Laminar Mixed Convection in a Concentric Annulus With Horizontal Axis

Abstract

Axial laminar flow in a horizontal annular pipe is influenced by the presence ofbuoyancy-induced secondary flows that are caused by the heat flow from the inner cylinder. A numerical study is presented for the fully developed region of the buoyancy-affected flow. The distributions of the axial and cross-sectional velocities are calculated along with the temperature variation in the cross section. Results are presented for a range of values of the Rayleigh number, the Prandtl number, and the radius ratio of the annulus. The Nusselt number increases significantly with the Rayleigh number; yet the corresponding increase in the friction factor is found to be rather small. Distributions of secondary flow and isotherms over the cross section are presented for different values of the parameters. In each half of the annulus on either side of the vertical centerline, the secondary flow displays a single-eddy pattern at low Rayleigh numbers and changes to a double-eddy pattern at high values. 902/ Vol. 107, NOVEMBER 1985 Transactions of the ASME Copyright © 1985 by ASME Downloaded From: http://heattransfer.asmedigitalcollection.asme.org/ on 05/27/2015 Terms of Use: http://asme.org/terms 908/Vol. 107, NOVEMBER 1985 Transactions of the ASME Downloaded From: http://heattransfer.asmedigitalcollection.asme.org/ on 05/27/2015 Terms of Use: http://asme.org/terms

3D Fully Developed Laminar Mixed Convection in Horizontal Concentric Annuli with the Presence of Porous Blocks

“…The discontinuity between the porous blocks and fully fluid zone is handled with the use of the harmonic mean formulation suggested by Patankar [18]. The present code was validated by comparing the results obtained with our code for the fully fluid case, with those of Nieckele and Patankar [4]. Good agreement between the results is observed in the Table II. The discrepancy for the mean Nusselt number and the friction factor values is less than 1%.…”

“…The main focus of these systems is to enhance the overall heat transfer coefficient. Laminar mixed convection between concentric horizontal cylinders is presented in [1]- [4]. Niekele and Patankar [4] have examined numerically the effect of buoyancy forces on heat transfer in an annulus.…”

“…Laminar mixed convection between concentric horizontal cylinders is presented in [1]- [4]. Niekele and Patankar [4] have examined numerically the effect of buoyancy forces on heat transfer in an annulus. Results are presented for a range of the values of the Gashoff number, the Prandtl number, and the radius ratio of the annulus.…”

Fully developed combined convection in a seven-rod horizontal bundle

“…(7), it was assumed that d pad z in the z-momentum equation equals d " padz, where " p is the cross-sectional average of p, and this has been shown to be valid for GraRe 2`1 [2]. Thermally developed ow with uniform heat¯ux condition yielded d…”

“…The results showed changes in lateral¯ow structures from a single to multiple cells as the Rayleigh number was increased. Nieckele and Patankar [2] carried out a similar study but for a wide range of radius ratios varying from 1.5 to 5.0. The study of mixed convection in horizontal annuli was preceded by that in plain tubes and most of these studies have been cited in [2].…”