The Big Freeze project?

Question

I am supposed to create a container that will keep an ice cube solid for as long as possible and i want to get the best score possible and i need design ideas

rules:
1. Container must be smaller than 25 centimeters on any side
2. Container must be created specifically for this event. It cannot be a container made to keep objects cool or hot. Ice coolers, styrofoam cups, thermos, etc. are not allowed in their original form.
3. Container must be able to hold any water from the melting ice-cube.
4. No electrical motors or similar devices allowed.
5. Container must be easy to load and check.
6. No part of the container can be frozen prior to the event. This includes water, other ice cubes, dry ice, or other chemical substances.

2nd Question: do you think that #6 includes liquid nitrogen?

Answer 1

Of interest --

I've just got ONE question --- if your ice cube is all nicely packed into an opaque container, how the devil is anyone going to KNOW whether it's melted or not? Opening a container to find out will ruin the entire experiment as warm goes in and cold goes out. Knowing what state it is in will effect its state! Think of it as Schroedinger's ice cube. (chuckle ... ask the physics teacher that assigned this project.)

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OK -- one off-the-wall suggestion to start:

#4 speaks only to motors. It says nothing about solar panels or batteries and Peletier devices. Neither of these are even remotely "similar" to a motor. Peletier devices are the thin plates used in little 12VDC mini-fridges to cool things "on the road". These plates transfer heat from one side (which cools as a result) to the other. You just need to figure out how to best get rid of the heat. Given your constraints, that might not be easy since your thermal losses in convection might overcome your cooling ability. Normally they use fans for this (which break rule #4 quite handily, I'm afraid).

The above might make an interesting addition to your container.

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Now for the serious stuff -- you'll need some killer insulation no matter what you're building...

For maximum "R" value in the thinnest possible material, you might want to look at polyisocyanurate roofing insulation panels. Much better than styrofoam or other commonly used insulating materials. The stuff is amazing, and is made by a number of manufacturers. Look for Hunter, Dyplast, Flintboard, Carlisle and others. Check with local building supply stores and be specific about the material. As you're limited to 25cm on a side, this isn't going to cost you much at all. Stack up as much of it as you can.

As for #6, "liquid nitrogen" is as much a chemical substance as "dry ice" (frozen CO2), so nope, no liquid nitrogen.

Answer 2

Rule 2.
Sounds like you can use styrofoam panels from HomeDepot as these panels are not containers but merely raw material. For that matter you can also use canned foam to fill up a 25cm cube box.

3. Canned foam also make a great adhesive so you can build a styrofoam box and fill it with foam. the foam can also be used to join panels

4. No electrical motors or similar devices. I was also thinking of a peliter junction but this may fall under similar devices. I have also used PJ's at work and found that they have heavy current demands. Also Pj's generate a differential temperature drop of 10to 20 degrees below ambient and they need a big heat sink.

6. Nitrogen - good idea The key is that no part can be frozen Prior to the event. It doesn't say that a chemicaly induced freezing could not be started at the beginning of the event. Nor does it specifically prohibit chilling he box to just above freezing. If any thing keep the box out of direct sunlight before the test and as cool as possible.

You could start a slow bleed from a can of dust off to chill the unit. If you mad a copper evaporator out of a coil of tubing and foamed it into place inside the box you would have a small refrigeration unit powered by an inverted can of Dust-Off.


You can use aluminum foil as a reflectice heat barrier on the out side to keep the box from absorbing radiant heat.

Also Back to rule 6... It doesn't prohibit using a hunk of cooled metal as a thermal mass. It can be cooled to below 32F/0C ... Notice I said cooled and not frozen . To freeze something implies a phase change and obviously a very cool piece of steel isn't going to be going through a phase change at room temps....

Answer 3

Factory made insulating containers are banned, but that doesn't mean you can't use the materials they are made of. First you'll need an open-topped box or beaker to put your ice cube in. I suggest the use of 1/2" styrofoam sheet. You can laminate succeedingly larger boxes around it , and for easy access an inverted pyramid for the lid, with sides rising to match the pyramid levels.

Liquid nitrogen is in the same category as dry ice, even if it is a liquid.

Answer 4

No, if you never saved it before it crashed (and, this is likely what made it freeze), there's no way to get it back now. Always give new files a name and save them, once, before drawing anything. Then, Auto-Save (if configured correctly), will take over, and save your file every "X" minutes.