5 replies to this topic

[LaneS]

We have a customer who has specified an air flow rate of 80 m3/min. The operating pressure is 1 barg. They have defined standard conditions at 45C and 1 bara. Please help me convert this to mass flow. I know that PV=nRT is the key.

Thanks!

[Art Montemayor]

Please read the Forum Guidelines before posting any queries. The Guidelines are found at:

http://www.cheresour...?showtopic=3313

Guideline #2 clearly instructs you to NOT MAKE MULTIPLE POSTINGS of the same query in different Forums.

I am deleting the other posting you made in the Student Forum.

[Art Montemayor]

It matters little that your client has re-defined Standard Conditions for gases. What matters is what is the definition of the 80 m3/min. Are these ACTUAL cubic meters or "STANDARD" cubic meters?

Do you want the 80 m3/min of air (at ? BarA & ? oC) converted to kg/min? If you do, you must tell us the air absolute pressure and temperature.

Await your reply.

[eilpar]

You may try the following simple formula for density calculation:

Density (Kg/m3) = 11.8 x Absolute Pressure in Kg/cm2 x M.Wt / ( T Deg K x Z ) where Z is the

compreesibility factor.

But as Art said please use the appropriate T and P conditions.

All the best

PAR

[djack77494]

But as Art said please use the appropriate T and P conditions.

This query reiterates the extreme importance of clearly specifying what you mean when you refer to "standard" or "normal" volumetric flowrates. We have clearly seen many times that both of these terms refer to different values in different geographic areas and in different industries. Also scientific usage is different from engineering usage. As "numbers oriented people", engineers must recognize the importance of clearly communicating their numbers. Murphy's Law (anything that can go wrong WILL go wrong) is clearly waiting in the background to strike.
Doug

[eilpar]

I find that there are four standards as given below:

1. STP - Standard Temperature and Pressure.STP is commonly used to define standard conditions for temperature and pressure which is important for the measurements and documentation of chemical and physical processes:

STP - Standard Temperature and Pressure - is defined as air at 0oC (273.15 K, 32oF) and 1 atm (101.325 kN/m2, 101.325 kPa, 14.7 psia, 0 psig, 29.92 in Hg, 760 torr, 33.95 Ft.H2O, 407.2 In.W.G, 2116.8 Lbs./Sq.Ft.)

2.NTP - Normal Temperature and Pressure
NTP is common for testing and documentation of fan capacities:

NTP - Normal Temperature and Pressure - is defined as air at 20oC (293.15 K, 68oF) and 1 atm ( 101.325 kN/m2, 101.325 kPa, 14.7 psia, 0 psig, 29.92 in Hg, 760 torr). Density 1.204 kg/m3 (0.075 pounds per cubic foot)

3. SATP - Standard Ambient Temperature and Pressure
SATP - Standard Ambient Temperature and Pressure is also used in chemistry as a reference:

SATP - Standard Ambient Temperature and Pressure is a reference with temperature of 25 degC (298.15 K) and pressure of 101 kPa.

4. ISA - International Standard Atmosphere
ISA - International Standard Atmosphere is used as a reference to aircraft performance:

ISA - International Standard Atmosphere is defined to 101.325 kPa, 15 degC and 0% humidity.

Please visit the website
http://www.engineeri...-air-d_772.html
for more information.

Regards

PAR