71.6°F 69.6°F 67.6°F 65.6°F 63.6°F 61.6°F 59.6°F 57.6°F 55.0°F -13°F 0°F 10°F 20°F 30°F 40°F 50°F 60°F 70°F OUTSIDE AIR TEMPERATURE RETURN AIR THERMAL RECOVERY VIA COLD WATER SPRAY HUMIDIFIERS M I X E D A I R T E M P E R A T U R E MIXED AIR VALUES AT SPECIFIC OUTSIDE AIR TEMPERATURES BASED ON 20% MINIMUM OUTSIDE AIR. AND A RETURN AIR TEMPERATURE OF 72°F. NOTES: -1- The mixed air set point is normally 55°F. Proportional controllers will droop below 55°F in cold weather conditions increasing the potential heat recovery. -2- If the outside air is -13°F, the return air is 72°F and the required quantity of minimum fresh air is 20%, the mixed air temperature will be 55°F. At this outside air temperature, or below, there is no savings available, via sequencing logic with the humidity sprays as the system is on minimum ventilation only. -3-The energy savings available, when the sprays are active, at outside air temperatures above -13°F, gradually increases as the outside air temperature rises. Example: At 20°F outside the control logic will automatically raise the mixed air from its normally controlled value of 55°F to 61.6°F. The humidification system will use the energy contained in the 6.6F° gain to evaporate the moisture in the sprays. -4- The heat recovered, during spray activation, from the return air per 1000 CFM = (Actual mixed air temperature - 55°F) x 1.08 x 1000 = BTU/HR/1000 CFM -5- When the fan system is on 100% outside air at 55°F and 100%RH the air will drop to 35%RH when the temperature rises to 72°F, if no other moisture is introduced into the air. GAIN 2.6F° GAIN 4.6F° GAIN 6.6F° GAIN 8.6F° GAIN 10.6F° GAIN 12.6F° HUMIDIFICATION REQUIREMENT IS UNLIKELY ABOVE 50°F OUTSIDE. GAIN 0F° 8.103
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