Topic: Can you provide the power number for anchor-type impeller and Cowles disc impeller?6 October 2009
Dave Dickey Forum Moderator 287 Posts
Re: Can you provide the power number for anchor-type impeller and Cowles disc impeller?6 October 2009 at 1:29pm
You won't find power numbers for most impellers in the handbooks. The power numbers are scattered through texts and published articles.
The power number for an anchor impeller is normally developed from the impeller geometry in the form a viscous power number, which is quite different from the turbulent power number you referenced in your question. Power_Number_Viscous_Anchor.pdf develops the viscous power number from the impeller geometry. Power_Number_Viscous_Evaluation_w_Definition.pdf shows how the viscous power number can be evaluated. Rearranging the viscous power number can compute power, speed, or diameter from viscosity and two of the three other variables. Viscous power is a constant for impeller Reynolds numbers less than 10. For higher Reynolds numbers, the viscous power number increases until it becomes proportional to Reynolds number for Reynolds numbers greater that 20,000. A graphical representation of the correction factor as applied to a viscous power number for Reynolds numbers greater than 10 is shown in Viscosity_Correction_Viscous_Power_No.pdf.
The turbulent power number for a Cowles impeller is probably somewhere between 0.4 and 0.6, depending on the teeth shape, size, and angle.