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Old 07-01-10, 10:03 AM   #11
Xringer
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Quote:
Originally Posted by Solar Mike View Post
Heat pipes would work very well clamped or soldered to the fins of a flat panel collector, I have been doing quite a lot of experimenting building heat pipes of various sorts over the past 6 months for extracting waste heat from gray water (shower drain).

A 2.4m heat pipe soldered to a copper fin 160mm wide would be extremely efficient at conducting the heat collected by the fin to the condensing end of the pipe, pipe dia would be only have to be 8 - 10mm, evacuated to 50 microns and using approx 1cc of water inside the tube. To do this the water is placed in the tube, frozen, then evacuated. This setup would be immune from frost but with a lot of added complexity, just to save a bit of copper with water flowing through it and you require specialist vacuum pump to get the pressure low enough to use water. I have used R22 refrigerant gas quite successfully in heat pipes when extracting heat from lower temperature surfaces.

Cheers
Mike

Do you use silver solder on those pipes?
What are the steps for make the R22 heat pipe?

I'm wondering if an R22 (lower temp extractor) heat pipe could be used
to fabricate a compact water-to-water heat scavenger to recover the
heat in waste Shower water.?. Luke warm water..
http://ecorenovator.org/forum/conser...ater-heat.html

A smaller exchanger might be just the thing for my shower..


Thanks,
Rich

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Old 07-02-10, 05:49 AM   #12
Solar Mike
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You can use silver solder for quick testing, I generally braise with silphos, a lot more reliable than any soft solder, you require an oxy acetylene torch or similar, I have a Multiplaz 3500 plasma welder which doesn't require any bottled gas to run.

To use R22, make a small delivery tank about 1-2% volume of the heat pipe, evacuate it and the heat pipe, fill the delivery tank then use it to gas the heat pipe.

As a coincidence I'm also using heat pipes for extracting heat from the shower drain water, pre-heating the incoming cold water to the shower mixer.

You can use water in the pipes rather than R22, at 50 microns water boils at -40c, so at waste water temp 28 c should work quite well. Still experimenting with this. Have just bought a new vacuum pump and a digital vac gauge as borrowed items had to be returned. A digital gauge is a must, its impossible to work out what is happening with a mechanical gauge. You have to use boiled water, I found after a few days dissolved gasses come out of the water and kill the vacuum enough to stop the pipe working at low temperatures.

Current heat exchanger is a drain pipe with 6m 12mm soft copper tube wound in a spiral, sitting inside; the waste water flows over the coils carrying the cold water to the mixer, sort of illegal but works very well. You have to make a filter for it that easily cleaned of especially hair, it gets caught in the coils and after 6 months stops working.

Cheers
Mike
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Old 07-02-10, 09:31 AM   #13
Xringer
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I looked up the Multiplaz 3500 and WOW! That's an amazing device.. Added to my wish list!

Anyways, you make it sound much simpler to use water. I'm pretty sure I can get close
to 50 microns with my pump, and I do have a good digital gauge.
Just need to pick up some silver solder for my old propane-MAP gas torch.
(No Multiplaz 3500 in sight yet).

We have chlorine gas infused? into the water here, so thanks for the boiling tip..

I've been thinking about using large PVC couplings (below the tub drain) with an SS mesh screen filter inside..
Something that could be located so it will be easy for my wife to reach, un-screw and clean.

Now I need to figure out a usable plumbing configuration for using a heat pipe to transfer heat from the drain line, into the incoming cold water..
I wonder if one of those Ebay SS flat-plate exchangers would hold 50 microns? Without leaking or collapsing.

Mike, you seem to be on the leading edge of DIY heat pipe fabrication..
We are learning a lot from you. Need more pics and maybe videos!

Thanks,
Rich
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Old 07-03-10, 07:28 PM   #14
Solar Mike
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Yes the Multiplaz is a great general purpose welder, as it can perform the same functions as a gas set, a tig welder and a plasma cutter, albeit at a somewhat high cost. Its fantastic for brazing especially copper as its 8000c flame can input a lot of heat very quickly.

I tried a large PVC pipe with a stainless poly pad teased out as a filter, bit messy to clean. Think the large bottle like brush that is used in spouting gutters to filter out leaves would work better, easier to clean and would be good at trapping hair.

This style of heat pipe doesn't have an internal wick to return the condensed fluid so must be vertically mounted for draining. However with a bit of lateral thinking its possible to make a horizontal heat pipe with the condensing part created by running small tubes carrying the cold water through the middle of the heat pipe. This ensures a true double barrier between the outer Grey water and the inner potable water.

Cheers
Mike
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Old 08-01-12, 03:42 PM   #15
Fordguy64
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So IM going to bring this one back from the grave.. Could you take 1"copper and run 1/2 copper through it with reducers on the end of the one inch to go to the 1/2. Then solder on a quick connect like one for hvac and pull the vac on the outside pipe( between the 1 and 1/2 pipe) if that makes sense??

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