Category: Air Knife

In compressed air applications, efficiency often comes down to how effectively you use the air you already have. One of the most important aerodynamic principles that allows modern air-powered devices to operate efficiently is the Coanda Effect. This phenomenon is the foundation behind several EXAIR engineered products, enabling powerful airflow while minimizing compressed air consumption.

Understanding how the Coanda profile works can help engineers and plant managers optimize processes such as drying, cooling, cleaning, and conveying.

What Is the Coanda Effect?

The Coanda Effect describes the tendency of a fluid stream—such as air—to follow along a nearby curved surface instead of continuing in a straight line. As the air travels along this surface, it pulls surrounding air into the stream, creating a region of low pressure and dramatically increasing total airflow.

In simple terms:

1. Compressed air exits a small opening.
2. The air adheres to a curved surface (the Coanda profile).
3. This creates a low-pressure area.
4. Surrounding air is entrained, or pulled into the airflow.

The result is a much larger volume of moving air than the compressed air supply alone would create.

This principle was originally studied by aeronautical engineer Henri Coandă in the early 1900s while researching airflow over aircraft surfaces.

EXAIR Products That Use the Coanda Profile

EXAIR incorporates this aerodynamic design into several of its Intelligent Compressed Air Products™.

1. Air Knives

EXAIR Air Knives use a Coanda profile to create a wide, high-velocity sheet of air across the entire length of the unit.

Examples include:

• EXAIR Standard Air Knife
• EXAIR Full-Flow Air Knife
• EXAIR Super Air Knife

Inside these units, compressed air enters a plenum chamber and exits through a narrow slot. The air then follows the curved Coanda surface, turning approximately 90° and flowing down the face of the knife.

As the air moves along the profile, it entrains large volumes of surrounding air—up to 30-40 parts ambient air for every 1 part of compressed air.

Common applications include:

• Parts drying after washing
• Conveyor cleaning
• Web or sheet drying
• Cooling components
• Pre-paint blowoff

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2. Air Amplifiers

Another product that relies heavily on the Coanda profile is the Air amplifier.

Example:

• EXAIR Super Air Amplifier
• EXAIR Adjustable Air Amplifier

Instead of producing a flat airflow like an air knife, air amplifiers generate a conical air stream. Compressed air flows across a circular Coanda profile that draws in large amounts of surrounding air.

This creates amplification ratios up to 25:1, meaning the airflow produced is far greater than the compressed air supplied.

Typical uses include:

• Cooling hot parts
• Ventilating smoke or fumes
• Circulating air in enclosures
• Removing heat from equipment

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3. Air Wipes

EXAIR also applies the Coanda profile in a circular configuration for drying or cleaning cylindrical materials.

Example:

• EXAIR Air Wipe
• EXAIR Super Air Wipe

These devices create a 360-degree ring of air that surrounds rods, tubes, wires, or cables. As air follows the Coanda profile around the ring, it entrains surrounding air and produces a strong, uniform drying or blowoff action.

Applications include:

• Drying wire or cable
• Removing coolant from tubing
• Cleaning rods or extrusions

The Coanda Effect might seem like a theoretical concept, but it has a very practical impact on industrial operations. By carefully designing curved surfaces that guide airflow and entrain surrounding air, EXAIR products turn a small supply of compressed air into a powerful and efficient airflow solution.

Whether drying parts, cooling electronics, or removing debris from a conveyor, the Coanda profile allows EXAIR products to deliver maximum performance with minimal energy use.

Jordan Shouse, CCASS

Application Engineer / Sales Operations Engineer

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