Cylindrical rods of polyethylene, with diameter D=0.01 m at an initial uniform temperature of 230C is exposed to air at 30C for which the convective heat transfer is 176 W/m.K. How long is required for the surface temperature to drop from 230C to 65C? What is the centre temperature at that time? How much heat has been lost from this cylindrical rod to the air during this process? Polyethylene has thermal diffusivity of a=. temperature range of interest. ks PsCp,s 1.3 x 10 m/s and k = 0.33 W/m.K in the S