cylindrical bed packed with cast iron $($density $7200$ kg$/$m$3$

$)$ has been used

for storing heat in the temperature range of $523-673$K$.$ Calculate required mass of cast

iron and stored thermal energy in the cylindrical bed having specification as follows;

Length of bed: $2$ m; Diameter of bed: $0\mathrm{.}75$ m

Number of tubes: $10$; Number of fins: $50$

High of fins: $0\mathrm{.}05$ mm; Thickness of fins: $0\mathrm{.}005$ mm; idd of charging tubes $3$mm$,$ and cp$=560$J$/$kg$.$k