Question About Cold Retaining Metal

What metal (or other fairly common substance) retains COLD the longest?
I was thinking of experimenting this hot Summer with placing various chunks of
metal in my freezer and...more or less using them like ice. Putting them in my cooler and seeing if they kept items nice and cold --without the side effect which ice has (melting to liquid).
If I'm not making myself clear, I mean...would iron or steel or brass or lead or what metal would likely "hold its cold" the longest?
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Surely your cooler should keep things cool without needing lumps of metal in it. However, to answer your question, Heat absorbed = specific heat x mass x temperature rise The metal with the largest specific heat will remain cool the longest assuming that it's shape and thermal conductivity are not limiting things. A better way is to involve a phase change like freezer blocks. The advantage of ice is that it absorbs a lot of heat just by melting. Get a flexible container, put some water in it and use that.
John

chunks of

in my

effect
lead
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The metal with the largest specific heat will remain cool the longest...John Manders>>
Okay...what metals might those be?
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On 20 May 2004 09:27:51 GMT, in sci.engr.mech snipped-for-privacy@wmconnect.com (AlWahrabi) wrote:

Excluding phase change, for a given volume, it will be the material with the highest value of density times specific heat. Copper is a good one. ________________________________________________________ Ed Ruf Lifetime AMA# 344007 ( snipped-for-privacy@EdwardG.Ruf.com) http://EdwardGRuf.com
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Excluding phase change, for a given volume, it will be the material with the highest value of density times specific heat. Copper is a good one. Ed Ruf>>
So, you're saying: copper (once placed in the freezer and chilled overnite) is a metal that will take a LONG time to lose its cold temperature? Longer than, say, iron or steel?
I appreciate the several replies, and in the meantime I am reviewing old postings. It seems like at least 2 parameters are at work: Specific Heat AND Thermal Conductivity.
Each year, when I buy dry ice for cooling in my vehicle, I notice that dry ice is a very POOR conductor of cold. Dry ice appears to have to be directly ontop of something, in order to chill it. Something one inch away from the dry ice is warm, while...whatever it is directly in contact with it is super-chilled...but only at that one point of contact with the dry ice.
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Ahem....copper 380 joules per kg .degC aluminum 886 sodium 1180 porcelain 755 (!!! but poor conductivity)
Brian W
wrote:

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On Fri, 21 May 2004 01:17:06 GMT, in sci.engr.mech Brian Whatcott

Ahem, got a frog in your throat? If you actually read my post, I said per unit volume. Given the density difference between copper and aluminum, it wins hands down. One of the reasons the heatsink copper scramjet models we test at work are made of copper.

________________________________________________________ Ed Ruf Lifetime AMA# 344007 ( snipped-for-privacy@EdwardG.Ruf.com) http://EdwardGRuf.com
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wrote:

Ed, I cut out the personal invective from your interesting response above, and offer this explanatory note. Hope it helps.
I'd like you to take the opportunity to think a little more about your response. 1) TERMS "Specific" is a keyword in physics for "per unit mass" so... Specific heat times density means heat capacity / mass X mass/volume heat capacity per volume.
Your sentence "For a given volume, the material with highest specific heat times density" [gives the highest heat capacity]
means
"For a given volume, the material with highest heat capacity per volume" gives the highest heat capacity.
I think you can see that this statement is not a deduction or conclusion, but a recasting of terms.
2) FIGURE OF MERIT. ... more importantly, if you are going to fly something as an engineering proposition, you work out a figure of merit.
Where the desired objective is maximizing heat capacity, it costs something to get the item aloft, and that cost is mass. So the reasonable figure of merit in your ram-jet case is heat capacity per mass which is - guess what? called specific heat capacity.
That's why recip valve stems are sodium filled, and engine cases not exposed to high temperature are...aluminum. They are not ever copper, which has a lower figure of merit for the application.
Sincerely
Brian Whatcott Altus OK
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On Sat, 22 May 2004 00:19:45 GMT, in sci.engr.mech Brian Whatcott

