Pressure Loss Through Flattened Pipe End

[tmartin125]

How can I determine the pressure loss through an open pipe end where the end of the pipe is smashed? See attached for pictorial representation. Would this be best analyzed as an orifice?

 

[1gibson]

How would you determine that pressure loss for a normal cross section pipe? Once it's out of the pipe, it's at atmospheric pressure.

I think what you want to do is calculate (or measure) the increase in backpressure from the nozzle, compared to an open pipe?

 

[tmartin125]

Yes, correct. I need to calculate the backpressure from the nozzle in order to predict velocity at nozzle end. Hope that makes sense. Tapered orifice best approach?

 

[racookpe1978]

Area ratio: Area of "squished nozzle = 1/8 inch x nozzle width (not on the prf!)/Area of the 6 inch (nominal OD) pipe

BUT! The nozzle bending will NOT be very uniform nor consistent unless you "machine out" the end after bending (squishing) the pipe. Most of the time, you will get a collapsed pipe end that is closed in the center, and rather more open (much larger than 1/8 inch!) at both ends.

Thus, completely squish the small pipe end completely closed. THEN, cut the irregular squished end to a uniform width and height so you get a uniform spray. And, of course, after testing proves you aren't getting enough fluid or too much fluid, then you simply change the regular, squared machined opening to be either higher, longer, or thinner or narrower.

 

[tmartin125]

How does one get from area ratio to differential pressure?

 

[tmartin125]

I'm guessing the Bernoulli Equation....q = cd A2 [ 2(p1 - p2) / ρ(1 - (A2 / A1)2) ]1/2

 

[bimr]

The simple method is empirical. Put a pressure gauge and flow meter on the pipe.

 

[LittleInch]

Looks a bit complex to me but for what it's worth, your "hydraulic diameter" is equivalent to about 6mm - 1/4" Going for an orifice calc with a 6mm hole would seem like a good first start point, but as said above, your chance of getting a nozzle exactly as drawn looks interesting.

Testing looks like a requirement to me.

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