Abstract
The aim of this paper is to address fluid flow behavior of natural circulation in a 2D-annular loop filled with water. A two-dimensional, numerical analysis of natural convection in a 2D-annular closed-loop thermosyphon has been performed for various radius ratios from 1.2 to 2.0, the loop being heated at a constant flux over the bottom half and cooled at a constant temperature over the top half. It has been numerically shown that natural convection in a 2D-annular closed-loop thermosyphon is capable of showing pseudoconductive regime at pitchfork bifurcation, stationary convective regimes without and with recirculating regions occurring at the entrance of the exchangers, oscillatory convection at Hopf bifurcation and Lorenz-like chaotic flow. The complexity of the dynamic properties experimentally encountered in toroidal or rectangular loops is thus also found here.
Highlights
Natural circulation is an important mechanism, and the knowledge of its behavior is of interest for cooling purposes in industrial processes, including solar water heaters, geothermal processes, gas turbine blade cooling, and as part of the emergency core cooling system in nuclear reactors
A twodimensional, numerical analysis of natural convection in a 2D-annular closed-loop thermosyphon has been performed for various radius ratios from 1.2 to 2.0, the loop being heated at a constant flux over the bottom half and cooled at a constant temperature over the top half
It has been numerically shown that natural convection in a 2D-annular closed-loop thermosyphon is capable of showing pseudoconductive regime at pitchfork bifurcation, stationary convective regimes without and with recirculating regions occurring at the entrance of the exchangers, oscillatory convection at Hopf bifurcation and Lorenz-like chaotic flow
Summary
Natural circulation is an important mechanism, and the knowledge of its behavior is of interest for cooling purposes in industrial processes, including solar water heaters, geothermal processes, gas turbine blade cooling, and as part of the emergency core cooling system in nuclear reactors. Some advanced nuclear plant designs rely on natural circulation to remove core power under normal operation (startup, normal power operation, and shutdown), and some designs rely on natural circulation to provide cooling of the containment. Because of their practical importance, thermosyphons have been the subject of a large number of theoretical and experimental studies. A review of the wide applications of natural circulation loops in engineering systems has been given by Zvirin [1]. The presence of a reverse flow region was first qualitatively reported by Creveling et al [6] who first observed the Lorenz-like chaotic flow in their experiments (see [7,8,9])
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