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Ask HN: DIY ice bath equation for water cooling

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Re: Ask HN: DIY ice bath equation for water cooling

#11

Post by kritiko »

It sounds like you have not done much research on this yet, but I'm sure DIY plans exist online given the popularity of cold plunges with athletes / bro science people (I don't know that there's actually much peer reviewed evidence on any benefit of this stuff).

The obvious answer would be "make a bunch of ice in the freezer" but I'm sure you could get more complicated. If you do go with a circulator, will you also be treating the water for reuse?

Edit: looking at reddit, it appears a bunch of people just turn their chest freezers into the plunge tank? Check out r/coldplunge

Re: Ask HN: DIY ice bath equation for water cooling

#13

Post by cameron_b »

Apart from the best answer of "get a water chiller"

The DIY solution would likely look like what Homebrew Beer folks call a Keezer.

https://homebrewacademy.com/how-to-build-a-keezer/

Most Freezers have at least some to all of the walls filled with chiller lines, so a collar is the best way to enter the freezer as in the link. You'll also need to interrupt the freezer's own duty cycle control to run less than normal so as to not actually freeze the lines, or else, do as was said elsewhere and use Glycol as an intermediate loop. That gets rather inefficient and redundant (the freezer is already a loop of coolant cooling your water-loop and venting the heat out the back) so either do it quick-and-dirty with a pond pump, a board on top of your freezer, a temperature sensor-tripped outlet, and some tubing, or else get a proper chiller.

Re: Ask HN: DIY ice bath equation for water cooling

#14

Post by fishbone »

anderiv wrote: post #5
nickhalfasleep wrote: post #2

Freezer compressors are sized for simply keeping the contents cold of their well insulated box. Trying to run an external load will likely overload it’s capacity.

Agreed. And even if the motor could take the load, the OP’s 25’ coil will be nowhere near enough. Think 4x that much in length and add fins/heat sink to increase thermal transfer.

The fins are a cool idea!

Re: Ask HN: DIY ice bath equation for water cooling

#15

Post by cameron_b »

anderiv wrote: post #5
nickhalfasleep wrote: post #2

Freezer compressors are sized for simply keeping the contents cold of their well insulated box. Trying to run an external load will likely overload it’s capacity.

Agreed. And even if the motor could take the load, the OP’s 25’ coil will be nowhere near enough. Think 4x that much in length and add fins/heat sink to increase thermal transfer.

just at face value though, the inefficiency of thermal transfer would make a sufficient buffer to prevent the freezer from taking too much load from the volume of water.

25' of copper would not be nearly enough to do the whole job but it would lower the temp some, and over time it would lower the temperature relatively safely ( safe against freezing the lines ) and likely consistently unless the tub is continuously filled with mammals or in sunlight or sunlight-warmed air.

Re: Ask HN: DIY ice bath equation for water cooling

#17

Post by fishbone »

kritiko wrote: post #11

It sounds like you have not done much research on this yet, but I'm sure DIY plans exist online given the popularity of cold plunges with athletes / bro science people (I don't know that there's actually much peer reviewed evidence on any benefit of this stuff). The obvious answer would be "make a bunch of ice in the freezer" but I'm sure you could get more complicated. If you do go with a circulator, will you also b…

Most of the DIY stuff I have seen involves putting the water directly in the chest freezer. Would need a much bigger chest freezer to fit in and I’m not crazy about the electrocution risk. I’m currently using the make a bunch of ice approach but it is cumbersome.

Re: Ask HN: DIY ice bath equation for water cooling

#18

Post by thenerdhead »

fishbone wrote: post #17
kritiko wrote: post #11

It sounds like you have not done much research on this yet, but I'm sure DIY plans exist online given the popularity of cold plunges with athletes / bro science people (I don't know that there's actually much peer reviewed evidence on any benefit of this stuff). The obvious answer would be "make a bunch of ice in the freezer" but I'm sure you could get more complicated. If you do go with a circulator, will you also b…

Most of the DIY stuff I have seen involves putting the water directly in the chest freezer. Would need a much bigger chest freezer to fit in and I’m not crazy about the electrocution risk. I’m currently using the make a bunch of ice approach but it is cumbersome.

You unplug the chest before getting in. It's really not that risky.

Re: Ask HN: DIY ice bath equation for water cooling

#19

Post by fishbone »

cameron_b wrote: post #13

Apart from the best answer of "get a water chiller" The DIY solution would likely look like what Homebrew Beer folks call a Keezer. https://homebrewacademy.com/how-to-build-a-keezer/ Most Freezers have at least some to all of the walls filled with chiller lines, so a collar is the best way to enter the freezer as in the link. You'll also need to interrupt the freezer's own duty cycle control to run less than normal s…

Thanks for the info. I was planning on using a timer and thermostat switch to turn the pump off once reaching target temp and to use gravity to empty the coil when the pump is off.

Re: Ask HN: DIY ice bath equation for water cooling

#20

Post by cameron_b »

fishbone wrote: post #19
cameron_b wrote: post #13

Apart from the best answer of "get a water chiller" The DIY solution would likely look like what Homebrew Beer folks call a Keezer. https://homebrewacademy.com/how-to-build-a-keezer/ Most Freezers have at least some to all of the walls filled with chiller lines, so a collar is the best way to enter the freezer as in the link. You'll also need to interrupt the freezer's own duty cycle control to run less than normal s…

Thanks for the info. I was planning on using a timer and thermostat switch to turn the pump off once reaching target temp and to use gravity to empty the coil when the pump is off.

don't leave the coil in the freezer without flow though, full or empty. It'll freeze the water when you try to start circulation again if it's totally frozen
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