Why air temperature gradients matter
Temperature gradients occur when air is not moving sufficiently to keep rising hot air mixed with descending cool air, creating warmer temperatures at the ceiling and cooler temperatures at the floor, with temperature variations equal to about .75 degrees per foot of rise. This means there could be six degrees difference from the floor to an 8′ ceiling. In a 40 ft ceiling room, temperatures can vary 30 degrees or more. At a glance this seems to be a good thing. The floor of your facility, where people have to operate is cooler than the air pressed against the ceiling.
Stratified air temperatures are counterproductive, far less energy efficient, and less comfortable. It’s commonly believed to be a positive, but it isn’t. Pushing warmer air to the floor will make everyone more comfortable in any temperature controlled environment.
Why is it important to break up temperature zones, particularly during hot weather?
- Stratified air costs more to heat or cool. If you air condition your facility, you’ll spend significantly more energy and more money doing so if you don’t de-stratify the air. Your HVAC system will have to work much harder to attack and cool that heated air lingering at the ceiling. When air temperatures are correctly integrated from floor to ceiling, heating and cooling costs are reduced due to less energy being used to warm or cool uncomfortable areas. Your systems will hammer away at that hot air, and will simply put out more work for less gain if they are present.
- De-stratification helps pull heat or cool from the ground. This creates a temperature sump in the floor and ground below the building. What’s good about this sump is that it adds warmth when it’s cold and cool during warmer temperatures due to radiant energy given off by the floor and the ground beneath it. That radiant energy seeps back into the building, allowing the stored warmth or coolness to assist your cooling and heating systems.
- Even during hot summer weather, equalizing temperatures in a building leads to energy (and productivity) gains due to the absence of “over-cooling”. Your systems will try to fill the “box” with cool air, in order to cool non-directly cooled areas. Workers may be very cool in some parts of the building, while others on the sun-side or upper levels of the building will be very warm – making work conditions uncomfortable for all and leading to lower productivity, let alone the extra energy expense in trying to cool off those warm zones. By equalizing temperatures, HVAC equipment doesn’t have to work as hard, workers have consistent temperatures from zone to zone, and energy costs go down while productivity goes up.
Thermal equalizer fans destroy temperature gradients by creating vertical air flow down toward the floor while drawing air from the ceiling area. As air is forced downward, it creates vortexes that flow outward from the downward column of air, mixing with each level of temperature gradient along its way to the lowest level. At the floor level, air is forced outward and up again, circulating from the walls toward the center of the air flow, continually mixing air temperatures.
Scott Stone is Cisco-Eagle's Advertising and E-business Manager. He is a 20-year veteran of the material handling industry. He publishes the award-winning Material Handling Tips & Information Newsletter and works on all aspects of the company's communications efforts. See Cisco-Eagle on Twitter