14 replies to this topic

[Bal]

Hello,

 

How to calculate the electrical power needed to operate a fan? I know the duty of the fan.

 

 

Thanks

 

[fallah]

Bal,

 

For quick estimation:

 

HP=(CFM*PSF)/(33000*Efficiency); where:

 

CFM: Cubic Feet per Minute): Delivered Volumetric Flow Rate

PSF: Pounds per Square Foot): Total pressure Increase

[Bal]

Thanks a lot Naser.

 

what typical values for efficiency and PSF can I assume (for a simplified solution)? 

[fallah]

 

what typical values for efficiency and PSF can I assume (for a simplified solution)? 

 

Bal,

 

Typical value for PSF is 100 (should be below around 300) and typical value for efficiency is around 70%...
 

[Bal]

Thanks.

One last question: where can I find this equation? cz i need the reference

[Bal]

Is it related to the one in GPSA?

CFM is the flow rate of the fluid or the air?

[breizh]

Hi Bal ,

 

Consider the excel sheet attached to support your work

 

Breizh

Edited by breizh, 18 October 2015 - 07:58 PM.

[Bobby Strain]

I found this among my collection. Maybe it still works.

 

Bobby

 

Attached Files

•  Blower Power.xlsm   33.11KB   97 downloads

[Bal]

Thanks a lot Breizh and Bobby.

[Bal]

Bal,

 

For quick estimation:

 

HP=(CFM*PSF)/(33000*Efficiency); where:

 

CFM: Cubic Feet per Minute): Delivered Volumetric Flow Rate

PSF: Pounds per Square Foot): Total pressure Increase

How to calculate CFM?

is there any rules of thumb?

[fallah]

 

How to calculate CFM?

 

is there any rules of thumb?

 

 

When it's intended the fan power to be calculated; the required CFM has to be specified by whom is performing such calculation...!
 

[Bal]

That's true, but I'm trying to estimate the fan power for a project and I can't deny my lack of knowledge this area.

 

The only information in my hand is the duty of the air cooler (2.73 e6 BTU/hr). 

The procedure in the GPSA is lengthy and considers some design details that I don't actually need. 

I found another book (rules of thumb of chemical engineers by Carl) and it gives a shorter path for calculating the fan power, but I can't use it even because it requires ACFM value and number of tube raws (I don't care about this one).

 

I realized that you can't proceed with the fan power calculations without the ACFM,,,,but 

 

Is there anyway to relate the ACFM needed with the duty of the fan?

[Bal]

Q=M Cp dl T??

[fallah]

Bal,

 

One BTU/hr is almost equal to 0.3 watts...Then considering a typical value of efficiency equal to 70% you can easily estimate the fan power value...

[Bal]

Thank you very much