| Parameter | Formula (US Units) | Notes | | :--- | :--- | :--- | | | E (gpm) = 0.00085 × Range (°F) × Circulation Rate (gpm) | Approx. 1% of flow per 10°F range | | Blowdown Rate | B (gpm) = E / (Cycles – 1) | Cycles = [Makeup]/[Blowdown] | | Drift Loss | D (gpm) = 0.0002 × Circulation Rate (gpm) | For efficient drift eliminators | | Fan Brake HP | BHP = (Air Volume × Static Pressure) / (6356 × Fan Efficiency) | Critical for energy audits |
Environmental regulations are strict regarding "drift"—the water droplets that escape the tower and carry chemicals/bacteria into the surrounding environment. Modern literature focuses heavily on high-efficiency drift eliminators, which can reduce drift loss to less than 0.001% of the cooling towers principles and practice pdf top