12-2 Cooling tank/ heat exchanger

[skeeter]

While I'm waiting for the concrete to arrive, I'm now focusing on putting into practice, the cooling system for my engine. Over the pass few months I've been kicking around ideas and gathering some material. Most of the schemes are CHP from the start, or at the minimum, will evolve into a CHP solution. I'm in the north country so additional heat is of major interest, along with my desire to  do things efficiently, when practical. The general idea that I've been entertaining, consists of  195 deg. thermostats on each of the upper cooling ports ( this part done), who's plumbing connects to a tee. One branch of the tee connects to an  elevated expansion/burp tank whose volume is a minimum 5 % of the overall cooling system. The other end of the tee is plumbed to a coil of soft copper tubing, whose connection is near the top of a 80 gal water tank. The bottom engine cooling connection are plumbed to the other end of the copper coil, exiting out the bottom of the tank. Now for reality, over the last number of months I have not come across my ideal water tank but have acquired a couple of (40 & 50 gal I believe) electric hot water tanks. I remember reading of at least two members who have used similar tanks for cooling 6-1's.  One fairly recent post describes plumbing to the upper and lower 1" heater element ports. With this in mind, my line of reasoning is to gain access to the interior of the tank to place and connect my copper coil heat exchanger to these ports, then use the normal hot and cold water connectings to run to a hot water heat loop. My real question is what will I find when I cut open a glass line water tank. Can someone describe the glass lining. Is their a place to cut that won't effect the lining, or is it just a matter of cracking the lining and removing it.

[hotater]

"Glass lined"  usually means a thin layer of spun-in fiberglass that can be re-sealed with a kit from Home Depot.  Cut the tank with a sawzall and not a torch.   

As I understand your system, it will only have about three (?) gallons of fluids in it?   And you counting on heat transfer from the copper coil heat exchanger to the 80 gallons of water in the hot water heater?

I'd be interested to know how that works.  My 6-1 produces about 6 gallons an hour of 195 degree water.  Assuming your's is double that it means the three gallons of water will be circulating about four times an hour to start with but will get faster as the heat sink tank heats up...but it should take a while.   

[Tom]

I cut my 40 gal water heater tank with a skill saw and abrasive blade. It came out real nice set the blade depth to just cut through the tank. The inside of the tank looked more plastic then glass lined. The fittings are 1" npt.

[skeeter]

hotator - I'm glad I asked the question before putting a torch to it. I was thinking of using a 50 ft coil of 3/4 or 7/8 inch dia. The liquid volume in the coolant loop works out to a little over 4 gal. for the 3/4, and about 5.25 gal. for the 7/8". Your view of what i'm trying to do is correct. My assumption,  based a 80% + load, should move to the tank between 17.4K - 20.0K Btu/ hour ( based on another assumption, 33% to gen, 33% to exhaust, 33% to coolant). Although, I havn't yet tried to re-figure with the real data you've giving, my sense is the 80 gal is going to have a longer heat/ reheat time then I would like. That I should try the 40 or 50 gal tank first, then add the other (maybe thermo storage in the heat circulation loop) if needed. Not withstanding the added problems with cooling the exhaust, I'm wondering if an added thermo siphon loop here might make sense, since I'm planning on loading it real well, which should keep exhaust temps up. What do you think.

[skeeter]

Tom - Skill saw with abrasive blade, sounds neat. Maybe after I do what I need to do inside, I could eplace the top just like new.

[Doug]

A sawz all will work just fine too. Done it for my Gassifier...

Doug

[hotater]

skeeter---

I have an aversion to using exhaust to capture heat except on a passive basis.  Listers aren't that easy to keep hot.  I've finally found which loads to keep connected all the time to keep the temps up but still have enough surge capacity left to handle surge and not kill the computer, but it's a fine line.  Cooling exhaust pipes leads to choking carbon....unless you give it a snort of propane every now and then.  

Why not a dual thermosiphon for your heat exchanger?  Run the copper outlet water coil through a fairly tight fitting pipe that has an outlet top and bottom leading to another, very well insulated container.

I'm still amazed at how LITTLE hot water comes out of a 6-1, but mine is running well water to waste right now and a five gallon bucket under the outlet takes 54 minutes to fill.

