flow straightener pressure drop

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Nick
Posts: 2
Joined: Wed Feb 29, 2012 12:08 am

flow straightener pressure drop

Post by Nick »

I would like to calculate the pressure drop across a flow straightener. The flow straightener consists of a tube bundle of 121 pipes of 50 mm NB sitting in 750 mm pipe. The calculation would have to take into account the inlet and exit losses of each pipe and the gap between pipes and the pressure drop for each pipe and the pressure drop between pipes. Does there exist a calculation for this?
PipeFlowCalcs
Posts: 57
Joined: Sat Sep 17, 2011 8:50 am

Re: flow straightener pressure drop

Post by PipeFlowCalcs »

Calculation of pressure drop through pipe is easy, but pressure drop between pipes is something else, but pressure drop is the same through pipe and around it as after the strainer pressure is constant.
In order to calculate pressure drop you must know not only geometry but also flow rate. It is possible to have different flow rates through pipe and around it, but pressure drop is the same.
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Nick
Posts: 2
Joined: Wed Feb 29, 2012 12:08 am

Re: flow straightener pressure drop

Post by Nick »

I have found an online calculator at http://www.pressure-drop.com/Online-Cal ... index.html. This calculates the pressure drop for a given flow straightener geometry using a perforated plate with thickness with circular openings inside a larger diameter pipe. It doesn't account for the spaces between the pipes but I have worked out the area and equated that to a circle to calculate the pressure drop as if the openings between the pipes were pipes themselves.

The aim is to calculate the increase in flow rate through the system between the current flow straightener and a proposed flow straightener with a large % open area. For this you would need the find the new operating point on a pump curve for the lower system resistance using the proposed flow straightener.

Is there an easier method to calculate the increase in flow rate by knowing the pressure drop between the two flow straighteners for a given flow rate? A rule fo thumb perhaps?
PipeFlowCalcs
Posts: 57
Joined: Sat Sep 17, 2011 8:50 am

Re: flow straightener pressure drop

Post by PipeFlowCalcs »

Pressure drop will be lower, for sure, but how much I can not tell exactly...
If you increase flow area - A by double, pressure drop will drop with A^2.5 = 2^2.5 = 5.65 times. This is very rough calculation as answer to your question, but I can not help more... (get from Darcy formula)
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