The insulating space among the walls of a cryogenic storage vessel used to store unfertilized embryos is 0.2cm in width and contains residual H2(g) at 1mbar pressure. The outside of the vessel is at 300K and the inside containing N2 (l) refrigerant, is at 77K. The area of the wall is 10000cm^2.
1. Calculate the rate of loss of N2(l) in g s^-1 due to heat conduction, assuming that the average temperature in the insulating space is 188.15K; the enthalpy of vaporization of N2(l) is5.586kJ mol^-1. The cross sectional area of H2 is 0.27*10^-18m^2
2. What will be the new rate of N2 (l) evaporation in g s^-1? The cross sectional area of CH4 is 0.46*10^-18m^2. An enterprising engineer decides to reduce the evaporation rate by replacing the residual H2(g) by CH4(g), using a natural gas feed available.