Mass vs Volumetric Flow Rates on the HVAC&R PE Exam

[bkuhn]

I am currently working through practice problems from several sources. I'm noticing many problem solutions are converting to mass flow rates even at standard temperatures, i.e., converting CFM to lb-air/minute GPM to lb-water/minute before solving.  For those who have taken the test, did you convert volumes to masses for any or all of the problems, or did you stick with CFM, GPM, etc.?

 

[MikeGlass1969]

I typically use the equations I am used to.   the ultra common Q=1.08*CFM*(T2-T1)  for air or Q=500*GPM*(T2-T1).

I only convert the mass flows if it requires that for an answer.