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harold_tr • May 4, 2008

What about volumetric loss in blowers and fans at high altitudes

😕Hi crazy people!

It's well know that at high altitude (> 1000 masl) there's a volumetric loss in blowers and fans. (usually air)

And I work at 3800 m.a.s.l. in a Cement Plant.

So I have a doubt:

- Does a blower or fan produce the same amount of VOLUME at 3800 m.a.s.l. than at Standard conditions (20ºC, 1 atm, 0 m.a.s.l., ...), but there's less amount of MASS (i.e. there's < AIR DENSITY) ?


- Does a blower or fan produce less amount of VOLUME at 3800 m.a.s.l. than at Standard conditions (20ºC, 1 atm, 0 m.a.s.l., ...) , and also less amount of MASS (i.e. also there's < DENSITY) ?

* And moreover there's less OXIGEN in the AIR (<23%) at high altitudes ...

Could you please recommend some literature about this topic ? , I like to understand about blowers and fans, and also about combustion at high altitudes.

Thanks for your help


How does a blower, fan, combustion engine change with altitude?
Just for comparison a alternative mechanism and roots blower, and centrifugal fan. And on the other hand Internal combustion engines (diesel or otto cycle)
gohm • May 4, 2008

An internal combustion engine will experience a change in its fuel/air ratio with altitude change. Fuel injection mapping can adjust and change to compensate. A carburated or natural aspiration engine will require jetting changes to compensate. These jets would need to be changed along with major altitude changes for optimal performance so if this is a moving vehicle that may not be possible. A "happy medium" needs to be reached depending on the altitude conditions most spent at. You are also on the right track with the fans. You could rig up a really easy fun test on this. Here's a link of info to get you stared on blowers.
Solving High Altitude Cooling Problems - Application Note
vinayak sathe
vinayak sathe • May 4, 2008
Please go through:
Solving High Altitude Cooling Problems - Application Note
The site will help you in getting all the answers.
The capacities of fans, blowers and compressors need to be adjusted for density of incoming air, which varies with altitude and or ambient temperature.
harold_tr • May 5, 2008
Thanks for your response!

I have one more question:

- If I have less air than at standard conditions for my blower, when I measure with a flowmeter I could get the air flow (VOLUME) , so I could get the SAME VOLUME that at standard conditions (with a minor density) or I`ll have less volume (and less density?)

Taking in count your recomendations I made a volumetric convertion for my blower:

- About blower:
Air Flow: 492 m3/min
Power: 355 KW
Intake pressure: 101 KPa
Pressure Rising 29.34 KPa

- About environmental Conditions:
Altitude: 3850 m.a.s.l.
Pressure: 0.64 bar
Temperature: 11ºC
Relative Humity: 37%

- About "Standard Conditions:
Pressure: 1 bar (101 KPa)
Temperature: 20ºC
Relative Humity: 36%

*Taking in count every thing above, I'll have 311 m3/min...

But I'll like to know if really I could reach this 311 m3/min or less, and how it's for a combustion process I'll like to know about MASS variation.

I don't have a manometer for this blower yet.

Now, I have the following parameters in operation:
162 m3/min , having 56% opening (at derivation valve after blower)

My doubt is just because of AMBIENT PRESSURE, air density is affected ??? or What else???

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