Water Cooling Devices
Most recent answer: 10/09/2013
- Eduardo (age 28)
Caracas Venezuela
This problem becomes easier if one converts all the various specs to some standard units. You need to cool about 1000 gm of water by about 20 K every 60 sec. (I assume your 1 Lts number was for the combined machines, not for each one.) Since the heat capacity of water is ~4.2 J/K-gm, you need about 1600 W of cooling power. (twice that if that's just for one machine) The device you bought is giving you ~200,000*4.2/(15*60) W ≈ 920 W. It sounds like one solution would be just to buy a second device and run it in parallel.
That device, by the way, isn't especially efficient. A good home air-conditioner can give more than 4W of cooling per 1W power used. It looks from the specs as if your device draws about 320 W of power, so 920 W cooling is mediocre. (However, I may be confused since I'm assuming that the 1.4 A current draw of the device is for British 230V supplies, not for standard 120 V Venezuelan supplies.) So, especially if you need 3200 W cooling rather than 1600 W, you might do best to buy just the compressor unit from a small split-style home air-conditioner, and use its cooling coils in a tank of flowing water.
There's another possible approach. Simply replacing all the water would use too much. However, cooling water by 20 K requires evaporating only about 4% of it, since the latent heat of evaporation is large. Sending your hot water through a sprayer to speed the evaporation might get most of the cooling you need and might still not require an unreasonable amount of water. The feasibility depends a lot on the price of water, compared to electrical power, and on the typical relative humidity.
Mike W.
(published on 10/09/2013)
Follow-Up #1: space-saving cooling
- Eduardo (age 28)
Caracas
I think that ice is about as good as you're likely to do: large latent heat per volume, inexpensive, very low toxicity! So freezing as much as possible overnight and using it to augment the cooling during the day could help a lot. The latent heat of melting ice is equivalent to about 80° C of cooling water.
Is that split air-conditioner really only 12 BTU/hour? That's under 4W, which sounds tiny. Could it be 12,000 BTU/hr? That would be plenty for your ice-cream needs, with some cooling power left for the room. It would require a little extra plumbing to divert some of the cooling to the ice-cream system, but not too elaborate.
Mike W.
p.s I'm posting this without Lee's checking, since he's on a trip and the information seems timely.
(published on 10/09/2013)