Wet-stack droplet rainout can result from demister carryover, stack-wall condensation, liquid-film stripping, duct condensate, or wash-cycle events. A normal-looking plume does not prove zero liquid fallout, and downstream liquid chemistry can help identify the source.

CFD can help evaluate demister maldistribution caused by inlet jets, side outlets, irregular vessel geometry, and internal obstructions. Single-phase models are especially useful for local gas velocity, while true droplet and wet-performance prediction requires more complex validated multiphase modeling.

Liquid mass balance can estimate or cross-check mist carryover when direct droplet sampling is difficult. Makeup, blowdown, evaporation, inventory change, drainage, condensation, deposits, and measurement uncertainty must all be included.

High-velocity jets, restrictions, elbows, turbulent expansions, and wet surfaces can break large droplets or strip liquid films into finer mist before the gas reaches the demister. This can make separation harder without increasing total liquid mass.

Vane drainage pockets and hooks can plug with salts, slurry, or solids before the main gas passages appear restricted. This can cause high carryover with only modest DP increase because droplet capture continues while protected liquid drainage fails.