It has a drain hole in the bottom that made this whole thing practical, because a PVC pipe hot-melt-glued atop the drain maintains the water level in the reservoir without any further attention:
The water line from the laser, formerly run directly into the bucket, now goes into the reservoir and through the drain into the bucket. The bucket holds about five gallons of water, with the pump submerged in the bottom.
The icemaker pumps water from the reservoir into the little icemaker tray, freezes nine little ice bullets, and scrapes them into the reservoir:
It does that about every eight minutes.
A plot of water temperature vs. time shows what happens:
It’s as exponential as you could want.
The ice bullets drop into the reservoir and melt there, the cooled water continuously flows into the bucket, and mixes with the rest of the water before being pumped back through the laser. As a result, there are no sudden water temperature changes and the laser remains perfectly happy.
Some numbers for an idea of the cooling capacity:
Freezing 28 pounds = 12.7 kg of ice a day (which, in normal use, would require me to babysit the thing overnight to empty the ice and refill the reservoir) works out to:
12.7 kg × 334 kJ/kg = 4.2 MJ
Spread across 24 hours, that’s 49 W of cooling power. There will be a bit more going into the chilled water surrounding the bullets, but most of the energy goes into the water-to-ice phase change.
Run another way, 5 gallons of water is 42 pounds. The initial cooling slope looks like 2 °C = 3.6 °F in 2 hr, which is 75 BTU/hr = 23 W. However, the water is cooling the laser (which was inert except for one brief cut) as well as the basement, plus (most importantly) there’s a water pump dissipating 20 W submerged in the bucket, so the icemaker is delivering at least 43 W, which is pretty much its rated performance.
It’s obviously incapable of keeping up with a laser doing full-time production work, but for my simple needs it seems better than dunking ice packs in the bucket.
More study (and maybe getting an air-cooled water pump) is in order …
The original data: