P$5)$ An electronic device is cooled by passing air at

$27C$ through six small tubular passages drilled through

the bottom of the device in parallel as shown. The mass

flow rate per tube is $7{10}^{-5}k\frac{g}{s}.$ Heat is generated in

the device, resulting in approximately uniform heat flux

to the air in the cooling passage. To determine the heat

flux, the air$-$outlet temperature is measured and found

to be $77C.$ Calculate the rate of heat generation, the

average heat transfer coefficient, and the surface

temperature of the cooling channel at the center and at

the outlet. $)=21\mathrm{.}3(W),e=23\mathrm{.}8\frac{W}{m^2}(K),Ts=(147C$

Single tubular passage