

@mastersthesis {6765,
	title = {Combined convection in horizontal circular sector ducts of various cross-sectional orientations},
	year = {1993},
	note = {NN85971},
	school = {The University of Manitoba (Canada)},
	type = {phdPh.{D}.},
	address = {Ann Arbor},
	abstract = {For laminar mixed convection in horizontal circular sector ducts with uniform heat input axially, fully developed Nusselt numbers (Nu) (and similarly for the product of friction factor (f) and Reynolds number (Re)) depend on duct apex angle (2\${\textbackslash}phi\$) and are functions of modified Grashof number (\$Gr{\textbackslash}sp+\$) (average heat flux level), Prandtl number (Pr) (fluid type) and duct orientation with respect to the gravity vector (as would occur, for example, in horizontal multi-passage tubes). A theoretical/numerical study was made of the fully developed results for the H1 thermal boundary condition. Nu and fRe were computed for various \${\textbackslash}phi\$, each at various orientations and Pr over a range of \$Gr{\textbackslash}sp+\$ up to approximately 5 \${\textbackslash}times\$ 10\${\textbackslash}sp7\$. For a fixed \$Gr{\textbackslash}sp+\$, Pr, and orientation, it was found that Nusselt ratios first increased rapidly with 2\${\textbackslash}phi\$ but tended to plateau between about 2\${\textbackslash}phi\$ = 120\${\textbackslash}sp{\textbackslash}circ\$ and 180\${\textbackslash}sp{\textbackslash}circ\$. In these plateau regions, enhancements, for example for \$Gr{\textbackslash}sp+\$ = 10\${\textbackslash}sp7\$ and Pr = 4, reached factors of between about 3.7 and 4.4 depending on orientation. On the other hand, under the same condition, fRe ratios fell in the range of about 1.4 to 1.6. For a given circular sector duct in a fixed orientation, it was found that buoyancy effects became progressively more influential as the heat flux level was increased. For a fixed duct and orientation, for a given \$Gr{\textbackslash}sp+\$, Nu increased with Pr whereas fRe decreased with Pr. These dependencies could be removed by scaling Nu on the product \$Gr{\textbackslash}sp+Pr\$ and fRe on the parameter \$Gr{\textbackslash}sp+/Pr{\textbackslash}sp2\$. Concerning the effect of orientation, for a fixed duct operating at fixed \$Gr{\textbackslash}sp+\$ and Pr, orientation was a fairly significant factor, being largest for large \${\textbackslash}phi\$. A series of experiments using a water loop were conducted on a semicircular duct oriented at 45\${\textbackslash}sp{\textbackslash}circ\$, 90\${\textbackslash}sp{\textbackslash}circ\$, 135\${\textbackslash}sp{\textbackslash}circ\$ and 180\${\textbackslash}sp{\textbackslash}circ\$ in addition to the 0\${\textbackslash}sp{\textbackslash}circ\$ orientation in the previous study. The various tests at different orientations spanned from Re of 500-1500 and Gr of 5 \${\textbackslash}times\$ 10\${\textbackslash}sp6\$-5 \${\textbackslash}times\$ 10\${\textbackslash}sp7\$. The magnitudes of local Nusselt numbers were observed to be steady in the region where x* was larger than about 0.01 consistently for all \${\textbackslash}alpha\$ and therefore the fully developed Nusselt numbers were determined in this region. Strong dependence between Nu and \$Gr{\textbackslash}sp+\$ were observed. The maximum Nusselt numbers were obtained with \${\textbackslash}alpha\$ = 90\${\textbackslash}sp{\textbackslash}circ\$ and 135\${\textbackslash}sp{\textbackslash}circ\$ whose magnitudes were similar. Similar Nu magnitudes were also observed for \${\textbackslash}alpha\$ = 45\${\textbackslash}sp{\textbackslash}circ\$ and 180\${\textbackslash}sp{\textbackslash}circ\$. Unlike the theoretical/numerical results, the correlation of Nu vs \$Gr{\textbackslash}sp+/Pr\$ showed little improvement as compared to Nu vs \$Gr{\textbackslash}sp+\$. The differences in Nusselt number magnitudes for \${\textbackslash}alpha\$ = 90\${\textbackslash}sp{\textbackslash}circ\$/135\${\textbackslash}sp{\textbackslash}circ\$ was about 10\% compared to \${\textbackslash}alpha\$ = 45\${\textbackslash}sp{\textbackslash}circ\$/180\${\textbackslash}sp{\textbackslash}circ\$ and about 40\% compared to \${\textbackslash}alpha\$ = 0\${\textbackslash}sp{\textbackslash}circ\$. (Abstract shortened by UMI.)},
	keywords = {0548:Mechanical engineering, Applied sciences, Mechanical engineering},
	url = {http://search.proquest.com/docview/304067271?accountid=14270},
	author = {Chinporncharoenpong, Chaisin}
}
