The physical behaviour of Laminar Flow Elements is based on the Hagen–Poiseuille equation. Subsequently the pressure drop of a laminar flowed tube section is directly proportional to the flow rate.
Laminar flow is a requirement for the function of the Laminar Flow Element. This presupposes a Reynolds number of smaller than 2300, which depends on viscosity, tightness and flow rate and also on the geometry of the pipe. To reach laminar flow inside the LFE, the volume flow of large flows must be divided in a number of capillaries.