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Anonymous Poster #1

### Density of Air

03/07/2012 12:20 PM

Can any one tell me how to calculate density of air 15500Nm³/hr @ 0.6kg/cm² at 800°C?.

Regards,

Santy

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Guru

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#1

### Re: Density of Air

03/07/2012 3:06 PM

Not with those numbers.

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#2

### Re: Density of Air

03/07/2012 6:09 PM

Yeah, I'm with Lyn on this one. To quote the weathered old gentleman at the gas station:

"Umm, you can't get there from here, you're gonna have to go back from where you started."

Components of the air density equation are absolute pressure, absolute temperature, and a gas constant. And at the temp you mentioned, you'll look for the constant for 'dry' air as I don't think it will be too humid at 800C.

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#3

### Re: Density of Air

03/07/2012 9:25 PM

Well, first of all, you do not need the flow rate to calculate this.

You can find a pretty good approximation using perhaps the:

Redlich-Kwong equation of state

Introduced in 1949 the Redlich-Kwong equation of state was a considerable improvement over other equations of the time. It is still of interest primarily due to its relatively simple form. While superior to the van der Waals equation of state, it performs poorly with respect to the liquid phase and thus cannot be used for accurately calculating vapor-liquid equilibria. However, it can be used in conjunction with separate liquid-phase correlations for this purpose.

The Redlich-Kwong equation is adequate for calculation of gas phase properties when the ratio of the pressure to the critical pressure (reduced pressure) is less than about one-half of the ratio of the temperature to the critical temperature (reduced temperature):

Make sure you use consistent units. Oh, and the temperature is absolute; mind your conversion. Oh, and the critical temperatures and pressures of gas mixtures (e.g. air) can be tricky! Oh, and make sure that you use the value of R that is consistent with your units.

Now, after all this, why do you need to know? Maybe there is a better way of getting the answer that you seek, grasshopper.

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#4

### Re: Density of Air

03/07/2012 9:31 PM

Oh man... I brought the plate, but you fed him. He didn't even need to break out the flatware.

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#5

### Re: Density of Air

03/07/2012 9:58 PM

Thanks. I love engineering!

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Anonymous Poster #1
#6

### Re: Density of Air

03/11/2012 12:59 AM

Dear Sir,

Thank you very much.