Predicting heat transfer coefficient of a shell-and-plate, moving packed-bed particle-to-sCO2 heat exchanger for concentrating solar power

Abstract

The particle-to-sCO2 heat exchanger plays a significant role in coupling the high temperature particle receiver to supercritical carbon dioxide Brayton cycle in concentrating solar power plants. In this work, heat transfer characteristics of a shell-and-plate, moving packed-bed heat exchanger are numerically evaluated through continuum modeling. It is found that the local heat transfer coefficient h for different input parameters have a similar shape: h quickly drops at the thermal entry region and then remains as a constant. The asymptotic value of h increases with the particle flow velocity but decreases with particle channel width. A universal correlation between the local heat transfer coefficient and the particle flow properties in terms of the dimensionless Nusselt number is then proposed. Moreover, by calculating the overall heat transfer coefficient and performing a sensitivity analysis, we show that the heat exchanger has a two-regime behavior: in the regime with low particle flow rate, the performance mostly depends on the particle flow velocity and the channel width, and is restricted by the small amount of energy stored in the particle flow. In the high flow rate regime, the effective conductivity of the particle flow becomes the determining factor on the performance of the heat exchanger.