air flow diagram of filter

What is a HEPA Filter?

EFS /

High-efficiency particulate arrestance (HEPA) is a type of air filter. When a Filter meets HEPA grade requirements they have several possible applications including clean rooms, medical facilities, aircraft and homes. The filter must appease certain standards of productivity set by the United States Department of Energy. To qualify as HEPA by US government standards, an air filter must remove (from the air that passes through) 99.97% of particles that have a size of 0.3 µm.
HEPA filters are composed of a mat of randomly arranged fibers. The fibers are typically composed of fiberglass and possess diameters between 0.5 and 2.0 micrometers. Key factors affecting its functions are fiber diameter, filter thickness, and face velocity. These particles are trapped (they stick to a fiber) through a combination of the following three mechanisms:

Interception: Where particles following a line of flow in the air stream come within one radius of a fiber and adhere to it.

Impaction: Where larger particles are unable to avoid fibers by following the curving contours of the air stream and are forced to embed in one of them directly; this effect increases with diminishing fiber separation and higher air flow velocity.

Diffusion: An enhancing mechanism that is a result of the collision with gas molecules by the smallest particles, especially those below 0.1 µm in diameter, which are thereby impeded and delayed in their path through the filter; this behavior is similar to Brownian motion and raises the probability that a particle will be stopped by either of the two mechanisms above; this mechanism becomes dominant at lower air flow velocities.

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clean room with several workers

Who uses V-Bank filters?

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A V-Bank filter is what we call a mini-pleated filter; it’s a high-efficiency filter with a higher media area than a standard box filter. The standard size is still 24 x 24 x 12, like the box filter, but there’s a big difference between the mini-pleated V-Bank filter and a box filter: most box filters have a metal frame and don’t have a large amount of filtration media. The actual pleat packs, which is what the media is manufactured into, are installed into the V-Bank filter in a ‘V’ shape – hence the term V-Bank. The majority of ours are 4 V’s.

The frames of those V-Banks are plastic, and though the majority of EFS V-Bank filters have both synthetic and a glass-laid media available, we see much more use for the synthetic media as it does not respond to moisture, which is important due to our work in high-humidity areas. Hospitals, gas turbine power plants, clean rooms, universities, data centers, airports, hotels, micro-electronics or pharmaceutical manufacturers, and pretty much any application that has a true air handler could use a V-Bank filter as their final filter. “We see in many instances where the V-Bank filter is the final filter and a standard pleat is a pre-filter”.

It is especially crucial in hospitals and cleanrooms to maintain a sterile environment and remain confident that airborne diseases or toxins are being filtered correctly and efficiently. Making the V- Bank filter the perfect fit using its high efficiency, low-pressure drop, long filter life and synthetic filter media that resists moisture. They are also designed to withstand high velocities and turbulence making them durable in most air handling systems. In any case, the V-Bank filter possesses very few cons in its application for air handing units.

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industrial plant

What are evaporating cooling pads?

EFS /

EFS primarily uses what would be considered evaporative cooling pads. Evaporative cooling pads are used to cool the air and keep moisture out of it. Their applications are primarily in gas turbine power plants, but there have been requests for them to be used in pig and mushroom farms, presumably for the same purpose.

Cooling through evaporation is a natural occurrence. The most common example we all experience is perspiration, or sweat. As perspiration evaporates it absorbs heat to cool your body. The principle underlying evaporative cooling is the fact that water must have heat applied to it to change from a liquid to a vapor. When evaporation occurs, this heat is taken from the water that remains in the liquid state, resulting in a cooler liquid. Evaporative cooling diverges from ordinary air conditioning setups which use vapor-compression or absorption refrigeration cycles.

Evaporative cooling works by utilizing water’s large potential of vaporization. The temperature of dry air can be depressed extremely through the transition of water to vapor (evaporation), which can cool the environment using less energy and proving to be much more efficient than refrigeration. In significantly dry climates, evaporative cooling of air has the extra benefit of modifying the air with added moisture for the convenience of present occupants. The cooling possibilities for evaporative cooling is dependent on the wet bulb rule, the difference between dry-bulb temperature and wet-bulb temperature. In barren climates, evaporative cooling can slim energy consumption and reduce equipment needed for conditioning as a substitute to compressor-based cooling. In climates not considered arid, indirect evaporative cooling can still gain favor of the evaporative cooling process without effecting humidity. Passive evaporative cooling strategies offer the same benefits of mechanical evaporative cooling systems without the complexity of equipment and ductwork.

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