Hello all,
i have a convection problem were i want to use the empirical formulas for computing the heat transfer coefficient. I already have a working model. So far, i used a constant for the heat transfer coefficient input in the convection model. Now i want to compute the heat transfer coefficient based on empircal data, so i need the media data. I have a closed volume with nitrogen as gas data, but i unluckely have nu glue how i can get data like the kinematic viscosity, thermal conductivity, heat capacity and density out to the modelling surface. Can someone please point me in the right direction?

Best Regards,

Markus

Hello, my model suddenly stopped working, with following error message:

C:/OpenModelica1.12.0-64bit//share/omc/scripts/Compile.bat 1D gcc mingw64 parallel 1 0
PATH = "C:\OpenModelica1.12.0-64bit\tools\msys\mingw64\bin;C:\OpenModelica1.12.0-64bit\tools\msys\mingw64\bin\..\..\usr\bin;"
gcc    -falign-functions -msse2 -mfpmath=sse      -I"C:/OpenModelica1.12.0-64bit//include/omc/c" -I. -DOPENMODELICA_XML_FROM_FILE_AT_RUNTIME -DOMC_MODEL_PREFIX=1D -DOMC_NUM_MIXED_SYSTEMS=0 -DOMC_NUM_LINEAR_SYSTEMS=19 -DOMC_NUM_NONLINEAR_SYSTEMS=5 -DOMC_NDELAY_EXPRESSIONS=0 -DOMC_NVAR_STRING=0  -c -o 1D.o 1D.c
In file included from 1D.c:2:0:
1D_model.h:2:14: error: operator "defined" requires an identifier
#if !defined(1D__MODEL_H)
              ^

other models are running fine. The error is right at the start of the compiling progress,

What is wrong here?

Best regards

Hello all, i have made a 3d network of thermal conductors and heatcapacitors, where i normally initialise the G and C parameter when i load the object as follows:

Modelica.Thermal.HeatTransfer.Components.HeatCapacitor cellElement[N - 2, M - 2, K - 2](each C = cp * m /((N-2)*(M-2)*(K-2)));
Modelica.Thermal.HeatTransfer.Components.ThermalConductor Conductor_X[N - 1, M - 2, K - 2](each G = (lambda * Ax / (L / (N - 1)))/((M-2)*(K-2)));

now i want to make a "hole" in the 3d network: set C and G values to extrem small values, so that negletible heat transfer takes place.

i have tried to load the objects without parameter initialization, for example: Modelica.Thermal.HeatTransfer.Components.HeatCapacitor cellElement[N - 2, M - 2, K - 2]

and then tried to set the values with: cellElement[i, j, k].C = 0.001; in the inital equation section. but OpenModelica tells me that i have redundant initial conditions
Assuming redundant initial conditions for the following 187 initial equations:
         steelplate1.Conductor_Z[1,5,8].G = 0.001 and so on...

how can i set the parameter values in the equation section without having the problem to have redundant inital conditions?

i rebuilt the model from scratch with increasing complexity and now everything works. it is a bit unsatisfying not knowing what caused the problem but at least it works

i have made a simple 3D conduction model which is working, but when i want to try my extended model of a heat capacity with an extended model of a thermal conductor the problem occurs. i have attached the simple model as well as the whole model which is not working proberly.

This is the basic 3D Cell system which is, when inserted in T0133System3D, is working proberly.
Cell3Dsimple.mo


This is the whole model (T0133System3D) with Cell3D, which, when inserted, delivers the mentioned error message.
OpenModelica-Pantelides-Problem.zip

So if someone wants to test my model just load all .mo files, open T0133System and try to run it. What i want to test is try to run the model in Dymola, but i do not have the software yet, so if someone could try it i would really appreciate it!

Many thanks in advance!

Hello, i know it is an old thread but i have quite the same error with my model. when i check the model evertyhing is just fine, x equations and x variables. But when i want to run the simulation it tells me that the model is structured singular.
I also get the message: Interner Fehler Transformation Module PFPlusExt index Reduction Method Pantelides failed!

I also have some matrices so i am not sure where the problem is. I have modeled a simple 3D conduction matrix in the same manner as the newThermal library from : NewThermal library. The problem with PFPlusExt should be solved based on : PFPlusExt Pantelides failed

Does anyone else experience such problems or know how to solve these?

Ok, i think i overcame the problem by making adjustments in the media compositions, i did not use pure N2 but instead a mixture with 99,95 % N2 and 0,01 % for each of the remaining gas components and also included a small amount of N2 in the other gas mixture.

One small thing: The mixing occurs, the mass percentaces changes, also the specific heat capacity of the mixture is changing, but not the molar mass of the mixture which is strange, but i cannot find the reason for this.

Hello all, i have following problem: I want to mix some mixture gas which consists of H2, CO, CO2, C2H4 and CH4 into a vessel where initially only N2 gas is present, but i can not initiate the model, it tells me following:
[3] 16:20:34 Translation Error
[TestFlow: 42:3-43:105]: Incompatible components in connect statement: connect(ports_a, volume.ports[1])
- ports_a has components {C_outflow, Xi_outflow, h_outflow, m_flow, p}
- volume.ports[1] has components {C_outflow, Xi_outflow, h_outflow, m_flow, p}

I have attached a simple example where the setup is visible. Can someone tells me what i need to change in my system that it is possible to simulate the mixing? also, i do not use port data so the mixing is without pressure loss.



Best regards,

Markus

Hi, i have a quite simple problem which i want to simulate. I have some heat generation inside a steel vessel filled with nitrogen and i want to compute the temperature and pressure rise inside the vessel. I have found the "ClosedVolume" model inside Modelica-Fluid-Vessels for this, but i am not sure if i use the correct heat transfer...

Inside the vessel a convection to nitrogen over a small surface should occur, so i connected the connection fluid port to the vessel heat port and enabled the heat transfer model for the vessel.

The strange thing is that the convection solid temperature and the convection fluid temperature are almost the same, i guess it is because of the ideal heat transfer model of the vessel but i do not really know. In addition, the thermal mass of the vessel should be connected to the fluid port of the nitrogen. Can someone give me a hint why this behaviour occurs or what i need to change in the system so that the heat transfer to the vessel is only over the small convection term?Volume heat transfer

Thank you, i tried it with the initial version 1.8.1 but without success, maybe i will try additional versions too, if i am successful i will post here.

Further, the programm is crashing all the time without warning and i cannot find the fault. Does anybody else experience these problems?

Hello, i want to optimize a parameter so that a certain simulation variable reaches a desired maximum value. I could only find this instruction:
https://www.openmodelica.org/doc/OpenMo … ation.html

But it seems not up to date and i need more information to successfully optimize my problem

So far a could start the optimization but wihout beeing sucessful. I am not sure what the difference between "optimized variable", Sampling variables" "Parameters" and Objectives" is.

Thank you for your help in advance!

Best regards

Markus

Hello, i have a small problem where i want to feed back the temperature of a port to evaluate a proper prescribed heat flow, but the simulation fails, it tells me to set proper start values for the temperature but i am not sure how to do this, i am very new to modelica and need some help with my problem please.


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