Ice blocks

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Re: Ice blocks

Postby VijayGupta » Mon Aug 04, 2014 7:21 am

Seems to me the limiting factor is the temp of your freezer. If it goes to 0F, then the melting point may not matter much. Bot fresh water and salt water ice is going to be 0F. Only difference might be if there is more "thermal mass" with salt water than fresh water. Quick search doesn't yield a definitive answer.

Fyddler wrote:Salt will make the ice freeze and melt at a lower temp, but not necessarily make the ice be a lower temp. Once water (or salt water) freezes it continues to get colder, so pure water ice melts at 32deg, the water around the ice will be 32deg, the ice may be quite colder. So the salt water will be lower than 32(depending on the amount of salt). I'd have to think about the benefits. Couldn't hurt.
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Re: Ice blocks

Postby Kharn » Wed Aug 06, 2014 7:33 am

I use milk jugs, or most 12-20oz bottled water will freeze without breaking the container.
VijayGupta wrote:Seems to me the limiting factor is the temp of your freezer. If it goes to 0F, then the melting point may not matter much. Bot fresh water and salt water ice is going to be 0F. Only difference might be if there is more "thermal mass" with salt water than fresh water. Quick search doesn't yield a definitive answer.

Fyddler wrote:Salt will make the ice freeze and melt at a lower temp, but not necessarily make the ice be a lower temp. Once water (or salt water) freezes it continues to get colder, so pure water ice melts at 32deg, the water around the ice will be 32deg, the ice may be quite colder. So the salt water will be lower than 32(depending on the amount of salt). I'd have to think about the benefits. Couldn't hurt.

The salt water will freeze and melt at a lower temperature than tap water, which would keep your cooler at a lower temperature than tap water alone. You can get the freezing point down to 0F by adding 35% salt to water by mass, but your freezer might not get cold enough to make use of that.
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Re: Ice blocks

Postby jstrubberg » Wed Aug 06, 2014 3:58 pm

Fyddler wrote:Salt will make the ice freeze and melt at a lower temp, but not necessarily make the ice be a lower temp. Once water (or salt water) freezes it continues to get colder, so pure water ice melts at 32deg, the water around the ice will be 32deg, the ice may be quite colder. So the salt water will be lower than 32(depending on the amount of salt). I'd have to think about the benefits. Couldn't hurt.



I don't think there is a benefit, actually. Yes, the water will freeze at a lower temp, but it won't stay at a lower temp any longer than freshwater ice.

Let's say that you add enough salt that the water now freezes at 15 degrees instead of 32 degrees. As soon as that ice returns to 15 degrees, it's going to melt again. The melted ice will continue to warm at the same rate as ice that has no (added) salt.

The only difference I can see is that your melt water would be colder for a short period of time than non-salted melt water. Of course, the non-salted ice wouldn't have melted yet, either.
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Re: Ice blocks

Postby Kharn » Wed Aug 06, 2014 4:12 pm

If you fill a cooler with a block of ice and allow it to melt, the contents of the cooler will remain at the freezing point of the ice used until the time at which all of the ice has melted, only after that point will the temperature inside the cooler rise above the freezing point temperature.

The salted ice will hold the cooler at a lower temperature than regular ice. But is it worth the weight penalty, the effort to make it, the salty contamination if any packages leak, and the inability to use the ice in drinks? :thinking:
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Re: Ice blocks

Postby Prototear » Thu Aug 07, 2014 1:00 am

We often use the single-serving aseptic juice boxes as ice and thermal mass http://en.wikipedia.org/wiki/Thermal_mass
A full cooler stays cold longer than one only half full.

The boxes take the expansion from freezing very well can be packed around nooks and crannies in the cooler or arranged into a bigger block. I haven't had one break open yet - the worst problem has been having the little straws break off before we get to use them but we can deal with that. This way we have juice for breakfast or snacks (pull it out of the cooler ahead of time if early in the trip) and no additional space is taken by ice or blue ice. There are probably 20-25 in the garage freezer now available for the next trip. They are even more useful backpacking where space and weight is a premium to keep some foods cold in an insulated lunch bag for a day or two.

