Consider a $15-$cm $320-$cm printed circuit board $($PCB$)$

that has electronic components on one side. The board is

placed in a room at $208$C$.$ The heat loss from the back sur$-$face

of the board is negligible. If the circuit board is dissipat$-$ing

$8$ W of power in steady operation, determine the average

temperature of the hot surface of the board, assuming the

board is $($a$)$ vertical, $($b$)$ horizontal with hot surface facing

up$,$ and $($c$)$ horizontal with hot surface facing down. Take the

emissivity of the surface of the board to be $0\mathrm{.}8$ and assume

the surrounding surfaces to be at the same temperature as

the air in the room. Evaluate air properties at a film tempera$-$ture

of $32\mathrm{.}58$C and $1$ atm pressure. Is this a good assumption?