Hi all, I have a question regarding the mass flow rate of air through a pipe. On paper, it looks like temperature and pressure effect the mass flow rate but I can't rationalize it in my head. Here's what I got: Goal: Calculate the actual mass flow rate of lets say, CH4 through a pipe Given: 10 SCFH (standard conditions are defined as 60F, 1atm) MW of CH4 = 16.04lb/lb-mol T=250F P=114.7psia My calculation: ACFH=10SCFH*(14.7psia/114.7psia)*((250+460)/(60+460))= 1.715ft^3/hr Molar volume=(RT)/P=0.143ft^3/mol Mass flow rate = molar volume/ACFM*MW=192.37lbs/hr However, I am told that the mass flow rate doesn't depend on T and P and the calculation should be as follows: Mass flow rate = SCFH/397*MW = 0.504lbs/hr The 397 is the molar volume at STP (60F, 1atm) Who is right in this case? Does the mass flow rate depend on T and P? Thank you for your time and comments.