Atmospheric air enters a 10-m-long, 150-mm-diameter uninsulated heating duct at 60°C and 0.04 kg/s. The duct surface temperature is approximately constant at Ts = 15°C.
(a) What are the outlet air temperature, the heat rate q, and pressure drop tip for these conditions?
To illustrate the tradeoff between heat transfer rate and pressure drop considerations, calculate q and tip for diameters in the range from 0.1 to 0.2 m.
In your analysis, maintain the total surface area, As = 7TDL, at the value computed for part (a). Plot q, tip, and L as a function of the duct diameter.