All the flow goes one way, so velocity stays high.

Solids are scoured along rather than settling.

A forming deposit narrows the channel locally.

That raises velocity there and washes it away.

Parallel passages do the opposite.

A blocked passage simply receives less flow.

The ones that block everything else.

Slurries, sludges and fibrous suspensions.

Effluent and anything carrying suspended solids.

Wastewater and pulp duties are classic.

Clean fluids do not need the geometry.

Specify by the solids, not by the duty.

True counter-current flow end to end.

That allows a close temperature approach.

A single unit can do what several otherwise would.

Turbulence is induced by the curvature itself.

That helps at lower velocities too.

Efficiency per pass is high as a result.

Surface area per unit volume.

The unit is larger and heavier for the same duty.

Capital cost is higher than a plate pack.

It is a fixed assembly with no expansion.

Repair of a wound body is specialist work.

That is the price of fouling tolerance.

By removing the covers at each end.

That gives access along the channels.

High pressure washing is the usual method.

It is straightforward but not quick.

A gasketed plate pack opens faster.

Cleaning is needed far less often here.

Moderately, and less than some alternatives.

The wound body limits pressure compared with a shell.

Plate-and-shell suits higher pressure duties.

Materials can be selected for corrosive media.

Check limits against the process conditions.

Fouling tolerance is what it is for.

The solids content above all.

Particle size and fibre length matter.

Viscosity at operating temperature.

Both flow rates and both temperature ranges.

Material compatibility for the wetted parts.

A duty alone will produce the wrong machine.