Thermally Driven Flow of Water in Partially Heated Tall Vertical Concentric Annulus.

Jawed Mustafa,Saeed Alqaed,Mohammad Altamush Siddiqui

doi:10.3390/e22101189

Abstract

Computational fluid dynamics (CFD) has become effective and crucial to several applications in science and engineering. The dynamic behavior of buoyancy induced flow of water in partially heated tall open-ended vertical annulus is analyzed based on a CFD technique. For a vertical annulus, the natural convective heat transfer has a broad application in engineering. The annulus is the most common structure used in various heat transmission systems, from the basic heat transfer device to the most sophisticated atomic reactors. The annular test sections of such a large aspect ratio are of practical importance in the design of equipment’s associated with the reactor systems. However, depending on the geometrical structure and heating conditions, it exhibits different flow behavior. The annulus may either be closed or open-ended. In this study, we carry out CFD analysis to examine the thermodynamics properties and the detailed thermal induced flow behavior of the water in Tall open-ended vertical concentric annuli. The purpose of this study is to evaluate the impact of a partially heating on mechanical properties and design parameters like Nusselt number, mass flow rate and pressure defect. For Rayleigh number ranging from 4.4 × 103 to 6.6 × 104, while the Prandtl number is 6.43, the numerical solution was obtained. The modelling result showing the measurement and transient behavior of different parameters is presented. The numerical results would be both qualitatively and quantitatively validated. The presentation of unstable state profiles and heat variables along the annulus are also discussed.

Highlights

The process of energy transfer on a surface to a fluid flowing over it; as a result, the difference between them is referred to as convection heat transfer
Since the rate of convective heat transfer is influenced by the flow field of the fluid, it will strongly depend upon how the flow is generated
We emphasize quantifying the impact of partial heating on design parameters like pressure distribution and coefficient of heat transfer for a very high aspect ratio and we further aim to identify flow physics as a flow pattern within the annuli

Summary

Introduction

The process of energy transfer on a surface to a fluid flowing over it; as a result, the difference between them is referred to as convection heat transfer. Since the rate of convective heat transfer is influenced by the flow field of the fluid, it will strongly depend upon how the flow is generated. The body forces are responsible for the flow and that occur due to the density difference arising caused by the changes of temperature in the flow field. The body forces are generated due to pressure gradients imposed on the whole fluid due to gravity. This results in the buoyancy force that causes the lighter fluid to rise upward. The buoyancy induced flow is generally due to density gradient in the flow, which can occur due to concentration gradient and temperature gradient

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