# Topic: Re: Is there a science for sizing submersible mixers?

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On August 29th, I recommended a design based on power per volume at 0.0014 kilowatts/cubic meter (0.007 hp/1000gal).&nbsp; That power per volume level is sufficient to mix large storage tanks with side-entry mixers.&nbsp; A submersible mixer creates the same type of motion as a as a side-entry mixer.&nbsp; Higher mixing intensities will be needed if the waste contains settling solids, such as sand particles.&nbsp; If other data is available from similar applications, then he should use that information in the form of power per volume.&nbsp;The basin geometry provided in the original question was typical, with length, width, and height of similar magnitudes.&nbsp; Had the basin been exceptionally wide, long, or shallow, two mixers might have been required, but the total power per volume level would have been similar.&nbsp;The "science" of all mixing is based on empirical observations.&nbsp; No mathematical methods exist for calculating mixing intensity other than those based on observed results that can be related to design requirements.&nbsp; Power per volume is a simple but effective method.&nbsp; Most side-entry and submersible mixers operate at similar rotational speeds, so mixing intensity can be related to power, although torque and thrust are probably the physical effects related to liquid motion.&nbsp;If you want to know the relationship between mixer operation and power: impeller power is proportional to liquid density, rotational speed cubed, and impeller diameter to the fifth power for turbulent conditions.&nbsp; The constant of proportionality is the impeller power number, which depends on number of blades, blade angle, blade width and blade shape.&nbsp; The power number is developed through experimental observation and can be unique for different types of impellers.
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