Heat transfer

A long 2mm diameter rod of steel has a uniform temperature of 650C. The rod is then suddenly immersed in a large container of 25C water. The hot rod causes the water to immediately boil, giving rise to a convective heat transfer coefficient of 5000w/m2K. The boiling stops when the temperature of the rod drops to 100C at which time the convective heat transfer coefficient drops to 750W/m2K. Steel properties: Density =7840kg/m3 Cp specific heat =460J/kgK k thermal conductivity =50W/mK i. Write the governing equation for the transfer from the rod to the water. ii. Find the time duration during which boiling occurs. (Check Biot number) iii. Find the total time required for the rod to reach the final temperature of 40C. (Check Biot number)