As the world's population increases, there is an increasing demand on our water resources, and we are constantly looking for ways to recycle and conserve. HVAC systems can consume large amounts of water, and it's important to be able to quantify how much water they consume. In the June 2003 report, we reviewed methods for determining the amount of water consumed by cooling towers through evaporation, blowdown, and drift. In this report, we'll take a look at humidifier water usage and cooling coil condensation.
This calculation can be done fairly easily using VLI data. By definition, the VLIlh (latent heating or humidification VLI) is the total annual humidification water consumption per cfm of outside air. The total annual VLIlh is based on the same calculation above for every hour that Woa is less than Wsp, or VLIlh = •(Wsp-Woa) x .075 x 60. To calculate water consumption, it's just a matter of multiplying outside air cfm by the total annual VLIlh. If the above system were located in Cleveland and operated 24/7, the annual water consumption would be 4.03 gal/cfm/year x 100,000 = 403,000 gal/yr.