Numerical investigation of heat losses through cascaded fully open cavity receiver at high temperatures up to 500°C

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 degrees to 90 degrees in steps of 30 degrees. 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.