Performance Characteristics of a Volumetric Solar Receiver: Presence of an Absorber Plate with a Selective Surface

Performance characteristics of a concentrated solar volumetric absorber are examined numerically. The thermal system considered consists of parabolic trough, glass tube, absorbing plate, and slurry containing 7% lauric acid as a phase change material and water as a carrier fluid. To assess the effect of the absorbing plate on performance characteristics, two locations of the absorbing plate on the glass tube surface are incorporated in the analysis. A selective surface is considered at the absorber plate surface for improved absorption of solar radiation and reduced thermal emission due to temperature increase at the surface. Temperature ratio, gain parameter, and pump power loss parameters are introduced to quantify the performance characteristics of the volumetric receiver. The study is extended to include the effect of Reynolds number on the receiver performance characteristics. A heating model incorporating radiation, convection, and conduction is adopted to simulate the thermal process. It is found that the gain parameter of the concentrated solar volumetric receiver improves by 15% when the absorber plate is located at the left face of the glass tube opposing the trough surface. The effect of Reynolds number on gain parameter is found to be inconsiderable.