Effective with perfectly clean gases…but in the wood-gas reality? It is a self-clogging cyclone. If you are willing to do an arrangement where you can draw out the internal part each second hour and blow and knock off the soot collected, so be it!
Speculating in different constructions, you have to take into account EVERY ASPECT AND PROPERTY that is, and CAN be envolved!
Beleaguering over one excellent property and going blindfold over all the rest, brings no practical advantage over conventional, proven constructions…
Half of the spiral ribbon surface as covered by soot laying down on it, is already an inexcusable loss of “material function”.
On the other hand, the outer cylinder gets a highly intensified gas sweep, which intensifies the heat exchange, if it can stay soot-free…
“Screwing” the dirty gas downwards between down-sloping (70 degree) ribbons, having “drop slots” (1 or 2 per turn) might help?
These kind of heat exchangers work best with clean liquids, which do not settle particles on horizontal surfaces.