Cooker Extractors

[SteamyTea]

After looking at that hob extractor thread, I was thinking, why not have an extractor that draws in cold air from outside and then the extractor just sucks up that air, with the fumes and flames from your cooking.

That way it may not unbalance any other extraction system the house has, and there should be enough 'leakage' of kitchen air to help get rid of excess smells.

Not the most energy efficient extractor, though a heat exchanger could be incorporated, but for the relatively short time a hob is used it should not matter.

 

Also.

Fitting an extractor at hob level and with the gubbins in a floor mounted kitchen unit would cure my problem of fitting an extractor i.e. I have no wall to put a pipe though, it is all window.

[dpmiller]

I've been thinking the same- a vent with a drop flap behind the cooker would be closed in normal conditions (mvhr positive pressure) but would open if the extractor was on  or if a woodburner pulled too hard with it's door open.

[Jeremy Harris]

Easy enough to do, just use a venturi eductor, driven by a fan that's sucking in outside air and using that as the motive drive to draw in cooking fumes.  With a bit of cunning a bleed could be arranged to to inject some of the venturi drive air across the cooker before the extraction point, to help keep the system balanced.

 

Venturi eductors are not that efficient, and one draw back is that you need to raise the velocity of the motive air stream a fair bit to get them to pull, but I think the idea still has promise.

 

Given that Dyson have been using venturi eductors for a while in their fans and hair dryers, I'm surprised they haven't come up with one.  The basis of a venturi eductor are the same  as the water-powered suction pumps you may have seen in a lab, except in this case the motive liquid would be air, rather than water.

[SteamyTea]

15 hours ago, dpmiller said:

I've been thinking the same

Not sure if it is just a bonkers idea or there is some mileage in it.  I think that it is only suitable for induction hobs, and probably not got gas as it could blow the flame out.

But people really should not be considering anything but induction hobs these days.

 

15 hours ago, JSHarris said:

Easy enough to do, just use a venturi eductor

I was not thinking along those lines, but does make the whole thing a lot easier, good call.

 

I may have to get the jigsaw out and that old hardboard I have kicking about.

[Jeremy Harris]

I've designed a few liquid/gas eductors  and have the formulae to hand somewhere if you need them.  Air to air eductors are a bit more hassle, because the density of both the motive and suction fluid is the same (unless you do a Dyson and accept the noise of accelerating the motive stream beyond the incompressibility limit - not a good idea in my view, for this application).

[SteamyTea]

Something to think about Christmas Day, not a lot happened then