DIY chiller?

[broken]

I have an old freezer and a 330gph pond pump that is not in use along with a 560gal tank that has temps that are a little on the high side.
I am thinking of turning the freezer into a chiller but from what I have read they are not efficient and usually break soon after not being able to keep up but I will not have much to loose because the only thing I would be spending money on is the tubing that cost $35.00 on eBay.

What I want to do is submerge 100ft of 1/2" tubing under frozen water to be pumped back into the tank.

If I do go through with this project do you guys think it will be a waist of time?


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[sbuse]

I was going to do something similar. I was going to could the tubing in the freezer and call it a day. Depending on the type of freezer if it has a big open space you could try to have a plastic container filled with water the the tubing is in then freeze it. Leaving room for expansion so the tubing won't get crushed. Then I think it would be more effective if the tubing was in a block of ice and the freezer wouldn't have to work as hard.

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[rodger]

A full freezer operates more efficiently then an empty one, or so I have always been told. Why not use sacks of something that won't freeze and coil water tubes through it. That way things can be removed or moved.

 

[David R]

Depending on how high your temps are then it may just be a big waste of electricity. What are you keeping that can't handle the temps, and how much hotter is the tank?

If you're planning on pumping the water through the freezer how will you stop it freezing solid if the pump stops and the freezer doesn't?

 

[broken]

I rally like the idea of putting something in that can not be frozen. I just need to figure out what I can use.

Chances are it will be a waist of time but I have very little to loose and its been a while sense I have done anything DIY lol.

As far as the water freezing I am not that concerned because there will be a couple of feet from the freezer to the tank and there is no way the water will freeze that far.


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[broken]

I rally like the idea of putting something in that can not be frozen. I just need to figure out what I can use.

Chances are it will be a waist of time but I have very little to loose and its been a while sense I have done anything DIY lol.

As far as the water freezing I am not that concerned because there will be a couple of feet from the freezer to the tank and there is no way the water will freeze that far.


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[Yoimbrian]

A big thing you need to think about is heat transfer and residence time.

First off heat transfer. Im guessing based on price you are looking at plastic tubing. The rate of heat transfer through steel is about 20x that of plastic, and copper is about 20x that of steel. On a similar note the cold medium on the other side, liquids are about 20x higher than air. So a steel pipe going through liquid would be 400x more effective than a plastic through air. On that note the simplest would be go to Costco and buy 5 gallons of vegetable oil and fill your freezer with that (wont freeze).

Contact time is also important. You want as much surface area on your tubing as possible and as long of contact time as possible.

You should also make some rough calculations on max cooling range just to be realistic, freezers are designed to keep stuff cold, not actively cool, so there isn't a lot of wattage there. If you post the wattage of your freezer and flow rate and volume of water I can calculate the theoretical max temperature drop for you. I'm a chemical engineer btw, so have done heat exchanger design before.


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[DREWSMITH]

Now this is a subject I could go way deep on as I am an HVAC tech. First you would need to calculate the expected load you want to chill. This is measured in tons of cooling or roughly 12000 btuh/ton. So lets get started we need the expected temperature drop. Or delta T the difference between the incoming and outgoing temperature. The amount of flow measured in gph or gpm. And we can plug in the formula 500x gpm x delta T= capacity in btuh. So if you have 90*F water and need to get it to 85*F the pump is capable of 10gpm the result would be some thing like this. 500 x 10gpm x 5= 25000 btuh our roughly 2 tons of cooling capacity. The next thing to consider is refrigerant operating temperatures. The refrigerant in your freezer is likely 134A which means that the operating pressure of that refrigerant at 85*F and a modest 5*F approach temp would mean that the saturated refrigerant temperature is roughly 86.7psig. With a normal compression ratio of 4:1 we can estimate that the discharge pressure will be 346 psig and a saturated refrigerant temp off my pt chart. That its why you can't use them for this application. The condenser pressure is just to high. Maybe with different refrigerant or different conditions it is possible. But the previous poster is correct time and temperature delta outline the rate of heat exchange. If you have different conditions than what I have listed above or a want to try some different scenarios please post back and we can work them together.

Drew


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[broken]

Ok, you guys are totally throwing me off with all this math lol.
If I give you guys the wattage, specs on pump, OD and ID and length of tubing along with temps would you be able to tell me what to expect?


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[DREWSMITH]

Before all of that please identify the refrigerant in the freezer and temperatures you want to run at. Then we can get started.

Drew

NO GOOD DEED SHALL GO UNPUNISHED!