Re: How To Calculate The Power Required
You almost got the name right. 
Now give us a clue as to what you're talking about & please furnish units to ISO practice. 
Power is the rate of doing work & the normal units of power are based on seconds whatever system of units is used. ■
Details Of Power Calculation
I need to calculate the power required to process the sample in a homogenizer and this homogenizer inturn utilize compressor to pump the liquid.
SCF is standard cubic foot and scfm is standard cubic foot per minute which can be calculated by the amount of liquid that is processed per hour which is converted per minute (according to the manufacturer's chart).
After calculating scfm the chart just mention that rule of thumb for the compressor is 4 scfm/hp.
I am also confused due to the last statement. what does the rule of thumb describes:
Is this describe if a compressor discharge 4 scfm then the rating is 1 hp per hour (as the compressor rating is normally given per hr)
or as louispanjang mentioned that the power is normally calculated as work done per second.
or it is per min as the scfm was calculated for the amount of liquid processed per min ■
How to Calculate the Power Required
According to the manufacturer's manual
scfm is calculated as below
Air flow rate (scf/mL) X Product flow rate (L/h) X 1000 (mL/L) X (1/60) (h/min)
and mentioned that the rule of thumb is 4 scfm is 1 hp.
So does this hp for 1 hr or 1min. ■