Hi, Daniel
I have tried a pipe unit with a two-phase flow. Lockhart-Martinelli and Petalas-Aziz correaltions gives results, but the Beggs-Brill method ends with Error calculating pressure error.
Furthermore, it seems that the pressure loss of the local resistance is not included in the pressure loss profile.
How is the loss of local resistance calculated? Is it important to specify number of increments, length, diameter?
When calling the result report, limited data (not according to the required specification) are displayed, the second call will cause error Cannot access a disposed object.Object name: 'FormReportConfig'.
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By local resistance I mean all except straight tube - elbows, valves, etc. I think their equivalent length is given by the number of diameters. Is their resistance counted as a straight pipe with their equivalent length and the same method (two phase flow)?
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Thank you for your explanation, I hope I understand the principle.
But what is my problem:
I begin with straight tube - the calculation run.
I add fiting - the calculation run, the pipe and the fitting are counted.
I add next straight tube - the calculation run, but only straight tubes are counted.
I add next fiting - the calculation run, counting both straight tubes and only end fitting.
I add next straight tube - the calculation run, but only straight tubes are counted.
It seems that only fitting at the end of the pipeline is included into pressure profile and presure drop. Is this some my mistake?
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Hi Daniel
now it looks better. And some questions:
What does fitting "FixedDeltaP (27)" mean? In the future, it would be useful to add user-defined fittings by K or Le / D.
Beggs-Brill correlation does not work. Reports error "Error calculating pressure".
I studied the code, I found a mistake in the "liquid velocity number" Nlv, but it is not a critical error.
BeggsBrill.vb line 173 Dim Nvl = 1.938 * vsl * (rhol / (32.2 * surft)) ^ 0.25. I think 32.2 is included in 1.938, so Nvl = 1.938 * vsl * (rhol / surft) ^ 0.25.
The correlation of Petalas-Aziz is in dll. Is there open code or is it a proprietary code?
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Fixed Delta-P should work by the user entering the actual pressure drop value for that segment, but I think I'd never got it working correctly... maybe it is time to revisit this feature.
I'll take a look at the BB code, thanks for the report.
Petalaz-Aziz source code is not free. I was able to download it from the author website about 12 years ago but it is not available anymore. It has a 32-bit windows DLL file which you could use on Excel VBA code. I was able to adapt the code so it could work on the other platforms.
Regards,
Daniel
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Hi, Daniel
I have tried a pipe unit with a two-phase flow. Lockhart-Martinelli and Petalas-Aziz correaltions gives results, but the Beggs-Brill method ends with Error calculating pressure error.
Furthermore, it seems that the pressure loss of the local resistance is not included in the pressure loss profile.
How is the loss of local resistance calculated? Is it important to specify number of increments, length, diameter?
When calling the result report, limited data (not according to the required specification) are displayed, the second call will cause error Cannot access a disposed object.Object name: 'FormReportConfig'.
Attachment
I don't understand what you mean with "local resistance"... the pressure drop is composed by two parts, frictional and hydrostatic.
By local resistance I mean all except straight tube - elbows, valves, etc. I think their equivalent length is given by the number of diameters. Is their resistance counted as a straight pipe with their equivalent length and the same method (two phase flow)?
resistance = pressure drop
They are converted to an equivalent length, and the pressure drop is calculated using the friction factor provided by the Kfit() method:
https://github.com/DanWBR/dwsim5/blob/master/DWSIM.UnitOperations/Unit%20Operations/Pipe.vb#L655
The method is the same as in https://neutrium.net/fluid_flow/pressure-loss-from-fittings-equivalent-length-method/
The two phase flow correlation is not used in this case.
The length that you enter for a non-straight pipe section is irrelevant (or at least it should...).
Thank you for your explanation, I hope I understand the principle.
But what is my problem:
I begin with straight tube - the calculation run.
I add fiting - the calculation run, the pipe and the fitting are counted.
I add next straight tube - the calculation run, but only straight tubes are counted.
I add next fiting - the calculation run, counting both straight tubes and only end fitting.
I add next straight tube - the calculation run, but only straight tubes are counted.
It seems that only fitting at the end of the pipeline is included into pressure profile and presure drop. Is this some my mistake?
I see. There is something wrong in the pipe model. I'll take a look.
Hi Milos,
It seems that I forgot to update the inlet pressure for the next section/segment on the pipe profile after the calculation of a fitting block.
Last edit: Daniel Medeiros 2017-10-02
Hi Daniel
now it looks better. And some questions:
What does fitting "FixedDeltaP (27)" mean? In the future, it would be useful to add user-defined fittings by K or Le / D.
Beggs-Brill correlation does not work. Reports error "Error calculating pressure".
I studied the code, I found a mistake in the "liquid velocity number" Nlv, but it is not a critical error.
BeggsBrill.vb line 173 Dim Nvl = 1.938 * vsl * (rhol / (32.2 * surft)) ^ 0.25. I think 32.2 is included in 1.938, so Nvl = 1.938 * vsl * (rhol / surft) ^ 0.25.
The correlation of Petalas-Aziz is in dll. Is there open code or is it a proprietary code?
Hi Milos,
Fixed Delta-P should work by the user entering the actual pressure drop value for that segment, but I think I'd never got it working correctly... maybe it is time to revisit this feature.
I'll take a look at the BB code, thanks for the report.
Petalaz-Aziz source code is not free. I was able to download it from the author website about 12 years ago but it is not available anymore. It has a 32-bit windows DLL file which you could use on Excel VBA code. I was able to adapt the code so it could work on the other platforms.
Regards,
Daniel
Hi, is the fixed delta P working in the hydraulic profile? I can se no effect by changing the Quantity.
Rgds
Tomas