Fuel & Fluid Filtration
Capture is exponential with depth, so the last decade of removal costs the same bed as the first. Aviation specs are written at the expensive end.
— %
Water removed across the full bed depth
Single fibre efficiency is entered rather than derived because it depends on droplet size, velocity, interfacial tension and wettability all at once, and a single number only describes one droplet size — a real inlet distribution needs the calculation run per size band and recombined. Coalescence is also not capture: the droplets have to grow and drain away, and a coalescer that captures perfectly but re-entrains at high face velocity performs far worse than this predicts. Surfactants in fuel disarm coalescers outright, which is why the specification tests use them. Aviation fuel filtration is safety-critical work governed by EI 1581 and equivalent standards.
Coalescing Filter Liquid-Liquid Separation Efficiency — free, with the formula and a worked example, at Textile School.