Pump delta_head_init always negative

[Christoph <buchner@…>]

Whenever I use a pump, I get such a warning:

Warning: Variable oil_pump.delta_head_init out of [min, max] interval: oil_pump.delta_head_init >= 0.0 has value: -0.00351929

I also see this with examples, e.g. Fluid.Examples.HeatingSystem.

I have dug into the code, and in /Modelica 3.2.1/Fluid/Machines.mo I find

final parameter SI.Height delta_head_init = flowCharacteristic(V_flow_single_init)-flowCharacteristic(0)
        "Used for simplified initialization model";

Now, if I don't misunderstand pump characteristics, the pump head is always decreasing with increasing volume flow, so doing the above calculation/initialization will _always_ result in a delta_head_init<0.
This seems to me do be a sign error in the above code, am I correct?

[Christoph Buchner <buchner@…>]

Cross-referencing the relevant ​MSL issue. I still would like to know if my analysis/understanding of this being a sign error is correct.

[Francesco Casella]

Replying to Christoph Buchner <buchner@…>:

Cross-referencing the relevant ​MSL issue. I still would like to know if my analysis/understanding of this being a sign error is correct.

Check my comment on the PR. I'm sorry but I really have zero time to deal with this right now. @buchner, if you want to make a pull request yourself where you change all the types Height into Position in the Pump model, I'd be happy to accept them. I guess we need one for the master branch and one for 3.2.3 maintenance.

[Christoph Buchner <buchner@…>]

Same with me actually, no time and no way currently set up to (locally) test any changes to MSL/OM/...let's see how the upstream MSL issue discussion resolves.

[Francesco Casella]

I'll take care of this after Apr 6.

[Christoph Buchner <buchner@…>]

Sure, there's no particular hurry.

[Francesco Casella]

Done, see ​PR 2384 of the MSL.

[Francesco Casella]

With ​PR 2876 the MSL fixes were ported to the MSL 3.2.3 mainenance branch. We will incorporate them in the version of MSL 3.2.3 shipped with OpenModelica in the next release.