$(3)$ An egg can be modelled as a sphere of diameter $40$ mm $.$ If the egg initially at $20C$ is placed in a

saucepan of boiling water for $4$ minutes, it attains the consumer's taste. For how long should a

similar egg for the same consumer be boiled when taken from a refrigerator at $5C?$

The egg properties are $k=2\frac{W}{m}-K,=1200k\frac{g}{m^3},C=2k\frac{J}{k}g-K$ and heat transfer coefficient

for the shell and shell water interface may be taken as $200\frac{W}{m^2}-K.$

Compare the centre temperature attained with that computed by treating the egg as a lumped

heat capacity system. Comment on your result.

$[$Ans: $4$min$20sec.,96C]$