Heating Engineer question?????

[LarryB]

I've got a hair-brained idea I can't stop thinking about.



How much heat energy does water hold? I'm thinking during my 35min commute I could be warming a water tank in the back of my pickup with engine cooling water instead of blowing that energy out the radiator. When I get home I park the PU in the basement and let the heated water warm my house overnight.



How far off base am I on this? Where would the shortcomings be? Should I just quit drinking coffee altogether? Do I have too much time on my hands?

 

[Partyat33]

Just a couple of thoughts,



1. Unless you want pressurized tank you could only heat the water to about 200 degrees.



2. I believe it would take a LARGE volume of water to get too much use out of it. That brings up its own set of problems.



If you are planning to directly inject the water into a heating system, water quality could be an issue.



If you just plan to put a fan on the hot water and let convection cool it, might work.



In 35 minutes I am not too sure how how you could get that much water.



OK I'm just rambling, but I LIKE the concept.



Dennis

 

[illflem]

Larry I don't think your truck would warm up enough to heat much water in just 35 miles. What may work better is to direct your exhaust into the bottom of a water tank. Need to figure a way so it doesn't siphon back to the engine when you shut down. Should heat the water pretty good and sound cool also. I've done this with a gas generator and a 5 Ga. bucket of water to cut down the noise, worked great and the hot water was a byproduct.

 

[LarryB]

Bill

I'm actually thinking of using my "R. E. E", Rolling Efficiency Experiment (aka diesel Rabbit pickup). It warms up fast but won't haul too much water. I'm sure I wouldn't produce much heat energy but it would be a fun exercise. Good idea on the exhaust. I could run 1-1/2" tubing coil inside the tank to exchange exhaust heat too.



Dennis

Convective cooling is what I was thinking. It would be parked inside all night so it would have plenty of time to dissipate the heat into the house. As it is, my garage is insulated and sheetrocked and I am surprised at how long it stays warm after my wife and I park our warm cars in it.

 

[LarryB]

Dennis

Maybe I should have posted this thread in "General Diesel". You could toss it over there if you want.

Larry

 

[jpolston]

LarryB,



You've got too much time on your hands and don't drink anymore coffee.



Or. you could devote your energy to a solar system; it's free energy and there's a lot of hardware already developed for the application.

 

[LarryB]

jpolston





A: Sorry but Solar in Western Washington is an oxymoron. Entirely so in the winter when the heat is needed.



B: I've rebuilt or modified everything in my motorhome and now need some new projects. More power will just cause more problems at this point.



C: Slowing down on the coffee is probably a strong consideration.



Maybe I'll go take a nap, my head hurts. :{

 

[WDaniels]

Larry,

I've always thought a couple of convex mirrors that tracked the sun with a black steel container filled with water at the center of their focal point. With the water getting hot it will circulate all by it's self with the cold replacing the hot in the steel container. Or some such like that. Now if I could convert that to work on snow for up here I'd make a fortune.

WD

 

[The patriot]

Larry, you could put a few electric fans on your truck, and put in some timer device.

When you get it in the garage, put the timer on 15-30 minutes. Whats in the radiator, and eng compartment should heat the garage nicely.



I've been thinking about a stainless tank in my attic to pre heat the cold water going to the hot water tank. These last few days it's been well over 100 up there.

Eric



BTW It requires 6550 BTU's to change 5 lbs of 0 degree f water to 212 degree f steam. Hope this gives you an idea.

 

[LarryB]

Thanks Eric, that's exactly what I needed.



Now!



How many BTUs in a gallon of diesel?



What is a common efficiency of a diesel engine?



I'll get this spreadsheet done yet.

 

[illflem]

Eric you forgeting that test stuff already or am I? I thought it was 6550 btu to make steam from 32°F water. Don't want Larry to screw up his spread sheet.

 

[Peter Campbell]

Each gallon of #2 is around (your content may vary) 126,000 BTU's. Assuming 2 gallons consumed on the commute 252,000 BTU's. Given that the heat rate of internnal combustion engines are poor . around 20% thermal efficiency. That leaves around 200,000 BTU's of waste heat ( heat rejected) . As you have already said some of this is going out with the exhaust heat, some goes out from the water jacket ( regular cooling system) and some goes out from the engine and manifolds conduction and then convection to the air. Assuming that you can catch half this energy- 100,000 BTU'S that would need either 555 LBM of wter going from 32 to 212F. but water at below 100F is sort of useless for space heating. So going from 100 to 190 (90F delta T) 190 was picked as the temp you could not cool the engine with the tank. then yoy would be up to 1110 LBM or oround 135 gallons. And finally 100,000 BTU'S delivered to the interior of the home costs around $1. 00. Enough of the math. OBTW I do know a small amount of thermodynamics, it is sort of my job.

 

[LarryB]

Wow! Thanks Peter. I knew there must be someone on TDR who could do this in their head.



My commute home is approximately 26mi/30 min and I use about . 5 gal. Looks like that puts me at about 35gal. of water, 25,000btu or about $. 25/trip savings, $5/mo or 10% of my avg heat bill. Mmmm.....

 

[TPCDrafting]

If this setup is for winter use, how is it you'll keep the water from freezing while your at work? I'm sure you have this figured out, but I'm curious none the less.

 

[The patriot]

No Bill, that's the correct answer. I never thought that test stuff would be needed.

Larry, if you got the specific gravity, or the API on the oil, I could tell you exactly how many BTU's in the fuel. I dont know if the filling station would show it to you, but it should be on the manifest for the fuel delivery.

Eric

 

[LarryB]

tpcdrafting

Here in Western WA is seldom freezes. I could also add antifreeze if needed.



Eric

Thanks but I think I'm close enough with Peter's figures.



I forgot to figure in that I don't need heat in the 3 summer months. Dang! That's gonna cost me $15 a year. :-laf Now I'm down to $45/yr savings. Not a very good return on this project I'm suspecting.

 

[illflem]

Larry what I did in my house in Chelan, which really doesn't get much winter sun, foggy, was mount a 4" thick frame with a 4'x8' double pane window on the south side of the house. On the side of the frame against the house was flat black painted metal roofing. Had a intake vent cut into the house at the bottom and a fan with damper, tstat set at 70° at the top. It didn't even need to be sunny for that simple device to crank out heat. When it did get sunny it was enough to heat the whole house. It think even the rainy Westside gets more winter sun than much of eastern WA, I can remember foggy periods for as long as 90 days without a break.