Heat transfer model of a particle energy storage-based moving packed bed heat exchanger

Moving packed bed particle/supercritical carbon dioxide (SCO2) heat exchanger (MPBE) is a critical equipment to integrate particle thermal energy storage technology with SCO2 power cycle block in the next-generation concentrated solar power plants. A predictive heat transfer model for designing and evaluation of shell and plate particle/SCO2 moving packed bed heat exchanger is presented, with radiation, pressure drop and SCO2 property variation taking into account. It is found that increasing particle diameter and solids bulk voidage will lower the overall heat transfer coefficient. Change of channel width imposes little effects on the overall heat transfer coefficient, while influences the total heat exchange greatly. MPBE with longer channel length allows smaller overall heat transfer coefficient. Due to approximate linear variation of specific heat and low pressure drop in the nominal boundary operating condition range, ignoring SCO2Cp variation is valid, and the relative error due to adopting a C-p invariable evaluated at the bulk temperature and constant pressure is less than 1%. Convection resistance generally ranks first in the contribution to thermal resistance, followed by solids-wall resistance and conduction resistance. Nevertheless, solids-wall resistance dominates at larger particle diameter (>= 550 mu m). Radiation is an important contributor to heat transfer behavior, especially at high particle diameter and solids bulk voidage. The relative error caused by neglecting radiation can be up to 23.76%.