Drift in ppm of circulation — rising as the fourth power of face velocity — and pressure drop in Pa — rising as the square — for a high-efficiency eliminator and a standard one, each anchored to the point its example states at 2.5 m/s; the plate prices the trade between them.

Reference conditions: face velocity 2.5 m/s, high-efficiency eliminator 0.005 % drift at 45 Pa, standard eliminator 0.020 % at 25 Pa, Q 100 m³/s and ηfan 0.70 — the extra 20 Pa costs 2.86 kW continuously and saves 108 kg/h of drift.

Formula: mD = drift fraction × mcirculation and ΔPshaft = Q ΔP / ηfan.

Illustrative, computed from the example’s two points — not a measurement. Drift in ppm in the upper panel and pressure drop in Pa in the lower one, both against face velocity, for an eliminator of each class.

Sources

Hensley, J.C. (ed.) — Cooling Tower Fundamentals, 2nd edition (SPX Cooling Technologies, 2009) — the definition of drift — circulating water lost as droplets in the exhaust air — and the drift loss approximation of 0.02% of the circulating flow that this article quotes.
U.S. Department of Energy & AMCA International — Improving Fan System Performance: A Sourcebook for Industry (2003) — the component pressure-loss relation behind this article’s statement that eliminator pressure drop rises with roughly the square of velocity.

Drift eliminator trade-off: drift against pressure drop