Liquified hydrogen is kept in a dewar flask that is stored in another dewar's flask where the hydrogen flask is surronded by liquified Nitrogen ........why isn't it just kept in one flask !! is there any heat that can reach the hydrogen flask through the metal or pyrex of the flask???

Question

anonymous · Answer

Even a dewar flask will conduct some heat by radiation. All matter radiates thermal radiation - according to its temperature. It was Max Planck who first calculated the correct frequency distribution for black body radiation incorporating the fact that light is quantised as photons.

By surrounding the liquid hydrogen (which has a boiling point of 33K) with liquid nitrogen (boiling point 77K) the amount of heat transfer is dramatically reduced.