The present work involves Computational Fluid Dynamics (CFD) modeling and validation of head and power characteristics of a Top Shrouded Turbine with Nonradial Rectangular Blades (TSTNRB) operated in backswept mode. Following the successful validation reported here and in two previous studies by the authors. CFD has been used to simulate the performance of different kinds of impellers viz. Straight Blade Paddle (SBP), Rushton Turbine (RT), Top Shrouded Turbine with Radial Rectangular Blades (TSTRRB), Top Shrouded Turbine with Radial Trapezoidal Blades (TSTRTB), Top Shrouded Turbine with Non-radial Rectangular Blades (TSTNRB), Top Shrouded Turbine with Curved Blades (TSTCB), and Both side Shrouded Turbine with Radial Trapezoidal Blades (BSTRTB), to compare them for pump-mix action. Baffle-impeller interaction has been modeled using the sliding mesh approach. Standard k-epsilon model has been used for turbulence modeling. The power number, head number, and flow number have been computed for each impeller. The impellers have been rated on the basis of head generated by them for equal specific power input. An attempt has been made to explain why different impellers operating at the same speed and handling the same inlet flow rate should give different heads. How this insight can be used to conceptualize better designs of pump-mix impeller is illustrated. (C) 2007 American Institute of Chemical Engineers.