Question

A physicist uses a cylindrical metal can 0.270 mm high and 0.090 mm in diameter to store liquid helium at 4.22 KK; at that temperature the heat of vaporization of helium is 2.09×104J/kg2.09×104J/kg. Completely surrounding the metal can are walls maintained at the temperature of liquid nitrogen, 77.3 KK, with vacuum between the can and the surrounding walls.

How much helium is lost per hour? The emissivity of the metal can is 0.200. The only heat transfer between the metal can and the surrounding walls is by radiation.

Answer 1

Given that cylinder consists of liquid helium at 4.22K and surronding temperature are maintained by liquid nitrogen

The heat emitided due to radiation is used for helium lost.