Solid Particle Receiver Flow Characerization Studies

The solid particle receiver (SPR) is a direct absorption central receiver that can provide a solar interface with thermal storage for thermochemical hydrogen production processes requiring heat input at temperatures up to 1000 C. In operation, a curtain consisting of ∼690 μm ceramic particles is dropped within the receiver cavity and directly illuminated by concentrated solar energy. The heated particles exit the receiver and may either be stored or sent through a heat exchanger to provide process heat input. The performance of the receiver is dependent on the characteristics of the particle flow including velocity and opacity (optical density). In addition, because the SPR will have an open aperture there is also a possibility that the flow may be disturbed by high ambient winds. Computational models have been and are currently being used to simulate receiver performance at power levels up to several MW_t. However, due to the complex two-phase nature of the solid particle flow, such models rely on experimental data both to provide physical input, such as boundary conditions, as well as to provide a point of comparison for model validation. In this paper, we present experimental results from tests performed using a small scale unheated solid particle curtain. These tests focus on the measurement of the flow characteristics of the solid particle curtain as it falls from a near-zero velocity discharge slot to a collection point three meters below. The results include measured values for the variation of velocity, solids volume fraction, curtain width, and curtain opacity along the length of the curtain.