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Old 05-27-2011, 07:58 PM   #1
tonyolympia
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Default Heat loss in cooler

I'm getting ready to brew my first all grain batch, and I performed a test run with my picnic cooler MT to measure its heat loss. I was surprised to see that after one hour, the cooler lost 10 degrees F. However, it was filled ONLY with water--no grains.

My question is this: does the presence of grain during the mash slow down the heat loss at all? Or can I expect the same drop of ten degrees to happen even when there's grain in there (that is, a 10 degree drop on top of the normal 10 - 15 degree drop when the grain and the strike water equalize)?

For the purposes of this analysis, I think I did everything right: I warmed the cooler up beforehand, left very little head space, and wrapped it in a blanket during the hour rest.

One possibly relevant piece of information: my cooler holds only two gallons. I am planning a half-batch stovetop mini-mash, and I'm testing this cooler to see if it can hold mash temps for an hour without the constant attention that a monitored brew pot requires. I'd like to use the cooler, if possible.

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Old 05-27-2011, 08:00 PM   #2
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not sure about grain holding heat but I would check your lid. a lot of them are hollow & you can fill it with "great stuff" foam just get the nonexpanding type. that will help keep the heat in.

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Old 05-27-2011, 08:09 PM   #3
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I have to think that the grains will help retain the heat.

You took the temp of the water inside the cooler after a couple of minutes to get your first temp right? If you tok that temp reading in the pot or right after dumping it in the cooler than that is going to account for some of that loss.

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Old 05-27-2011, 08:22 PM   #4
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Also, make sure you pre-heat your cooler with hot water for an hour before you dump it and begin to add your grain/water. I use 10 gallon igloo coolers and I only lose 1-2 degrees over the course of mashing/sparging.

Hope this helps...

WD

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Old 05-27-2011, 08:28 PM   #5
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Quote:
Originally Posted by WortDog View Post
Also, make sure you pre-heat your cooler with hot water for an hour before you dump it and begin to add your grain/water. I use 10 gallon igloo coolers and I only lose 1-2 degrees over the course of mashing/sparging.

Hope this helps...

WD
You preheat for an hour?? I preheat mine for 5-10 min and it does the trick.

I'm pretty sure that the grain has a much higher thermal mass than the plain water, so it will hold temps for longer.
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Old 05-27-2011, 08:35 PM   #6
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You preheat for an hour?? I preheat mine for 5-10 min and it does the trick.

I'm pretty sure that the grain has a much higher thermal mass than the plain water, so it will hold temps for longer.
Ok...30 minutes . But sometimes an hour depending on how much prep I have to do.

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Old 05-27-2011, 08:37 PM   #7
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Quote:
Originally Posted by BendBrewer
You took the temp of the water inside the cooler after a couple of minutes to get your first temp right? If you tok that temp reading in the pot or right after dumping it in the cooler than that is going to account for some of that loss.
Very good point, BB. I'm sure I took the temp too soon after filling the cooler. I might've lost those 10 degrees in the first few minutes. I'll fill my lid with some foam and run the test again.
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Old 05-27-2011, 08:55 PM   #8
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Very good point, BB. I'm sure I took the temp too soon after filling the cooler. I might've lost those 10 degrees in the first few minutes. I'll fill my lid with some foam and run the test again.
Just overheat your strike water by 5-10 degress, throw it in the cooler and close the lid. When the strike water has dropped to the strike temp you want (heat transferred to the cooler) then add your grist. That's how I do it and it works well. Only lose about 1*F over an hour in a 5gal cooler MLT.
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Old 05-27-2011, 09:15 PM   #9
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I tried filling my lids with GreatStuff (Window and Door) foam - both a 10 gallon RubberMaid and a 5 gallon Igloo. In both cases after injecting the foam and getting foam coming out from holes in the lid, the foam then collaspsed and turned into a liquid which of course didn't insulate very well. I ended up just cutting a piece of Reflectix the size of the lid and taping it to the top which seems to work fairly well -certainly better than my aborted foam job.

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Old 05-27-2011, 09:25 PM   #10
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I tried filling my lids with GreatStuff (Window and Door) foam - both a 10 gallon RubberMaid and a 5 gallon Igloo. In both cases after injecting the foam and getting foam coming out from holes in the lid, the foam then collaspsed and turned into a liquid which of course didn't insulate very well. I ended up just cutting a piece of Reflectix the size of the lid and taping it to the top which seems to work fairly well -certainly better than my aborted foam job.
A floating piece of styrofoam (zero dead air space), something stuck to the lid, or even a sleeping bag over the top will help. Remember, these things are primarily designed as a cooler and hot air rises so the lids are the weak point.

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