How much heat comes out of a 20hp diesel?

[zmoz]

Soon I'm going to be buying a small diesel engine to run on WVO, probably around 20hp. I haven't decided what kind of engine I'll use, probably a Lister clone or Changfa. How much heat can I expect to come out of a ~20hp diesel? I think I want to use it to heat my house, at least partially. How would it compare to say...a propane heater?

[tecker]

  Really good I think there was a post not too long ago of a gent that used a gas water heater running the exhaust through the flue . fill it full of antifrezze and pump it to a heat exchanger. Winter is a good motivator isn't it.

[TomW]

Hmmm; my math yields about 15 KW equals 20 horse and would assume all the power went to heat which it won't.

T

[bob golding]

think diesel engines  are about 30% effeicent i seem to recall. so about  10 kw? i would guess. not to be sneezed at.

bob golding

[hvirtane]

A thumb rule often used is that

with a diesel from the burned

fuel energy you can get

1. /3 out as the shaft power,
   
1. /3 goes with the exhaust as the heat,
   
1. /3 with the cooling system as the heat.
   
   

So if you'll run your 20 hp diesel

with 10 hp shaft output,

from the cooling fluid you could

get another 10 hp = 7,5 kW heat energy,

and another 7,5 kW heat energy amount

from the exhaust piping system, if a heat

system would be built around that.

- Hannu

[cujet]

Keep in mind that the diesel engine will probably not be running at full throttle, so the heat energy will be far less than the calculations indicate.

Still, my neighbor's Lister Diesel 16HP radiator really puts out the heat under normal load. I would say that it is enough to heat a home under moderate winter conditions.

Chris

[DanOpto]

Calculate the gallons of diesel per hour.

At One gallon of diesel per hour, you burn 140,040 Btu per hour.

If you are 30% efficient on your load, then 70% goes in heat.

So you will have about 98,000 btu per gallon that you can try to save with a water jacket and exhaust reclaimer.

I would suggest that you use a diesel engine with a water cooled cylinders.

Then you can use a water pump to distribute the heat throughout the house without any risk of exhaust gas leakage.

[zmoz]

So I could actually heat my whole house with it? Geez...I was thinking more like one room! How many BTUs/kilowatts is a heater for an average sized house? (my house is about 2000 sq ft, and Oregon's winters are pretty mild)

[sh123469]

Hi zmoz,

My central heat unit is 50,000 btu. (oil) 1800 sq. ft. heated.  House is 50 years old, very low insulation.  Never had a problem.  Although it does run almost constantly when the temp outside is close to 0 deg. F.  I am in S.C.

[troy]

Yes, the numbers look pretty attractive.  There are a few little hitches though:

1.  You're talking about big heat exchangers if you hope to recapture most of the heat.  Big usually means expensive.
   
2.  The exhaust heat exchanger will probably soot up, reducing efficiency unless you have a handy way to remove the insulating soot at regular intervals.
   
3.  If you set up a spreadsheet and look at the numbers, it is unlikely that you use enough electricity to run a 20 horse diesel at 80% load.  In ballpark figures, that would be 8 kilowatts continuous production, or 5,760 kwh per month running 24/7.
   
4.  You can't use hard water in the coolant loop, or you eventually calcify the coolant passages in the head and block and end up with overheating problems.  That either means you have to run a heat exchanger with soft water/antifreeze on the one side, and your "normal" water for heating purposes on the other side, or you run soft distilled water in the entire system.  
   
   

These are not insurmountable problems, but you want to go in with a good idea of how to deal with them rather than fail repeatedly while you work the kinks out.  There will be enough kinks even when you go into it with open eyes.

Good luck and have fun doing it!

troy

[Ex Mek]

 using the wast heat from the coolant is a great idea, with one problem , it would be like using a car with no thermostat in , so as the engine runs cooler its efficiency goes down and if its too cool the combustion process will cause acids to build up in the cylinders,causing premature wear, you will have to fugure out how to fit a thermostat in the engine cooling system to keep the engine HOT

[Bill Kichman]

Your numbers for efficiency look roughly correct. I understand the Lister is quite efficient, on the order of about 37-38%. So the rest is almost all heat.  1 gallon of heating oil contains 139,000 Btu, so roughly  62% of that is heat and noise energy.  Some of the heat will be lost in belts and other friction lost heating the room where the engine resides.  I would figure overall to expect to cheaply recover 60% of avaible heat.  Keep in mind that heat transfer depends on difference in temps.  When your cooling water is cold, the rate of recovery is great.   I can leave my hand om ny exhaust pipe after the heat exchanger when the water is cold.  But at 190 degrees water temp, the rate of recovery is much less.  Diesel exhaust is much cooler than on a gasoline gasoline, an effect realized by their greater efficiency.  But you can recover the heat, and rightly you should.  The biggest problem is carbon build up on the transfer surfaces.  I use a domestic copper coil containing water over which exhaust passes and noticed drop off in transfer rate quickly.  There is one really good way to recover nearly all the heat, and that is using a wet scrubber.  I plan to further investigate this option. However, you must then deal with all the crud that builds up in the water.  The exhaust gets nearly perfectlt clear of particulates as a result, all or nearly all the particulates get filtered out, but you need to do something with them in the water.  I see marine heat exchangers of this type advertised that boast of a max 10 degree difference between water temp in the unit and final exhaust gas temp. This is truly remarkable.  But they are simply dumping the water.  I need to recirculate it through my hydronic system.  I believe the key here will be using a separate water loop from my hydronic water, which allows the matter to settle out separately, for occasional cleaning, and a copper coil from the house heating water through this hot water.  More complexity but it satisfies the requirements.  If anybody has already designed a working solution, I would greatly enjoy reading about it to save some aggravation.

Thanks

[Bill Kichman]

A few more notes and comments for you to ponder....the statement about the 20hp single engine is exactly correct.  Consider what I am doing instead...a 12hp and another 10hp engine each with generators...always run at least one of them at near full load.  Enough to cover most of the use we need...when I want to run the shop tools run both. I weould also like to add a big UPS with a big battery bank, so I can avoid constant run of the gensets if I go off-grid.  2 separate engines also lets you have power while servicing one of them.  Just some thoughts to consider.

[mikeptag]

A point that didnt get mentioned, is running electric heaters to get the 80% load efficiency. So you have the btu's from the waste heat and power load.  Were talking home heating with WVO!