Expert ForumsMixing

Topic: Re: How do I design a multi-concentric shaft for a fixed tank unit?

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Try the "Handbook of Industrial Mixing: Science and Practice," Edward L. Paul (Editor), Victor Atiemo-Obeng (Editor), and Suzanne M. Kresta (Editor), North American Mixing Forum, John Wiley and Sons, 2003.
You will not find a complete design guide for the mixer you describe.  That sort of information is manufacturer specific and considered proprietary by the company making the equipment.  The handbook will give you some basic guidance on the design requirements.