Chemistry Converting scfm to lb/hr, which density should I use?

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To convert cubic feet per minute (CFM) to pounds per hour (lb/hr), the actual density of the air at the given conditions must be used, which is 0.61 lb/ft³ at 150 F and 125 psig. For standard conditions, the density is 0.0765 lb/ft³. When converting 500 CFM to standard cubic feet per minute (SCFM), the correct method involves multiplying by the actual density and then converting to lb/hr by multiplying by 60 minutes. The discussion highlights the importance of understanding the difference between CFM and SCFM in these calculations. Accurate conversions rely on the consistent application of mass principles in fluid dynamics.
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Homework Statement
If I convert from cfm to scfm, should I use the density of the material at standard conditions or what the conditions the material is actually at?
Relevant Equations
lb/hr = cubic feet/min * 60 min/hr * lb/cubic feet
For air for example at conditions 150 F and 125 psig, density is 0.61lb/ft3

At standard conditions it's 0.0765lb/ft3

If I convert 500 cfm to scfm, does this mean I should multiply by 0.0765lb/ft3*60min/hr to convert to lb/hr?
 
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It is not clear to me what are cfm and scfm, never seen these units (I can guess, but I prefer to be sure).
 
To convert CFM to lb/hr, you multiply by the actual density. To convert lb/hr to scfm, you then divide by the standard density.
 
In general the only invariant thing in such calculations is the mass.
 
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