To fully understand how latent heat makes high-volume, low-speed (HVLS) fans a superior solution to traditional cooling systems, one must first understand how heat can be exchanged through objects ― even humans ― in work environments.
Latent heat is the exchange of heat that occurs with a change of a state of matter. All pure substances in nature are able to change their state. Solids can become liquids (ice to water) and liquids can become gases (water to vapor), but changes such as these require the addition or removal of heat. The heat released when water vapor condenses to water (changes state) is about 1,060 BTU (British thermal unit measurement), a thousand times greater than the 1 BTU of sensible heat example.
Sensible heat is heat exchanged when the temperature changes, for example, in a room. When an object is heated, its temperature rises. The increase in heat, which causes the temperature to rise, is called sensible heat. Similarly, when heat is removed from an object and its temperature falls, the heat that is removed also is called sensible heat.
For example, it takes 1 BTU to heat 1 lb of water by 1°F. Traditional systems like air-conditioning systems have what is called a sensible cooling load to overcome as it works to cool a room. To be effective, these systems must battle glass doors and windows, sunlight through skylights, area partitions, ceiling heights, roofs, air infiltration, and heat from humans in order to lower the temperature in the room.
Evaporation and Air Movement
Latent heat of vaporization cannot happen if the moisture is not allowed to evaporate. Stagnant, humid air on moist skin hinders evaporation and therefore reduces the latent heat absorbed.
Consider the fact that moisture on your skin is potential energy (heat) waiting to be used to help cool your body. The introduction of moving air, through HVLS fans, removes the stagnant, humid air from moist skin, allowing evaporation to take place, thus increasing the latent heat absorbed (in this way, the potential energy is released). The old air near our bodies is replaced by drier air that can continue to absorb evaporating sweat.
By assisting air conditioning units to continuously mix incoming fresh air with stale air, HVLS fans minimize the total amount of ventilation required to achieve adequate air quality, and use less energy, which helps lower HVAC costs.
HVLS fan technology helps keep employees comfortable, safe and productive, and keeps products and machinery balanced and controlled at the correct temperatures.
For more information, see related feature article, "HVLS Fans Help Keep Processing Facilities Cool."