The HVLS Fan Principle
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A New Application of A Proven Concept
People have been aware of this for thousands of years - long before the advent of modern physics. It was logical then, that with the advent of the electric motor, fans would be one of the first things to be mechanized.
At some point however, engineers became so focused on using speed to increase fan displacement - the cubic feet of air per minute (CFM) moved through the fan - that some important physics-based issues were overlooked:
- High velocity air movement - wind - is both unpleasant and disruptive.
- Air speed beyond four or five miles per hour usually offers little, if any, additional cooling benefit.
- In very hot, low humidity conditions, very slow moving air actually cools best.
- Small high-speed fans create a pressure differential that is essential for many applications, but where slow movement of free air is the objective, pressure differential is not important.
- Displacement-the amount of air actually moved through the fan-is of no real significance. It's the down-stream effects that are important. A turbulent, high velocity air jet dissipates very quickly.
- A large column of air "travels" farther than a small one. The friction between moving and stationary air occurs at the periphery of the moving column. The perimeter of a column varies directly with the diameter. And while the cross-sectional area varies with the square of the diameter, the large column has proportionately less periphery, and therefore, less "drag." The air column from a 3 ft. diameter fan has more than 6 times as much "friction interface" per cu. ft. as a the air column from a 20 ft. fan.
- Because of this far-reaching effect, large low-speed fans, properly arranged, are capable of establishing continuously circulating air currents that transport vastly more air than smaller high-speed fans of equivalent displacement.
- The power to drive a fan increases roughly with the cube of the average air speed through the fan.
- A fan delivering air at 20 mph requires about 64 times as much power as one the same size delivering air at 5 mph!
This, combined with the "effectiveness" factors, means that when free air movement for cooling people is the objective, low-speed fans are enormously more energy efficient than high-speed fans.
MacroAir Technologies, and its design, development, and production teams have taken the long overdue step of scaling-up the ceiling fan for use in large industrial, commercial and agricultural/farm buildings, regardless of roof/ceiling structures and geometries.
Then, we took it a step further and added some modern technology to both ceiling mount and vertical mount fans (which direct low speed mass air flow into areas not accessible to overhead fans): an air foil blade. This air foil design, a shape reminiscent of a helicopter blade, has physical properties that maximize its ability to capture and direct large air volume.
These fans constitute an altogether new category of fans we call High Volume Low Speed (HVLS). Airvolution™ fans, and the techniques of effectively deploying them, have created new possibilities for increasing comfort in large buildings.
MacroAir Fans in Various Applications (click here for QuickTime video short)
Walt Boyd On Inventing HVLS fans (click here for QuickTime video short)
MacroAir HVLS fans in motion (click here for QuickTime video short)
Hear what a customer has to say (click here for QuickTime video short)