modelDynamicPipe

Information

This components allows to model the mass flow rate through a pipe from a pressure difference at boundaries and the pressure loss coefficient ksi.

Compared with a static pipe, the following assumptions are performed:

1. The mass balance is assumed quasi-static
2. Density is assumed constant along the exchanger
• Mass conservation within the control volume is not respected
• Change of kinetic energy from contraction or expansion in neglected
• Change of temperature from kinetic energy variation is neglected

ksi expresses how many dynamic pressure is lost. It is assumed to be constant and therefore independent of the flow regime.

The mass flow rate relation derives:

Where:

• dp is the pressure difference between port_a.p and port_b.p
• ksi is the pressure loss coefficient
• d is the upstream density
• Vel is fluid velocity
• m_flow is the mass flow rate through the pipe
• A is cross section of the pipe

To avoid infinite derivative at dp=0, The square root is replaced by the function regRoot2 of the MSL that replace the square root by a polynomial expression to insure a finite derivative. The threshold to switch between the polynom and the square root is abs(dp≤0.1) Pa

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