Q. 11.17 A ‘thermacole’ icebox is a cheap and an efficient method for storing small quantities of cooked food in summer in particular. A cubical icebox of side 30 cm has a thickness of If of ice is put in the box, estimate the amount of ice remaining after 6 h. The outside temperature is and co-efficient of thermal conductivity of thermacole is
Side of the box s = 30 cm
Area available for conduction A
A = 6s2
A=6(30)2
A=5400 cm2 = 0.54 m2
Temperature difference = 45 oC
Co-efficient of thermal conductivity of thermacole is k = 0.01 J s-1 m-1 K-1
Width of the box is d = 5 cm
Heat absorbed by the box in 6 hours is
Heat of fusion of water is
Amount of ice which has melted is m'
Amount of ice left after 6 hours = 4 - 0.313 = 3.687 kg