The meaning of rho*v^2 is that with too high values of this term you could have mechanical and hydraulic problems like noise, vibration of piping and liquid dragging inside the vessel
For the inlet nozzle I think the following is also to be considered: d * V2 < 1000 where d is the vapour density in kg/m3 and V is the vapour velocity in m/s inside the inlet nozzle.
