Fluid Mechanics and Flow Through Pipe

So long as there is flow, there is pressure drop. To minimise it, you need to turn the flow down. Did you miss the Fluid Mechanics course, then?

If we assume an increase in cross section, if flow is sufficiently fast, don't you think there could be a pressure increase?

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What would Bernoulli say, Mildred?

Do tell.

See #5 below.

It depends, with flow, diameter of pipe and length.

It could be negligible at low flow, bigger exhaust diameter and shorty downstream given that there are no muffler, reducer, expander and bends downstream and any other extra accessories.

I believe he's asking about exhaust of a mine...not an engine!

Those aren't necessarily mutually exclusive.

Neither are a Piper J-3 and a P-51 Mustang.

But...............................................

Wait. Are you saying there is a plane which is both Piper J-3 AND P-51 Mustang?

Pistang Muper PJ-351 ?!?

Easy.. there.. cutey!

You can, sort of.

A GA vote will reduce the OT vote count by one.

For our resident troll, I'd prefer a remote keyboard lock feature or maybe a remote "destruct" button?

1/2 ρ v^2 + ρ h + p = constant

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Assuming for the change in question the height (h) and density (ρ) do not change, then so long as head loss in that short transition is less than 2 ρ v, then there should be an increase in pressure (p) as the crossectional area doubles and the velocity (v) is reduced to 50%.

This the best answer so far. Of course there is pressure drop! The only question is how much drop, and how much is acceptable.

If the drop exceeds what's allowable, it will be necessary to vary some combination of duct, geometry, flow rate. Usually the process parameters are specified so varying the flow rate, temperature and density are is likely options. However, geometry is.

To the original poster: You next a good textbook or handbook to guide you so you can evaluate the effects of geometry changes.

Except for vacuum lines (pun) any flow will cause a pressure drop in a system whether it be straight line or a loop system. You can control it a small bit by making it have less restrictions and hydraulic losses. Some ways of decreasing the losses include, but are not limited to: using pipe with smoother interior wall surfaces, fewer elbow or elbows with wider radiuses, fewer fittings, shorter line runs, replace tees with "Y''s; remove fittings that have changes in the interior configurations such as threaded pipe fittings, make sure the supply flow to and from "T"'s is straight through the runs and not in/out of the branch and a run. An example of this would be to replace a threaded pipe section with glued plastic pipe section, replace elbows with long radius sweep elbows, sanitary "T"'s, ball valves instead of globe or gate valves, etc.

The first step in controlling pressure drops is to plan it for low losses, design it that way, do an assessment of it and build it that way. Listen to suggestions from those who are familiar with working on these types of systems (keep your eyes and ears open to the trades persons when they speak) and monitor the actual installation.

Once you begin operations you can only increase the pressure drops. It is too late to decrease it without shutting down the system for modifications/changes.

Good Luck, Old Salt

Are you asking about a flowing pressure loss or are you asking about a reduction in backpressure by increasing the total flow area of one pipe by adding another parallel pipe?