Abo Bibliothek: Guest

ISSN Online: 2377-424X

ISBN Print: 0-85295-345-3

International Heat Transfer Conference 10
August, 14-18, 1994, Brighton, UK

EFFECTS OF TUBE INCLINATION AND WALL CHARACTERISTICS ON FULLY DEVELOPED MIXED CONVECTION IN A CIRCULAR TUBE

Get access (open in a dialog) DOI: 10.1615/IHTC10.3320
pages 507-512

Abstrakt

The fully developed ascending laminar flow of an incompressible fluid within a circular inclined tube uniformly heated on its outer surface has been studied numerically. The solution of the five coupled partial differential equations governing this conjugate heat transfer problem, based on the SIMPLER algorithm , was obtained for three Prandtl numbers (0.7, 7, 100), a Reynolds number of 500, several Grashof numbers ranging from 5×104 to 106, for thin and thick walled tubes with different wall materials, and for several tube inclinations α. For vertical tubes the hydrodynamic and thermal fields in the fluid region are independent of the tube characteristics. For this inclination the effect of Pr disappears while the values of the average Nusselt number Nu and the average dimensionless wall shear stress τ increase significantly as Gr increases. This effect of Gr on Nu and τ is valid for all fluids and all tube inclinations. For horizontal tubes, Nu and τ are smaller for low conductivity tubes. Small values of the wall to fluid conductivities ratio (kp ≤ 0.1) lead to a uniform interfacial heat flux while high values of this ratio (kp ≥ 103) lead to a uniform interfacial temperature for all inclinations, all fluids and all Gr investigated. The value of kp has an important influence on the relationship between Nu and α: for all Gr and Pr investigated, as α increases from 0° to 90°, Nu decreases monotonically if kp ≥ 103 while it exhibits a maximum for kp ≤ 0.1. This maximum is more pronounced for high Gr and it occurs at larger values of α as Pr increases.