An investigation into the effect of aspect ratio on the heat loss from a solar cavity receiver

Abstract

The effect of aspect ratio and head-on wind speed on the force and natural (combined) convective heat loss and area-averaged convective heat flux from a cylindrical solar cavity receiver has been assessed using three dimensional computational fluid dynamics (CFD) simulations. The cavity assessment was performed with one end of the cavity open and the other end closed, assuming an uniform internal wall temperature (i.e. the cavity walls were heated). The numerical analysis shows that there are ranges of wind speeds for which the combined convective heat losses are lower than the natural convective heat loss from the cavity and that this range depends on the aspect ratio of the cavity. In addition, the effect of wind speed on the area-averaged flux of convective heat loss from a heated cavity is smaller for long aspect ratios than for short ones, which indicates that the overall efficiency of the solar cavity receiver increases with the aspect ratio for all conditions tested in this study.