If the juice boxes end up sitting in water after several days the outer coated paper layer starts to fade and eventually weaken but the strength of the boxes comes from internal layers and it still doesn't leak.

Juice bags also work the same but these seem to loose their little straws more easily although they don't have the coated paper to fade or disintegrate.

The disadvantage of the boxes or bags is the excess packaging that has to be packed out and gets discarded (or recycled in a few areas).
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Re: Ice blocks

Postby lawsonpix » Thu Aug 14, 2014 8:19 am

Virtually any commercially available plastic liquid container will be designed to be frozen. Manufacturers know that they have to ship product in all climates and freezing is likely to happen during that delivery process to at least some of their products. (think delivering bottled water in Canada in January)
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Juicy Juice for example has a flat front and back which will expand when freezing. And note the decorative ridges mid way up for even more expansion.

I usually freeze a bunch of ~16 oz (1 liter) bottles. They fit nice in all the corners and between my food.
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And of course I have plenty of cold drinking water as they thaw.
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Re: Ice blocks

Postby lawsonpix » Thu Aug 14, 2014 8:36 am

razorback wrote:This is what I use. very slim. holds 1 1/4 gallons or about 10 lbs.
I lay one on the bottom of my small chest and in my larger chest I use two of them standing up.
works well for me
http://www.walmart.com/ip/Arrow-H2O-1.2 ... e/15915152
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Wow! what a great idea for running water in my teardrop kitchen! And look :FNP it's only $13 on Amazon!

http://www.amazon.com/Gallon-Slimline-Beverage-Container-Clear/dp/B000QRAMNC/ref=sr_sp-atf_title_1_1?ie=UTF8&qid=1408023033&sr=8-1&keywords=Slimline+Beverage+Dispenser

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Re: Ice blocks

Postby jstrubberg » Tue Aug 19, 2014 1:12 pm

Kharn wrote:If you fill a cooler with a block of ice and allow it to melt, the contents of the cooler will remain at the freezing point of the ice used until the time at which all of the ice has melted, only after that point will the temperature inside the cooler rise above the freezing point temperature.

The salted ice will hold the cooler at a lower temperature than regular ice. But is it worth the weight penalty, the effort to make it, the salty contamination if any packages leak, and the inability to use the ice in drinks? :thinking:



I still don't think so. The question here isn't how cold your ice is, but how long it takes that ice to warm up. As far as I know, salting the water will not change this equation at all. The ice will freeze at a lower temperature, but it will also revert to water at a lower temp.
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Re: Ice blocks

Postby cleburnescv1937 » Sun Aug 24, 2014 10:52 am

I use a sizes of bottles from 1 gallon down to Power Aid or individual 16 oz bottles.
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Ice blocks

Postby abqlloyd » Mon Sep 08, 2014 11:25 pm

Sam's Club sells stainless food service pans that make great block ice. They are used for steam tables, and they never crack.

If you want crystal clear ice, place water in the pan, top with a piece of polycarbonate with a rubber gasket and draw a vacuum. This removes the air bubbles from the water. This is how they make clear block ice for carving.
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Re: Ice blocks

Postby kd8cgo » Tue Sep 09, 2014 12:27 am

Salt does work to depress the melting temperature of water, but does not necessarily give you a longer "cold cooler" time. The reason that it works and also the reason ice is a great way to keep stored foods cold is because water is undergoing a phase change, from a solid to a liquid. During the phase change process, it takes more energy to warm up the block. The block will go from 0F to 32 F at a faster rate than it will go from 32F to 33F during the phase change.

Salt water pushes that phase change "energy bonus" to a lower temperature. It is most useful when you have food that you want to keep colder than freezing, and that's also why it is used to make homemade ice cream, as it keeps the melt point at a lower temperature. Also salt water does not have a constant X degree temperature (like 32 F for normal water is constant) during phase change, it varies, which gets rid of some of its colder temperature bonus for storing the cold for long periods. And unfortunately, the colder the temperature inside the cooler, the more differential temperature there is. A 32 degree cooler on a 70 degree day has a 38 degree differential. A 4 degree cooler inside has a 66 degree differential, and gains heat through the cooler walls at a much faster rate because of that. Which brings me to the next point!

