Aug 03 2021

Understanding the Difference Between Axial Flow Impellers and Radial Flow Impellers

Industrial impellers, also known as agitator blades, can be split into two main categories based on the type of fluid motion they generate during operation: axial flow and radial flow. The distinction between axial vs radial flow is crucial when choosing the right impeller for your mixing process. To dive deeper into selecting the right impeller for your specific needs, check out our comprehensive guide on impeller selection.

Axial Flow Motion: How Axial Flow Impellers Work

In fluid motion, axial flow refers to the movement of the fluid in an up and down, cyclic pattern. The rotation of axial flow impellers makes the fluid move downward and later upward before being pushed down again to repeat the cycle. These impellers are known for generating high flow with low shear, making them ideal for blending and circulation applications. Choosing the right axial impeller can significantly improve efficiency depending on the viscosity of the fluid and process requirements.

Radial Flow Motion: The Role of Radial Flow Impellers

Radial flow impellers are designed to move fluid sideways during rotation. The displaced fluid then either moves upwards or downwards and then back to the center towards the impellers only to be pushed outwards again to repeat the cycle. This sideways motion generates high shear but low flow, making radial impellers suitable for dispersion and gas-liquid reactions. Understanding the core difference in motion helps clarify the debate of axial flow vs radial flow and guides better impeller selection for targeted applications.

Different Designs of Axial Flow Impellers

Pitched axial flow blades: These are impellers with blades that are pitched at an angle, typically 45 degrees. These impellers produce a good balance between shear and fluid flow when rotated, making them suitable for a wide variety of applications. Examples include blending and solid suspension. They are a popular choice when comparing axial vs radial pump applications, as pitched blades ensure efficient fluid handling with lower energy consumption.
Propeller blades: These blades also generate axial fluid flow but with less shear stress compared to pitched blades. Axial flow impellers like propellers are commonly used in mixing due to their high efficiency and are more often found in portable mixers. This type of axial impeller is ideal for applications that require gentle yet effective fluid movement.
Hydrofoils: These axial flow impellers generate the least amount of shear stress and are designed to produce high flow with minimal turbulence. Hydrofoils are perfect for large-scale blending operations and are often compared to larger propellers in terms of efficiency and cost. In the context of axial pump vs radial pump, hydrofoils illustrate the benefits of high-flow, low-shear design in sensitive processing environments.

Different Designs of Radial Flow Impellers

Radial flow impellers: These impellers have blades that are not pitched and they are usually have between 4 and 6 blades. Designs with more blades exist for specialized use. Due to their sideways fluid motion, radial flow impellers generate a high degree of shear stress but produce low flow. This makes them ideal for dispersion, emulsification, and other high-shear processes.
Dispersion blades: Dispersion blades are specialty radial impellers designed to maximize shear through flat or disc-like shapes with teeth at the edges. These teeth effectively break down agglomerations and speed up the mixing process. As an advanced form of radial flow technology, dispersion blades are widely used in pharmaceutical, cosmetic, and chemical industries.

Axial vs Radial Flow: Which One Should You Choose?

Choosing between axial flow vs radial flow impellers depends on your specific mixing goals. Axial flow impellers provide high flow and are best suited for applications where uniform mixing and circulation are key. On the other hand, radial impellers create more shear and are optimal for breaking down particles and dispersing materials.

When considering axial vs radial pump systems, think about whether your application requires high flow or high shear. For instance, axial pump vs radial pump decisions often revolve around fluid viscosity, tank geometry, and mixing intensity requirements.