The boundary layer at the pipe wall would become more viscous and effectively reduce the cross-sectional area of the pipe.https://www.google.com/search?q=why+does+gas+viscosity+increase+with+temperature wrote:Physical causes
Since the momentum transfer is caused by free motion of gas molecules between collisions, increasing thermal agitation of the molecules results in a larger viscosity. Hence, gaseous viscosity increases with temperature.
As always, test, test, test. You cannot make bricks without clay.