Question

Hot air at an average temperature of 100 degC flows through a 3 m long tube with an inside diameter of 60 mm. The temperature of the tube is 20 degC along its entire length. The average convective film coefficient is 20.1 W/m2*K. what is most nearly the rate of convective heat transfer from the air to the tube?

Answer 1

The most nearly rate of convective heat transfer from the air to the tube is 1.52 W

Step-by-step explanation:

P = hA(T1 - T2)/L

P is rate of convective heat transfer from the air to the tube

h is average convective film coefficient = 20.1 W/m^2.K

A is area of the tube = πd^2/4 = 3.142×0.06^2/4 = 2.8278×10^-3 m^2

T1 is temperature of air = 100 °C = 100+273 = 373 K

T2 is temperature of the tube = 20 °C = 20+273 = 293 K

L is length of the tube = 3 m

P = 20.1×2.8278×10^-3(373-293)/3 = 1.52 W

Answer 2

`\dot Q = 912.017\,W`

Step-by-step explanation:

The heat transfer rate due to convection is calculated by this formula:

`\dot Q = h_(air)\cdot A_(tube, in)\cdot (T_(air) - T_(tube))`

The output is determined by replacing terms:

`\dot Q = (20.1\,(W)/(m^(2)\cdot ^(\textdegree)C))\cdot (\pi )\cdot (0.06\,m)\cdot (3\,m)\cdot (100^(\textdegree)C-20^(\textdegree)C)`

`\dot Q = 912.017\,W`