Increasing Air flow 1

[lukin1977]

Sorry if this is the wrong forum for this question.
We have one electrical dryer (oven) which has a centrifucal fan to recirculate inside air. I dont have the fan´s curve and I need to increase the air flow inside the dryer

I can increase fan rpm by simply changing it´s pulley.
Motor is 5,5kW
FLC= 12 A

Motor current with the actual pulley configuration is only 6 A so I have "room" to increase load on the motor
Question: Increasing fan rpm will increase air flow?
Any thoughts?

 

[chicopee]

As long as system characteristic curve remains the same, air density and fan size do not change, CFM will increase to the same proportion as RPM ratio of the new RPM to the original RPM; however, shaft horsepower will also increase to the cube of the same RPM ratio; so will current usage which could trip your circuit breaker. ME handbooks have excellent details on the basic and corollary laws on fans.

 

[Drazen]

what do you want with increasing air flow'

 

[lukin1977]

I want to increase air flow to improve the "drying performance" of the oven. The product been dryed is not uniformly dryed

Product: Stick electrodes

I am looking to achieve more air turbulence

 

[Hatem2014]

theoretically
the rpm is proportional to the flow
and
the static pressure is proportional to square flow
and
power is proportional to cubic flow
so, in you case the current (witch proportional to power)is 6 A and the max. current is 12 A
then simply theoretically: the max. available flow rate is about 1.25 times your flow rate now

 

[Hatem2014]

note: carefully check your ampere immediately after changing the pulley because all previous calculations is theoretical and the practical one sure is different

 

[Drazen]

i have no clear idea how electrodes are stocked in drying room - i worked similar thing with sausages , but would it not be an issue of air distribution system in drying room?

i don't see how more flow itself will guarantee more uniformity. with cold air you can always have issue of air stream drop if velocity is too low, but it's not the case with warm/hot air.

 

[Drazen]

... and yes, i feel chicopee has star tip...

 

[lukin1977]

Drazen

Yes. first thing I did was improve the air distribiution. I installed bufflers with good results.

 

[lukin1977]

Another picture of the electrodes ready to be dryed

 

[lukin1977]

Drazen

can you exlain more? "with cold air you can always have issue of air stream drop if velocity is too low, but it's not the case with warm/hot air"

I dont understand

 

[willard3]

You will want to know what the fan curve looks like before you change volume. Changing voluble can cause instability with certain fan types.

 

[Drazen]

lukin, you can best google some air distribution devices tech overview, it's beyond tips level to explain it. google trox, for instance, and take a look at air pattern of any wall grille.

we see now how electrodes are laying, but we don't see how air distribution elements look like. anyhow, increasing flow would rather disturb uniform distribution than improve it. that's only general statement, of course.

your original question is answered by others, i was just suspicious about your intentions and now i'm little more confident that you are not going in right direction.

i will switch back to my sausage experience - "improving performance" of drying process is in direct contradiction with unifrom drying - the slower you drive, the better uniformity. you want one or another - or some good compromise.

 

[lukin1977]

A basic scheme of the oven. Front view

 

[lukin1977]

Here is a picture of the inside (right side wall)
Left side is the same