×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

no fan curves

no fan curves

no fan curves

(OP)
hi
We have an old spray dryer. it has an inlet fan and an exhaust fan.
currently it pulls the inlet air from the the plant causing major air flow issues through out the plant.
The plan is to duct the inlet to the outside so it has its own air source.Then the plant air flow can be straightened out.

the problem is there is no name plate on the fans and no record of what these fans are.
We can get air flows of the inlet and amp reads of the motors.

how can I determine if the current inlet fan can handle the added duct work and merv 13 filters that will be added or if it needs a larger motor or it just won't work.

thanks
tom
 

RE: no fan curves

Can you install a damper on the outlet on a tempory basis and plot the pressure rise and amperage draw as you close the damper ?
 Thereby generating your own fan curve.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them.  Old professor

RE: no fan curves

What type of fan is it?

At any rate, this is a case where the fan laws can be nicely applied.

 

RE: no fan curves

(OP)
thanks guys great suggestions.
There is a damper on the inlet of the fan. It looks like it has not moved in decades. But maybe it is time to make it do some work.

these are centrifugal fans. and I will start digging into the fan laws to see if I can make heads or tails of them.

Do you have any recommendations  of where to find the best explanation the fan laws, in laymans terms?
thanks again
Tom

RE: no fan curves

Simple calculator here:  http://www.engineeringtoolbox.com/fan-affinity-laws-d_196.html

Assumed:  You want to keep the same fan.  You want to keep the same flow.

You are adding ductwork and filters, so you are adding pressure drop.  You should be able to calculate the new total pressure drop.

That leaves you with speed to play with.

So to use the calculator:

Enter the known and needed air flow.

Enter your known current fan rpm.

Enter some new speed and calculate.  Repeat until the calculation result returns the existing flow rate.  Then note the new power requirement.

RE: no fan curves

Spend some time also on different fan types (forward curved,  backward inclined, radial, axial and etc) as they have different pressure/flow characteristics.

Then make your own curve using a manometer and a VOA meter.

Most fans with the same  wheel design and size have similar flow characteristics. Fan laws are your friend.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources