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I've been theorizing and doing some experimenting with an uninsulated air mattress. They are really cheap, they are very lightweight and very comfortable to sleep on. The only downside people say is they insulate for crap. I think if used properly these can actually insulate pretty good.
In the added image i sketched on the left side how a air mattress is normally used. The top is the cross section and on the bottom it's the length section of one tube. The green is the sleeping bag. Red is warm air, yellow is air that is cooling down, blue is cold air
Your body heats up the air in the air mattress from the top down. Under normal circumstances the warm air will stay on top, and the cold air stays against the ground, and there will be no convection. But on the sides of the mattress, where it is in contact with the cold outside air (purple), it cools down and gets pushed away by the hot air next to it, which cools down in its turn so it creates a convection cell in the tube. The cold air passes the ground and gets pushed up and this will cool down the adjacent tube in the same way but to a lesser extent. Another factor helping the convection is better illustrated in the length section. The heaviest parts of our body well press the mattress down, while also heating it up the most, this will actually warm up air at the lowest body contact point that will have the opportunity to raise, and keep the convection going. Another factor that gets the convection going is sleep movement and breathing.
Now i explained how the convection cells work, my next post will contain some methods to reduce this.
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