I need insulators for a thermos that is able to keep water Warmer than 25 c

[spencer87]

I need insulators for a thermos that is able to keep water Warmer than 25 c for three hours in a fridge. Any ideas?

[pwagen]

Are you making it yourself? What's the starting temperature of the water?

 

The best insulator is vacuum. So if you're able to make a container with double walls with vacuum in between, that would probably be the best you can get. Second best is probably some kind of gas, but regular air actually works all right. Three hours is a long time though, so not sure how advanced a thermos would be required to keep the water warm for that long.

[spencer87]

Pwagen yes I have to make it myself, and it is in a fridge for three hours. The starting temperature is 80 degrees Celsius and after three hours it has to be above 25 celcius

[pwagen]

Well, I have a somewhat decent idea, which I tried to draw. And failed.

 

But the main principle is this: Get two containers, one smaller than the other. One has to fit inside the other without the walls touching. Also, the lid of the inner container should fit without touching the lid of the bigger one.

 

Now, the idea is for there to be as little contact as possible between the two containers. So what you could do, is make small "bars" which will hold the inner container in place, while providing very little contact to the outside. I'm not quite sure how to explain this in a good way (and if it's homework or a project, I probably shouldn't), but have a look at this masterpiece and see if you understand what I mean.

 

 

There are probably lots of other ways as well, but this is the first that came to mind.

[StringJunky]

Well, I have a somewhat decent idea, which I tried to draw. And failed.

 

But the main principle is this: Get two containers, one smaller than the other. One has to fit inside the other without the walls touching. Also, the lid of the inner container should fit without touching the lid of the bigger one.

 

Now, the idea is for there to be as little contact as possible between the two containers. So what you could do, is make small "bars" which will hold the inner container in place, while providing very little contact to the outside. I'm not quite sure how to explain this in a good way (and if it's homework or a project, I probably shouldn't), but have a look at this masterpiece and see if you understand what I mean.

 

 

There are probably lots of other ways as well, but this is the first that came to mind.

To enhance this idea you could get some mirror film or sheet (Mylar), cut it to size and bend it cylindrically with the reflective side facing inwards and line inside both tins with it...base and lids as well. You could fill the space between the two tins with packing foam nuggets or small poly balls so that the inner tin is sitting on the nuggets and is packed with them on top before putting the outer lid on...pack some down the sides as well.

Edited April 10, 2013 by StringJunky

[pwagen]

You could fill the space between the two tins with packing foam nuggets or small poly balls so that the inner tin is sitting on the nuggets and is packed with them on top before putting the outer lid on...pack some down the sides as well.

You know, that would probably be a lot easier than to make whatever I had in mind. Occam's razor to the rescue!

[StringJunky]

You know, that would probably be a lot easier than to make whatever I had in mind. Occam's razor to the rescue!

 

I'm just building on a good idea...yours.

[spencer87]

Thanks guys! 😃😜😛

[pwagen]

 

I'm just building on a good idea...yours.

 

Thanks guys! 😃😜😛

Let us know how it works out!

[StringJunky]

Spencer

 

If you can, think about using thick strong plastic containers as they are less thermally conductive..the rate of heat loss should be less with plastic

Edited April 10, 2013 by StringJunky

[spencer87]

Thanks StringJunky

[michel123456]

It's the 3rd time I see a similar question on this Forum.

I guess there must be a teacher somewhere putting the same exercise again and again.

[StringJunky]

It's the 3rd time I see a similar question on this Forum.

I guess there must be a teacher somewhere putting the same exercise again and again.

I think it's probably a universal first year physics question on the same theme getting students to understand and control conduction, convection and radiation pathways.

[michel123456]

I think it's probably a universal first year physics question on the same theme getting students to understand and control conduction, convection and radiation pathways.

Maybe the Forum could provide a database for that kind of questions. A FAQ section.

 

I need insulators for a thermos that is able to keep water Warmer than 25 c for three hours in a fridge. Any ideas?

First thing to do: unplug the fridge.

 

Second thing to do: don't put a thermos bottle in the fridge, put a hundred.

[Bill Angel]

I need insulators for a thermos that is able to keep water Warmer than 25 c for three hours in a fridge. Any ideas?

Another approach would be to purchase or mix your own chemical heat packs to keep the water warm inside the refrigerator.

Heat packs contain 40 g of calcium chloride or magnesium sulfate per 100 ml of water. The chemical is kept separated from the water until heat is needed. The temperature typically will rise to about 90F (32 C) and last for 15 to 30 minutes .

One way to utilize this approach would be to place a plastic bottle whose contents are to be kept warm inside of an insulating container, as shown in the image. The container could then be filled up with the heat packs, the top put on, and the container placed in the refrigerator. The bottle in the image holds 450 ml of liquid.

It would be an interesting exercise to measure what the temperature of the water was after three hours in the refrigerator no heat packs in the container, with just one heat pack, two heat packs, etc.

Edited April 12, 2013 by Bill Angel