$15\mathrm{.}8-4.$ Heat Transfer in a Finned Tube Exchanger. Air at an average temperature or $5$ C

is being heated by flowing outside a steel tube $(k=45\mathrm{.}1\frac{W}{m}*K$ having an inside

diameter of $35$ mm and a wall thickness of $3$ mm $.$ The outside of the tube is covered

with $16$ longitudinal steel fins with a length $L=13mm$ and a thickness of $t=1\mathrm{.}0mm.$

Condensing steam inside the tube at $120C$ has a coefficient of $7000\frac{W}{m^2}.$ K$.$ The

outside coefficient of the air has been estimated as $30\frac{W}{m^2}*K.$ Neglecting fouling

factors and using a tube $1\mathrm{.}0$ m long, calculate the overall heat$-$transfer coefficient $U_i$

based on the inside area $A_i.$

$15\mathrm{.}8-4.$ Heat Transfer in a Finned Tube Exchanger. Air at an average

temperature of $50C$ is being heated by flowing outside a steel tube

$(k=45\mathrm{.}1\frac{W}{m}*K)$ having an inside diameter of $35$ mm and a wall

thickness of $3$ mm $.$ The outside of the tube is covered with $16$

longitudinal steel fins with a length $L=13mm$ and a thickness of $t=$

$1\mathrm{.}0$ mm $.$ Condensing steam inside the tube at $120C$ has a coefficient

of $7000\frac{W}{m^2}*K.$ The outside coefficient of the air has been

estimated as $30\frac{W}{m^2}*K.$ Neglecting fouling factors and using a

tube $1\mathrm{.}0$ m long, calculate the overall heat$-$transfer coefficient $U_i$

based on the inside area $A_i.$