Ali,
as far as I understood the nature of your question, I would say that it does not necessarily involve phase changes or heating, but is the consequence of the hydrodynamics and momentum transfer.
Local pressure drop occurs on plumbing fittings with specific geometrical features (like valves, bends, filters) that cause rapid pressure loss on very short distance, mainly because of the collisions between fluid particles and various obstructions in the fitting geometry. It is a function of empirical factor called local resistance coefficient (as far as I know, assumed constant for certain fitting) and kinetic energy of the fluid.
On the other side, distributed pressure drop occurs during the flow through prolonged sections of the straight pipeline, where the friction forces between the fluid and the pipe internal surface, contribute to energy dissipation and cause steady decline of the total pressure. Look up Darcy-Weisbach equation and Moody chart.
Heating and phase changes may involve also other phenomena, as we would observe multiphase flow, but I am not sure if that changes the very definition of aforementioned pressure drops.
I hope it is what you asked for. If I am wrong, may the more experienced users will help you.
Kind regards,
Ali,
as far as I understood the nature of your question, I would say that it does not necessarily involve phase changes or heating, but is the consequence of the hydrodynamics and momentum transfer.
Local pressure drop occurs on plumbing fittings with specific geometrical features (like valves, bends, filters) that cause rapid pressure loss on very short distance, mainly because of the collisions between fluid particles and various obstructions in the fitting geometry. It is a function of empirical factor called local resistance coefficient (as far as I know, assumed constant for certain fitting) and kinetic energy of the fluid.
On the other side, distributed pressure drop occurs during the flow through prolonged sections of the straight pipeline, where the friction forces between the fluid and the pipe internal surface, contribute to energy dissipation and cause steady decline of the total pressure. Look up Darcy-Weisbach equation and Moody chart.
Heating and phase changes may involve also other phenomena, as we would observe multiphase flow, but I am not sure if that changes the very definition of aforementioned pressure drops.
I hope it is what you asked for. If I am wrong, may the more experienced users will help you.
Kind regards,
Krzysztof is right.
I attach some images to visualize...
Thanx to Shoaib Azhar.
Dear Krzysztof Skrzypek. Thanks a lot for your usufull answer. Dear you are not wrong for response at contrasts to you are give good response where I find usuffull informations. I had indicated heat flow bkz I'm interested of boiling two phase flow in absorption machines where I defined distribute pressure drop.
Thanks a lot again
Ali Benhmidene .........Good question… Please check references below.. hope it will be helpful for you…
Regards…
http://orbit.dtu.dk/files/137687845/RevisedManuscript.pdf
https://pdfs.semanticscholar.org/34b7/d0b2b14b7e784df3261939afb52df30431e7.pdf
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