I'm worried about the pipe drag on that small of copper tubing for that distance....it might take well over 200 degrees to overcome the drag and make the thermo work.

I'd be tempted to make your main engine cooling tank from a 10 gallon propane bottle with the copper heat exchanger inside but have the system reversed from your plan....run a small circulator pump to move water through  the coil to be heated by the engine coolant.  The *problem* here is that the ten gallon tank HAS to be cooled by the exchanger coil, otherwise it's too small for the engine.  A larger tank would take too long to get useful heat out of, I think.

[skeeter]

Ok, it's becoming clear to me that I have to step back and examine this with a fresh look . First, am I in the ballpark with the amount of heat that can be obtained from the cooling fluid . If I am, will it be enough to add significant supplemental heat to a couple of rooms (my office and lab/ bench area), rooms totaling about 280 sqft and having ample HW baseboard length to accomadate lower then ideal water temp . Rooms are fairly well insulated with low ceiings, and are 45 ft from the engine room, and will be connected with good quality insulated PEX tubing. Was I wrong to believe that a 12-2 can produce enough heat to make this application of CHP worth while? Has anyone else been able to implement a similar application? I guess I have some re-figuring to do.

[Geno]

I’ve read Hotaters info on how little hot water comes out of his 6/1 and find it surprisingly small. But his several thousand hours means more than my few hours. I do know that this radiator, at 70°F ambient, is 190° at the inlet, 150° or so at the outlet and puts out a LOT of heat with 2000 watts on the engine. I want that heat in the house but I keep thinking about what Hotater has found. My house is about 40’ away from the generator and the piping would go another 20’ or so from there. I may only have ½ the engine you do but I am NOT spending a bunch of $, digging trenches, cutting holes in my house or any other such thing until I find out how warm my engine room stays when its real cold outside. I will, almost certainly, do some testing with a wood boiler heat exchanger attached to the hot water inlet of the radiator. These exchangers can be had on ebay for $50.00 (used) to $150.00 Even the smallest one should be big enough for a 12/2. They’re pressure tested and good to several hundred degrees. Copper tubing can cost as much and there is much less fabrication with the exchanger. I’ve said it before but it’s worth repeating, “my primary engine coolant loop must be as robust as possible”
Anyway, if I don’t get enough heat to run it to the house I know where I can scrounge an old cast iron bathtub to create my own mini hot spring/hot tub.

http://cgi.ebay.com/BRAZED-PLATE-HEAT-EXCHANGER-10-PLATE-STAINLESS-STEEL_W0QQitemZ7622992292QQihZ017QQcategoryZ109484QQssPageNameZWD1VQQrdZ1QQcmdZViewItem

http://www.genedevera.com/temp/radiator2.jpg
The rad is mounted this way because the top fittings are stuck. Its hung with 3/16” winch cable and the lags go into the header behind the wall. I’m often wrong but I don’t see a problem with it.

Side note: I wanted to wrap some copper tubing around my muffler to see how much heat I can get off it but the cost of copper scared me off. Can anyone think of a cheaper way to test this?

Thanks, Geno


(edit) skeeterscooter: It sounds like your tanks will not be in the house. 40-80 gallons of antifreeze will sure cost a lot. I won't be
running 24/7 all winter so smaller, more efficient rads and heat exchangers are a must for me.

[skeeter]

I've had a chance to look back at my notes this morning from when I started this project. Instead of going through the calculations myself (laziness),  I noticed, and made assumptions gleaned from what is specified for electric hot tanks. With a power consumption rate of 5500 watts, they specify a recovery rate (raise water temp by 90 deg. F) of around 21 gal/ hour. If I were to consider the 12-2  coolant system, as having an equivalent capability, based on the 33% - 33% - 33% hypothesis, the result should be similar. The real world result obtained by hotater, ~ 6 gal/ hr, after raising his 105 degree spring water by the same 90 deg, seems to contradict this 33% - 33% - 33% hypothesis. Can anyone shed more light on this.

Geno -

I’ve read Hotaters info on how little hot water comes out of his 6/1 and find it surprisingly small. But his several thousand hours means more than my few hours

I agree.

