Need refrigerant selection advice for custom chiller project, to freeze water
Hey guys, I'm in the process of fleshing out some design details for a liquid chiller project for a thermal systems design course at school and am wondering if anyone has some advice for what refrigerant would be practical.
We get 7 min to cool a 500 mL bottle of water as much as possible using a bucket of ice water with between 4 and 8 lb of ice. I'm working on determining what sort of system will be able to completely freeze the bottle before 7 min so as to reach a final temp lower than freezing. My preliminary calculations show I'm looking for at least an 800W system with an evaporator temp probably between -20 and -30 degrees C in a glycol liquid bath. The condensor will be a shell and tube HX with the water from the icebucket circulated through it, hence very cold condensor temps.
So my question is, would R-22 be a practical choice in this case? Is there another non exotic refrigerant that would work better? I'm trying to find a solution that does not require a huge compressor (R-134a and R-152a have been ruled out in favor of R-22 so far for this reason, going by the research I've done so far). I'm also trying to limit it to any relatively common refrigerants to keep cost and complexity down (primarily sourcing major components from scrap equipment/ebay, meaning selection is limited to mostly common stuff, plus whatever else that common stuff could be made to work with, like what refrigerants have a chance of working well in an R-22 compressor).
I do have my 608 type 1 certification, so legality is squared away.
Thanks in advance!
You would have to pump less 404 than 22
So if you used 404 you could use a smaller compressor. Just dump out the oil and refill with POE.
Why are you using the S&T condenser? Do you already have it?
What is the metering device?
(ice water condenser water and) "very cold condenser temps" are not going to cut it. How are you going to create the TD across the orifice?
Can the 500ml of water be in a container of any shape? Or is it to be in a fixed size/shape bottle? I ask because a part of your challenge is going to be surface area / heat exchange.
BTW: was the 500ml size chosen because it's one pound? Who came up with the rules of this test?
If you can do whatever you want why not set a bottle of liquid CO2 in the bucket of ice water and the 500ml bottle of water into another bucket - and then blast CO2 into the second bucket? A total-loss refrigeration system.
Originally Posted by twophase
Maybe both of the R-22 rotaries. <g>
Just for some rough perspective: an R-22 air conditioning compressor running at a 25 lb. suction will pump about 40% of it's rated capacity.
You're going to need some fire power to do what you want. Off the top of my head I am thinking 1HP or more to run a -35º F. suction and get all the heat out in seven minutes.
Hell; just the pulldown will take more than a minute - have you considered the the insulating value of the building ice layer? The thermal mass of all the components?
Originally Posted by twophase