Do We Really Need Cozies?

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sarge
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Re: Do We Really Need Cozies?

#16

Post by sarge » Sat May 07, 2016 7:44 am

Mophead wrote:
Good point about the starting temp. Water cools faster the hotter it is... if that makes sense. So the curve of cooling water is going to look like a negative exponent. You wouldn't be at 212 for very long, maybe not even by the time you poured into the bag. But your cook temp will average much higher than 160. If you noticed by the time the water was out of the microwave to the time you got starting temp you are at about a 15 degree loss (assuming the water was at 212 which I think is reasonable) That's about half the loss experienced during the 15min cook time and maybe happened in 2 minutes? I like how you did your tests, it has me thinking about this subject differently now.

FWIW The more I read and think about this, especially the refrigerator test, I wonder if reflectix is even a suitable material for this task if one were to go with a coozie. Is a food bag really losing heat through radiant loss (reflectix is a radiant barrier) or could it be conductive loss from the bag setting on the cold shelf of the fridge? If a food bag is really losing its heat through radiant loss then a space blanket with an air gap from the bag should work equally as well.
Yah. The water was at a rolling boil (212 degrees) when the microwave stopped, but measured fairly consistently at 200 when I put the probe into the bag, so there was an almost immediate 12 degree loss. The recording of both time and temperature didn't begin until the probe was put in so we can't really say that its half of the reported loss. We could say that 1/3 of the total temperature loss from boiling occurred in the time between opening the microwave door to inserting the probe, but we didn't measure the time it took to do that.

Whatever contribution to heat loss comes from convection is mitigated by the design of the bag as the contents of the bag are never in contact with any surface other than the plastic of the bag itself. The bowl sits about an inch from the bottom of the bag.

When I test the heat loss with the cozy I'm going to compare that to covering the bag with at least one other thing that I normally bring along in my pack: a bandanna, shemagh, shirt, etc., to see if they are comparable in effectiveness to the reflectix. I suspect that the difference between throwing something like your top quilt or the skivvies you're going to wear the next day over the bag will be at least as effective as the cozy, IF the cozy makes any appreciable difference at all.


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Re: Do We Really Need Cozies?

#17

Post by Mophead » Sun May 08, 2016 3:56 pm

Ok made a new coozie and did some tests. Coozie was rectangular like sarge's but angled to a point toward the opening. Thermometer was reading off but I did some math checking the numbers by assuming the highest temp = 212 at boiling and subtracting the temperature difference and even did a calibration curve based off boiling, freezing and room temp and the numbers were pretty close both ways and not far off from sarge's.

Tests were done indoors next to an open window with an outdoor temp in the high 50s. Temps read at boiling and after 15 min.

No coozie = loss of 41 degrees

Inside light weight fleece = loss of 31 degrees

Inside reflectix coozie = loss of 31 degrees

So I'm going to say agree and conclude most of spring to fall the use of a coozie is not necessary or at least not worth it to me. If I do use a coozie I won't be making it out of reflectix. Reflectix looks to be about 220g per square yard and my fleece was only 100g per square yard and performed the same. If I had some synthetic insulation to test I might consider even consider a climashield coozie over both for winter.

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Re: Do We Really Need Cozies?

#18

Post by DuxDawg » Wed May 25, 2016 10:11 am

That crotchpot brought back memories of tucking MREs there while hiking in the 1990s.
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Re: Do We Really Need Cozies?

#19

Post by sarge » Wed May 25, 2016 11:45 am

DuxDawg wrote:That crotchpot brought back memories of tucking MREs there while hiking in the 1990s.

We didn't do that when I was in the Army.

C Rations aren't really the best thing to stuff into your pants.

But we could set them on top of the jeep engine to heat them up-----
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