Hey Everybody,
I was just curious to find out what materials would be the best insulators, for a device that is supposed to keep a cold pop can(refrigerator temp.) cold from breakfast to lunch. I would really appreciate if I could get some ideas on materials. Thanks alot!
-Sylvia
Ice.
Ice, sure, but Sylvia wanted an insulating material.
Vacuum is a good insulator, used in form of a vacuum flask (Thermos). Heat is then transferred only by radiation; A further improvement is to cover the facing surfaces with a clean metal (silver) that radiates and absorbs very little heat (infrared radiation). Even better, you may stack many plies of metalized plastic film, so that heat has to be emitted and absorbed many times on its way: This is called a superinsulator and is used on satellites.
The second best insulators are gases. Preferably with monoatomic molecules that store less heat, and heavy molecules that transport this heat slowly. This explains why light bulbs filled with heavier krypton are more efficient than with cheaper argon: less heat is wasted through the gas, hence more is radiated in light.
Third are solids consisting mainly of gases: aerogels, and much more common, polyurethane foam or polystyrene foam. The latter is used to insulate homes or hold liquid nitrogen for weeks. They can be (and often are) better than gases, as the foam prevents the trapped gas from moving and carrying heat with them. It may well be your solution, apart from the Thermos bottle. Use special glue for polystyrene foam.
Vacuum is a good insulator, used in form of a vacuum flask (Thermos). Heat is then transferred only by radiation; A further improvement is to cover the facing surfaces with a clean metal (silver) that radiates and absorbs very little heat (infrared radiation). Even better, you may stack many plies of metalized plastic film, so that heat has to be emitted and absorbed many times on its way: This is called a superinsulator and is used on satellites.
The second best insulators are gases. Preferably with monoatomic molecules that store less heat, and heavy molecules that transport this heat slowly. This explains why light bulbs filled with heavier krypton are more efficient than with cheaper argon: less heat is wasted through the gas, hence more is radiated in light.
Third are solids consisting mainly of gases: aerogels, and much more common, polyurethane foam or polystyrene foam. The latter is used to insulate homes or hold liquid nitrogen for weeks. They can be (and often are) better than gases, as the foam prevents the trapped gas from moving and carrying heat with them. It may well be your solution, apart from the Thermos bottle. Use special glue for polystyrene foam.
Hello Sylvia
There are many good insulation materials available, from foams, to fiberglass.
The primary considerations in addition to insulating properties, should be durability versus cost amortization over the life of the product. Styrofoam is a good cheap product as evidenced by its use in making insulating cups. Fiberglass is also an excellent material easily available and easy to use. On the expensive side is material such as that used for heat shielding on the Space Shuttle. A visit to the local builders supply should provide plenty of conservative options.
On the very cheap side... wadding newspaper and stuffing it around the items you wish to maintain at a constant temperature works very well. As a child we used this method to keep food hot or tea and water iced for up to two days. The containers for the crushed newspaper were either cardboard boxes or large paper grocery bags.
Sawdust also makes an excellent, and cheap, insulator. Before commercial refrigeration was available, ice houses used sawdust as insulation for keeping ice all season. Rail cars for transporting ice and cold goods, and even early commercially available ice boxes for home use, used sawdust as the insulating material.
Cheers
Jack
There are many good insulation materials available, from foams, to fiberglass.
The primary considerations in addition to insulating properties, should be durability versus cost amortization over the life of the product. Styrofoam is a good cheap product as evidenced by its use in making insulating cups. Fiberglass is also an excellent material easily available and easy to use. On the expensive side is material such as that used for heat shielding on the Space Shuttle. A visit to the local builders supply should provide plenty of conservative options.
On the very cheap side... wadding newspaper and stuffing it around the items you wish to maintain at a constant temperature works very well. As a child we used this method to keep food hot or tea and water iced for up to two days. The containers for the crushed newspaper were either cardboard boxes or large paper grocery bags.
Sawdust also makes an excellent, and cheap, insulator. Before commercial refrigeration was available, ice houses used sawdust as insulation for keeping ice all season. Rail cars for transporting ice and cold goods, and even early commercially available ice boxes for home use, used sawdust as the insulating material.
Cheers
Jack
The best insulator known is a vacuum. Moderen insulating containers have an inner and outer container with psudo vacuum in between. They pull out much of the air. There is a minimal heat transfer between this vacuum and then the major source of heat leaking, or coldness warming up is from the neck of the bottle. As this neck is typically a plastic or other insulating material, it is slower to transfer heat.
If you wanted the ultimate thermas, you would want to minimize the size of the neck versus the size of the inside of the container. You would also want to make the insulating material at the neck a better insulating material.
For even better of a thermas, you could go to the extreme of taking your thermas into space on a rocket. From there, evacuate the air in a complete vacuum of space and then welding the container shut in space. I am not sure if the costs involved would provide a significantly better thermas than the air evacuations that are already done though.
With any work done at making a better vacuum, you would probably get better insulating effect by focusing on the neck of the bottle and using better insulating materials here.
If you wanted the ultimate thermas, you would want to minimize the size of the neck versus the size of the inside of the container. You would also want to make the insulating material at the neck a better insulating material.
For even better of a thermas, you could go to the extreme of taking your thermas into space on a rocket. From there, evacuate the air in a complete vacuum of space and then welding the container shut in space. I am not sure if the costs involved would provide a significantly better thermas than the air evacuations that are already done though.
With any work done at making a better vacuum, you would probably get better insulating effect by focusing on the neck of the bottle and using better insulating materials here.
Mount a battery operated vacuum pump to the lid of a small igloo cooler. Add a rubber weather strip to the lid to make it air tight. Don't try this with the larger coolers, they'll simply implode.
You could experiment with using or not using ice. The only transfer should be from surface contact between the soda can and the cooler.
Also don't put eggs in there...very messy.
You could experiment with using or not using ice. The only transfer should be from surface contact between the soda can and the cooler.
Also don't put eggs in there...very messy.
Just for fun then, as we have already diverged from practical quick solutions:
Mechanical stability is the ultimate limit to heat insulation, as both depend ultimately on material sections. But arriving to this limit needs an optimized form.
Holding an inner bottle by its neck is far from this optimum (however, it permits introducing objects in the bottle, thus qualifying it as a practical solution...). A closed inner bottle hold by thin rods is better.
In fact, rods should be made as thin as tensile strength allows (and stiffness if needed). Then, as these rods become very thin, they won't accept any compression force. The solution is to replace them with strings, at least two for each of the 3 dimensions, so that you can pre-stress them. Some materials like aramide or polyethylene combine strength and stiffness with good insulation.
Of course, fill everything with superinsulator, and keep contacts (for power or data transfer or whatever) to a minimum, preferably through fiber optics.
Mechanical stability is the ultimate limit to heat insulation, as both depend ultimately on material sections. But arriving to this limit needs an optimized form.
Holding an inner bottle by its neck is far from this optimum (however, it permits introducing objects in the bottle, thus qualifying it as a practical solution...). A closed inner bottle hold by thin rods is better.
In fact, rods should be made as thin as tensile strength allows (and stiffness if needed). Then, as these rods become very thin, they won't accept any compression force. The solution is to replace them with strings, at least two for each of the 3 dimensions, so that you can pre-stress them. Some materials like aramide or polyethylene combine strength and stiffness with good insulation.
Of course, fill everything with superinsulator, and keep contacts (for power or data transfer or whatever) to a minimum, preferably through fiber optics.