For example, if i were mailing a box of chocolates and lined the inside of the box with foil, then wrapped the chocolate in bubble wrap and placed it inside the foil lined box, would the box heat up slower than without foil?
My theory is that at first, the box (at room temperature), when left outside in hot air, will heat up, but the foil will slow down the chocolates from heating up as quickly because of the foil and bubble wrap/distance between the foil and chocolate. Sooner or later, the air inside the box will eventually heat up quite a bit, but the point being that it would take longer to heat up than if there were no foil.
Is that true?
Best Answer
Foil is good at reducing heating due to thermal radiation because it reflects a large part of the radiation. It is absolutely useless at reducing heating due to convection because it has a high thermal conductivity.
So what happens in your case depends on whether the dominant mechanism of heat flow is radiation or convection. Since the foil is inside a cardboard box I would guess the dominant mechanism for heat transfer inside the box is convection, and therefore that the foil will have very little effect.