LAMINAR NATURAL CONVECTIVE HEAT TRANSFER IN PARABOLIC ENCLOSURES

Ola Kamiyo

doi:10.30572/2018/kje/120406

Abstract

A finite volume analysis of laminar natural convection of air within full parabolic enclosures heated from below is reported for the enclosure aspect ratio 0.27 £ AR £ 0.7 and a range of the Rayleigh number 5.5 x 106 £ Ra £ 9.8 x 107. The shape of the enclosures strongly affects the results obtained. Quasi-symmetrically arranged counter-rotating vortices are formed in each of the enclosures. The shape of the cells are influenced by the bounding curved and flat surfaces as they change from being rectangular at the periphery to circular at the core. There are reduction in the size and intensity of the on the cells from the center to the bottom corners. At steady state, there exists in each enclosure a central thermal plume that thickens as the roof pitch angle increases. The heat transfer pattern matches the flow of the plumes and jets from the walls. For the 15o roof pitch enclosure, the heat transfer rate increases sharply at a critical Ra value of 5 x 106.

Highlights

Over the years, exterior architecture of the roofs of most large buildings such as factories, warehouses, worship centres, aircraft hangars, shopping malls and indoor sport halls are mostly parabolic in nature
The effect of design pressure coefficients on hyperbolic paraboloid roof was examined by Rizzo and Riccardelli (2017) and Colliers et al (2020)
Streams of hot, rarefied air rising from the hot horizontal wall in form of plumes hit the cold parabolic wall perpendicularly

Summary

Introduction

Exterior architecture of the roofs of most large buildings such as factories, warehouses, worship centres, aircraft hangars, shopping malls and indoor sport halls are mostly parabolic in nature. Parabolic roof shed off rain and snow, effectively diffuse sunrays and minimize accumulation of dirt. The interior view of roofs of parabolic shape has inimitable decorative features characterized by large space volume and aesthetic magnificence. A number of researchers have reported various investigations on the parabolic roof. The effect of design pressure coefficients on hyperbolic paraboloid roof was examined by Rizzo and Riccardelli (2017) and Colliers et al (2020). Rizzo et al (2018) reported the peak factor statistics of wind effects while Shen et al (2020) numerically studied the dynamics of the same paraboloid roof. Simoni and Nordestgaard (2017) used hyperbolic paraboloid shape shell structure as a roof for an outdoor music stage The effect of design pressure coefficients on hyperbolic paraboloid roof was examined by Rizzo and Riccardelli (2017) and Colliers et al (2020). Rizzo et al (2018) reported the peak factor statistics of wind effects while Shen et al (2020) numerically studied the dynamics of the same paraboloid roof. Simoni and Nordestgaard (2017) used hyperbolic paraboloid shape shell structure as a roof for an outdoor music stage

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Conclusion