Can anyone help on this problem encountered in gas chromatography: Two helium incoming gas lines A and B are connected together via a cross-shaped connector to two outlets C and D. All in and out lines are capillaries with diametre in the 0.1-1 mm range and lengths in the 10s of cm to 10s of metre range. Inlet pressure is in the 100s of kPa range (controlled by pressure regulators) for lines A and B. Outlet pressure is high vacuum for line C and 100 kPa (atmospheric pressure) for line D. Inlet and outlet pressures and diametres and lengths of capillaries are known. How to calculate flow rate for each line? Thanks for your help!