Pressure drop 2

[Leo165]

According to Idelchick, headloss across perforated plates can be found by
h = K ( [V]2/[2g]
Is this is Permanent pressure loss (head) or Differential pressure (head) across plate ?


ahmad

 

[bimr]

The headloss across a perforated plate is differential across the plate and is a permanent headloss.

 

[LittleInch]

Leo, your question is quite strange, but the head loss will only occur when flow is present. The greater the flow the great the differential head loss. I'm confused by your term "permanent". If you mean does the pressure recover like d/s of an venture, then no it doesn't.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[katmar]

The permanent pressure loss is measured a few diameters downstream of the vena contracta - after any pressure recovery from decreasing velocity has occurred. This is the only pressure drop that piping engineers are interested in. The maximum pressure differential occurs at the vena contracta and this is the pressure that the instrument engineers will want to measure. Idelchik's book is for piping engineers, so he gives the permanent pressure loss.

Instrument engineers tend to use the symbol C_D for their orifice coefficient, whereas piping engineers use the same k symbol we use for all permanent losses. The relationship between these two is discussed in Crane TP410 page A-20.



Katmar Software - AioFlo Pipe Hydraulics

http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"

 

[bimr]

Here is an example of headloss across a preforated plate using airflow.

Headloss is plotted versus velocity.

 

[katmar]

That is a very interesting and potentially uesful chart bimr - thanks for posting it. Can you give a reference for the source?

Katmar Software - AioFlo Pipe Hydraulics

http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"

 

[bimr]

From the Perforated Metals Organization:

http://www.iperf.org/