CENTRIFUGAL FAN SHELL

[pardal]

Hi all HVAC-R people.

I need to know what is the profile of the shell for a given centrifugal wheel fan.

Seem to be a involute or a spiral , but I do not know what mathematic function rule the drawing of such profile.

Thanks in advance.




Pardal

 

[Jcubed00]

Pardal

I do not know the mathmatic function of determining the scroll, but the scroll profile can be drawn from any fan manufacturers catalog dimensions, given wheel/fan size. This info can be found on most manufacturers web sites.

Regards

 

[pardal]

Hi Jcubed00.

Of course I can , and I will do so.
But I always try , al least, to know why I do a new thing.

Seem to be that the only concern is to give the outlet area to have a given air speed.

I had seen centrifugal fans on a plenun without any scroll.

Thanks for your tip.



Pardal

 

[mangua]

Pardal
You need a fan catalog, choose the wheel diameter.
Take the dimension horizontal and/or vertical of the shell or involute.
You draw un quarter in the center, each side is "L"
The quarter has four points. In each point is your center. Suppose the rotation is clockwise,discharge is vertical up.
The first point is in (L/2,-L/2) radio "R"
The second point is in (-L/2,-L/2)rdio R+L
The third point is in (-L/2,L/2)rdio R+2L
Resolve the equation with the dimension in catalog.
R+L/2 = dimension1
R+ 2L+L/2 = dimension2
R + 3L+L/2 = dimension3

Ojala me haya entendido
Atentamente
Mangua

 

[saeidj]

Hi Pardal
Here is a formula you can use.
You should know the wheel diameter and then base on the fan model (forward, backward) you can choos constant coeficient.

R=R0 * (1 + K * Teta)

R0 = wheel radius
R = Shell radius at teta angle
Teta = angle (radian)

K=0.0023 for backward and K=0.0021 for forward

Also the width of the shell depends on the width of wheel at the tip.
for forward
width = 1.25 * wheel width

backward
width = 2.5 * wheel width

regars