Homemade heat exchanger

  • Thread starter lurch85
  • Start date
  • #1
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Looking to make a heat exchanger so that I can have a less than adequately antifreeze treated water (easily over 750 gallons, so very expensive) from the outdoor wood boiler constantly circulating through a water jacket, and heat an adequately treated fluid (glycol treated water) and can turn the circulating pumps off to the garage, which contains underfloor (concrete) and some modine style hot water to air heat exchangers.
my plan is to use some old air conditioner coils and place inside a water jacket.
assume the radiator coils to be 3/8 diameter spaced 2 inches apart with a 2 inch square of aluminum per 1/8 inch of length.
thickness of tubing and aluminum fins unknown at this time and I'm hoping negligible (make your own assumptions if you would)
would like to see the math for anyone that feels up to it.

im hoping to get an answer in the form of something like (x btu per foot of tubing with 10 gallon per minute of water supply (to the both the water jacket and heating coils in the garage)and at a temperature difference of 150 degrees)

feel free to change, ask questions, or add anything you may see as far as variables go... Adding as much information as I can think of to make it easier

If questions are asked, I will add to the original question as needed and make additions in bold/underlined and red

respectfully submitted
 
Last edited:

Answers and Replies

  • #2
779
527
less than adequately antifreeze treated water from the outdoor wood boiler constantly circulating through a water jacket
Why not treat this boiler water (to -40°F, or whatever is appropriate) instead? If flow is lost through pump failure, or power outage, this is the loop most prone to freezing.
 
  • #3
33
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unfortunately I would have to treat 750 plus gallons of fluid... cost prohibitive
 
  • #4
JRMichler
Some thoughts and questions:

Water with a low concentration of antifreeze will turn into slush at low temperatures. This could be enough protection.

What is the calculated amount of heat to maintain 35 deg F in the boiler at design outdoor temperature?

Is the circulating pump shut down when not in use, or when the boiler water temperature is below some setpoint?

What is the heat source for your proposed heat exchanger?

Have you considered an electric heating element from a water heater?
 
  • #5
OmCheeto
Gold Member
2,189
2,639
Where exactly is this heat exchanger going to be?
Did something in your system break since last time?: Garage heating (Dec 21, 2015)
Or are you just now getting around to thinking about building it?

ps. I think if you ask politely, you can get an old locked thread reopened. It looks like a lot of people did a lot of maths for you back then.
 
  • #6
33
0
The idea is to keep the circulating pump to the water jacket of the heat exchanger going 24/7
The other idea is to save would not having to heat an area 40 by 60 by 14 when it is 10゚ below 0 , and to be able to heat the garage in a few hours .
The idea of the heat exchanger only came after I had a Propane boiler Installed in my basement toSupplement and backup the wood boiler system. They use a pressurized 12PSI system for the Propane a boiler side, going through the heat exchanger, and then The other side being the boiler and a low (open actually)pressure. Only then did I come up with the idea of having such a system for the garage .
As for previous Calculations on the previous heating thread , my math is not that great and had trouble converting the formulas over to what I wanted to do.
I also didn't know calculations for going from water to water through metal versus water to air .This also gave me a new starting point on how to think of this, because, honestly, I got pretty confused with the last one
 
  • #7
33
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Also directing information as to heat input/output of the heat exchangers/modines. As long as the beat echangers can keep hp to the modines i build. I can build more modines easily.. the heat echanger a kittle tougher, so easier to start too big.
 

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