Computational fluid dynamics has been applied to investigate the flow field which develops above the vapour feed in packed separation columns. The uniformity of the flow below the packing is assessed by means of the coefficient of variation K-p. The resulting K-p for the standard inlet is input into an empirical correlation depending on the three most important, basically geometrical, dimensionless parameters. Other feed systems including an orifice baffle, the Schoepentoeter and the vapour horn are compared with the standard inlet.