Abstract
In solar thermal systems, especially for high concentration applications, natural convection and radiation contributes a significant fraction of energy loss. Its characteristics hence need to be understood to improve system efficiency. In this work a numerical study is carried out to investigate the heat loss through a cascaded cavity receiver of a solar dish collector. The effect of increase in area ratio on heat loss is studied. The cascaded cavity receiver model is electrically heated with constant heat flux. A simulation model for combined natural convection and surface radiation is developed. The influence of orientation of the receiver, and the geometry on total heat loss from the receiver is investigated. The cavity inclination is varied from 0° to 90° in steps of 30°. The Computational Fluid Dynamics package “ANSYS 19.2 Fluent” has been used to numerically investigate the influence of cavity geometry and inclination on the convective loss through the aperture.The cascaded cavity receiver is found to reduce the natural convection and radiation heat losses.
Highlights
The concentrating solar technology has the potential to be used for supplying industrial process heat as well as for generating power
The convective losses from these solar cavity receivers are found to be dependent on various parameters like receiver inclination (θ), receiver wall boundary condition, aspect ratio (L/D), opening ratio (d/D), and external wind
To account for the radiation exchange in an internal surface of the modified cavity receiver along with the natural convection heat loss, S2S model is chosen in the present numerical procedure
Summary
The concentrating solar technology has the potential to be used for supplying industrial process heat as well as for generating power. Eyler (1981) [6] carried out a 2-dimensional numerical analysis of convective losses in rectangular and hemispherical solar cavity receiver respectively His results confirmed the dependency of convective loss on cavity dimensions and wall temperature. A numerical study of combined laminar natural convection and surface radiation heat transfer in a 2D side vented open cavity for different aspect ratios, side-vent ratios and surface emissivities using air as the working fluid was carried out by Singh and Venkateshan [11] and based on their study, several Nusselt number correlations were developed for convective and radiative heat transfer. A 2D numerical model with a steady state combined laminar natural convection and surface radiation heat transfer from a modified cylindrical cavity receiver of a solar parabolic dish system for various orientations has been developed
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