Exhaust Heat Systems

[veggie delight]

I'm begining to think about my next conversion project, and in designing a system I think it might make sense to try to use exhaust heat to help heat the oil. Temps in my area are below freezing for half the year so my conversion will need to be well heated. My current car is a Mercedes 250D (think 190D only full sized) with a 2.5L naturally aspirated deisel. I took a greasecar system and added reflective hot water tank insulation to the filter area, and pipe insulation to the injection lines, I have added an in line fuel temperature monitor (unfortunately it only registers at 140-300) and neoterics Veg-Therm heater. When parked and with access to 120V I have 300 watts of heat for the engine, and 300 watts for the fuel tank.
When its below 20 degrees ambient I'm running below 140 fuel temps. At 25-50 I get around 150 degrees unless Im on the interstate, which causes a 5-10 degree drop in temp.
I'm thinking I might need to scrap some of the existing system, namely the filter and replace it with a more efficiently heated one.
The alternator is only rated for 70amp, so with the electric inline heater on, headlites on high, wipers and radio on, I'm maxed out, so I have to look at better heat exchangers, also since the engine is already a little slow to get to temp I don't think using more coolant heat is the best bet.
I was thinking that if the fuel pickup from the tank incorporated a metal coil looped around the exhaust and the return could be switched between the tank (a relatively cool thermal mass) or piped directly back in right before the exhaust heat exchanger and the switch could be controlled via a temp sensor and relay. There seems to be a reasonable amount of heat in the exhaust system, and the odds are that I'm gonna be under the car in a few months to replace everything from the manifold back (gotta love that vermont salt :eek: )
My questions are:
1) Can I use brass for the coil?
2) How many loops should the coil have?
3) What kind of failsafe should be incorporated to eliminate the chance of overheating the fuel when warmer temperatures return, or in the event of a stuck switching valve?

[Mandilon]

unless Im on the interstate, which causes a 5-10 degree drop in temp.

Have you seen the 18 wheelers with a radiator curtain blocking part of the airflow in winter months?

If I remember correctly, in my experments (many moons ago, --many, many, many!) I blocked about 50% of the radiator airflow in a '63 Ford three duce 406 4 spd. (plus removed the fan blades) and drove it on the the freeway with no signs of overheating.

Why don't you try blocking some airflow. If I were you I'd start with 50%.

A vehicle doesn't need a radiator fan at 30 MPH and above. I presently don't have one in my Volvo.

I've found out that diesels (at least my volvo) run cooler, MUCH cooler then gasoline engines.

What kind of failsafe should be incorporated to eliminate the chance of overheating the fuel when warmer temperatures return, or in the event of a stuck switching valve?

I'm starting with a 'mechanical' exhaust cut-out from JC Whitney. I will place temp sensors in different locations and monitor them via switches and the factory gauge.

I'm going to run exhaust heat exchangers *through* the factory fuel tank and a smaller pre-filter fuel tank (about one gallon) in the engine compartment.

*To get things rolling* I'm going to try a glow plug (or four) in the factory fuel tank and the smaller tank.

Once I know *what works* I'll start using carbon fiber for my *assistant* tanks.

Should I use brass piping?

To each his own, I'm going via corrugated stainless steel.

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Shove It OPEC big 3 *com

[Twanoh Tom]

I have toyed with the idea of using the JC Whitney cast iron exhaust cut-out as well. My thoughts were that if a fuel heating line were in contact with the "auxiliary exhaust pipe" and some sort of automatic thermostatic control were placed on the control rod for the cut-out device to control the amount of heat flowing through the cut-out (placed downstream from the muffler) then perhaps this heat resource could be tapped. What stops me from actually persuing this further is the thought of this malfunctioning and overheating the oil, possibly resulting in a fire. That's when I go back to thinking about coolant and 12 volt sources. I'd rather wrestle with a alternator than screw around with exhaust pipes anyway.
TT

[Donniej]

Yea, running oil through piping on the exhaust manifold just screams bad idea...
There has to be a good was to use the heat from the exhaust manifold. I'd make up some stainless steel lines to go around the manifold and then circulate water through them. If you put the reservoir lower then the manifold you could have it rigged up to allow the fluid in the lines to drain back into the reservoir when the pump is shut off.

Another idea would be to make a water jacket around the down pipe where temperatures are lower. Depending on the temps back there you might be able to run VO through such a water jacket... Most down pipes are steel so it might be as 'easy' as MIG welding a large diameter pipe around the down pipe...

[akghound]

How about this, seen on a stationary air cooled generator. A PIP (Pipe-In Pipe), copper inside of copper, is replaces the vertical exhaust pipe just above the engine but below the muffler. The outside copper pipe is a loop filled with anti-freeze, it thermo-siphons to a small holding tank above the generator. The VO flows through a heat exchanger coil inside the holding tank then down along the outside copper pipe to the IP. I don’t know what temperatures are attained with this system. Take this concept, use a circulation pump for the anti-freeze and put a heat exchanger in the VO tank. ??? Just thinking out loud. My mind is going, (some say it is gone) I’ll be back. …Ken

[Wreckerman]

I feel like I'm beating a dead horse here but here goes: I met Dave Goree (racewrench@charter.net) at an alternative energy fair in Asheville, NC, last year. He has two Dodge pickups with Cummings engines running on SVO. He is using exhaust heat exchangers that are basically sealed stainless steel tubes around the exhaust pipe. There is an inlet and outlet fuel line and the oil is heated as it passes through the chamber. It is located far enough back from the turbo that the temperture is low enough to prevent overheating the oil. He said oil temp at the Injector pump is about 210 degrees. As I understand it, this "boils out" and vaporizes any water left in the WVO. There is an escape valve for steam I think. Hope this helps. Contact Dave for exact specs.

[veggiesuburban]

There are some guys in the 5.0 mustang crowd running crazy boost through superchargers. They intercool the intake charge with a air to liquid heat exchanger that they circulate chilled water through on the track. I'm sure someone could use a similar exhanger with exhaust gas and wvo. My friend tells me that there are manufacturers that do custom applications, if you're really interested you could take that approach as well...

[Mandilon]

Our upcoming 'Shove-It-OPEC-big3' single-tank system will consist of 99.9999% exhaust-heated SVO .

Main component materials will consist of stainless steel and ceramics with carbon fiber enclosures.

Exhaust for 'instant gratification' (heat?).

California Design & Engineering

[cgoodwin]

Copper with exhaust running through it.... Not a good plan.

Coolant in pipes around the exhaust manifold? What happens when the water boils?

Exhaust passages better be pretty big in the HE or they will plug with particulate buildup.

Exhaust systems rot and need to be replaced, they vibrate, they leak and I just don't see an application here. It would be nice if I was wrong as there is a great deal of heat waste.

Remember if you overheat the fuel where it contacts the HE it will turn to carbon.

Good luck.

Chris

PS. I would rethink the carbon fibre tank, I made Kayaks from CF and they all had cracking issues, composits continue to harden over time, they delaminate, don't like UV and tend not to like acid or solvents much. Why not stick with SS or Alum?