A block of ice is preferred for coolers why? If you have a 10lb. block and 10lbs. of cubes, what's the difference? Surface area! The more surface that is in contact with the air in the cooler, the faster the ice can gain heat by convection between the two materials. Cube ice is much more likely to get your cooler colder, faster, than a big block due to this. But it will also pass through the phase change faster. Often times you will find that the big block will keep your cooler much closer to a refrigerator temperature than a freezer temp, somewhere around 40 degrees. This also slows down the transfer of heat across the cooler's insulation to the outside air, because the differential temperature is lower! If your cooler is too warm but the block is not melting very fast, just make several, smaller blocks of ice and your cooler temp will be colder next time, and your ice will melt a bit faster.

Which block will last longer? Salt or no salt? Well, you have a complex problem, that depends on the size and number of your ice blocks, and the R-value of your cooler as well. If it is exposed to radiant heating from the sun, most coolers do not have a foil backed insulation to protect them from that, but you can make your own! If you like to experiment, you can test your cooler and ice blocks in the back yard with a thermometer and a timer, or just watch the clock. If you are geeky, you can set up a data logger. So much fun! :lol:

Here is a little paper I searched Google and found, it discussed the basic differences between specific heat and latent heat in phase change materials, like ice!

Want to make a radiant insulated cooler cozy? You might try this stuff!

Also, are you going to climb the Himalayas and need to keep your beer cold? Well, that should not be a problem in the Himalayas - but for sake of argument, at a higher elevation, the freezing point of water is just a little bit higher, due to the lower air pressure. This is different than most phase change materials because water expands when it freezes which is unusual. But anyway, the higher melting point means your differential temperature might be a bit better, and you'll get a few more minutes of cold beer! If you want to super geek out, you need to know about the specific heat, the latent heat, and the change in volume of a substance during its phase change! :R

Even more fun! What is the best shape to have the most interior volume but the least surface area to slow down convection heat transfer? It's a sphere! So the next time you are doing your cooler experiments, freeze some water in a latex balloon and see what the difference is! :?
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Re: Ice blocks

Postby Tripmaker » Tue Sep 09, 2014 6:12 pm

That is a wonderful, thought out, and knowledgeable dissertation on ice. Unfortunately it is much too complex for me of a simple mind to understand in its entirety. :thinking: I think I will just use ice to keep my cooler cold and live with the results. Whatever they may be. :)
Jim



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Re: Ice blocks

Postby kd8cgo » Tue Sep 09, 2014 7:57 pm

Ah yes, the eternal question, and answer: at what point are we satisfied with the answer we have found? We can ask "why" or "how" forever!

Feynman explains it well, with magnets.

All for a block of ice, a seemingly simple question with a limitless procession of answers, which leads to more questions, at least until enough is enough! :R
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Re: Ice blocks

Postby Tripmaker » Wed Sep 10, 2014 7:52 am

My observations do confirm what you say. Blocks last longer than cubes. Simple logic tells me that a container, with dimensions equal to those of a block of ice, filled with cubes, half moons, or cylinders of ice, will contain less ice than the solid block due to the voids between the cubes. The logical conclusion is that more ice will last longer than less ice. Q.E.D.
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Re: Ice blocks

Postby lawsonpix » Wed Sep 10, 2014 12:46 pm

Just for fun, kd8cgo. From an engineer to engineer: My attempt at a simpler translation:

Salt water freezes at a lower temperature than fresh water. However, it melts quicker because it is colder. Therefore, it is most useful when you have food that you want to keep colder than freezing.

A block of ice is will last longer in a cooler, but your cooler will cool back down slower after you open the lid.

If your cooler isn’t cold enough with a block of ice, then use a few smaller blocks for quicker cooling times. However, the smaller ice blocks will melt faster.

If you want your ice to last longer, no matter what kind of ice you use, buy a “5 day” cooler.

:thinking:
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