Chapter 1, Problem 1.54P

Convection ovens operate on the principle of inducing forced convection inside the oven chamber with a fan. A small cake is to be baked in an oven when the convection feature is disabled. For this situation, the free convection coefficient associated with the cake and its pan is $h_{\text{fr}}=3{\text{W/m}}^{\text{2}}\cdot \text{K}\text{.}$ The oven air and wall are at temperatures $T_{\infty }=T_{\text{sur}}=180°\text{C}\text{.}$ Determine the heat flux delivered to the cake pan and cake batter when they are initially inserted into the oven and are at a temperature of $T_i=24°\text{C}\text{.}$ If the convection feature is activated, the forced convection heat transfer coefficient is $h_{\text{fo}}=27{\text{W/m}}^{\text{2}}\cdot \text{K}\text{.}$ What is the heat flux at the batter or pan surface when the oven is operated in the convection mode? Assume a value of 0.97 for the emissivity of the cake batter and pan.