Graphic: Visualization of How HVLS Fans Destratify Air

April 16, 2013 by Eddie

HVLS fans work in tandem with natural ventilation or HVAC systems, but while HVAC systems can help with distributing air, there is no means of mixing it.

A turbulent, high velocity air jet dissipates very quickly. A large column of air however, travels farther than a small column. The friction between moving air and stationary air occurs at the periphery of the moving column. The perimeter of a column varies directly with column 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-foot diameter fan has more than six times as much “friction interface” per cubic foot as does the air column from a 20-foot fan. This is why a large, slow moving fan actually cools better and more efficiently than a small high-speed fan.

Without a HVLS Fan Moving Air:

How HVLS Fans Destratify Air - Stratified Environment Before Fan is Turned On

The example facility with heat having naturally risen to the ceiling; there is no HVLS in motion.

When the down column of air from an HVLS fan reaches the floor, the air turns in the horizontal direction away from the column in all directions. The air flowing outward is called the “horizontal floor jet.” Since the height of the floor jet is determined by the diameter of the column of air, a larger diameter fan naturally produces a larger air column and thus a higher floor jet. Smaller high-speed fans of equivalent displacement are incapable of producing the same effect.

With a HVLS Fan Moving Air:

How HVLS Fans Destratify Air

A “floor jet” can be seen covering most of the floor space in the example facility, which creates a cooling breeze for the occupants along with fully distributing the air. Wind speed is indicated by the left color scale.

Efficiency of HVLS Fans

The power to drive a fan increases roughly with the cube of the average air speed through the fan. A commercial fan delivering air at 20 miles per hour (mph) requires about 64 times as much power as a similar sized fan delivering air at 5 mph. Airspeed, combined with fan effectiveness means that when the objective is to distribute air, large, low-speed commercial fans are enormously more efficient and effective than small high-speed fans. One HVLS fan consumes about the same amount of electricity as one high-speed fan while moving more than 12 times the amount of air.

Before you decide on a specific fan, it’s helpful to see how the airflow will affect your space. AirViz, MacroAir’s virtual airflow simulation software provides you with an opportunity to actually see the potential airflow of the fans in your space.  With AirViz, you get a scientifically proven recommendation on how many fans to get and where to place them in your facility.

Try AirViz by clicking the button below and try MacroAir fans in your space before you buy.

One comment on “Graphic: Visualization of How HVLS Fans Destratify Air

  1. Barry Heugly on

    Heather was a great help today on the phone : Very knowledgeable – Very kind and happy – I could feel the smile on her face through the phone. When I am having a bad day I will be calling her – her cheerful voice will cheer me up.


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