Cryogenic liquids (liquid N2, He, etc) are typically stored inDewar flasks (fancy thermos bottles) that consist of mirrored glasswalls (to reduce radiative heating) separated by vacuum (a cylinderwithin a cylinder). How long would a liter sample of liquid argonlast in a flat bottomed cylindrical Dewar with an inner radius of5cm and height of 20cm and an outer radius of 10cm and height of 25cm assuming that the only energy transfer that occurs is radiativebetween the walls of the Dewar (the top surface does not receiveany radiation). The emissivity of silvered glass is 0.02 over allwavelengths, the outer surface of the Dewar is at 300K, thetemperature of liquid Argon is 87 K, the density of liquid argon is1.40 g cm3 , and the latent heat of vaporization is 1200 J/g. , Thelatent heat of vaporization is a measure of how much “extra” energyis required to vaporize a substance at its boiling point (theboiling point of argon is 87K). (Assume that all of the energyimpinging on the inner cylinder is used to vaporize the Argon).
