Choosing The Correct Mixer Impeller For High Viscosity Liquids

Mixing two or more low viscosity liquids such as water is easily achieved. That is not the case, however, with high viscosity liquids, which don’t mix into a homogeneous liquid quite as readily. And no, you can’t force two or more high viscosity liquids into mixing well by increasing the speed of rotation of your mixer impellers. Doing so, in addition to being useless, could result in expensive mechanical failure.

To get the best results, a basic understanding of how these high viscosity liquids behave when agitated is needed. Agitation results in high turbulence in liquids like water, while high viscosity liquids don’t immediately achieve turbulent flow. The Reynolds number of each liquid gives you a good measure of its turbulence and helps understand the flow characteristics of high viscosity liquids.

The Reynolds Number And A Turbulent State Of Liquid.

The Reynolds number of a liquid is a dimensionless number that is usually 20,000 or more. This is the level at which turbulent flow is achieved (i.e. when liquids readily start mixing). For a high viscosity liquid to reach its turbulent state, it first has to break-free from its laminar state (this is when different liquids hold in distinct layers based on their viscosity). The transition to turbulence is called laminar-turbulent transition. A good mix can only be achieved by pushing a high viscosity liquid into turbulent state.

Laminar Impellers

A high Reynolds number (turbulence) can only be achieved by disrupting the uniform flow of horizontal layers of the viscous liquids in laminar flow. Using the right impeller is imperative to achieve this. An impeller used to mix a low viscosity fluid (turbulent impeller) will fail to agitate the fluid sufficiently to turn laminar flow into turbulent flow. Even if it does, the result achieved will be underwhelming. Sometimes, this can also lead to a build-up of heat, which can spell other trouble.

On the other hand, a laminar impeller has a much larger surface area, which can disrupt the uniformity of flow, turning a laminar flow into a turbulent flow with a sufficiently high Reynolds number. In other words, a very good mix!

While this information aims to give you some basic knowledge of the mechanics of mixing high viscosity liquids, the task itself is a complex and specialist one. When it comes to choosing the right mixer for industrial work, there are several parameters that you need to consider including the type of mix you need to achieve, the load capacity, power consumption, longevity, liquid type, and much more. Last but not least, all of this needs to work for you while still fitting into your budget.

Vissers can help you. For more information about the different types of industrial mixers and mixer impellers contact us. Our experts can help you select the right equipment for your applications based on your requirements and then help you install it. Please use our toll-free number 1-800-367-4180 to speak to our professionals.