Formula for Natural Convection in Calm Air 2

[ChEMatt]

From Chopey (2nd and 3rd edition) I have this formula (reproduced on this web page in part two of the calculation procedure).

I'm trying to find an equivalent formula in a reference text (started with McCabe Smith & Harriott) but I can't find any support. My problem is knowing where the coefficient 0.27 came from. Is it dependent on the carbon steel pipe? Or some other property? I need to know if this formula can be applied to any situation, regardless of the piping material or whatever "air" is (maybe a pipe in a nitrogen environment or something, who knows?)

Thanks! I'm looking in Perry's now... Hopefully someone can direct me to the source of that linked equation?

Q/A = (0.27 dT^1.25)/D^0.25

Thanks!

 

[IRstuff]

It looks to be a deconstruction of the standard natural convection equation. The 0.27 is usually the multiplier of the Rayleigh term to get the Nusselt number.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

faq731-376 forum1529 Entire Forum list

http://www.eng-tips.com/forumlist.cfm

 

[georgeverghese]

The detailed expression is derived from a combination of the fluid's Grashof and Prandtl numbers - see the subsection on natural convection in the chapter on Heat and Mass Transfer in Perry.

 

[srfish]

Equivalent formulas in a reference text can be found in Heat Transfer in Process Engineering by Eduardo Cao. It has simplified equations for different objects,