Air is flowing at 300 K through a 150 mm diameter and 50 m length pipeline made of commercial steel (ε=0.05 mm) under polytrophic conditions. (air viscosity is 0.018 ×10-3 Pa s; air molecular weight: 29 g/mol)

(1) If the flow rate of air is 0.3 kg/s, determine the maximal upstream pressure to make sure the pressure drop along the pipeline is less than 60% of the upstream pressure. Assume the ideal gas law applies.

(2) If the upstream pressure is 200 kPa, what is the maximal air flow rate that can achieved in the pipeline?