## Hole amount and size calculation for perforated pipe (Sparger)

## Hole amount and size calculation for perforated pipe (Sparger)

(OP)

Hey everyone,

I am trying to calculate how many holes I need for an equal air release in a perforated pipe scenario.

I have a 5 HP blower with max. 2,500CFM airflow at 1.000in SP. I would like to have a hole size of 1/2" if possible.

You can find the pipe geometry attached.(everything is horizontal) I would like to have the same hole size everywhere and the holes have to be on the bottom of the distributor pipes. The surrounding medium is air.

I calculated that at 1.000in-SP the pressure difference to the surrounding air is 0.0364psig.

Therefore the airflow through each hole is = 1/60 * 4.17 * C * (10/4.654)^2 * 103.08kpa * (1- (103.08-101.325)/103.08)/(3*0.71*0.72)) * sqrt((103.08-101.325)/103.08)/(20+273.15)

= 0.2567 * 103.08kpa * (1- (103.08-101.325)/103.08)/(3*0.71*0.72)) * sqrt((103.08-101.325)/103.08)/(20+273.15)

= 0.2567 * 103.08kpa * 0.989 * sqrt((103.08-101.325)/103.08)/(20+273.15)

= 26.17 * 0.00762

I just assumed 0.8 for the discharge coefficient. Then I get to an airflow of 0.2Nm3/min which equals 7SCFM or 357 holes

However when I type my numbers into this formula here https://www.tlv.com/global/ME/calculator/air-flow-... I geta result of 2.65SCFM per hole or 944 holes total.

Where is my mistake? And can I calculate it in this way?

I am trying to calculate how many holes I need for an equal air release in a perforated pipe scenario.

I have a 5 HP blower with max. 2,500CFM airflow at 1.000in SP. I would like to have a hole size of 1/2" if possible.

You can find the pipe geometry attached.(everything is horizontal) I would like to have the same hole size everywhere and the holes have to be on the bottom of the distributor pipes. The surrounding medium is air.

I calculated that at 1.000in-SP the pressure difference to the surrounding air is 0.0364psig.

Therefore the airflow through each hole is = 1/60 * 4.17 * C * (10/4.654)^2 * 103.08kpa * (1- (103.08-101.325)/103.08)/(3*0.71*0.72)) * sqrt((103.08-101.325)/103.08)/(20+273.15)

= 0.2567 * 103.08kpa * (1- (103.08-101.325)/103.08)/(3*0.71*0.72)) * sqrt((103.08-101.325)/103.08)/(20+273.15)

= 0.2567 * 103.08kpa * 0.989 * sqrt((103.08-101.325)/103.08)/(20+273.15)

= 26.17 * 0.00762

I just assumed 0.8 for the discharge coefficient. Then I get to an airflow of 0.2Nm3/min which equals 7SCFM or 357 holes

However when I type my numbers into this formula here https://www.tlv.com/global/ME/calculator/air-flow-... I geta result of 2.65SCFM per hole or 944 holes total.

Where is my mistake? And can I calculate it in this way?

## RE: Hole amount and size calculation for perforated pipe (Sparger)

## RE: Hole amount and size calculation for perforated pipe (Sparger)

Good Luck,

Latexman

## RE: Hole amount and size calculation for perforated pipe (Sparger)

## RE: Hole amount and size calculation for perforated pipe (Sparger)

## RE: Hole amount and size calculation for perforated pipe (Sparger)

Katmar Software - AioFlo Pipe Hydraulics

http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"

## RE: Hole amount and size calculation for perforated pipe (Sparger)

## RE: Hole amount and size calculation for perforated pipe (Sparger)

There are 16 possible routes for the air to follow. Thanks to symmetry we only have to analyze 8 of them. The pressure drop through each of these routes is the same (i.e. 1" H2O), and the aim is to have the flow rate the same (i.e. 156 scfm) at each exit point. The pressure drop for each route is made up of 3 components, ie from the middle of the 10" manifold to the hole, through the hole, and from the hole to atmosphere via the 4" pipe. All the flow rates are known so it is possible to calculate the first and last of these components, and then by difference determine the pressure drop through each hole and therefore size that hole.

This is all far too much work for me. I prefer to make the first and last components negligible, making the pressure drop through the hole 1" H2O in all cases. Total pressure drop for any of the routes = negligible + 1 + negligible = 1.

Having all the holes the same size also reduces the chances of fabrication errors.

Katmar Software - AioFlo Pipe Hydraulics

http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"

## RE: Hole amount and size calculation for perforated pipe (Sparger)

1" H2O within .0001" H2o is far different from 1" H2O within .5" H2O

Same for flow - does the flow have to be equal to 1 part in a 1000 or 1 part in 1?