Heating Water from the Exhaust

[Capt Fred]

The Bloody solar water heater blew another seal - sick of fixin' it - run the 'roid most every day figure might as well heat water for household use.

Saw Mobile Bob's setup coupla years back - really awesome - wondering if He might be interested in doing a White Paper on his setup. 

Anyway, want to heat water from the exhaust without creating any steam explosions.

Ideas and thoughts, as always, greatly appreciated.

Cheers, Fred

[mobile_bob]

Fred:

it can't have been that long since we got together! has it?
nah,, the heat exchanger was from last fall iirc

sure was nice to meet you in any event, btw, you left without your pyro gage!

as for the exhaust exchanger, i haven't decided what do do about the plans yet.

i have about 50 folks on a list should i ever finish the planset, so maybe i should just
get it done and put it up here on the new forum? i will give that some thought.

i guess we do have a section for that sort of thing now, don't we!

bob g

[Capt Fred]

Howdy Jens and Bob good to be back in this forray agin'

Yeah, Jens you're right, I just didn't want to mess with a good thing, cooling system is reliable and working well, but it would be the easiest and quickest to get on line - I've a nice ss keel cooler that would work nicely with a proper fitted box.

Bob, you're right, how could i forget - it was freakin' cold - I popped into the "Grey(t) Northwest over thanksgiving.

Anyway that exhaust is still awesome If you can get it together write that paper, please, it would be very popular here.

Cheers,
fred

[Capt Fred]

Hi Jens

Again good points, I don't have to raise water temps much here - water probably starts at 26C (no need to say it I'm a wimp ) - will look at welding something up in the iron pipe section and use the groco circulation pump I picked up on ebay - will push forward this weekend and see what comes up. 

Thanks again for all the great info.

Cheers, Fred

[Ronmar]

If you thermosiphon now, you can still thermosiphon with a flat plate heatex.  They have very low flow restriction.  I am doing it and it works great.  I don't even have a radiator on mine, it is only the heat exchanger and I pull all the heat into a storage tank.  The heatex outputs 3/4 GPM of 120F water at 3KW of electrical load on the generator... 

Mine is setup like this with a small taco 4GPM pump on the secondary loop.  Once the tank is full of hot water, the fan-coil starts to dissipate heat, so the water temp returning to the heatex secondary is near air temperature.  This is to scale, the heatex is tiny 5" X 10" X 1.25"...


A system that incorporates a radiator could be setup like this, just put the flat plate at the top to have first crack at the heat before the radiator dissipates the excess.  If I ever put a radiator on my primary loop, this is how I will do it. 


Ron

[Capt Fred]

wow, thanks Ronmar

Running a radiator system with a indian mechanical pump (reason I picked up the groco pump as a backup) -looking at your diagrams think a little extra thought on my part might go a long way to a better system.

Had another thought -  to use a heatex unit in my wvo process system to help in the heat process - your two best friends, gravity and heat.



Cheers, Fred

[panaceabeachbum]

little off topic but Ron I saw this vid in your album and thought it was really neat  http://s270.photobucket.com/albums/jj85/rmarlett/?action=view&current=generatorstart1.flv

I have a number of water heating questions also . We currently use propane but I would like to be able to tie one of my water cooled gen sets into the sytem.

Is there some sort of differential valve that control when the water from the tank should circulate thru heat exchanger attached to the engine?

I also have a couple of really neat warner swasey multifuel water heaters that will burn a variety of different oils , their rated 25K btu, all stainless mil surplus . I was curious about tying one into the hot water system also for the occasion when it might be more economical to heat water with oil instead of propane .  It was originaly designed to act as a coolant heater for large trucks and gen sets in artic climates.  I dont know that its practical for heating water for household use but thought it might be a neat backup , that and I have 3 or 4 of them still in the crates I would like to do something with.   Once its up to temp they really roar and seem to heat water to hot to touch just about as fast as it can pass thru the heater


There is another version that heats air designed for the old air cooled APU thats rated 35kbtu , seems to heat my shop just fine in the winter on #2

[Ronmar]

Well to heat the domestic water, you are going to need a pump to get the domestic water to the heat exchanger secondary loop like in the first one of the drawings I attached above.  The simplest thing would be to control this pump using a thermostat switch at the hot water tank set slightly higher than the propane thermostat/controller.  Tank gets cold, thermostat kicks on pump and circulates water thru the heat exchanger untll the tank reaches the thermostat shutoff temp just like the normal tank thermostat controls the gas burner.  You would need a switch in the circuit to enable/disable the pump so it would only cycle when the engine was running. 

In my drawing above, the tank is actually part of the cooling system and the pump is wired into the generator output and runs whenever the genertor does.  The heatex has a thermostat on the output which modulates the secondary flow to output 120F water from the heat exchanger secondary.  The coldest water from the bottom of the tank is drawn thru the fan-coil unit.  Since hot water "floats" on top of cooler water the tank fills with warm water from the top down.  Once warmer water starts to come out the bottom of the tank(tank full), the fan coil unit dissipates more and more heat and continues to send near room temp water back to the heatex.  This fan-coil dissipates heat into the house, or if I don't need it there, it can be placed outside and work like a normal radiator to maintain engine temp and a full tank of hot water.  I can't run my electric hot water heater on the generator so it is turned off when on generator power. 

As for your oil fired heaters, are they pressure rated?  Could they withstand your domestic system water pressure if plummed directly into the system?  If not, you will need a heat exchanger and make a low pressure primary loop with the heater in it, and a high pressure secondary loop that runs to the domestic water tank.  Now from the killing two birds with one stone department, you could probably put one of these heaters in the water cooled engine primary loop(low pressure) that has the heat exchanger in it, and use one heat exchanger to transfer either engine or oil fired boiler heat into your domestic water tank.

Ron 

[panaceabeachbum]

very good Ron , I will be looking for sources for solenoid valves and thermostat .

The oil fired units are rated for 200 psi  continuos so i assume they would work OK tied into the system directly .  I played with one a good while yesterday and it heats the water quickly enough to be used as a demand heater , flows eough volume to shower at a temp higher than is comfortable 

[Capt Fred]

Here's an idea for a solenoid valve - sterlco 56T temperature regulated valve - check it out on ebay - here's a link     

http://cgi.ebay.com/STERLCO-56T-SERIES-TEMPERATURE-ACTUATED-VALVE_W0QQitemZ230380841709QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item35a3c4aaed&_trksid=p3286.c0.m14

Used them in charles 803 reflux alcohol still to open at  that all important 78.4 C temperature. (experimental fuel purposes only - not for consumption) ha ha (damn smileys still don't freakin' work.)F

Anyway, These are first class valves (no financial interest etc) will do the job and that one is cheap - i paid a bunch more for mine.

Be warned -  all 56 t's are not the same - they varry by temperature the one on epay is up to 140 F

Cheers, Fred

[Ronmar]

Personally I don't think I would bother with solenoid valves.  I might put a checkvalve on the line feeding back into the top of the tank if I was going vertical and might have the possibility of thermosiphon robbing heat from the tank.  I would put some fixed valves for isolation to allow me to do work out on the heatex without having to shut down the whole water system.  Fewer parts is always better IMO.