Backyard Aquaponics
A place to discuss aquaponics

Hi all,
Have just converted an old small freezer ( see photos) and don`t know whether it will work yet but will be very grateful of observations and advice on what we are trying to achieve.
The principle is quite simple in that plastic flexible pipe is hot-glued aroound the inside of the freezer, the flexi pipe forms a continuous loop with one end attached to a submersible pump and the other end left clear in the fish tank. The two empty hydroponic nutrient containers are filled with water and will become frozen. and will provide cooling for the pipework if the pump is turned off by a timer or whatever.
The two control valves on the flow and return of the pipe will adjust the flow of fluid through the freezer.

As cooling is going to present a problem for the water in the fish tanks in the summer weather (if we ever have one again) - we need to tackle the problem now!!!!!!
WD and OH

more photos of project


must learn to upload photos last in order first and the first last!!

OH

How will you keep the pipes from freezing?

Hi TC

The pump in the fish tank will be moving the warm water through the pipe so there should not be an opportunity for it to freeze unless the pump packed in.Once the water inside the blue containers has frozen the freezer could be turned off by a timer switch for a predetermined time until the returning water was no longer being chilled.
I need the tank water to warm up a bit to actually see if the model will work.
Having seen the price of commercial water chillers I am hoping this will work out much cheaper.

WD

Make sure you have enough room in the blue drum for the ice to expand. Also while your running pipe it could go down to the bottom(more pipe). I wonder how it would perform filling the freezer up with something. Water could damage things. But sand.

From friends of mine in the aquarium business, I would have to say your design is good. They always recommended putting pipes into a bucket filled with water that would freeze, so ice coats the pipe entirely, but your design is not bad.

I think the water around the pipe would be due to the lousy heat transfer through air, and the excellent transfer through water... I would fear that the water in your pipes wont get cold enough whilst passing by.

Give it a try though, I never did see any of these designs actually built and running.

You can buy a temp control unit.
Tempmate and/or Fridgemate.
you can set minimum and maximum Temps.

Power lead from Wall to unit to fridge/freezer, would be more economical (on electricity) than a hit and miss timer.
there is a probe that goes from the unit into the fridge/freezer
I think the Fridgemate is the one with Dual probes so you can send 1 to the tank to turn the pump on and off and the other to the freezer to keep the temp you require
They cost about $60 aussie. ( single Probe) and about $20 for the 2nd probe

Just a thought

Cheers
Ron

That would be the way to do it.

They are good for keeping beer fridges at 1 deg c too

I tried my own hand at water chilling - I busted open a fridge/freezer - had the water running over the cooling fins which were attached to the freezer element. It sort of worked, but could only chill about 1-1.2 degrees C at a low flow rate (not sure exactly how slow, but it was maybe int the order of 0.5-2L/min???)
Anyway - it worked, but not nearly as good as I thought, and could not do much even for a 450L tank in hot weather. my insulation wasn't nearly as good as what you have pictured (I couldn't close the freezer door properly), and had none around the tank.

I would imagine a good way is to keep a sump of cool water in the freezer and flush it through as required, rather than trying to cool water as it flows through a loop of pipe???

... but my designs often fail

It may pay to actually work out how much heat you need to dissipate and what the freezer is rated at..
eg - work out the energy required to cool ... litres of water by ... degrees over ... hours of the day. You may find that the freezer wont be able to handle it anyway, or that it will be more than fine - assuming you can get the heat transfer ok.

That's a very good point. The power needed to cool an outdoor system would be too much for any freezer.
if the tank is inside, and there was aircon, and/or decent insulation in the house, perhaps then it would be enough... I would be VERY pleased if I could achieve a delta T of more than 5 degrees.

How do those ground fridges work. We used to bury food stuff under the fire while camping as a kid to keep it cool. Something about the heat dragging the cold from deeper down. A solar oven and buried pipes could make a passive cooling unit. And there is something about using solar ovens as fridges at night with the tops off them.
http://www.solarcooking.org/radiant-fridge.htm
http://littleshop.physics.colostate.edu ... Fridge.pdf

Fill the freezer with water and add a fair amount of salt to keep it from freezing (a brime). Water can store a lot of heat energy (or lack of heat energy). Over night the water will get very cold and during the day when it cant keep up with the heat load it will release the stored up cool.

Thanks for all your observations.

Strangely the simplest mistakes are overlooked and here we have a classic example. The hot glue holding the pipe to the wall of the freezer has come "unstuck" so I shall have to use a more permanent method of attaching it probably armoured cable adjustable straps attached with a small self tapping screw. As there will be no liquid in the freezer itself there will be nothing to leak out.. I have logged all your comments and when we go for lift off I shall report back. In the UK old fridges and freezers are discarded at the local rubbish collecting site for proper disposal so a visit there may well give me access to a veritable treasure trove of old freezers to play with.

The old geezer with an old freezer.
WD

quick thought, maybe pack the coil in bags of vodka or something else with a low freezing point...easy to disassemble without thawing the whole thing out, better thermal transfer to the coil, more thermal mass for stability, no glueing...

expensive and heavy though

you can't treat vodka like that. Its meant have ice added to it.