyethylene oxide (PEO) was used as a drag-reducing additive in a continuous-flow-stirred tank and its influence on mixing and residence times was investigated. It was found that the presence of a small amount of PEO (as low as 40 ppm) caused a noticeable change in the mixing time data as compared to that of pure water. The direction of change was found to be dependent on the liquid flow rate. The average residence time decreased with an increase in PEO concentration. The depression in the mixing time curve, observed at the critical impeller speed by other investigators,disappeared due to the presence of PEO. In agreement with the literature, mixing time was found to be proportional to the Froude number raised to an exponent a. where a is a constant which depends on the type of impeller used.