natural convection over cylinders
natural convection over cylinders
(OP)
Which is the most precise correlation for natural convection around horizontal cylinders?
Heat transfer books gives different expresions but they do not say anything about precission or preferred range of application
Could somebody recommend me any reference about it?
Heat transfer books gives different expresions but they do not say anything about precission or preferred range of application
Could somebody recommend me any reference about it?





RE: natural convection over cylinders
J.P. Holman (Heat Transfer) gives for free convection of air around horizontal cylinders the following simplified equations:
for laminar flow, i.e., 104<Gr.Pr<109, h = 1.32 (ΔT/d)0.25
for turbulent flow, i.e., Gr.Pr>109, h = 1.24(ΔT)1/3
h = heat-transfer coefficient, W/(m2.oC);
d = diameter, m;
ΔT = Tw - T∞ , oC
RE: natural convection over cylinders
For Ra<=1012
Nu = [0.6 + ((0.387 Ra1/6)/(1+(0.559/Pr)9/16)8/27)]2
Properties of air should be at average air temperature and temperature of the cylinder is skin temperature.
RE: natural convection over cylinders
This appears to be the fourth time you've posted a question regarding natural convection over horizontal cylinders. All of them have been very general about what you're wanting. How about a bit more information as to your application and what you're trying to achieve.
At this point, I'm thinking your a student who's not willing to look beyond his text book...
Patricia Lougheed
Please see FAQ731-376 for tips on how to make the best use of the Eng-Tips Forums.
RE: natural convection over cylinders
For example, does the distance between the wall and the tubes matter? Of course it does. But noone has written about this that I know of.
Good luck.