## Description

Concentrating solar power systems are currently the predominant solar power technology for generating electricity at the utility scale. The central receiver system, which is a concentrating solar power system, uses a field of mirrors to concentrate solar radiation onto a receiver where a working fluid is heated to drive a turbine. The current central receiver systems operate on a Rankine cycle, which has a large demand for cooling water. This demand for water presents a challenge for the current central receiver systems as the ideal locations for solar power plants have arid climates. An alternative to the current receiver technology is the small particle receiver. The small particle central receiver has the potential to produce working fluid temperatures suitable for use in a Brayton cycle. In this thesis, a detailed numerical investigation for an axisymmetric, cylindrical small particle receiver was performed. The highly accurate Monte Carlo Ray Trace (MCRT) method was used to model the radiation heat transfer inside the receiver. A new MCRT code was developed and can accommodate spectral particle properties along with anisotropic scattering by the small particles. The MCRT program provides a source term to the energy equation. This in turn, produces a new temperature field for the MCRT program; together the equations are solved iteratively. This iteration repeats until convergence is reached for a steady temperature field. The energy equation was solved using a finite volume method assuming a simplified velocity field and an effective thermal conductivity that can account for turbulent flow conditions. The numerical model was used to investigate the effects of the particle diameter, particle mass loading, receiver wall properties, and the angular distribution of incident concentrated solar radiation on the efficiency of the receiver. In addition to investigating the receiver efficiency, the outlet temperatures of the small particle solar were also studied to confirm that the receiver can drive a Brayton cycle. The simulations of the small particle solar receiver showed outlet temperatures over 1400 K for essentially all parameters investigated. This confirms the suitability of the receiver to drive a Brayton cycle. In addition to the high outlet temperatures, the receiver efficiency was in excess of 90 percent for some cases. The results from the model show 0.2 _m diameter particles at a 0.30 g/m_ mass loading with aluminum oxide receiver walls exposed to an input solar flux with the 45° cone angle distribution will produce the highest receiver efficiency for the range of parameters investigated. For this set of parameters, the receiver efficiency was 91.42 ± 0.04 percent.