HeatExchanger-Simulation does not work, error messages cannot be comprehended - simulation

Question

I want to simulate a Plate Heat Exchanger Model and I use the default-Version in the Modelica-Fluid-Library. To specify the default-Version, I build in all neccessary parameters and equations for heat transfer (Nusselt, etc.) and pressure loss accordingly to the VDI Wärmeatlas 2006, Mm1. I have tried for a long time to find and correct all mistakes, but finally I come to a "dead point".
The error last messages were:
Check of Fluid_Test1_PHE_Temp7.Examples.HeatExchanger.HeatExchangerSimulation:
Error: The model is not well-posed.
The model has
484
scalar unknowns and
480
scalar equations.
Using the given settings of the parameters, the difference could be reduced to
4
Error: The following parameters don't have any value:
HEX.pipe_1.diameter
HEX.pipe_2.diameter
Warning: The following inputs lack binding equations:
HEX.pipe_1.heatTransfer.roughnesses
HEX.pipe_2.heatTransfer.roughnesses
Error: The problem is structurally singular:
It has 488 scalar unknowns and 484 scalar equations.
The Real part has 456 unknowns and 452 equations.
The Integer part has 32 unknowns and 32 equations.
The Boolean part has 0 unknowns and 0 equations.
The String part has 0 unknowns and 0 equations.
Attempting to further localize singularity.
The model has the same number of unknowns and equations.
Attempting to further localize singularity.
The model has the same number of unknowns and equations.
Attempting to further localize singularity.
The model has the same number of unknowns and equations.
The model has the same number of unknowns and equations.
Note: The input connector p of HEX.pipe_1.mediums[1] is not connected from the outside.
It is likely that it should have been connected, and recursive check will assume this.
The missing connection is a likely cause of errors in the model.
Note: The input connector h of HEX.pipe_1.mediums[1] is not connected from the outside.
It is likely that it should have been connected, and recursive check will assume this.
The missing connection is a likely cause of errors in the model.
The model has the same number of unknowns and equations.
Note: The input connector p of HEX.pipe_1.mediums[2] is not connected from the outside.
It is likely that it should have been connected, and recursive check will assume this.
The missing connection is a likely cause of errors in the model.
Note: The input connector h of HEX.pipe_1.mediums[2] is not connected from the outside.
It is likely that it should have been connected, and recursive check will assume this.
The missing connection is a likely cause of errors in the model.
The model has the same number of unknowns and equations.
The model Fluid_Test1_PHE_Temp7.Examples.HeatExchanger.HeatExchangerSimulation component HEX.pipe_1 is structurally singular.
when assuming the most generic outside couplings to all the flow variables of its connectors
and that non-physical connectors will impose suitable constraints.
The reported problems with connections are the likely cause of the singularity.
Singularity of Fluid_Test1_PHE_Temp7.Examples.HeatExchanger.HeatExchangerSimulation is in the component HEX.pipe_1, class Fluid_Test1_PHE_Temp7.Pipes.DynamicPipe.
ERROR: 3 errors were found
WARNING: 1 warning was issued
May anybody can help me? I also can send the model by Mail to somebody to let it check.
Greets
Georg

Answer 1

I don't have access to your model, but the error messages indicate that the issue is with the connections to HEX.pipe_1.mediums (which is an array). It would seem they are not (properly?) connected.
Do you have some reason to think that this is not the problem?
Also, before doing any more testing I would also strongly urge you to provide (non-zero) diameters for the HEX.pipe_1 and HEX.pipe_2 as well as provide "binding equations" for the roughness components of the heat transfer model. Such issues might "mask" other concerns.
Let me know if that helps.