Flow Resistance (IL)

Description

The Flow Resistance (IL) block models a general pressure drop in an isothermal-liquid network branch. The pressure drop is proportional to the square of the mass flow rate. The constant of proportionality is determined from a nominal operating condition specified in the block dialog box.

Use this block when the only data available for a component is the typical pressure drop and flow rate. This block is useful for representing complex components, where it is difficult to determine theoretical pressure loss from the geometry.

The volume of fluid inside the flow resistance is assumed to be negligible. The mass flow rate in through one port must then exactly equal the mass flow rate out through the other port:

where $${\dot{m}}_{\text{A}}$$ and $${\dot{m}}_{\text{B}}$$ are defined as the mass flow rates into the component through ports A and B, respectively.

The pressure drop is assumed proportional to the square of the mass flow rate. The square of the mass flow rate is linearized in a small laminar flow region near zero flow, resulting in

where:

K is the proportionality constant,

where Δp_nom is the Nominal pressure drop parameter value and $$\dot{m}$$_nom is the Nominal mass flow rate parameter value.