High-Temperature Flow Testing and Heat Transfer for a Moving Packed-Bed Particle/sCO2 Heat Exchanger

Experiments for measuring the heat transfer coefficients and visualization of dense granular flows in rectangular vertical channels are reported. The experiments are directed at the development of a moving packed-bed heat exchanger to transfer thermal energy from solar-heated particles to drive a supercritical carbon dioxide (sCO(2)) power cycle. Particle-wall heat transfer coefficients are found to agree with Nusselt number correlations for plug flow in a parallel plate configuration. The plate spacing and particle properties in the prototype design result in experimentally measured particle-wall heat transfer coefficients of 200 W/m(2)-K at intermediate temperature and are expected to be higher at elevated temperature due to improved packed bed thermal conductivity. The high-temperature (600 degrees C) visualization experiments indicate that uniform particle flow distribution through the vertical channels of a shell-and-plate heat exchanger can be achieved through a mass flow cone particle feeder. Uniform drawdown was experienced for both 77 degrees and 72 degrees feeder angles over a range of particle mass flow rates between 0.05 and 0.175 kg/s controlled by a slide gate to modulate the outlet flow cross-sectional area.