Chapt06

For laminar flow in rectangles and triangles the wall

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: yet to be achieved, although numerical models are improving [36]. e-Text Main Menu | Textbook Table of Contents | Study Guide 366 Chapter 6 Viscous Flow in Ducts Midplane Fig. 6.16 Illustration of secondary turbulent flow in noncircular ducts: (a) axial mean-velocity contours; (b) secondary-flow cellular motions. (After J. Nikuradse, dissertation, Göttingen, 1926.) (a) (b) EXAMPLE 6.15 Air, with 0.00237 slug/ft3 and 0.000157 ft2/s, is forced through a horizontal square 3 9-by 9-in duct 100 ft long at 25 ft /s. Find the pressure drop if 0.0003 ft. Solution Compute the mean velocity and hydraulic diameter V Dh From Table 6.4, for b/a 25 ft3/s (0.75 ft)2 4A 9 in 0.75 ft 1.0, the effective diameter is Deff whence Reeff From the Moody chart, read f ghf gf or 64 Dh 56.91 VDeff Deff p 4(81 in2) 36 in 44.4 ft/s 0.843 ft 44.4(0.843) 0.000157 0.0003 0.843 239,000 0.000356 0.0177. Then the pressure drop is L V2 Dh 2g 0.00237(32.2) 0.0177 p 100 44.42 0.75 2(32.2) 5.5 lbf/ft2 Ans. | v v Pressure drop in air ducts is usually...
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