A pipe, with an inner diameter of 30 cm and a length of 8 m, carries nitrogen. The nitrogen average pressure is 5 bars, and its mean temperature at inlet is 70°C. The inner surface of the pipe is at a...

A pipe, with an inner diameter of 30 cm and a length of 8 m, carries nitrogen. The nitrogen average pressure is 5 bars, and its mean temperature at inlet is 70°C. The inner surface of the pipe is at a uniform temperature of 30°C.

 a. Assume that the pipe is horizontal. Estimate the minimum nitrogen mean velocity for the natural convection effect to be unimportant.

b. Repeat Part b, this time assuming that the pipe is vertical and the flow is upward. Discuss the difference between your results for Parts a and b.

c. For Part b, assume that nitrogen flow is imposed with a mean velocity of 0.25 m/s. Estimate the average heat transfer coefficient and the mean gas temperature at exit for the pipe using the most appropriate method/correlation to which you have access. Discuss the pros and cons of the correlation that you have chosen.