Cooling with radiator gone wrong

[Jedon]

The "redhead" concrete anchors worked great and I got it all bolted down ( not without a lot of effort though! ) and got it running and generating about 1500W ( 6 amps at 127V at each pole ) into my inverters. I watched it for 10-15 minutes and felt the output pipe getting warm but not uniformly, the heat was slowly creeping up the hose.  I then went to get some lunch and have the wife come take a gander.  Wife wanted to look sooner than my PB&J was ready so we went down and took a look, just then it made terrible noises and steam started coming out of the radiator and water was bubbling in the overflow hose. I shut it down and left the shed to the safety of the out of doors, it was really loud and scary in there! The radiator does not have a cap, the car I took it off of had two caps, one on the overflow and one on another housing. I figured leaving the top of the overflow open would allow air to bubble out of the system and have it be 0 pressure. I'm guessing either I totally misunderstand the way the system works in regard to pressure, the radiator has flow issues, or maybe it's too high up for the water pump which seems to be low pressure.
Ideas? Suggestions? My first order of business is to flow test the radiator with a hose.
Thank!
-Jedon

ps here is a video about 10 minutes before overheating.  http://www.youtube.com/watch?v=WYuAFAWSU4M

[veggie]

Hi Jedon,

Nice looking setup.

From looking at the video, I could not see if you had a fan on the other side of that radiator.
If you do not have a fan, it's quite possible that you heated the coolant at a faster rate than the radiator could get rid of it.
(Engine making more BTU's than the Cooler can expel).
The small amount of water held in the block and rad. would heat up rapidly without considerable air flow across the radiator.
If that's the case, you need a fan and a source of cool air.

Good luck,
Veggie

[Jedon]

I don't have a fan on it yet, I have one sitting there I could try that and take video of the resulting success or fail.

[veggie]

I would say the fan should make a big difference.
Remember to leave the building door open during the test because the air in the room will heat up rapidly.
Ideally, one would have a cool air inlet ahead of the fan.

Looking forward to the next video.

Good luck,
Veggie

[Ronmar]

If it was running like it is plummed in the above picture, you have more issues than just needing some airflow:
1. The first issue I see is that the hot hose immediatly goes down comming out of the head...  It needs to go up.  If you had a wood stove, would you run the chimney down thru the floor and still expect a proper draft? Like hot air, hot water likes to go up, not down.  the opposite can be said of cool water, it likes to go down, but not up.  You are breaking both of these basic rules.  You want that hot water to easilly rise away from the head up to the radiator inlet with no dips.  You want the cold line from the radiator to go directly down to the cylinder inlet with no rises.  Because of those dips in the lines, I doubt you had any thermosiphon flow at all.  Hopefully the head wasn't full of air, and the engine just tank cooled by boiling the water in the head and blowing it up the line to the radiator along with the steam and air bubbles, to be replaced by gulping cooler water back down the hoses to replace the steam.  If you filled it like that, you may not have gotten all the air out of the head, and that could have done some damage...

2.  With a small radiator, you have drastically limited the liquid mass of the system.  Thermosiphon is powered by gravity's effect on the water density in the system.  You heat the water, it gets less dense than the water lower in the cylinder and it rises up and out the head.  The cooler water in the radiator and downhose is more dense and therfore wants to fall.  This falling cooler water helps pull the warmer water over the top, and helps to push up on the warmer water as it flows into the bottom of the cylinder.  Here is the rub.  The weight of the cool water on the downward side(radiator and hose down to cylinder) needs to weigh more than the warm water on the up side(cylinder, head and hose up to the top of the radiator).  If this difference is not there, you will not have good flow, or enough flow to overcome any drags in the plumbing.  That small radiator dosn't have much fluid in it so it might be that the weight of the cool water isn't enough to overcome the larger volume of warm water.

In your case, vertical is your friend.  The more vertical the flows are in a thermosiphon system, the better it will perform.  Raise your radiator.  This will get rid of the dips in the lines and more properly align them so gravity can help out on the downside.  Also make sure that the radiator stays completely full and the top inlet port is always completely submerged.  Putting the rad on a slight angle so any air that works out of the system will move toward where the expansion tank is connected will help make sure it stays submurged.

