A pipe conveys 0.25 kg/sec of air at 300K under an absolute pressure of 2.25bar. Calculate minimum diameter of the pipe required if the fluid velocity is limited to 7.5 m/sec.

 A pipe conveys 0.25 kg/sec of air at 300K under an absolute pressure of 2.25bar. Calculate minimum diameter of the pipe required if the fluid velocity is limited to 7.5 m/sec. 

Solution: 

 Density of air ρ= P/RT= (2.25*105 )/(287*300)= 2.61kg/m3 

 Mass flow of air, m = ρAV 0.25 

                                 =2.61*A*7.5

 Min. area (A)  = (0.25*1) / (2.61*7.5) = 0.01277 m 2 

 Min. dia. =√(0.01277*4)/π = 0.1275m 

                                        = 12.75 mm