$2-69$ A pipe in a manufacturing plant is transporting super$-$

heated vapor at a mass flow rate of $0\mathrm{.}3k\frac{g}{s}.$ The pipe is $10$ m

long, has an inner diameter of $5$ cm and pipe wall thickness of

$6$ mm $.$ The pipe has a thermal conductivity of $17\frac{W}{m}*K,$ and

the inner pipe surface is at a uniform temperature of $120C.$ The

temperature drop between the inlet and exit of the pipe is $7C,$

and the constant pressure specific heat of vapor is $2190\frac{J}{k}g*C.$

If the air temperature in the manufacturing plant is $25C,$ deter$-$

mine the heat transfer coefficient as a result of convection be$-$

tween the outer pipe surface and the surrounding air.

FIGURE P$2-69$