My house is about 40’ away from the generator and the piping would go another 20’ or so from there. I may only have ½ the engine you do but I am NOT spending a bunch of $, digging trenches, cutting holes in my house or any other such thing until I find out how warm my engine room stays when its real cold outside. I will, almost certainly, do some testing with a wood boiler heat exchanger attached to the hot water inlet of the radiator

Good point.

These exchangers can be had on ebay for $50.00 (used) to $150.00 Even the smallest one should be big enough for a 12/2. They’re pressure tested and good to several hundred degrees. Copper tubing can cost as much and there is much less fabrication with the exchanger. I’ve said it before but it’s worth repeating, “my primary engine coolant loop must be as robust as possible”

Good point, but if I understand you correctly, these will require a water pump in the engine coolant loop. Excess copper tubing can also be obtained at a good price.

“my primary engine coolant loop must be as robust as possible”

I agree.

A trench running to my house panel is already dug. It goes right by the room where the water line would enter. 3 1/2 feet away. Most of the other component costs, (HW baseboards, piping, water pump (heat loop, not coolant), transformer, thermostat) can be gotten for a reasonable amount, but the cost of the insulated pipe is nothing to sneeze at.

[Quinnf]

I just ran Hotater's numbers through the formula for heat flow and it looks like 5 gallons/54 minutes starting at 105 F and ending at 180 (where the thermostat opens) calculates out to 3300 Btu/hr.  A small portable 115V electric heater generates about 12,000 Btu, so there's not much energy to capture.  A 12/2 will consume about twice the fuel that a 6/1 burns, so double that figure and there still isn't much available heat with which to do anything useful.

I think what's throwing the 1/3-1/3-1/3 assumption off is the huge amount of surface area of a Listeroid available to draw heat off through conduction and radiation.  Jack's low Btu output is consistent with his observation that the oil in the  sump never gets very warm.  The sump and the entire crankcase are acting as a heat sink.

Quinn

[fuddyduddy]

To the best of my feeble memory, the diesel engine is about 30% efficient, about 20% of the energy (heat) goes into the coolant, block, etc, and about 50% goes out the smokestack.  So 1/3, 1/3, 1/3 is only a very crude approximation. 

[Quinnf]

Agreed.  It's only an approximation, and one that probably was not based on an engine like our beloved Lister(oid)s. 

Nobody likes to see heat thrown away, especially is you live in a cold climate.  But you get the most out of what you have, you have to design the engine into your entire heating system.  Placing it in the basement and heating the basement with waste heat would at least keep your 1st floor warm.  Beyond that, there's not enough energy to justify the expense of all the modifications.

Personally, I'm in favor of using the accumulated waste heat in a cooling tank to pre-heat the domestic water entering the house before it goes to your domestic water heater.  I'm amazed at how common it is to take water right out of the cold hard ground and pump it into your hot water tank while you're taking a shower.  If the water could first go through your Lister(oid) cooling tank, you'd save some energy right there and it would cost nothing.

George shows such a setup on his CD

Quinn

[skeeter]

Having just worked backwards from the 12/2's approx fuel consumption/kWhr (268 ml), to come up with approx. BTU output at rated load, ~ 68k btu's/hr, then subtracting the requirement for the mechanical motion to move the generator at rated load, ~ 21K btu's /hr (approx. 30% of total, sounds good). We are left with 47K btu's/hr. If we use fuddyduddy's 50% up the stack, 34K btu's, with the remaining 20% for cooling, 13k btu's, we could conclude that hotater's 6/1 is loaded to near half of rated spec, 3300 btu/hr or 1.65 kw's. We could further conclude that a 12/2 coolant potential is equivalent to Quinnf's 1200 Watt electric heater, with the 6/1's coolant half that much. Does this sound reasonable? From this, I've got to conclude that capturing the btu's going out the exhust is the only real way to do CHP, other then passive, with these small hp engines.

[dkwflight]

Hi One of the things you might not be alowing for is the radiant heat from the engine and pipes. I know mine radiats almost enough to keep my water below the boiling point in 85f ambiant aiir temps
If it is cold around the engine the heat losses to the air will be higher.
Dennis