Air at 10°C enters a 12-cm-diameter and 5-m-long pipe at a rate of 0.065 kg/s. The inner surface of the pipe has a roughness of 0.22 mm, and the pipe is nearly isothermal at 50°C. Determine the rate of heat transfer to air using the Nusselt number relation given by

(a) Eq. 19€“79.

(b) Eq. 19€“84. Evaluate air properties at a bulk mean temperature of 20°C. Is this a good assumption?

Transcribed Image Text:

Nu = 0.125 fRePr/3 Nu (f/8)(Re – 1000) Pr (0.5 < Pr< 2000 (3 x 10³ < Re < 5 × 10) Nu %3D 1+ 12.7(f/8)05(Pr23 – 1)