Capturing Engine Heat

[Yianie]

Hello, I am new to the forum so excuse my lack of knowledge.  I was wondering if there is an easy way to capture heat from a small diesel engine, but at the same time, still enclose it tight enough to lower the noise level.  A water cooled engine will be ideal, but finding a cheap small water cooled diesel engine doen't seem easy.  Thank you.

[Ronmar]

Yea, cheap and watercooled don't go together...  An aircooled engine must have enough airmass at an appropriate temperature to dissipate the engines heat.  Now in theory, you could compartmemtalize an insulated enclosure, and pass the air thru a radiator to take the heat out of the air.  With some carefull air ductwork, the engine blower might be able to provide all the airflow.  The issue with this is that you need to get a certain air temp out of the radiator, say 120F maximum, which means you need a lower water temp than that in the radiator to get that air temp...  100F heat is only usefull for building heat.  These numbers are just out of my head, but not unreasonable.  You also need a place for the heat to go.  This could be as simple as another radiator transfering the heat to the atmosphere if a dwelling dosn't need it.  Doable with big enough radiators...

[mobile_bob]

another approach is to mount an A/C compressor within the containment, with an evaporator
and then use the condenser elsewhere to move the heat out of the cabinet.

basically trying to aircondition the inside of the cabinet,

this would work well if you have a use for the heat that is removed, otherwise it is an expensive way to ventilate the case.

there are many contained aircooled engine cabinets, that are very effective at abating the noise, and allowing airflow through
to keep the engine cool, however it take careful design to get it right so as not to overheat your air cooled engine.



bob g

[Yianie]

I was planning on using the heat to heat water for my hydronic system heating my home.  Any additional ideas are welcomed.

[BioHazard]

I think the two easiest ways to extract heat from an air cooled engine would be through an exhaust heat exchanger, and an oil cooler. The exhaust and oil take a lot of the heat load on an air cooled engine. Taking from the air cooled part of the engine is going to be more difficult.

[Yianie]

The oil cooled method seams very interesting.  I believe you would be able to capture most of the heat, but with fluid there is a thermostat, how about with oil?
The exhaust might be easier.  You can use a simple controller and a pump, but how woud you consider controlling oil temp?

[Henry W]

One thing you do not want to happen is cool the oil to much. It is best to keep engine oil near 212 deg.F. The oil is more effective at that temp. to lubricate Piston, Cylinders and Rings properly. The oil viscosity has an important role in determining life. You cool the oil to much than engine life will decrease because the oil cannot flow properly between Piston, Cylinders and Rings.

And beleave it or not an oil that is hotter will cool an engine more effectively than an oil that is cool. The oil can flow properly between Piston, Cylinders and Rings when hot to displace heat more effectivly.
This is why so many modern engine manufactures dropped oil viscosity requirements.

I hope this made sence.

If anyone can help explane it more thourghly please do.

Henry

[BioHazard]

Yeah, you need to make sure your oil isn't too cold, but, with an air cooled engine it generally runs pretty hot. Standard automotive type oil coolers come with thermostats in them, I'm not exactly sure how they work...

[Henry W]

I have one automotve type oil cooler that does not allow most of the oil to flow through the cooling tubes when the oil is cold. I my guess is when the oil heats up the viscosity thins out and then it allows to flow. There is a bypass tube on it with no thermostat. I need to look at it and take a picture of it. When I put it in my Diesel Chevette to cool the TH200 there was about a 10-12 degF. drop in the trans fluid temp on the return side. Never had any trans problems at all.

Henry

[deeiche]

rm /

[BioHazard]

Have you seen the Yanmar engine Suplus Center is selling?
https://www.surpluscenter.com/item.asp?item=28-1684&catname=engines
Only slightly more expensive than an air cooled diesel, and by the time you build some sort of heat exchanger it would probably be a wash.