Chapter 1, Problem 1.70P

A computer consists of an array of five printed circuit boards (PCBs), each dissipating $P_b=\text{2}0\text{ W}$ 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 $h=200{\text{W/m}}^{\text{2}}\cdot \text{K}$ . Air enters the computer console at a temperature of $T_i=20°\text{C}$ , and flow is driven by a fan whose power consumption is $P_f=\text{25 W}$ .

(a) If the temperature rise of the airflow. $\left(T_0-T_i\right)$ , is not to exceed 15°C,what is the minimum allowable Volumetric flow rate $\stackrel{\dot{}}{\forall }$ of’ the air? The density and specificheat of the air may be approximated as $\rho =1.161{\text{kg/m}}^3$ and $c_p=\text{1007}\text{J/kg}\cdot \text{K}$ . respectively.
(h) The component that is most susceptible to thermalfailure dissipates $\text{1}{\text{W/cm}}^3$ of surface area. To minimize the potential for thermal failure, where shouldthe component be installed on a PCB? What is itssurface temperature at this location?