Bug in the dynamic viscosity conditional equation

[msielemann]

In some pipe models, the conditional equation to calculate the dynamic viscosity at port_b seems to use the wrong mass flow rate to distinguish which side is upstream.

The original equation basically reads

eta_b=if m_flow[1]<0
  then
    medium.dynamicViscosity(Medium.setState_phX(port_b.p, port_b.h, port_b.Xi))
  else 
    Medium.dynamicViscosity(medium[n].state)

It seems as if the following was the correct formulation

eta_b=if m_flow[n + 1]<0
  then
    Medium.dynamicViscosity(Medium.setState_phX(port_b.p, port_b.h, port_b.Xi))
  else
    Medium.dynamicViscosity(medium[n].state)

This is the case for the following models

• DistributedPipeLumpedPressure: source:/trunk/Modelica_Fluid/Pipes.mo@293#L247
• DistributedPipe: source:/trunk/Modelica_Fluid/Pipes.mo@293#L437
• DistributedPipeSb: source:/trunk/Modelica_Fluid/Pipes.mo@293#L658
• DistributedPipeSa: source:/trunk/Modelica_Fluid/Pipes.mo@293#L855

[dietmarw]

Clean up of code quote (was a bit hard to read ;)