Hi there,
I have a model which is a quit complex building of pipes, which are in parallel and in serial and in additional with some flow resistance (ellbows and so on). At the end I have a outlet-lit, which represents a fan.
Now I like to get the pressure drop at this lit, so I can choose the proper fan in reality.
On the otherside of the model, I have some other lits (which represents several inlets to the parallel pipes, and opened to the ambient surrounding).
By now I tried to use following setup:
- internal analysis
- fluid: air; laminar and turbulent
- adiabatic wall; roughness 10 µm
- standard thermodynamic parameters; no velocity
this boundary condition:
- Inlet lit: ambient pressure
- outlet lit: constant flow rate
and this goals:
- total pressure at inlet and outlet
(here I am not sure, if I choosed the proper pressure (static?), and do I need to set a velocity goal as well, since this is a significant value for the pressure?)
in the next step, i vary the flowrate to create a pressure - flowrate - chart (the characteristic curve of that model).
I never expected to get a value which corresponds to 100 % to the real measurement.
But as I now measured, it doesn`t correspond at all.
So what kind of mistake did i make?
Where is my logical failure?
Thanks in advance.
Lukas, I think you are on the right track but your methodology is flawed. If you set a flow rate at the outlet, and ambient conditions at the inlet, you will not see the correct pressure distribution. This is because the "outlet flow" condition has a set thermodynamic state, which means your pressure and temperature are constant. By default they will be at the ambient conditions defined in your project options.
What you should do is define an outlet static pressure (below ambient of course.) Then as your goal you should measure the flow rate. This way you should be able to build a resistance relationship for your piping.
By the way, I must say that Flow Sim is not the best tool for pipe systems. If you can justify the cost I would recommend looking at 1D flow network analysis software such as Macroflow: http://inresllc.com/products/macroflow/overview.html