Question

A thin‐walled tube with a diameter of 12 mm and length of 25 m is used to carry exhaust gas from a smoke stack to the laboratory in a nearby building for analysis. The gas enters the tube at 200°C and with a mass flow rate of 0.006 kg/s. Autumn winds at a temperature of 15°C blow directly across the tube at a velocity of 2.5 m/s. Assume the thermophysical properties of the exhaust gas are those of air

Estimate the average heat transfer coefficient for the exhaust gas flowing inside the tube.

Answer 1

The average heat transfer coefficient for the exhaust gas flowing inside the tube, h = 204.41 W/m^2 - K

Step-by-step explanation:

The detailed solution is attached as files below.

However, the steps followed are highlighted:

1) The average temperature was calculated as 380.5 K

2) The properties of air at 380.5 K was highlighted

3) The Prandti number was calculated. Pr = 0.693

4) The Reynold number was calculated, Re = 28716.77

5) The Nusselt umber was calculated, Nu = 75.94

6) From Nu = (hD)/k , the average heat transfer coefficient, h, was calculated and a value of 204.41 W/m^2 - K was gotten.