Compressed air flow rate?

[JustBob]

Anyone know how to, or the location of an online calculator for determining compressed air flow rate through multiple tubes in parallel?

Example: I was thinking of using a 4.5 ton air handler to make a compressor after-cooler, it has the motor, fan, and coil already boxed. The coil I want to use is a W shaped instead of an A coil, and the air would flow through 8, 1/4" inside diameter tubing simultaneous.

3/4" inlet tubing, branching off into 8, 1/4" tubes, then combining back into 3/4" for an outlet.


If the calculations come out ok, I will go ahead with the build since the equipment is free.

 

[Stinger]

I wouldn't count on you finding any calculators that calculate what you are asking. First step would be to calculate the internal area of the 8 tubes vs the 3/4" inlet to make sure they don't cause a restriction.

 

[MattT]

I wouldn't count on you finding any calculators that calculate what you are asking. First step would be to calculate the internal area of the 8 tubes vs the 3/4" inlet to make sure they don't cause a restriction.

Pretty much. Isn't just the cross sectional area that affects flow though. You've got to figure the bends too.

Also for a cooler you need to watch velocity. The cooler ain't gonna do you any good if the air is running thru' it faster 'n' a scalded dawg.

 

[JustBob]

I am pretty sure I was overthinking this, since an aftercooler goes between the pump and tank. The pump to tank line is only 1/2", so I believe 8, 1/4" lines should not be a problem for 12 cfm.

The coil has 10 square ft total area, with 146.6 feet of tubing. Each line is18.3 feet in length. It should have a lot cooling capacity...

Since the parts were all free I will go ahead and build it, if nothing else just to see how well it works. I can post up a build thread after I get started if anyone would be interested.

 

[MattT]

I am pretty sure I was overthinking this, since an aftercooler goes between the pump and tank. The pump to tank line is only 1/2", so I believe 8, 1/4" lines should not be a problem for 12 cfm.

For 12cfm you're good

 

[pistolpete]

Just for future reference.... a real basic calculator.

http://www.gates.com/industrial/pressure/airFlow.cfm

 

[larry_g]

Is your air handler rated for the pressure you will be using?

lg
no neat sig line

 

[JustBob]

Is your air handler rated for the pressure you will be using?

lg
no neat sig line

Yes, all tubing is ACR grade, good for 1100 psi for 5/16 tubing. I will be brazing the incoming line fittings, and then siver soldering the new manifold on the outlet side. Inlet temp will be 300 F, reason for brazing instead of soldering.

 

[JustBob]

Just for future reference.... a real basic calculator.

http://www.gates.com/industrial/pressure/airFlow.cfm

Thank you, just what I needed. Using that calculator, and dividing the total cfm by 8(1.56 cfm each .250 line), it shows a pressure drop of .20 psi. It should be good for future upgrade as well, at 24cfm/90psi it shows a pressure loss of .73 psi. At 175 psi/24cfm it shows .4 psi drop.

 

[pcmeiners]

This calculator is pretty nifty...

http://www.freecalc.com/gasfram.htm


PS: The spacey look in your picture caused by initial GJ addition (GJ Syndrome) goes away after a year or two (at least in most cases). Mean while, just accept the fact you will be scaring the **** out of the people at the take out windows of your favorite fast food establishment.