Tips for Using Froude Numbers

If you have purchased an industrial blender, you probably have heard of a Froude Number. However, you may not know exactly what this entails or how it applies to your blending business. Reviewing the definition of a Froude Number, learning how to calculate it and understanding what it means for your applications all help contribute to a successful operation. 

What Is a Froude Number?

Froude numbers are used to compare forces during the mixing process. Your Froude number will generally compare centrifugal force to gravity and help determine how particles get mixed in your machine. This is especially helpful when you are mixing crucial materials, such as bed gasifiers

How Do You Find It?

The Froude number for your mixer is calculated by multiplying the mixer’s radius with its squared angular velocity. This number is then divided by gravity. The final number is generally used for fluidizing blenders. 

There is a different version that many people prefer when using a ribbon or paddle blender. To calculate the Froude number for one of these, square your paddle or other mixing element’s tip speed. Then, divide the diameter of your mixing element by two and multiply this number by gravity. Divide the altered tip speed by the altered diameter, and you will find your Froude number. 

What Does It Mean?

Froude numbers are important for determining how particles will be combined in a mixer. They can also help you determine if you are using the right type of mixer. 

If your Froude number is less than one, gravity is exerting more force on your ingredients than the mixer, and these particles are generally being churned slowly around each other. Tumblers and ribbon blenders generally work best when the Froude number is less than one. 

If your Froude number is one, it means that you have balanced forces being applied to your ingredients. The particles you are mixing will likely remain in suspension during the mixing process. A paddle blender or fluidizer is the best option for these mixes. 

Lastly, if your Froude number is greater than one, your mixer is exerting an extreme amount of force on your ingredients, and they will likely stick to the sides of the machine. If this is your goal, a shear mixer is typically your best option. 

Froude numbers are important in the industrial blending industry. Be sure to calculate yours to make sure you are working with the right type of blender for your product.

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