Photo courtesy Entrematic

Those used to residential fans often believe it best to run fans at the highest speed for the most air flow. However, aquatics facilities need to view air movement from another perspective — one more on the industrial level.

HVLS fans and aquatics facilities

Industrial high-volume low-speed fans—or HVLS—are in a league of their own, with diameters up to 24 feet. Unlike their distant high-speed cousins, HVLS fans are engineered to move the highest volume of air possible at a relatively low speed. They work to destratify the air, or mix the air in a building to eliminate layers and achieve equal temperatures at all levels of an interior space.

A large number of high-speed fans running simultaneously in an aquatics facility simply cannot control air movement and destratify air the way a single large HVLS fan can. And running multiple high-speed fans for the desired air movement draws more amperage. As a result, high-speed fans are more expensive to operate than one or two HVLS fans.

Even for HVLS fans, better performance or increased flow of air volume are not guaranteed by more revolutions per minute or more blades per fan.

HIGH IMPACT The vectors in this wind velocity profile show airflow being drawn up from the pool surface, then forced downward and away from the fan center at a higher velocity (yellow and red vectors indicate the fastest speeds in miles per hour). Unhealthy chloramines in the air directly above the water surface then are displaced. Due to a constant downdraft, the HVLS fan produces a steady flow of fresh, healthy air toward the water surface.
Image courtesy Entrematic HIGH IMPACT The vectors in this wind velocity profile show airflow being drawn up from the pool surface, then forced downward and away from the fan center at a higher velocity (yellow and red vectors indicate the fastest speeds in miles per hour). Unhealthy chloramines in the air directly above the water surface then are displaced. Due to a constant downdraft, the HVLS fan produces a steady flow of fresh, healthy air toward the water surface.

HVLS fans are most commonly found in industrial or warehouse environments with high temperatures and humidity. But aquatics operators nationwide increasingly understand the benefits HVLS fans provide patrons, especially swimmers who breathe in air directly above the water’s surface.

These fans make an especially good match for older facilities where air quality requirements must be addressed, but budgets are tight. Properly sized, located and installed HVLS fans can provide the extra air flow needed to help existing HVAC systems work as efficiently as possible.

HVLS fans do not necessarily bring more fresh air into a facility, but they are instrumental in keeping air in the facility in constant motion to remove stagnant air in problem areas, especially directly above the water surface.

HVLS fans reduce the effects of ‘bad air’

What makes an industrial HVLS fan so different from residential high-speed ceiling fans? Size is one aspect, with diameters from 8 to 24 feet.

The most critical feature of HVLS fans is the design of the blades. They feature a unique airfoil profile and angle of attack designed for rotary motion that directly impacts the air movement in front of and behind each blade as it’s turning. In addition, the width, or chord length, then affects how much volume of air is pushed down toward the water surface. This also affects the consistency of airflow distribution throughout the fan’s different speed settings. That means blade efficiency remains the same at all speed settings. The most noticeable features, winglets at the tip of each blade, affect efficiency and overall power consumption. They also affect how much air is pulled over each blade and pushed down to the water surface.

Larger diameter HVLS fans move a higher volume of air than smaller fans of the same style and design. They also provide more flexible operation for different purposes. For example, during practice sessions with minimal spectators, fans can operate at slower speeds. During swim meets with many spectators, fans should run at higher speeds for added comfort. More blades don’t necessarily mean a better fan or more air movement. On an HVLS fan, it can result in less downward air movement from the central hub where the blades meet. More blades also mean more noise.

Adding HVLS fans to an aquatics facility is more than pointing to specific spots and deciding that fans will “look really good there." Approaching installation from an engineering perspective requires several steps, including taking the time to understand your facility, and providing a comprehensive site layout to optimize each fan location for best air movement.