Garn Stratification vs. Homogenization

[TCaldwell]

Did the high temp sump pump come in yet?

 

[jebatty]

Just for the fun of it, three days ago I fired the Tarm, turned off all draws on the system/storage, turned on a circ that draws from top of tank and returns to the bottom at about the middle of the tank, and with a weighed wood burn brought storage top up to 201F (12" down from the top), middle 201F, and bottom 195F. Horizontal 1000 gal tank. The Tarm hi-limit sensor at very high temp supply reads about 8-10F less than the actual hot water output, so I was able to do this without causing the Tarm to idle. All sensors are DS18B20 fixed to the tank surface under all of the tank insulation.

The horizontal tank would mimic a Garn tank.

 

[gregwhs2000]

Did the high temp sump pump come in yet?

I've got everything ready to go ... but still waiting for the pump to ship. Hopefully next week.

 

[R. Snyder]

I've got everything ready to go ... but still waiting for the pump to ship. Hopefully next week.

Hi,
Just wondered about the progress on this project.

 

[heaterman]

Hi,
Just wondered about the progress on this project.

I heard from Greg this morning and he was hoping to get some results in the next week or so.

 

[gregwhs2000]

I heard from Greg this morning and he was hoping to get some results in the next week or so.

Yes the pump was delayed but is in route so hopefully next week I'll have some results. Here is my simplified plan for manually measuring the potential benefits of mixing:

• Burn as normal and get to a max temp of 185-190 and record the LWCO temp
• After the burn is over, run the pump for 15 minutes and record the new LWCO temp
• Weigh some dry hardwood and then start a new burn with a target 180 LWCO temp
• As 180 approaches, run the pump another 15 minutes while the burn is in progress and measure LWCO temp
• Add more weighed wood if needed and repeat mixing and adding wood as many times as practical
• When the fire is out, record final LWCO temp (and burn time just for kicks)
• Calculate additional BTU's added by the additional burning that was enabled by the mixing capability

I will calculate the additional BTU total by estimating based on the weight of the wood burned and also with the total additional degrees of heat added to the water. I'll have to assume that the tank temp is homogeneous at the end of the first and last mix in order to calculate the later. Maybe that's not a perfect calculation if it's not 100% mixed, but with the other calculation based on wood weight, it should give some decent data points and if they are close to the same, then both are probably good measures.

I'll also make sure the external pump is off during the measurements. Once I have some results, I'll post them in this thread and then decide how to best automate the mixing for next winter.

 

[Boil&Toil]

Might be able to adapt a milk bulk tank mixing paddle/propellor as a "destratifier" (but no filter) - designed for pretty much the same job in pretty similar tanks, going the opposite direction (cooling the warm milk.) Would only be practical if you found one going for junk price, though.

For controller logic I'd probably look at "is blower running" and "is top within 5 degrees of cutoff?" (or 10, or whatever floats your boat) and punch a 3 minute minimum run relay. After 3 minutes it would either stop until the top got hot again, or keep going if it was still hot.

For the external loop/filter version, I have a combination SS mesh/vortex filter on my well - those are also made in hot water versions. Good idea to box it though - inspection is nice (clear filter case), but algae can be surprisingly adaptable, so not lighting any part of the system is a good precaution IMHO. Plus the box would help limit the circulating loop from blowing heat to the boiler shed.

 

[gregwhs2000]

Pump arrived and I have it in the tank, but am not happy with it yet. The exchanger tubes prevent the pump from resting straight down vertically, so the discharge "T" is at an angle instead of being level with the water. I'm going to get four street 45's and loop the discharge downward, then mount the pump on a chain just below the water level so that I am pumping top to bottom. The discharge "T" will slide right between two of the exchanger pipes. Hopefully I'll get time for that over the weekend. I've really thought all along that pumping down is better anyway.

I did run the pump once last night just for kicks. I had a burn almost to the end at the time and the LWCO temp was 183 when I turned the pump on. After 20 minutes, it was 177, and that's with one of the discharge outlets angling downward, so I think this pump will get a good mix going in a short amount of time. That should allow for a full charge of the "battery".

 

[Buzz Saw]

Greg, did you make anymore burns with your mixing pump before the season ended?

How were the results if you did?