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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

Numerical Study of Heat Transfer Characteristics for Different Solar Flux Distributions on Linear Fresnel Collector Absorber Tubes in Laminar Flow

Get access (open in a dialog) DOI: 10.1615/IHTC15.fcv.009221
pages 2847-2861

Abstract

In this study the influence of different circumferential solar heat flux distributions on the heat transfer characteristics of the absorber tubes of a linear Fresnel concentrator was investigated under steady-state and laminar flow conditions. Three-dimensional numerical simulations considering circumferential uniform and non-uniform heat flux distributions on the absorber tubes was implemented using ANSYS Fluent version 14. The non-uniform solar heat flux distribution was modeled as a sinusoidal function of the irradiation heat flux incident on the exterior surface of the absorber tubes. The average internal, overall and axial local heat transfer coefficients for non-uniform heat flux distributions spans of 160°, 180°, 200° and 240°, and a 360° uniform heat flux for tubes of 10 m in length, with an inner diameter of 6.3 mm, a wall thickness of 5.2 mm and a thermal conductivity of 16.27 W/mK were determined for an inlet Reynolds number range of 180 to 2200. It was found that for both uniform and non-uniform heat flux distributions, the average internal heat transfer coefficients increased with Reynolds number. It was also found that the average internal and axial local heat transfer coefficients for the absorber tubes modeled with non-uniform heat flux distributions were higher than the uniform heat flux due to a dominant influence of buoyancy-driven secondary flow. The average internal and overall heat transfer coefficients, thermal efficiency, pressure drop and its consequent increase in pumping power to sustain fluid flow and heat transfer, were found to increase with the decreased in the absorber tube inner diameter.