and
Yes, it is a tautology. I was trying to point out in the freezer problem the major constraint one has is volume, not mass (within reason, of course). Which your other reply suggesting water filled bottles would seem to follow. Given a freezer filled with food, one is space limited, no? If this didn't come across in my posts in the wee hours of the morning, it is my fault.
FWIW, Though Cu is better than Al, as I said in this regard, carbon steel is a bit better than copper as well. The OP asked about metals, but even neglecting the phase change, water is still better than common metals in this regard, too. Adding the phase change and water wins hands down. Which is why the original icebox came to be, no? As to your figure of merit. You have chosen this as your figure of merit. It need not be the figure of merit for every application, even if it is that for some.
As far as our models, volume limited total heat sink capacity is of major importance. Another is the ability to survive very high heat fluxes. You will find OFHC (Oxygen Free High Conductivity) Cu is used as a standard material in environments such as this. Where more strength is needed Glidcop, a alumina dispersion strengthened copper alloy is used.
For example see: http://hapb-www.larc.nasa.gov/Public/Engines/3-strut/3-strut.html http://hapb-www.larc.nasa.gov/Public/Engines/Engine_A/Engine_A.html http://hapb-www.larc.nasa.gov/Public/Engines/Sxpe/SXPE.html http://hapb-www.larc.nasa.gov/Public/Engines/CDE/CDE.html http://hapb-www.larc.nasa.gov/Public/Engines/Hxem/Hxem.html http://hapb-www.larc.nasa.gov/Public/Engines/Hxfe/Hxfe.html
Yes, the above is ground test hardware. I did not necessarily say fly in my post. However, the HXFE test hardware is a spare flight engine. The actual flight engine hardware flown at Mach 7 on March 27, 2004 was the same, almost entirely made from Glidcop, as can be seen at: http://www.dfrc.nasa.gov/gallery/photo/X-43A/HTML/EC99-45265-11.html http://www.dfrc.nasa.gov/gallery/photo/X-43A/HTML/EC99-45265-22.html http://www.dfrc.nasa.gov/gallery/photo/X-43A/HTML/EC99-45265-23.html
It performed as designed, with the vehicle accelerating while in a climb.
As with any problem, one must be sure of the design requirements and constraints, as these will define the bounds of the possible solution space. Surely, sodium is outside the solution space of the problem posed by the OP, no?
________________________________________________________ Ed Ruf Lifetime AMA# 344007 ( snipped-for-privacy@EdwardG.Ruf.com) http://EdwardGRuf.com
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replying to Ed Ruf, Johnathan Standridge wrote: Everyone is debating how long any metal will stay cold, but I wonder, will copper leach out into the drink, and if so, is that really safe? Just to be on the safe side, I'd say iron or someone said porcelain. Personally, I'd love to see someone make some neat porcelain drink coolers.
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Dear AlWahrabi:

longest...John
Using google advanced and searching for all words: density metal table exact phrase: specific heat URL:http://metals.about.com/gi/dynamic/offsite.htm?site=http://www.apo.nmsu.edu/Telescopes/SDSS/eng.papers/19950926%255FConversionFactors/19950926%255FMProperties.html
They call specific heat "heat capacity", for some reason. As John Manders said, you would look for some mass times the specific heat, or on a unit volume basis, density times specific heat.
You may also want to consider "metering" the cold out slowly (thermal conductivity), so that it feels cool longer, but doesn't freeze you out for a short period of time.
David A. Smith
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you won't be impressed with the results of your experiment--it's the phase change from solid to liquid that makes ice a good source of cooling.
to put things in perspective, assume that you cool 1 pound chunks of copper and ice to 0F.
Question: how much energy do you have to put into each of them to heat up to 60F??
Answer: Copper: 5.64 BTU; Ice: 188.1 BTU
The ice absorbs about 33 times as much energy as the copper.
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you won't be impressed with the results of your experiment--it's the phase change from solid to liquid that makes ice a good source of cooling. MBush>>
Yes, I understand that frozen water (ice) would be best, cause it requires calories of heat to change state from ice to water. But, it is sloppy and always leaks (in the back of my truck, each Summer).
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Dear AlWahrabi:

phase
MBush>>
requires
If you have good ventillation, you could then use solid carbon dioxide, which sublimes from solid direct to gas...
David A. Smith
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Huh?! I've never, ever, had a plastic pop bottle (either 600 mL or 2 L) leak on me when refilled with water. Bags of ice always leak--there's nothing you can do about that, but put water in pop bottles and freeze them the night before your trip (just as you would do with your metal block), and you'll have something far more effective, taking up less volume, and weighing less, while working faaaaar better. Plus when they melt, you've got a source of fresh water--often useful when you venture into the boondocks!
-Paul
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replying to AlWahrabi, lucid wrote:

may want to look into peltier chips?
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High specific heats sodium, then aluminum. But better yet is a material that gets its coolth from a change of state: you'd never guess: a plolythene bottle filled with water and frozen.
Brian W
On 20 May 2004 05:50:44 GMT, snipped-for-privacy@wmconnect.com (AlWahrabi) wrote:

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On Fri, 21 May 2004 01:11:54 GMT, in sci.engr.mech Brian Whatcott

Really, who would have thought?.... Wait, maybe there was a reason behind the design and name of the original invention called an icebox, you think? :-)
Seriously, one of the first hurricane preps I take is to fill my freezers to the brim with any kind of plastic jug/bottle filled with water. This came in quite handy in the aftermath of Isabel were we were without power for almost two weeks and had water supply systems issues in the days immediately following the storm. Keeps the fridge/freezer contents cold longer and you have drinking water after the ice melts. Which at the time were not such trivial matters. ________________________________________________________ Ed Ruf Lifetime AMA# 344007 ( snipped-for-privacy@EdwardG.Ruf.com) http://EdwardGRuf.com
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