Backyard Aquaponics
A place to discuss aquaponics

If it's in a glass house I'd try cooling the air or dropping regular amounts of dry ice into a container in the sump. When I was about 8 years old there was a building that dispensed large blocks of ice. we were little so could climb inside and borrow some blocks. (we used them as reverse sledges to luge down steep roads. I've been looking for the guy who owned it ever since, I figure I owe him a hundred bucks by now with all the interest. Sorry universe)

That's if you just need a day or two to wait out the heat and grow for another few weeks of cooler weather.

But what ever you do I'd pull half out so you dont loose the lot, and leave the others room to breathe.

But you might find block ice is pretty cheap. Try the fish markets.

Thanks Sleepe, i was not aware of Harold Hay's work, sounds like a very clever guy. however I have seen his principles applied many times.

What has an Australian Rules footballer who played for Melbourne in the 1880s got to do with anything?

My first thought is that few appliances are very efficient working on 24V.. and was yours, a compressor device or an Absorption one..

Given that a commercial fridge is near identical in mechanics to an Air-Conditioner, I just cant think that they would not have a COP near the same.. (even if manufacturers NEVER consider COP for a fridge) ie.. I suspect that you could NEVER get a consistent comparison of COP between makes and designs..

FWIW

FRIDAY last - Sydney - Predicted Heat Wave
With the temperature climbing to 37DegC, I decided to put my silly idea to the test..

Early, at dawn, the water temp was 18.5 and it rose continually all morn' to Midday 21.5C

I wheeled the fridge to the AP system ...
got another air-line.. Fed it through a length of Air-Cond insulation. (for the full exposed tube length)..
connected it to a small coil of 1/4 copper refrigeration tube and connected that tube to the air pump.. (all within the freezer)
Remember that this is a frost free freezer = FAN circulating the air through the Evaporator.
( This could NEVER-EVER work with a Cyclic-Defrost Fridge )

At 1400 - Air Temp 38C - the water temp hit 21.6..
1430 Temp now 41 (in absolute shade) and water temp 21.8
1615 - Air Temp now 31C - water temp near the same 22C

No - it aint as scientific as some would do, but I am pretty pleased that I halted the rapid temperature rise, and it has clearly shown that a direct application (evaporator within the tank) will work very well..

The bottom line is that in 41C heat, I managed to stabilise the tanks water temperature..

Remember that this is only a super aquarium (IBC) 800Ltr (with complications) and I am aware that it would do NOTHING for Gordon's more exposed and large FT

My belief - It did work and could be enhanced.. with an improved heat-exchanger.. within the freezer..

Now the fridge is a paltry SAMSUNG and the compressor drain is about 150W, and thus I could not expect more than about 600W of cooling.. The condenser was running very hot (as expected)

and , we are not considering what happened to stuff inside the freezer..

Something to consider.. MOST refrigerators "Control" the Produce Compartment temperature, and the temp. of the freezer becomes somewhat relative..
A problem that I noted today - a very mild day - is that the fridge was continually shutting off..
This is because there was sufficient cooling to activate the PC thermostat, whilst I would have liked the freezer to be continually operating..

Were you to try it yourself, then I would simply block the COLD and the return ducts to the PC compartment, such that the machine will run continually... (One way or the other)

I now look forward to modifying that old Portable Air-Cond... that I know will seriously work..

BTW.. I had some bottles of frozen Sodium-Nitrate water in a freezer..
Three ltr of that did not see any change in temp..
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If you mean allowing it to bubble through the FT, then I would wonder what saturating the FT CO2 level might do for the FUSHes..
and if you did not put it in the water, then I would suspect you would get very poor heat transfer..

Bottom Line - it's interesting what others have tried and what actually works, rather that speculated about.. So much is just Common Sense..
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It's a compressor, and keep in mind that the COP will decrease as deltaT increases, ie the cold inside vs air temp difference. It is probably ~60 years old, but still works fine, although I had it re-gassed in the mid 90s, due to a split pipe.

I wouldn't be dropping solid CO2 into my FT, it's not going to do the fish any good at all- they need all the O2 they can get in warm water, and increasing CO2 concentrations wont help. It will also acidify the water a bit, which may or may not be a problem.
You really need to run the experiment on a day with the same temperature profile and water starting temp, with all other variable being the same, before you can apportion a particular amount of assistance to the cold air. Other factors are no doubt also influencing the rate of temperate rise variance.

If you pumped 700000 litres of air at 10C through your 21C water, and there was a 50% efficient exchange of energy between water and air, and no extra heat was added during that time, you might see water cooling equivalent to a bit over 1 degree, if your system obeyed the laws of thermodynamics
How much air, and at what temp did you put through it? What temperature was the air as it reached the surface? So many unknown variables!

Check the temp of the air from your air pump you will be surprised

My belief is it didn't work. Just saying.

I did and the air hose was quite COLD...
It was hot with just the Air Pump outside the fridge
It was warm when I first had just the pump and a few mm of air line in the freezer.
The difference came when I threw in the roll of copper tube, and that dissipated the compression heat..

All that I can attest to is that the air hose was distinctly cold and the water temperature barely rose during the afternoon AND the fridge condenser was very hot, showing that heat was being pumped from somewhere.

The clear need is to have significant heat transfer in the normal freezer air flow...

PS... the Silicon Air-Line was only exposed from under 50mm under the door seal, to the heavy RAC insulation
There was nothing exposed at the FT

And I will repeat the experiment, with an even larger heat exchanger in the freezer..
Likely what the weather is more stable and thus expect to see a decrease in water temp...

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Clearly, I have not attempted a fully data logged experiment as you might have done... GG
ALL that I can say is what I did and what I observed...

Again... I'll repeat at normal temperatures and MUST expect a temp fall.. or else it was as Charlie suggeste. .. imagination or worse..
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Ben... What is the INPUT power of the chiller..?
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If you have an old fridge then what about getting a small fountain pump and lots of plastic tubing. Put the foutain pump in the pond and run the tubing from the fountain pump into the freezer and coil several meters of tubing inside the freezer and back out into the pond. Seal the gap where tube goes in and out with duct tape.

If that isn't cold enough try putting the coil of tube in a tub of water in the freezer. Make sure you keep the pump running or the tube will freeze.

Belatedly - circulating water continuously, was my first thought, but running the water through COPPER pipes, is said to be a NO-NO...
I have been looking for a roll of 304 Stainless tube for that task..

ATLAS Steel sell if at a fair price...
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