A horizontal pipeline carries methane gas at 100 bar pressure. The pipeline is made of carbon steel, is 15 cm in diameter, and has a thickness of the pipe wall of 6 mm. At a time of low gas...

A horizontal pipeline carries methane gas at 100 bar pressure. The pipeline is made of carbon steel, is 15 cm in diameter, and has a thickness of the pipe wall of 6 mm. At a time of low gas consumption, natural gas flows through the pipeline at a Reynolds number of Re_D
= 2100. Indirect solar radiation delivers a circumferentially averaged heat flux of 200 W/m²
to the gas in the pipeline.

a. Calculate the pipeline inner surface temperature at a location where the bulk gas temperature is 22°C. Is the contribution of natural convection significant?

b. Repeat Part a, this time assuming the flow rate is reduced by half.