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Heat exchange coil

PostPosted: Fri Dec 13, 2019 11:20 am
by Lesgold
Hi Folks,

Read a comment somewhere on the forum about using a coil and waste hot water from a stripping run to preheat a wash prior to distilling. Thought this was a good idea as I needed to strip a couple of FFV’s. Took about a hour to knock up a simple coil from 1/2” copper, a couple of fittings and an off cut of timber.
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Pretty simple really. Cost me about $25 for the stuff I didn’t have. I was in a bit off a rush trying to get some neutral organised for Xmas holidays so I cold crashed the two washes. The first wash came out of the fridge yesterday and was put into the boiler at 18 degrees. The boiler took 46 minutes to get to 78 degrees. I was running the pot quite hard and the output water was reasonably warm. Ran it through the coil that was placed into the second wash.
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The second wash was only removed from the fridge this morning and was only 6 degrees when the coil was placed in the fermenter. At the end of the first stripping run, the second wash had warmed to 35 degrees. This reduced the heat up time by 11 minutes on the second wash. Looks like this may be a simple way to make some use of waste water. Will be using this technique from now on.

Cheers

Les

Re: Heat exchange coil

PostPosted: Fri Dec 13, 2019 1:23 pm
by bluc
:handgestures-thumbupleft:

Re: Heat exchange coil

PostPosted: Fri Dec 13, 2019 3:20 pm
by RC Al
Good one mate :handgestures-thumbupleft:

Just as a design critique, that coil needs to be pretty much at the bottom of the bucket, heat travels upwards. I saw a post somewhere where a heating element was placed too high on a boiler - the large wattage element wasnt heating wash a few inches below it, the user could literally comfortably touch the bottom of the boiler at full noise

Re: Heat exchange coil

PostPosted: Fri Dec 13, 2019 6:56 pm
by Lesgold
You are switched on RC. Should have mentioned that the coil could have been about 100mm lower in the wash. The bottom 50mm was cooler than the rest of the wash when ran my hand over the fermenter. Just gave it a stir to raise the cold wash. My intention was to add about 100 mm to the length of the coil to keep it closer to the bottom. Must have been sipping on heads when I constructed it. No real damage done though. At least others may learn from my shallow thinking at the time. I am pleased with how it does work and will use it every time I use the pot still on stripping runs.

Cheers

Les

Re: Heat exchange coil

PostPosted: Sun Dec 15, 2019 6:32 am
by warramungas
I use it all the time but mine just sits in the barrel under the lid attached to tubes that let it go to the bottom of the wash.
Greatly decreases heat up time when you want to do back to back washes and if you recirc your water reduces wome of the heat load back to your water supply.
Mind you, mine is about three times the length of yours to maximise heat transfer.

Re: Heat exchange coil

PostPosted: Sun Dec 15, 2019 7:54 am
by woodduck
I like this idea. I'm thinking maybe pump the dunder through it after a run as well? Although it wouldn't be for long it would be hot?

Re: Heat exchange coil

PostPosted: Sun Dec 15, 2019 7:03 pm
by warramungas
woodduck wrote:I like this idea. I'm thinking maybe pump the dunder through it after a run as well? Although it wouldn't be for long it would be hot?


Only thing i can say is keep an eye on your wash temp as it can get quite hot on big runs amd you dont want too much alcohol to evaporate.

Re: Heat exchange coil

PostPosted: Sun Dec 15, 2019 8:13 pm
by Lesgold
Yep. That’s why I wanted a lid to keep all the good stuff inside the fermenter. I agree with you warramungas, the bigger the coil, the greater the heat transfer.

Re: Heat exchange coil

PostPosted: Tue Dec 17, 2019 9:29 am
by db1979
Looks good, apart from the above critiques. Maybe just a couple of 1/2" couplers and some more 1/2" to get it lower in the fermenter?

I think I remember hillzabilly mentioning this.

Re: Heat exchange coil

PostPosted: Tue Dec 17, 2019 12:37 pm
by Lesgold
A 10 minute job and problem sorted.
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Re: Heat exchange coil

PostPosted: Wed Dec 18, 2019 11:46 am
by Lesgold
Well I have just completed a stripping run on an FFV. Didn’t have another wash to warm up so I just sat the coil in a fermenter filled to 25l with water (the size of my usual washes) The Coil now sits about 20 mm up from the bottom of the fermenter. The water in the fermenter started at 21 degrees. Took some readings towards the end of the run with really pleasing results. Water output temp from the still - 41 degrees. Temp at dump tank was 40 degrees. Fermenter temp was also 40 degrees. Pretty good efficiency I reckon. This will save heaps of time on multiple stripping runs.