Is the CFM Rating of a Compressor Measured in Intake or Discharge Side

Compressor manufactureres always use the unit in SCFM or Nm3/h to define its capacity (flow rate at normal temp and pressure). So whether it is measured at the intake side or discharge side of the compressor, it is one and the same.

"Did I make the correct use of cfm of the compressors?"

I don't think so.

So it means that i can directly use the cfm ratings of compressors in sizing its dessicant dryer?

why do you think that i was not right in making the cfm rating of the compressors as my basis in sizing the dessicant dryer?

Compressor output is roughly equal to air in, minus seal losses. Performance is rated at the output, not input.

"Dryers are specified with a flow rate in SCFM at 100 PSIG and 100°F. However, it is recommended that the actual operating conditions be determined to correctly size a dryer. It is rare that a given application will actually be running at the typical specified conditions. If the actual pressure is below the specified pressure and/or the actual temperature is above the specified condition, the dryer will most likely be undersized for the given flow rate and will most likely not produce the desired effluent dew point."

The above is quoted from www.dryersystems.com

Yes, and the capacity varies as the square root of the absolute pressure.

So it means that i can directly use the cfm ratings of compressors in sizing its desiccant dryer?

As I commented that compressor manufacturers always specify the capacities in SCFM or Nm3/hr, please check it. You have not clarified and always say cfm only. please check the instruction manuals supplied by the manufacturers (I'Rand & A'Copco), you will definitely get it that what standard pressure and temp they have considered for CFM rating. You can directly use the cfm ratings of compressors in sizing its desiccant dryer if standard pressure and temp considered are same for both, otherwise not.

why do you think that i was not right in making the cfm rating of the compressors as my basis in sizing the desiccant dryer?

Because of the reasons I have explained above.

Not always. They often rate them as "free air delivered", FAD. This is roughly the same as SCFM (provided the compressor is at sea level). I suppose this avoids specifying the inlet P and T to give rated performance.

Compresser rating is at the discharge side.

The pressure is, but definitely not the volume.

I think you are saying that it is the mass which is the same on both sides...But the volume will be different because air was compressed....

I beg to disagree

CFM (and SCFM) is air flow, not volume. Air flow in = air flow out (its physics).

GA.

ronjameso5,

"But the volume will be different because air was compressed...."

Standard CFM is like mass flow, almost same at intake and outlet. Actual volume will be different when air is compressed, not the standard volume.

i agree with lyn. it's the air output under optimal conditions.

Then I suggest you speak to a compressor supplier, who will tell you different.

It doesn't just apply to compressors, but to vacuum pumps as well. In the case of vacuum pumps, a cynic might think it was to get a bigger figure, but it also means the flow vs vacuum curve stays flatter, until ultimate vacuum of the particular pump is approached.