- #1

downeast

- 11

- 11

My current project involves constructing an air bubble system to protect stationary docks from ice heave or ice jacking during the winter months. Ice jacking is the vertical lift as ice expands. When this grabs piles supporting stationary docks, it can wreak havoc.

I am mainly confused as to the order of calculations, and have been going in circles in an attempt at calculating the amount and diameter of orifices to drill so as to utilize an energy efficient linear diaphragm compressor. I have no particular model selected, but have chosen one below as an example. There are two docks to protect, and this is my current design layout. Both loops are identical, and pressure drops from pipe and fittings appear to be insignificant based on the tools I used to calculate. 28 holes per loop for a total of 56 holes.

This is one pump's performance curve, and I just added a few notes to the printed material:

Regarding orifice diameter air flow, this is the online tool I've been playing with:

https://www.tlv.com/global/US/calculator/air-flow-rate-through-orifice.html

I left the defaults for temp and discharge coefficient, and put in:

1.3 psig secondary pressure (3 feet depth below water --> 36 in/27.7 = 1.3 psig)

0.028 inch orifice size (equal to the 0.7 mm holes I will drill about 2 ft OC).

This is where my confusion comes in. Given the compressor's performance curve, and given the 36 inch water depth, what should I use as the primary pressure? Increasing the pressure will increase the air flow result, and multiplying that by 56 holes gives me total consumption. But going to the pump's curve to find the corresponding psi at that cfm, I get a new psi. That new psi, plugged into the orifice diameter air flow tool, results in a new cfm per hole and a new total flow. Hence my endless loop in calculations.

I at least know that I can't be thinking about this correctly, and I have no background in this subject. Any guidance on the order of calculations I should be taking would be greatly appreciated!

I am mainly confused as to the order of calculations, and have been going in circles in an attempt at calculating the amount and diameter of orifices to drill so as to utilize an energy efficient linear diaphragm compressor. I have no particular model selected, but have chosen one below as an example. There are two docks to protect, and this is my current design layout. Both loops are identical, and pressure drops from pipe and fittings appear to be insignificant based on the tools I used to calculate. 28 holes per loop for a total of 56 holes.

This is one pump's performance curve, and I just added a few notes to the printed material:

Regarding orifice diameter air flow, this is the online tool I've been playing with:

https://www.tlv.com/global/US/calculator/air-flow-rate-through-orifice.html

I left the defaults for temp and discharge coefficient, and put in:

1.3 psig secondary pressure (3 feet depth below water --> 36 in/27.7 = 1.3 psig)

0.028 inch orifice size (equal to the 0.7 mm holes I will drill about 2 ft OC).

This is where my confusion comes in. Given the compressor's performance curve, and given the 36 inch water depth, what should I use as the primary pressure? Increasing the pressure will increase the air flow result, and multiplying that by 56 holes gives me total consumption. But going to the pump's curve to find the corresponding psi at that cfm, I get a new psi. That new psi, plugged into the orifice diameter air flow tool, results in a new cfm per hole and a new total flow. Hence my endless loop in calculations.

I at least know that I can't be thinking about this correctly, and I have no background in this subject. Any guidance on the order of calculations I should be taking would be greatly appreciated!

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