Peltier Cooled Fridge Mark III Started Testing

[avandonk]

Managed to get the water pump and CPU water block and other bits. Below are the pictures of it set up to test it. When these pictures were taken the water in the esky was at 25.8C and the fridge was at -4.2C.
There is no vibration due to the pump.

Earlier I had put a bag of ice in the esky and the water temperature dropped to about 3C. The Peltier fridge managed to get to -14C without a load. I have tested 50% antifreeze down to -25C and it stays liquid.

The freezer I got second hand can get down to -25C when it's thermostat is set to max. So I should get -30C in the Peltier fridge with ease even on a hot night.

The tubing is Tygon and it stays flexible down to -40C. I will cover the tubing with neoprene foam insulation. The water block will be insulated with expanding foam.

Tomorrow I will drill some holes in the side of the freezer to test with anti freeze.

Bert

[AlexN]

Tygon tubing is definitely the goods.. I used to use Tygon 7/16" as it gives just that little bit more head pressure than using 1/2" tubing I suppose given the temps you're running at, you're not likely to gain more than 0.5 degree difference from doing that...

Is that a Davies Craig pump or the swiftech version of the same (MCP-655 from memory) They are great little pumps, very low noise, next to no vibration, they draw very little power..

This setup definitely looks like it will result in a much cooler sensor, and much less noise..

Looking forward to a pic of the whole lot setup for first light...

[multiweb]

Vodka's better. I always have ample supplies handy in case clouds roll in. Just a thought :shrug: ;)

[avandonk]

Put the whole lot in the freezer as I can't cut holes until I find the mandrel for my hole saws.

At least I can test if there is enough heat transfer to the coolant. The freezer copes with just the electrical heat load with ease. Total electrical heat load is 7A x 14V = 98W. The freezer is rated at 190W so it should pump 400W+.

It looks like I need a radiator or long length of copper pipe inside the freezer to cool the coolant as it slowly heats up even though the freezer is at -18C. The copper based cooking pot is not transfering enough heat to the freezer.

Heat getting in to the coolant depends how well the Tygon tubes are insulated.

Bert

[leon]

jeepers creepes Bert :eyepop:when will you stop, :shrug:than again I suppose it keeps you out of trouble, nice job mate.;)

Leon:thumbsup:

[Garyh]

Now that`s real cool! Maybe you can get some piping of the back of a old fridge at the tip to bung in the freezer to run the antifreeze through?
Will your camera still work at these super low temps but..?
What is the working temp for your 5D?

[avandonk]

Gary I have run the air cooled Peltier fridge at -24C when it was 1C in Melbourne. The darks were very dark and the Canon was none the worse for wear. With my method the camera cools down quite slowly and once the Peltier fridge is at 0C the interior of the fridge is bone dry as all the water is now frozen on the cool side of the Peltier heat exchanger.

I am sure the camera can handle -30C. Even at this temperature the sensor due to its own heating is at -13C.

I have ordered a radiator

http://www.pccasegear.com/index.php?main_page=product_info&cPath=207_160_297_919&products_id=13082

and with two 120mm fans will easily cool the coolant down to nearly the fridge temperature.

I am going to use a pressure cooker as the reservoir to stop water from the anti freeze evaporating/sublimating and frosting up the cold metal bits inside the fridge. Its just a matter of drilling and tapping a couple of holes to take a 1/2" barbs

http://www.pccasegear.com/index.php?main_page=product_info&cPath=207_160_300&products_id=11196

Bert

[avandonk]

Yes Leon it keeps me out of trouble. A couple of months ago a group of people attacked me in Greensborough. One tried to hit me repeatedly with an iron bar. I woke up in hospital. No permanent damage fortunately. They scattered when another bloke turned up to help me just in time as I was losing. If I was twenty years younger I would have wrapped it around his neck and then pulled it tight.

The police are on the case. They have video footage. The young police woman who interviewed me some days later asked me 'what made you think at sixty you could take them on?' I told her I had no choice. She said from the footage you gave them a hell of a surprise.

The usual thing of course mug anyone to feed a drug habit.

It is much safer staying at home and playing with my fridges.

Bert

[avandonk]

After rigorous testing have put the new fridge on the system. It is already exceeding all expectations. The expanding foam as insulation has made all the difference. The temperature is still dropping. My PID temperature controller only goes down to -20C. SAD!


Bert

[trent_julie]

Thats an impressive setup!

I was admiring your original peltier setup, now this!
One Question though........
Does it keep a beer cool as well?

Cheers,

Trent & Julie

[Garyh]

Exactly what I was thinking on those hot summer nights!
:cheers::cheers::cheers:
Your darks should have less noise than a bias shot now Bert!
Have you done some tests to compare them?
cheers Gary

[avandonk]

The freezer would freeze any can of beer quicker than you could drink it..

The air cooled fridge can get to -10C at the Peltier heat exchanger cold side when ambient is at or below 12C. This means the inside of the P_fridge is at -5.0C. On a hot summer night say 20C the best the P_fridge can manage is about 0C.

In winter when ambient is about 3C say it does much better and can get to -10C or less inside the fridge.

All the big freezer is doing is supplying coolant to the Peltier heat exchanger hot side at down to -5C under load. It can do this on a hot 'night' of even 30C.

I am getting about -17C at the cold side of the P heat exchanger even when ambient is at above 25C. This means I can get a controllable -10C in the P_fridge even in summer.

This is what I was after. To go lower the insulation of nearly everything has to improve.

Below is an eight minute dark at 1600 ISO with the inside of the P_fridge at -10C. The EXIF should be intact 5MB.

http://d1355990.i49.quadrahosting.com.au/2010_01/IMG_0067.jpg

The actual temperature of the sensor is 7C. The 5DH's sensor is 17C hotter than camera ambient when continuously exposing.

Bert