A computer consists of an array of five printed circuit boards (PCBs), each dissipating P(b) = 20W of power. Cooling of the electronic components on a board is provided by the forced flow of air, equally distributed in passages formed by adjoining boards, and the convection coefficient associated with heat transfer from the components to the air is approximately h = 200 W/m^2 K. Air enters the computer console at a temperature of T(i) - 20C, and flow is driven by a fan whose power consumption is P(f) = 25W.
a) If the temperature rise of the airflow, (T(o) - T(i)), is not to exceed 15C, what is the minimum allowable volumetric flow rate of the air? The density and specific heat of the air may be approximated as p = 1.161 kg/m^3 and c(p) = 1007 J/kg K, respectively.
b) The component that is most suceptible to thermal failure dissipates 1 W/cm^2 of surface area. To minimize the potential for thermal failure, where should the component be installed on a PCB? What is its surface temperature at this location?