A wall is constructed with three different materials layered in series. The first layer is

$10\mathrm{.}0$ cm thick of brick $($kbrick $=0\mathrm{.}72$W$/$m$$C$).$ The second layer is $5\mathrm{.}0$ cm thick of

insulation $($kinsulation $=0\mathrm{.}04$W$/$m$$C$).$ The final layer is $2$ cm thick of concrete $($kconcrete $=$

$1\mathrm{.}4$W$/$m$$C$).$ The temperatures on the brick and on the concrete sides are $30$C and $5$

$$C$,$ respectively.

a$)$ Calculate the rate of heat transfer through the wall per square meter.

b$)$ Determine the temperatures at the interfaces.

c$)$ If the emissivity of the concrete is $0\mathrm{.}85,$ calculate the nett heat transferred through

radiation in every hour. Assume the temperature of the surrounding air is $0$ oC$.$