Backyard Aquaponics
A place to discuss aquaponics

no its a cooling coil out of a post mix m/c i pu all the od shaped ss bits that come in to the recycling center

[quote="veggie boy"]F&F is that from a water heater? PS - you are a skyte, Well there you go then my point is why try and set up something when there is a supply. All the old postmix mc/s are beeing pulled out for the new glycol mc/s I have given away 4 so far to brew club members for cooling wart [ steve was gratefull for the the solar water panel and the pump for his system the gas bottels he could not get elsewere and the neighbours for there grey water systems] if i did not [SKYTE] how would allthe people know where to go when they want something for free

I think its great that you are willing to share "your" riches F&F. I wish we lived closer so I could come over and scrounge from you!

You pay the postage and i will send

hmmm, what did I see earlier..... thanks mate!

I am building my own greenhouse. It wraps around two sides of my existing shop building. I read several books on solar greenhouses and wanted to implement the better ideas I read about. Handling both ends of long beams took time and fixture ceation, but it came out O.K. The shared walls with my shop do not allow outside temperatures on these sides. I did use a concrete contractor to do my inground tank and floor. He said that the way I over-designed the building, it could be my tornado shelter (just get in the tank!). I used pressure treated wood and screws rather than nails in most places.

The sixty feet of 1/2" copper is in direct sun at the top of my glazing with flat black paint on backer board and copper tube. The other end is 40 feet of copper tube in the fish tank. Heat exchange is much higher in water. The system is closed with RV antifreeze(not poison). Getting the antifreeze in and the air out is a little tricky. I bought an air bleed valve at Aquatic Ecosystems $10US and plumbed it at the highest point. It will bleed air but closes to liquids. each run of copper tube runs up hill slightly (2" in ten feet) from the previous level. The pump is small and is inline. The pump input is from the xchngr in the fish tank but also can pull liquid from a reservoir when a valve is opened (that is how the system is filled). BTW, that is the plan. I will build it over the next ten days (along with other draws on my time). As far as amount of heat added (or removed) by the exchanger, it is small but free. It works best with a high delta temperature. The high point in the greenhouse is always the warmest and the direct sun can really help.

The comments on copper poisoning of the fish made here has had its affect. I am going to test for copper levels at intervals. Also, I am going to paint the copper that will be in the tank. The heat xchng in water is high, so the paint should not be a problem.

Thanks njh for the great info on the heat exchange. The grow bed may add more heat, but every little bit helps.

What do you all think about painting the copper in the tank?
A thin layer of paint in a liquid medium should be acceptable for heat transfer.

Stainless steel heat exchangers are very expensive if purchased as such.

doug, toxcicity for yabbies and the like range into the high parts per billion think

njh, don't have time to check the maths, but that coil that F&F posted cools beer from ambient temp to 3C on call. the fluid it sits in (glycol mix) is -10C from memory so if the beer in the basement is at say 15C then thats a 25C difference, by your workings thats 37.5W of cooling transfer, somehow that doesn't sound right. i don't think you'd chill a galss of beer down by 7C in 5 seconds with 37.5W of cooling.................of couse i don;t have the figures at my fingertips, only the "vibe"

Al most right steve that coil had refrigerant in and it sat in soda water from a post mix al i know is it cools beer from boiling to 25 deg in 15 min with only tap water

Steve, my reading is a "post mix" machine i.e. the syrupy crap they pass off as various softdrink/mixers....

From my experience they are barely chilled... certainly not anywhere near beer temperature.

Doug, If you are building that soon could you please post some pictures as you go along? Have you started a thread on your system in the "Member Systems" forum? I would love to follow the progress.

I may have missed it but why did you decide on copper rather than black poly? Also did you have any reading material that helped you considerably with the design of your structure?

VB, why not try Beva Tube, it's what they use to run drinks thru at pubs etc. It's food safe and when painted black, the guy assured me it wouldn't break down. Alternatively, lay it flat on a roof with a sheet of black plastic around it. Just a thought.

F&F - I hope you know that I accussed you of skyting with tongue in cheek. As I said - not all of us know how to scrounge like you, it is not that I am not willing to, just don't know how to and have no contacts. Where do you think I may be able to get something like this in Brisi?

Depends on the boundary layer most likely. The pipe conductivity for stainless and copper is negligible, the inner boundary layer is probably reasonable, it's the outside with no movement that causes problems. I'll have to look up a book and get back to you.

I may be getting confused with air-liquid heat exchange rather than liquid-liquid (the vastly higher thermal mass reduces the flow requirements correspondingly.

I can certainly vouch that using black poly pipe as a heat exchanger is ineffective. I also suspect that the post mix system stores a lump of coldness and its actual cooling rate is not as high as you would think.

If you are cooling 1 pint of beer 7C in 5 seconds that's 1pint * (kcal/l) * 7 / 5s = 2.8kW of cooling power. Dubious design.