MEP Heat Recovery System

[DieselAddict]

Has anyone done any experiments on heat recovery systems with a MEP?

I'm considering putting together a HEX setup that would fit on a 80x series and a heat pipe arrangement that could be used on a 80x or 00x series.

This could be useful for domestic water heating and/or space heating.

 

[Korgoth1]

This isn't an mep, and he isn't recovering the heat, but he could easily route the "raw waterpump" to pump it from the engine's heat exchanger into your house. He also mentions water being injected into the exhaust , so even the exhaust gas heat is recovered. The great thing about it is the waterpump being on the engine side, instead of electric...

https://www.youtube.com/watch?v=NsVRwhny_Qg

 

[Korgoth1]

I have thought about just using the engine's waterpump, routing through copper tubing wrapped around the exhaust, but I'm afraid it may not flow enough.

 

[DieselAddict]

There is an extra port on the water pump on the MEP80x that I'm considering piping over to a HEX for heat recovery. I recently put in a solar hot water setup for domestic hot water and I could tap that loop. When the generator is running it could provide hot water for the house.

Secondly for an air cooled generator and/or exhaust heat recovery heatpipes to a water manifold could be used. The trick with exhaust heat recovery is to do it in the right place so you don't cause a bunch of gunk to collect and mess things up.

 

[Korgoth1]

I forgot about that port!
I read in the TM they don't want you to put more than a 90* turn in the exhaust, that is kinda limiting...

 

[Korgoth1]

An egr exchanger from a diesel truck would make scavenging the exhaust heat easy. Something like this with a straight through design might not upset the engine to much...

https://images.search.yahoo.com/ima...-001&fr2=piv-web&hsimp=yhs-001&hspart=mozilla

 

[Jeepsinker]

So plumb the exhaust into a "hotbox" with a large coil of copper tubing inside. Make it work like a reverse distillery. Build your box with the exhaust plumbed in at the bottom, and an adjustable vent at the top for controlling exhaust flow and heat loss. Insulate the box. It'll cut down on exhaust noise too.

 

[tim292stro]

Just make sure you don't hyper-cool the exhaust - if you get it below the dew point of the exhaust (somewhere around 130°F/54°C), it'll rust out quickly. Also on an engine with a turbo, you're not going to see much more than 15% of the produced HP as exhaust heat energy after the turbo.

I recommend that you allow drainage away from the engine and construct with material that will survive hot acidic environments (more expensive stainless like 347H) - and control the water process temperatures carefully. If you don't have any experience witht boilers or hydronic heating system, you should read up on them first. Thermostatic mixing valves are good for ensuring that water entering the heat exchanger will not be too cold, but you'll need a good flow isolation system.

 

[tim292stro]

If your're thinking of using the coolant, look at plate heat exchangers. To be realistic, figure about 30% of the engine's actual generated power being avilable in the coolant. If you're doing domestic/potable water heating, you will need to look at double-wall heat exchangers for safety.

Again, you will want to allow the engine coolant to achieve operational temperature before you start harvesting heat from it - wet-stacking and washdown are likely outcomes for your generator's engine if you run it cold for extended periods. Like the thermostat that keeps water in the block and out of the radiator until it gets to temp, you need to prevent the heating operation from hurting the engine.

I recommend a buffer tank (a hydronic heater tank with a boiler loop) that only circulates coolant when the radiator hose is getting good heat - if you're doing a permanent install, consider making the heat loop the first cooling system and the radiator the second sytem to reject heat. A large volume of fluid at 185°F, or whatever your thermostat setting is, will then be avialable to heat domestic water to 125-140°F.

 

[DieselAddict]

I'm looking at using heatpipes for the exhaust scavenging. Specifically because the heatpipe can be designed to work only within certain ranges of temperatures. Making a heatpipe that doesn't turn on until its at a higher temp will reduce condensation and soot collection.

Definitely will use double wall HEXs for any coolant applications.

I've decided to keep the cosmetically damaged 803 I recently picked up. Its in such nice shape mechanically that it should work for a very long time. I'm going to use it as the test mule for my mad scientist musings.

 

[Ratch]

I thought a lot about this in order to reduce electrical load on the genset, since I have an electric hot water heater.
Somewhere, I have a schematic/drawing I made of an exhaust system with water coils that would capture reject heat and stay isolated from the genset; so no overcooling of a water cooled engine, no damage to the stock exhaust from corrosive cooled exhaust, and portability to an air-cooled mep-00x.
I'll post my drawings if I remember when I'm back on my computer. Post pics if you put something together.