# Natural Convection - horizontal cylinder

1. Mar 15, 2010

### MET

Nusselt number:

1) The only correlation I could find so far is the one described here http://en.wikipedia.org/wiki/Natural_convection which seems to be from Churchill/Thelen. There seem however to exist some questions regarding the characteristic length and the value to use for Nuo (see discussion). Could someone here may be clarify these points?

2) Does someone know of an alternative correlation which could be used instead of the one from Chruchill/Thelen for the Grasshof range 0.01<Gr<50 and air (Pr=0.7)?

3) Does someone know of such a correlation which considers also the length to diameter ratio of the cylinder?