Problem $2-$ Energy Transfer by Heat $(10$ pts$)$

a$.$ A $15-$cm$-$thick firebrick has thermal conductivity $k_b$ of $0\mathrm{.}75\frac{W}{m}*K.$ At steady state, a

temperature difference of $250C$ occurs across the firebrick. What is the rate of conduction

heat transfer through the firebrick, in kW per $m^2$ of surface area?

b$.$ For a heat transfer purpose, a standing person is modeled as a $30-cm$ diameter, $175-cm$

long vertical cylinder with both the top and bottom surfaces insulated and with the side

surface at an average temperature of $35C.$ For a convection heat transfer coefficient of $15$

$\frac{W}{m^2}.C,$ determine the rate of heat loss from this man by convection in an environmental

at $25C.$ What is the rate of heat loss by radiation if the emissivity of the human skin is taken

as $0\mathrm{.}95?$ Could the radiation heat loss be neglected compared to convection heat loss?