2-52 A spherical metal ball of radius ro is heated in an oven to a temperature of Ti throughout and is then taken out of the oven and allowed to cool in ambient air at T by convection and radiation. The emissivity of the outer surface of the cylinder is , and the temperature of the surrounding surfaces is Tsurr. The average convection heat transfer coefficient is estimated to be h. Assuming variable thermal conductivity and transient one-dimensional heat transfer, express the mathematical formulation (the differential equation and the boundary and initial conditions) of this heat conduction problem. Do not solve. FIGURE P2-52