Air Knife Flow Thrust Calculator
Determine compressed air consumption (SCFM), laminar impact thrust force (lbf), compressor horsepower, and operating utility costs.
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Air Knife Fluid Dynamics & The Coanda Effect
Precision air knives convert a small volume of high-pressure compressed air into a continuous, uniform sheet of high-velocity air. By passing primary compressed air through an engineered narrow orifice (typically 0.002 inches) and directing it along a curved profile, the Coanda effect creates a localized low-pressure zone that entrains surrounding ambient room air at amplification ratios up to 25:1 to 40:1.
Operating & Energy Equations
- Air Consumption per Inch:
SCFM/in ≈ 2.9 × (Shim Gap / 0.002") × [ (P_psig + 14.7) / 94.7 ] - Compressor Power Requirement:
Industrial rotary screw compressors require approximately 1 Brake Horsepower (BHP) for every 4.5 SCFM delivered at 100 psig. - Annual Electricity Operating Cost:
Cost ($/yr) = [ (BHP × 0.746 kW/HP) / Motor Efficiency ] × Hours/yr × $/kWh
Frequently Asked Questions
How much compressed air does an industrial air knife consume?
A standard 0.002-inch gap air knife operating at 80 psig consumes approximately 2.9 SCFM per linear inch. A 24-inch knife consumes about 70 SCFM.
What is air amplification in air knives?
Air knives use the Coanda effect to entrain surrounding ambient air at ratios of 25:1 or higher, converting a small amount of compressed air into a high-mass laminar curtain.
Why should air knives over 18 inches be plumbed from both ends?
Feeding longer air knives from both ends prevents internal pressure starvation and guarantees uniform exit velocity across the entire knife length.