Evaporation capacity (W) is derived by mass balance between liquid feed rate (F) and finished dry powder yield (P): P = F * (s1 / [1 - x2]) and W = F - P, where s1 is feed dry solids fraction and x2 is finished powder target moisture fraction.

Mean downward air velocity inside the cylindrical chamber is limited to 0.40 to 0.50 m/s (80 to 100 ft/min). Exceeding this velocity induces recirculation eddies that carry wet, partially dried droplets into the cylinder walls, causing severe product wall deposition, scorching, and powder fires.

Exhaust relative humidity dictates whether powder reaches its sticky glass transition point (Tg). If exhaust air RH exceeds 45% to 50%, hygroscopic amorphous sugars absorb moisture from the air, turning sticky and clogging ductwork, cyclones, and baghouses.

Rotary atomizers use a high-speed rotating disc (12,000 to 25,000 RPM) to fling droplets outward, creating a wide, horizontal spray cloud ideal for wide-body chambers. Pressure nozzles force slurry through carbide orifices at 100 to 250 bar, creating a narrow, downward spray plume suited for tall-form tower dryers.

Thermal drying efficiency is defined as ηth = (Tin - Tout) / (Tin - T0). Increasing inlet air temperature from 180°C to 280°C significantly boosts thermal efficiency (from ~55% to over 75%), reducing required air volume and fuel consumption per kilogram of water evaporated.