Consider a hollow-core printed circuit board 9 cm high and 18 cm long, dissipating a total of 15.5 w. the width of the air gap in the middle of the pcb is 0.25 cm. if the cooling air enters the 12-cm-wide core at 25°c and 1 atm at a rate of 0.8 l/s, determine the average temperature at which the air leaves the hollow core. the gas constant of air is r = 0.287 kpa·m3/kg·°c. the specific heat of air at room temperature is cp = 1.005 kj/kg·°c.
determine (a) the temperature at which the air leaves the hollow core and (b) the highest temperature on the inner surface of the core.