Compressor installation at high altitude

[HawksHockey]

Hi, this may have been asked previously, but... I have a compressor rated for 1500 SCFM (14.7 psia, 60 F), that will be installed at 3,369 ft above sea level (12.93 psia). The discharge pressure of the compressor is 105 psig, so at standard conditions my volumetric flow rate would be about 195 ACFM (as calculated).
My assumption is that the volumetric flow rate from the compressor is going to be decreased. I've used Crane Tech Paper No. 410, as well as other sources, but most of them deal with standard conditions and not installations above or below sea level.
I've calculated that the 1500 SCFM will actually be reduced to 1,320 ACFM at the inlet. Using the ACFM as the input to the compressor, I get an output of 171.4 ACFM at 105 psig. Anyone know if this is in the ballpark?
I'm not looking for confirmation on the numbers, only on the theory that at higher altitude, the compressor will have a reduced discharge volumetric flow rate.

 

[BigInch]

Assuming you are taking in gases at that altitude, the compressor takes in less air than at sea level, so it puts less out. What might be more of a concern is how the higher altitude affects your engine/motor. With higher altitude comes a lesser quantity of combustion air and less cooling.

http://virtualpipeline.spaces.msn.com

 

[HawksHockey]

Thanks, so far so good. We've been talkling about it in our office so the Electrical portion is also in motion. I'll have to check the services availability at the location (water, power, ...)

 

[budt]

Carry your altitude scenario to the Space Shuttle orbiting above the Earths Atmosphere and you would see that an Air Compressor operating in the Open Cargo Bay would run and produce no air flow. It twould be operating in 0 PSIA surroundings, or a Vacuum, and would have nothing to move.


Bud Trinkel, Fluid Power Consultant
HYDRA-PNEU CONSULTING

 

[dcasto]

The compressor moves 1500 SCFM at 14.7psia and 60 F. It's ACFM is the same if the the location has 14.7@60. So the piston swept volume (corrected for VE and such) is 1500 CFM.

At 12.93 @60, the compressor will move 1500 CFM. When adjusted for pressure, it will move 12.93/14.7*1500=1319.4 SCFM and still 1500 ACFM.

At the discharge you will get 1319.4 SCFM at 117.93 psia and we will assume 60f, so the ACFM = 1319.4/117.93/14.7= 164.5 ACFM

 

[zdas04]

Your design conditions at sea level call for 8.1 compression ratios. For the same discharge pressure at 3369 ft, you need 9.1 compression ratios. This takes about 5% more power, more suction flow (possibly softer valves that open earlier), and possibly bigger cylinders.

If the machine will compress 1500 SCFM at sea level then it will produce 1500 ACFM at sea level, and it will produce 1319 ACFM at your elevation.

David

 

[saplanti]

If the driver of the compressor is an internal combustable engine you need to consider the engine efficiency into consideration as well. Similar to compressors they will intake less oxygen for combustion and their combustion efficiency will drop down.

You need to solve the efficiency issues at the high altitude for the engine and the compressor by consulting the vendor. They have plenty good information to make everything suit for your needs. If the engine-compressor system is alrady available you still need to consult the maker or their representative.

Ibrahim Demir