Induced Draft Cooling

[rcavictim]

I changed my 6/1 to induced draft, ala the Rumely Oil Pull line of tractors, with their induced-draft cooling systems.  The exhaust is directed into the 8" galvanized duct, and extends up to within about 16 inches of the top of the top pipe.  The cap is a standard vent cap, for rain protection. It reduces the air flow , but it still pulls plenty of air.

This works very well, requiring no AC power, which is nice when I'm just running my air compressor.

From the second photo you can see that only about 6x11 inches of radiator is being used- which works fine for full load at 80F.  This is a thermosiphon cooling system also, so now I'm looking for an appropriately small radiator with large inlet and outlet.  So far, the Geo Metro (12x12) is the smallest I can find with adequate inlet and outlet for thermosiphon.  Any tips for a very small, non-plastic radiator would appreciated.

I previously had no fan at all, just the large radiator, which worked fine except for the rare day here  with dead calm air and a long run time at full load, when I'd start to boil off some coolant.

The Rumely method was something I wanted to try for fun.  If I was starting over with an engine room now, I'd put a small radiator near the ceiling (near horizontal, outlet tilted down a bit), with the exhaust line faired into 8" duct connected to the radiator, and go up through the roof with 8 inch duct.  Then the induced draft system would also pull the hot ceiling air out of the engine room.  (I presently use wind turbines for that now.)

Bruce
Metro 6/1
Off grid near Concho, AZ

I like that setup Bruce!  I would have changed the shape of the radiator air outlet funnel however so that the air flow through the top section of the radiator did not have to go downwards before it could reach the vertical outlet stack.

[sailawayrb]

Thanks, BobB.
The Vortex tube is sure interesting!

The hot air stack effect is not significant in the case of the Rumely induced draft setup. The high velocity air (exhaust) exiting the 8" duct creates a very strong negative pressure area behind it, and this is the induced draft effect.  By comparison, the stack effect relies on the different density of hot vs cold air, and requires a tall column of hot air to achieve typically weaker draft.  The Rumely induced draft approach does not require that the vent pipe is vertical, and it could be quite short; just 3 foot would do it. The induced draft method creates a strong airflow comparable to a radiator fan.

Glad you enjoyed the vortex tube...figured you would 

Yes, that was my point in providing the stack effect equations.  The normal stack effect is quite feeble compared to induced effect.  You would probably need to triple the pipe area and go 60 feet high to obtain the CFM you have now.

Bob B.

[BruceM]

Hi RCAvictim,
The Rumely induced draft method sucks like a fiend, there is no need for upwards only flow. It is NOT driven by a rising hot air column.  The radiator and vent pipe could be any orientation that suits your setup.  The suction is so great that the vent shroud around the radiator could be any shape without worrying about airflow efficiency. The vent duct might even be downsized to 6".

I do agree that the radiator and vent shroud could be much smaller, and of course there's no point in a shroud covering inactive radiator area. I just didn't know what that area would be until after testing.

This was just a fun experiment with my pre-existing radiator but at least it's quite usable until I get around to the MKII version.

Thanks, BobB.  Sorry I misunderstood. Until you've felt how strong the induced draft effect is with your own hands, I guess it's hard for people to realize that it's NOT stack effect/thermally driven.  You can move a lot of air with a thermal chimney, but it is low suction, requiring a big, tall pipe, and relatively unrestricted air flow.

Best Wishes,
Bruce M