SUMMARY
Design of the impeller blade is a determining factor in power consumption and mixing quality, which determines consequently the cost of the mixing operation. This study explores the flow patterns and the power required for stirring a Newtonian fluid by paddle impellers. Investigations are carried out via three dimensional (3D) numerical simulations. Effects of the blade curvature, blade diameter, blade number and Reynolds number are analyzed. The curved blade is found to be more efficient to reduce the power consumption, compared with the straight blade. A new correlation is proposed for predicting the power required with two-curved-bladed impellers. The straight and very large blade creates a dead zone in the space between the blade tip and the vertical wall of vessel. This issue may be overcome by the curved blade, which increases consequently the well-mixed region size. A wider well-mixed region may be obtained with the larger curved blade, but with an additional energy cost.