Crane #410 has 400% more friction factor. Why?

[sdtobin]

Crane #410 has 400% more friction factor in the "fiction factors versus Reynold #" table. Does anyone know why?

I compared the Crane #410 table to the Moody, Trans. ASME 66, 671 [1944] friction factor table. This table is located in the Perry's Chemical Engineering Handbook in the Fluid and Particle Dynamics section.

How I found the discrepancy is as follows:
- My frictional factors, calculated by the Churchill equation, were 4 times smaller than the Crane #410 table.
- The Laminar flow region in one table says f=16/Reynolds # and another say f=64/Reynolds #.

Therefore, why is Crane #410 400% more stringent than the college texts. What are you thoughts?

 

[tickle]

In Coulson and Richardson it defines two fs, the Moody and Fanning friction factors. The Moody factor is four times the Fanning factor. I think from my unused memory bank that there is a third factor which is twice the Fanning factor.

Therefore I suggest you look at the relevant pressure drop equations to see if they give the same results.

 

[sdtobin]

Good news, I notice the Perry's pipe friction loss equation has a 4 coefficient, and the chart is 4 time less than Crane # 410. Now Crane #410's chart is 400% larger, but their friction loss equation drops the 4 coefficient. Therefore, both ways produce the same numbers in the end.

They confused everything for people like me. For example, if I use Perry's Chemical Engineering Handbook and they use Crane #410, we would produce the same friction loss equation numbers but different frictional factor constants.

 

[zdas04]

Fanning friction factor is defined as Moody Friction Factor divided by 4. Moody is generally used for liquids. Fanning is generally used for gases. I have never seen a book (even Perry's) that mentioned one without mentioning the other and the conversion factor.

David

 

[MortenA]

I think it depends on your school which you are used to. I'm from Denmark, and we learn it as Fanning, whereas I have guessed that UK and USA learns the Moody variation. Danish higher learning being influenced more by Germany and France i think that continental Europe learns Fanning and UK/USA learns Moody - then again i could be wrong Just an early Tuesday morning at a summer quite office!

Best regards

Morten

 

[Latexman]

I was taught there were two friction factors and to be extremely careful to know which one you are using. That was 35 years ago in US.

Good luck,
Latexman

 

[SNORGY]

North Americans are typically more moody than the Danes.

(I can say that because I am both of the above.)

Regards,

SNORGY.

 

[sdtobin]

I have the narrative for why as follows:

http://files.engineering.com/getfil...0ae3a18e&file=BizHub35020110928125442_Rev.jpg

 

[25362]

If I'm not mistaken, the 4 stems from the simple fact that the shear stress between the conduit's wall and the fluid was originally estimated for a circular cross-section (as for tubes and pipes) with a value of [π]D²/4.

 

[chemebabak]

The graphs in Crane #410 (A-24 and A-25) are for Moody Friction factor, which is 4 times Fanning friction factor. That is, f = 64/Re is Moody and f = 16/Re is Fanning.

Be careful. It is easy to mix the two and calculate 400% greater (or 25% less) head loss. The calculation for head loss in feet is:

using Moody Friction factor -
h(friction) = f(M) * (L/D) * v^2 / (2 * g)

using Fanning Friction factor -
h(friction) = 4*f(F) * (L/D) * v^2 / (2 * g)

where,
f(M) = Moody Friction factor
f(F) = Fanning Friction factor
L = length in feet
D = pipe inside diameter in feet
v = velocity in ft/s
g = 32.174 ft/s^2, acceleration due to gravity

The Colebrook-White equation is an iterative method that calculates Fanning friction factor.
f(F)^2 = 1 / ( -4 * Log(eps / (3.7 * D) + 1.256 / (Re * ?f(F) )

where,
eps = pipe roughness in feet
Re = Reynold's number

 

[chemebabak]

See faq124-1746