HVLS stands for high volume low speed and is a type of fan. HVLS fans are the devices to utilize in order to reduce the apparent temperature in huge buildings in either case.
fans are defined by two characteristics: first, high volume, or the HV bit; and second, low volume, or the L bit. The Evel HVLS fan series includes 15 types, with the smallest having 1.4m blades moving 41,000m3/hr of air and the largest having 7m blades moving 850,000m3/hr. That is a massive airflow by any standard.
The LS bit, or Low Speed, is the second part. It relates to the fan blades’ speed as well as the air discharge velocity.
The largest in the series, for example, revolves at a sloth-like 50 rpm and moves a massive 850,000 m3/hr. To put it another way, a revolution takes over a second to complete at full speed.
It took a moment or two for someone like myself who was used to fans spinning at 960 rpm or higher on a direct drive to realize how slowly they moved.
Their sluggishness, on the other hand, is a wonderful thing.
The huge airflow from these HVLS fans slowly washes over you due to the languid sweep of these vast blades. Instead of a busy tiny throw of air from a typical fan that knocks your socks off, the enormous airflow from these HVLS fans blows your socks off.
It’s tough to put into words how the effect feels. The airflow from a single HVLS fan affects a vast area, and wherever you walk in this area, you are aware of pleasant air movement but are not ruffled by it.
This steady soft air circulation is invigorating and makes you feel cool and at ease.
What is the definition of apparent temperature?
Even if the temperature is 35°C on a still hot day, it will feel hot and uncomfortable, especially if it is humid.
However, if there is a light breeze, the temperature will remain at 35°C but will seem cooler.
Evaporation of moisture from our skin cools our skin, making us feel colder, and we are kept cooler when this happens on a regular basis.
In other words, our body’s natural cooling process is more effective when there is air movement.
The relationship is straightforward, resulting in the following apparent temperature changes:
• Increases as humidity rises, and vice versa.
• Decreases as airspeed increases, and vice versa.
As a result, apparent and perceived temperature are the same thing, but they differ from dry bulb temperature, which is affected by airspeed and humidity.
Knowing it’s a hot day outside but being inside a large building where you’re fairly comfortable is a strange experience – not cold, but not hot either, and with a constant sensation of air circulation throughout the structure. It contributes to a pleasant working environment.
The fixed point of 27°C and 50% RH falls outside the comfort zone when there is no air movement.
The setpoint of 27°C and 50% RH falls readily into the comfort zone when there is 1m/s air movement.