Hydraulic and heat transfer characteristics in structured packed beds with methane steam reforming reaction for energy storage

Abstract

Packed beds with methane steam reforming reaction (MSR) can be used as thermochemical storage devices. The packing configuration can have a significant effect on the flow distribution which will further influence the heat/mass transfer, dispersion and reaction characteristics. In the present paper, the hydraulic, dispersion, heat/mass transfer and the MSR reaction properties are investigated in packed beds with the simple-cubic (SC) packing, the body-centered cubic (BCC) packing and face-centered cubic (FCC) packing forms. ANSYS FLUENT integrated with user defined scalars (UDS) and user defined functions (UDF) are used to perform the simulations. Results show that firstly, the residence time distribution (RTD) can be used to evaluate the dispersion property in packed beds where a narrower RTD curve reflects a more uniform velocity distribution with less dispersion. Secondly it is found that, regions with backflow are not beneficial for heat/mass transfer and chemical reactions from two aspects. One is that the heat transfer between the main fluid and the particle surfaces is weak and low temperature of the particles will reduce the reaction rates. The other is that the poor species transport will prevent the reactant to flow into the reaction region and the products cannot be taken away by the main flow timely, which will have a negative effect on the reaction. Thirdly, it is revealed that, the dimensionless variation of the residence time distribution (DVRTD) can reflect the heat/mass transfer and reaction performances, where a smaller DVRTD corresponds to better heat/mass transfer and higher reaction rates.