Calculation of "Minor" Pressure Losses

Posted in: , on 28. Oct. 2009 - 20:53

Hi all,

I want to calculate "minor" pressure lost in a pneumatic system using only air.

In the literature i've found a LOT of K coefficients or equivalent length particulary from this references:

Crane

Pneumatic Conveying Design Guide - David Mills

Piping Handbook 7th Edition

gas engineering data book

Fluids mechanics books: Mott, Shames, White, Munson

but i dont know which use.

Any recommendation?

(sorry my english)

Regards ■

Andrés Miller V. PRDW-Aldunate Vásquez Consulting Port and Coastal Engineers
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Re: Calculation Of "Minor" Pressure Losses

Posted on 28. Oct. 2009 - 09:40

Dear Andrs,

Have you visited the following links?

Pneumatic conveying, Performance and Calculations:

https://news.bulk-online.com/?p=65

Dense phase- or dilute phase pneumatic conveying:

https://news.bulk-online.com/?p=238

Pneumatic conveying, turbo- or positive displacement air mover:

https://news.bulk-online.com/?p=309

Energy consumption per ton of a pneumatic conveying system:

https://news.bulk-online.com/?p=331

Pneumatic conveying, an unexpected relationship.

https://news.bulk-online.com/?p=445

Influence of electro static charge on pneumatic conveying.

https://news.bulk-online.com/?author=15

The air only pressure drop can be calculated as follows:

According Darcy-Weisbach, the head loss of a flow due to friction is:

dp = fDW * v^2 / 2* dL/D/g (meter of air at p and T)

where :

fDW= the Darcy friction factor (fanning factor)

v = velocity in m/sec

L = pipe length covered

D = pipe diameter

g = acceleration of gravity

The K factor is a multiplication factor relating to this air only pressure drop.

If you receive Mr Agarwal’s article, study it and in case of more needed info, please return to the forum.

Have nice day

Teus ■

Teus

Re: Calculation Of "Minor" Pressure Losses

Posted on 29. Oct. 2009 - 02:06

Dear Teus Tuinenburg

I dont have the article of Mr Agarwal because i'm hoping that he sends it to me.

I want to know which K or equivalent length use to calculate the pressure drop in a bend (45º or 90º), elbow, or tee, when i work with air only.

I know the relationship from Darcy-Weisbach, but i want to know what references you use to calculate that.

Regards! ■

Andrés Miller V. PRDW-Aldunate Vásquez Consulting Port and Coastal Engineers

Re: Calculation Of "Minor" Pressure Losses

Posted on 29. Oct. 2009 - 09:11

Dear Andrs,

The pressure drop in a bend can be calculated according the

general formula for resistance :

dp(bend) = beta/1.57 * 1/2 * zeta(bend) * rho(air) * v-air^2

In which :

rho(air) = local air density (p.V.T conditions)

beta = covered angle in radians

zeta(bend) = friction factor for a bend of 90 degrees ( pi/2 radians ).

The “K-factor” represents the presence of material in the airflow.

The value of K depends on the material and is different for each pressure drop calculation algorithm.

Best regards

Teus ■

Teus