So, what is an evaporative cooling system capable of doing to the supply air temperature? One facility added evaporative cooling to condition its space and improved labor productivity by 10 percent.

At the Mestex plant in Dallas, Texas, there is both direct evaporative cooling equipment and an indirect/direct evaporative cooling unit on site, which are monitored with a digital control system.

The temperatures below include heat that is added by the air handler fan and motor combination.

Conditions as of 3:21 p.m., 10/6/14

  • Ambient air temperature: 87.53°F.
  • Ambient relative humidity: 50.08 percent.
  • Direct evaporative cooling unit: Leaving air temperature at 82.5°F.
  • Direct evaporative cooling unit: Leaving air relative humidity at 79.7 percent.
  • Indirect/direct evaporative cooling unit: Leaving air temperature 76.9°F.
  • Indirect/direct evaporative cooling unit: Leaving air relative humidity 70.2 percent.


The direct evaporative cooling unit is located on the roof of one of the buildings. The indirect/direct evaporative cooling unit is mounted on the ground adjacent to one of the buildings. The ambient temperature and humidity readings from each location were essentially the same.

When looking at these numbers, it is important to note that this is a snapshot in time. Evaporative cooling unit performance depends entirely on the wet bulb depression. On humid days, an evaporative cooling unit will not reduce the air temperature as much as it will on a dry day. However, note that both systems reduce the ambient air temperature delivered to the space and will improve employee comfort and productivity.

See the related feature article, "Evaporative Cooling: The Inside Story," to learn how industrial process and temperature controls are changing with the times.