CFM PSI MPH Velocity and Static Pressure

[Mike vB]

Anyone have recommendations on books I can read that explains the differences between things like CFM PSI MPH Velocity and Static Pressure?

I have a project I'm working on that I need forceful air (think leafblower) for a lottery type drawing machine that uses air to circulate ping pong balls...ranging from 1000 to 6000.

My druthers would be like a 24" diameter fan, but the force, as most of you know, is very week. I've been looking at fans from those "sky dancer" things as the 24" fans they carry at Lowes/Home Depot just don't have the ooompf I'm looking for.

Oh, and it needs to be as quiet as possible for indoor use - if it matters.

Thoughts? Suggestions?

Thanks in advance!

Mike

 

[Nealcrenshaw]

Hey Mike, Check out a book called Marks Mechanical Engineering by Eugene A. Avallone. It's filled to max on hydraulics,Pneumatics,Robotics,mathematical theory,Machining,electrical Theory,motors,piping and Stuffed with tons of theory on all mechanical applications.

i just ordered one today off of Alibris.com for about $8.
I think it's the 9th or 10th edition i orderded but they just released a Eleventh edition last year i read it was about 1800 pages, I would tell you to get it from the library which i thought about doing but you might not ever returned it.

 

[speed bump]

CFM=Cubic Feet per minute. This is a measure of how many 1x1x1 Ft. boxes of air are moved in 1 minute.

PSI=Pounds per Square Inch. This is a measure of how many pounds of force are applied to a 1 in x 1 in square.

MPH=miles per hour. This is a measurement of Velocity or speed. How many miles you will travel in 1 hour.

Velocity=speed this is measure in various units that are some length (be it Meters, inches, feet miles) over some amount of time (seconds, minutes, hours, days)

Static pressure=the maximum amount of pressure that a system can have which occurs when the flow rate is 0.

As far as books to further help you understand what you want to do I would suggest just picking up an entry level Fluid mechanics text.

For what you are doing I would suggest using a blower rather than a fan since you don't need to move alot of air but you want pressure to keep those balls moving.

 

[Blacktooth Grin]

As far as books to further help you understand what you want to do I would suggest just picking up an entry level Fluid mechanics text.

My first thought.

Hey Mike, Check out a book called Marks Mechanical Engineering by Eugene A. Avallone. It's filled to max on hydraulics,Pneumatics,Robotics,mathematical theory,Machining,electrical Theory,motors,piping and Stuffed with tons of theory on all mechanical applications.

Sounds like a good book.

Disclaimer: I have never found an engineering book that is not difficult to read and decipher, and I have had my fair share of them.

 

[ddawg16]

I actually have experience with something similar....

In your case you need a combination of CFM and velocity (MPH) with enough static pressure to keep them going.

Consider this...you move x amount of air (CFM) through a tube...it comes out at y speed (velocity). Now, reduce that area of the tube by half...assuming your fan can handle the difference, the velocity will about double in order to keep the same CFM.

Now enters static pressure...this is the difference between inside and outside....or, to put it in terms that most people, torque....and the above would be your HP.

The fan design dictates the amount of static pressure. The typical bladed fan can move a lot of air but does not have much torque (static pressure). To get that you need a squirl cage design (like the typical central heater fan type).

Now the bad news...quite? Well, that is basically a function of the air velocity....the higher the velocity, the more noise you have.

I think the best option for you would be to use a fan of the type that is found on a dust collector. Quieter than a leaf blower and more manageable.

To regulate the air flow, put an adjustable dampner on the intake.

Hoep this helps.

 

[Mike vB]

Thanks all. I think CFM is NOT what I'm looking for - which most indor fans use for comparison.

Ddawg, could you recommend a manufacturer or two so I can start my search?

What about a home condenser fan unit? Those seem quiet enough, and put out a nice amount of air with good speed.