I ran into the small volume problem on my system when I put in the heat exchanger.  The total system volume is 2 gallons, including that in the expansion tank.  I Initially put the heat exchanger about 12" above the head.  The system would not flow enough to remove all the heat at full load.  I wound up raising the heat exchanger about 30" above the head.  This increased the volume in the cool water downpipe  and raised the flow enough to transfer all the heat generated at maximum load.  

Here is a clickable thumbnail scale drawing of my system.  The heatex is that high above the engine because it has to be with so little a cooling volume. Note the coolant lines are as near vertical as i could get them.  You are nearly in the same boat with a small radiator.  That radiator has plenty of surface area to remove the heat it needs to with a fan.  With good airflow, it could probably cool two 6/1's

[veggie]

Ronmar,

Good points.

I was going to mention the thermo-siphon also, but then I noticed he has a water pump driven off a crank pulley.
Although vertical travel in the lines is important, it's probably not so much of an issue unless his rad is too far from the pump.

Cheers,
Veggie

PS: I really like your CHP system drawings. Any pictures of the unit that you can post ?

[XYZER]

I watched it for 10-15 minutes and felt the output pipe getting warm but not uniformly, the heat was slowly creeping up the hose. 

I'm a thermo siphon guy and the way you describe the heat creeping up the hose I would say the pump isn't doing its job!? I would figure a pump would circulate the water with an even temperature rise with no thermostat. I never had a pump so what do I know. Even with a pump I would keep my hoses from drooping so a thermo siphon could keep my engine alive if the pump failed. The radiator should be sufficient but no airflow will defeat even a big one.

[Ronmar]

The youtube vid didn't load for me, and I missed the pump in the pic:(  I wonder how much head those indian pumps are capable of.  If there was an air pocket in the head, it might not have been able to overcome that and raise all that water in the cylinder up enough to push water thru the upper hose.  I agree with dave, the description of heat creeping along dosn't sound like the work of a pump in a system without a thermostat...  If it was circulating, I think it would appear to get warm everywhere as the warm water from the engine was quickly distributed thru the system.

I am a big fan of thermosiphon.  If you can do it without a pump, why bother with a pump???  That is energy that could go to making KW.

[Jedon]

Thanks everybody! I'm going to lower the radiator, turn it so it faces the engine, put a fan on it, and plumb in a air bleed at the top to get the air out. I could also shorten the hoses.

[harv_44]

Jedon
I put a fan on my 20/2 and also a relay kit so it comes on at a certain temperture and no need of a thermostat. So far it works quite well.

    Harv

[Carlb]

Jedon
I put a fan on my 20/2 and also a relay kit so it comes on at a certain temperture and no need of a thermostat. So far it works quite well.


    Harv

In cold weather (if you live where it gets cold) without a thermostat the engine may never get up to operating  temperature even without the fan if the radiator is reasonably large.

Carl

[Jedon]

It gets down to around 20F at the coldest, we will have 4-5ft of snow most of the winter ( Jan-April )
I don't have a thermostat yet just because I don't have a way to install one, I was discussing joining two housings together with the guy at the local junkyard. I tried ordering one from George at Utterpower but he must be out and about.
I did see some of the radiators at the junkyard that had sensors on them and I think a couple still had fans + sensors so they might just work if I hook 12V up to them ( computer power supply? )

[harv_44]

carlb


   That's true,I see your point but I think you could size your radiator a bit small. I've run mine below freezing and it worked good.I know our neighbors to the north get a lot colder and would make it more difficult to get to normal operating temp. I just didn't want my fan running all the time. I wonder if you could have both so if the thermostat opened and still wasn't getting enough cooling the fan would kick on. Kinda like a car works.

             Harv

[SHIPCHIEF]

If it gets too cool, cover part of the radiator with plastic or something.
That's how I regulate the temp on mine. I should get back on that project and do some more upgrades.

[cujet]

While you can't see it perfectly in the pic, Under the rad is a Grundfos electric water pump that circulates the water just fine. It's hard mounted to the lower water manifold via pipe fittings.

Chris