Required flowbench blower drive horsepower

By popular vote a place to add formulas. If you post a formula please make sure your abbreviations are spelled out so it avoids a lot of follow-up postings.  I know a lot of abbreviations are common or taken to be common knowledge. Please be sure to checkout the new FAQ of common abbreviations.

Please post formulas in separate topics, do not add formulas to someone else's post unless it relates to the original post. Also in the topic line make a note of what your posted formula is about . Thanks

Postby 84-1074663779 » Sun Nov 13, 2005 7:08 pm

Assuming an 100% efficient blower (impossible) the horsepower required to compress air thermodynamically. Temperature and barometric pressure will affect this, but for simplicity let's assume standard air conditions.

Hp = CFM x inches of water / 6339

By dividing that figure by blower efficiency you get the required total shaft drive power of the blower rotor(s). If the actual blower efficiency is not known, assume 40% as that is a fairly typical conservative figure for most vacuum motors and superchargers. You may actually do a little better than that, but don't count on it at the design stage.

Motor output horsepower can then be converted to watts by multiplying by 745.7

Motor input power = Motor output watts / motor efficiency

If the motor efficiency is not known, assume 85%. A more accurate figure can be worked out from the motor rating plate, if it has one.

Total Amps = Motor input watts / mains supply voltage




Here is a worked through example:

Hp = 500 CFM x 45 inches of water / 6339
Hp = 3.549

Shaft power = 3.549 / blower efficiency
Shaft power = 3.549 / 0.4
Shaft power = 8.8725 Hp

8.8728 Hp x 745.7 = 6,616 watts

Motor input power = 6,616 watts / motor efficiency
Motor input power = 6,616 watts / .85
Motor input power = 7,783 watts

Total Amps = Motor input watts / mains voltage
Total Amps = 7,783 / 240v
Total Amps = 32.43 A

So you can see a decent sized flow bench can be very power hungry !
84-1074663779
 

Return to Formulas

Who is online

Users browsing this forum: No registered users and 1 guest