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Old 06-03-21, 06:46 PM   #1
TobyB
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Default Making ice cubes

This is just something that rattles around in my head when it's raining-

so, we get a lot of rain here. Air and water temps in the 40's, lots of wet.

I'm trying to figure out how to use the heat out of the water by
freezing it- then dumping the ice, to freeze more water.
At a relatively large scale, like, enough to provide domestic
heat and hot water.

Freezing's not a huge problem. Run a heat pump for a while.
But-
then how to get rid of the ice? Make sheets, then let them slide
off into a pile? Hundreds of re- purposed refrigerator ice makers?

By the time I get the next batch of water ready to freeze,
a regular old air source heat pump looks pretty elegant,
especially from a reliability standpoint.

Any thoughts on how to get phase change heat out of water and
make it a continuous process?

Goodness knows, the rain is continuous...

just thinkin',

t

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Old 06-13-21, 11:33 PM   #2
jeff5may
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You just described how a commercial ice machine works. Cycle starts, and a valve fills up a tank to a preset level. A pump recirculates the water over the evaporator / mold. A probe senses the ice thickness and advances the cycle once the desired thickness is achieved. The refrigeration loop is then switched to "hot gas defrost", where the metering device is bypassed. Hot compressor gas goes through the mold, and the ice falls out. After a short time, the cycle starts over.

These commercial ice makers are a whole lot more efficient at making ice than a home refrigerator ice maker. For a 6000 btu machine, it's typically able to make 500 pounds of ice per day. That's a lotta ice!
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Old 06-24-21, 04:23 PM   #3
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I had a tour of a pigment factory (SunChemical)....they use ice for the reaction somehow...there was a 20ft tall cylinder about 15ft dia. with scrapers on the outside to knock the ice off. The cylinder was about 1/2 thick but hollow. It had ammonia circulated inside and water sprayed on the outside. It turned very slowly but made crapload of ice.
Supported top and bottom by mounted bearings that were quite small (I thought). Seemed like an amazingly simple system.
Not sure of the science behind ammonia for heat transfer but must be cost effective, they had been using it for years.
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Old 06-25-21, 12:45 PM   #4
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Dguzzi,

Google ammonia absorption refrigeration.
https://en.m.wikipedia.org/wiki/Absorption_refrigerator

Same basic thing as phase change refrigeration, but without the power hungry compressor. The ammonia cycle leverages ammonia's affinity for water. Lithium bromide and calcium chloride can also be used in similar cycles. I've used road runner ice melter to make a solar dehumidifier slash clean water source, and it worked pretty well. So...

Down another rabbit hole we go...

I was thinking about trying absorption refrigeration out with a couple of flat plate solar collector panels I'm building right now. The idea behind the experiment is to utilize the solar thermal panels to assist the HVAC system year round.

In winter, the thermal energy harvested can directly heat up the basement. Super simple: space heater rigged to a car radiator and a washing machine drain pump will do it. Heater thermostat call energizes the fan and pump, and presto: heat!

Summer heat gathering is going to outpace the domestic hot water needs by a fairly large margin, so it looks like I'll have gobs of energy leftover. The absorption cycle uses raw heat to boil the ammonia out of the water (or the water out of the salt) rather than mechanically compressing the refrigeration gas. So once my hot water tank is satisfied, I can divert the scalding hot water to run the ammonia refrigerator.

The objective of this contraption is to have zero moving parts: no heater, no pumps, just the hot water makes it do its thing. If I'm lucky, it will start doing its job somewhere close to the cutout temperature of my DHW store tank. Yes, stratification and blah blah blah, but I don't need skin melting heat store water.

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Old 06-26-21, 08:04 AM   #5
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Nice food for thought! I don't have the chemical knowledge and so would be concerned with leaks and corrosion problems. Certainly seems like a good alternative to standard refrigeration for many applications. Thank you for that write-up!

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