The inner sphere of a Dewar flask is of 300 mm diameter and outer sphere is of 360 mm diameter. Both spheres are plated for which e = 0.5. The space between them is evacuated. Determine the rate at...

The inner sphere of a Dewar flask is of 300 mm diameter and outer sphere is of 360 mm diameter. Both spheres are plated for which e = 0.5. The space between them is evacuated. Determine the rate at which liquid oxygen would evaporate at –183°C when the outer sphere temperature is 20°C. The latent heat of vaporisation of liquid oxygen is 14.2 kJ/kg.