A computer consists of an array of five printed circuit boards (PCBs), each dissipating P_b = 20 W 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/m² ∙K. Air enters the computer console at a temperature of T_i = 20°C, and flow is driven by a fan whose power consumption is P_f = 25 W.

(a) If the temperature rise of the air flow, (To - Ti), is not to exceed 15°C, what is the minimum allowable volumetric flow rate ∀ of the air? The density and specific heat of the air may be approximated as ρ = 1.161 kg/m3 and c p = 1007J/kg ∙ K, respectively.

(b) The component that is most susceptible to thermal failure dissipates 1 W/cm2 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?

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