Induced Draft Cooling

[BruceM]

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

[mbryner]

That's cool, Bruce!

[squarebob]

Really like your setup!! My 6/1 is feeding a small heatex by thermosiphon. I am using 5/8" heater hose out from the head, and 1/2" heater hose return. No flow problems with the small hose. The top of the heatex is 48" above the engine head. Total coolant capacity on the engine side of the heatex is about 1.5 gallon.

Bob

[BruceM]

Thanks for the helpful info on coolant pipe sizes that work, Bob.  I could use a large auto heater core or a motorcycle radiator.  They tend to be 1/2 & 5/8 inlet/outlet, and I didn't know that would work!

Marcus- yes, the radiator does get cool, but the appearance is Rube Goldberg!  

[Ronmar]

Squarebob. What temp are you harvesting out of the heatex secondary?

[squarebob]

Ronmar, my setup is modeled (stolen) from your avatar. No thermostat on the secondary side yet. My storage tank is a one gallon jug with about 1/2 gal antifreeze. I keep the flow throttled back quite a bit and get about 160 to the rad and about 100 out and back to the heatex. My plan is to be able to use the secondary loop for radiant heating or hot water use down the road.

Bob

[veggie]

BruceM,

That's an excellent setup !
Simple and very effective. AND you even have a separate engine/generator building !
Some of us can only dream of that 

very nice system,
veggie

[BruceM]

Thanks Veggie.  The engine/generator/compressor shed (aka "The House of Lister" was the first building on my site, since the sound of 3600 rpm generators makes my epilepsy go bad, fast. The HOL was also the only place to securely store tools and such at first, also.

It provided all the power (plus water) and compressed air for the construction of the pump/battery shed, shop and house.  I'm very grateful for the help I got here, and from Utterpower, and Joel... I couldn't have gotten the job finished without the Listeroid. I lost a year for liver failure, from an experimental drug, but I did "git 'er done".  

Bruce

[cujet]

That's not at all unlike the old steam locomotives, with a motive flow ejector in the "stack".

I'd love to know the results of this setup under various conditions. Such as no load, high wind, hot/humid days, etc.

That's a great idea and I congratulate you on it's implementation.

[BruceM]

Cujet, Glad you liked it.

I've used the same 8" galvanized vent caps before- on windy days they generate an impressive suction regardless of wind direction;  no induced draft by exhaust would be needed.  Compared to a 90 degree duct elbow, they tend to restrict the exhaust induced draft somewhat; there is more of a (10Hz) pulsed character, though it is still quite strong. There is no back drafting despite the pulsing- you cannot smell exhaust at the radiator inlet.  I knew there would be no problem with high wind from any direction (or rain), so using the standard 8" vent cap was the easy, low risk solution. 

I don't have a way to measure the CFM of the induced draft; I can only judge the air suction from the affect on a piece of manila folder held near the radiator inlet.  The flow is such that paper will be sucked up to and held against the radiator; the paper won't fall off.

When we get some windless 100F days this summer I can do another extended full load test to see if I need to expose more radiator area than 6x11" for summer use.  At 80F with extended full load, the return line was cooler than necessary (95F), to allow for summer use, but it does warrant further adjustment at 100F. I have a thermostat, but I was also interested to see how small of a radiator could be used with the induced draft configuration.  A smaller radiator and volume of coolant would make for faster warm up time.

[sailawayrb]

Very innovative and well executed Bruce!  It would be good to quantify the CFM you are able to achieve.  I suspect with smaller radiators that the reduced flow rate resulting from less flow area coupled with the need for increased flow rate from having smaller radiator might prove limiting.

Marcus, this might be good option for your situation!

Bob B.

[BruceM]

Thanks, BobB,

The suction you can get with induced air draft is quite impressive.

The suction for my Rumely-exhaust induced draft setup is quite strong, as I reduced the radiator area the air velocity kept increasing proportionally.  I don't think a motorcycle radiator or heater core would be a problem.

I have a small, hand-held pneumatic vacuum that I purchased some years ago.  It has a canvas bag for debris collection on the outlet; all the air must go through the bag. Despite a dirty bag, it will still suck air through the 1" inlet nozzle quite strongly.  This unit uses a hollow ring around the vacuum air path with lots of small air holes to induce the strong vacuum, and it does use a fair amount of air to do so (about 5 cfm at 90psi). 

I also use induced draft for starting the air flow on a gas stove vent hood. A tiny stream of compressed air via 1/4" tubing injected in the center of 8" duct produces a huge draft at low pressure. (not even a 1/4 cfm- was metered by a needle valve).

[sailawayrb]

Bruce, I think your use of the engine exhaust to induce and significantly increase the normal stack effect is absolutely brilliant and could likely be put to good use in a multitude of ways.  In case you didn't have the physics equations for stack effect, here's the Wikipedia link that contains them:

http://en.wikipedia.org/wiki/Stack_effect

Here's another use of compressed air that you might enjoy and find interesting:

http://en.wikipedia.org/wiki/Vortex_tube

I built one of these several years ago for one of my kid's science projects and I was quite impressed at the time with the hot and cold temps one could achieve. 

Happy experimenting! 

Bob B.

[mbryner]

this might be good option for your situation!

Hey Bob!  Actually, I love the idea, and I've been seriously considering it.

Bruce, how did you fabricate the connection between the pipe and the radiator?

[BruceM]

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.

Marcus, to fair the exhaust into the 8" duct at an angle, I first marked two parallel lines the width of the 2" exhaust pipe in the section of the duct pipe where the exhaust would enter.  I then held a pipe at the appropriate angle and eyeballed/marked the top and bottom. I then eyeballed and drew an ellipse and cut it out just inside my lines with my pneumatic high speed body saw, and filed the sides to just fit the exhaust pipe. By dumb luck, my first attempt fit so tightly when angled properly that I didn't have to use high temperature silicone to seal any gaps.  If I had botched it, I would have just cut another small piece of tin to fit the exhaust, then pop riveted it over the larger, botched hole.  A small leak area at the exhaust entry is not a concern, it just reduces the flow through the radiator by a proportional amount.

Edit-  if you were thinking of the fairing to the radiator, that was just a "pup tent" of  28 gauge galvanized steel sheet by the TLAR (that looks about right) method.  It was pop riveted together of three pieces and sealed to the radiator with silicone caulk.

I have a homemade sheet metal "bending aid" which attaches to the edge of my 8 foot butcher block maple workbench; it's just two pieces of heavy angle iron.  One goes over the edge of the bench to make a hard edge for bending, the other is held against it as a clamp by big lag bolts into the edge of the bench.  There are a few holes so you can clamp the piece close to its width. The initial fold is started by hand, and the bend is completed with a rubber mallet.  For light gauge steel or soft aluminum, it works pretty damn well.  I have a small "bender" (2" angle) and a large "bender" that uses a 6" angle for the clamp piece.