Chapt06

91 ur fig 615 fully developed flow through a

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: on the wall shear because there are two shear stresses, the inner stress being greater than the outer. It is better to define f with respect to the head loss, as in Eq. (6.73), f hf Dh 2g L V2 Q (a2 b2) where V (6.94) The hydraulic diameter for an annulus is Dh 4 (a2 2 (a b2) b) 2(a b) (6.95) It is twice the clearance, rather like the parallel-plate result of twice the distance between plates [Eq. (6.82)]. Substituting hf, Dh, and V into Eq. (6.94), we find that the friction factor for laminar flow in a concentric annulus is of the form f 64 ReDh a4 b)2(a2 b2) (a2 b2)2/ln (a/b) (a b4 (6.96) The dimensionless term is a sort of correction factor for the hydraulic diameter. We could rewrite Eq. (6.96) as Concentric annulus: f 64 Reeff 1 Reeff ReDh (6.97) | v v Some numerical values of f ReDh and Deff/Dh 1/ are given in Table 6.3. For turbulent flow through a concentric annulus, the analysis might proceed by patching together two logarithmic-law profiles, one going out from the inner wall to meet the other coming i...
View Full Document

This note was uploaded on 10/27/2009 for the course MAE 101a taught by Professor Sakar during the Spring '08 term at UCSD.

Ask a homework question - tutors are online