Traditional chimneys are wide to allow for natural flow of hot exhaust gasses, the heat making the chimney draw and so allow for the fire to consume more air and dispose of its exhaust.
Given that the technical requirement is to remove a certain volume of air I don't see why the flue has to function as a typical warm-air-displacement chimney.
A powerful fan system should be able to draw the same amount of gas through a small-bore (say 10mm) tube, as a naturally venting chimney draws through a six-inch flue.
This system simply requires the 10mm tube to be laid from the top of the fireplace to outside the building, and for a suitably powerful extractor fan system to be wired in.-- pocmloc, Jun 30 2019 Hmmm. One problem is going to be making a fan that will work despite soot and ash.
Also, a regular flue is maybe 20cm in diameter, and has a speed of maybe 2m/s. To get the same volume flow through a 10mm tube, air will have to move at 800m/s, or around Mach 2.5.-- MaxwellBuchanan, Jun 30 2019 ... and your point is ...?
You don't need to put the fan in the gas stream. Put a device using the venturi effect (think Dyson air-mulitiplier) at the top of the flue. No moving parts in the airstream, it can be made of ceramic just like a conventional chimney pot.
The advantage of a positively pumped system is that you can have long horizontal runs.
A 50mm diameter flue gives much more manageable speeds for the same volume.-- 8th of 7, Jun 30 2019 You'll have to find some especially crackly logs, to drown out the noise coming down the chimney.-- MaxwellBuchanan, Jun 30 2019 OK so 10mm may be optimistic. But never the less, venturi is a nice idea. Also low friction or non-stick lining.-- pocmloc, Jul 01 2019 Chimney top extractors are widely known to exist.-- xenzag, Jul 01 2019 I know but they fit onto normal chimneys. I want to run a 50mm flue pipe along the skirting board and up the wall and out through a small hole drilled through the wall.-- pocmloc, Jul 01 2019 Go ahead, then. Just make sure you're finished and gone before the homeowner returns.-- 8th of 7, Jul 01 2019 If you remove the 'open fire' requirement, you could reduce the size of the fire, increase combustion efficiency and put the fan upstream of the fire. You could put a nice big glass window on the combustion chamber for the display of the enclosed inferno that your inner pyromaniac mandates.
Then you might be able to get away with the narrow-bore exhaust vent you desire.-- Loris, Jul 01 2019 // If you remove the 'open fire' requirement, //
... you immediately destroy the greater part of the entertainment value.
// the enclosed inferno that your inner pyromaniac mandates. //
You clearly aren't a pyromaniac. The whole point of an inferno is that it should not be contained. An enclosed inferno is no fun at all.-- 8th of 7, Jul 01 2019 No prizes for guessing your favourite part of the phrase "controlled explosion", then.-- MaxwellBuchanan, Jul 01 2019 A wye fitting down near the fire end of the pipe could have a quiet fan forcing air into the smoke stream and out of the building. Outside air would be sourced such that less inside air is lost.
If this works, the original exhaust pipe could run through the open air across the room and back again, thus heating the room more better, before meeting up with the wye/fan arrangement and heading outside.-- whatrock, Jul 01 2019 Simply increase the ambient pressure in the house by 2-10 atmospheres. This should allow for ample mass flow through smaller diameter tubing. It turns out flames change shape slightly at higher pressures, so that will be fun.-- bs0u0155, Jul 03 2019 //... you immediately destroy the greater part of the entertainment value.//
Hold on. Those cube-ships of yours are really old-folks homes, arn't they? Travelling the universe, picking up ('assimilating') the decrepit Grans and Grandads, providing the best hip- replacements or other prosthetics, serving tea and letting them have a nice sit down in front of a roaring fire.
You're so misunderstood.-- Loris, Jul 03 2019 // are really old-folks homes //
Thankfully, nothing could be further from the truth.-- 8th of 7, Jul 04 2019 " OK so 10mm may be optimistic "
(marked-for-tagline)-- normzone, Jul 04 2019 //10mm bore// Or a scaled down, bulk lot of micro-fires but don't know, could be just a theory light.-- wjt, Jul 06 2019 random, halfbakery