Dynamic Similarity of Inertial and Viscous Forces  

For this scale-up method, you keep the Reynolds Number the same for both vessels.  Sounds easy enough, but what's Re?  Re = density*D^2*N/viscosity

Will density and viscosity change for the scaled up vessel?  If not, only the impeller diameter and rotation speed change.

You know the laboratory tank diameter and the rotation speed of the impeller.  You are the engineer who is deciding the scaled up vessel diameter.  You have everything you need.  Knowing the two tank diameters, you know the "scale-up ratio."  Therefore, you can calculate many of the parameters for the full size mixer.

Now you can calculate Re1, and Fr1.   (Fr = D*N^2/g ;  g=gravitational acceleration)

You can use these values and Figure 7.6 to find the Power Number (Np) and the Power (P) of the lab-scale mixer.

Lastly, you should determine the power requirements for the mixer, and the power per unit volume of stirred liquid for both the lab-scale and full-scale mixers.