Why is there a discrepancy between the methods I am using?

[n8cole]

Propane has a mass flow rate of 9 lbs/hr and I am tasked with converting it to liters/hr. I chose to do the conversion two ways.

Method 1: 9lbs/hr *(21600 BTU/lbs) * (24000 BTU/liter)[sup]-1[/sup] = 8.1 liter/hr
Method 2: 9lbs/hr *(44.1 lb/lbmol)[sup]-1[/sup] * (379 scf/lbmol) * ((460+70)/530)*(14.7/(14.7+100)) {scfh to acfh} * (28.31 L/cu.ft) = 280.63 liter/hr

Why am I getting different liter/hr? shouldn't the answers be the same?

 

[EdStainless]

Check your units, you have a couple of errors

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[Compositepro]

Method one is for liquid volume. Method 2 for gas volume.

 

[pierreick]

Hi,
This is very weird! Where did you learn the method 1?
Mass flow rate = volumetric flow rate * Density, get the density of your material at the appropriate condition.
You should know whether it's a liquid, a gas or a mixture.

https://webbook.nist.gov/chemistry/fluid/

Good luck,
Pierre